Report on the Erosion
of Concrete in Hydraulic
Structures
Reported by ACI Committee 207
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Report on the Erosion of Concrete in Hydraulic Structures
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ACI 207.6R-17
Report on the Erosion of Concrete in Hydraulic
Structures
Reported by ACI Committee 207
John W. Gajda, Chair
Christopher C. Ferraro, Secretary
Fares Y. Abdo
Oscar R. Antommattei
Terrence E. Arnold
Katie J. Bartojay'
Teck L. Chua
Timothy P. Dolen
Darrell Elliott
Barry D. Fehl
Mario Garza
Melissa 0. Harrison
Michael G. Hernandez
James K. Hicks
Jeffrey C. Allen
Randall P. Bass
Anthony A. Bombich
Robert W. Cannon
Eric J. Ditchey
Brian A. Forbes
Rodney E. Holderbaum
Ronald L. Kozikowski
Tibor J. Pataky
Jonathan L. Poole
Henry B. Prenger
Ernest A. Rogalla
Ernest K. Schrader
Kuntay K. Talay
Nathaniel F. Tarbox
Stephen B. Tatro
Michael A. Whisonant
Fouad H. Yazbeck
Consulting Members
Allen J. Hulshizer
Richard A. Kaden
William F. Kepler
David E. Kiefer
'Primary author of this report.
!Deceased.
Committee 207 would like to thank the following individuals for their contribution to this report: J. Ballentine, J. F. Best, G .
Mass, W. McEwen, M. Petrovsky, and M. Stegallo.
Keywords: abrasion; aeration; cavitation; chemical attack; concrete dams;
corrosion; erosion; hydraulic structures; spillways.
This report outlines the causes, control, maintenance, and repair
of erosion in hydraulic structures. Such erosion occurs from three
major causes: cavitation, abrasion, and chemical attack. Design
parameters,
materials
selection
and
quality,
CO NTE NTS
environmental
factors, and other issues affecting the performance of concrete are
discussed.
Evidence exists to suggest that, given the operating characteris­
tics and conditions to which a hydraulic structure will be subjected,
the concrete can be designed to mitigate future erosion. However,
when operational factors change or are not clearly known and
erosion of concrete surfaces occurs, repairs should follow. This
report addresses the subject of concrete erosion, inspection tech­
niques, and repair strategies, providing references to a more
detailed treatment of the subject.
CHAPTER 1-I NTRO DUCTIO N AND SCOPE, p. 2
1 . 1 -Introduction, p. 2
1 .2-Scope, p. 2
CHAPTER 2-NOTAT ION, p. 2
2 . 1 -Notation, p. 2
CHAPTER 3-EROSIO N BY CAVITATION, p. 3
3 . 1 -Mechanism of cavitation, p. 3
3 .2-Cavitation index, p. 3
ACI Committee Reports, Guides, and Commentaries are
intended for guidance in planning, designing, executing, and
inspecting construction. This document is intended for the use
of individuals who are competent to evaluate the significance
and limitations of its content and recommendations and who
will accept responsibility for the application of the material it
3 .3-Cavitation damage, p. 4
CHAPTER 4-EROSIO N BY ABRASIO N, p. 6
4 . 1 -General, p. 6
4.2-Stilling basin damage, p. 6
contains. The American Concrete Institute disclaims any and
all responsibility for the stated principles. The Institute shall
not be liable for any loss or damage arising therefrom.
Reference to this document shall not be made in contract
documents. If items found in this document are desired by
the Architect/Engineer to be a part of the contract documents,
they shall be restated in mandatory language for incorporation
by the Architect/Engineer.
ACI 207.6R-17 supersedes ACI 21OR-93(08) and was adopted and published
September 2017.
Copyright© 2017, American Concrete Institute.
All rights reserved including rights of reproduction and use in any form or by
any means, including the making of copies by any photo process, or by electronic
or mechanical device, printed, written, or oral, or recording for sound or visual
reproduction or for use in any knowledge or retrieval system or device, unless
permission in writing is obtained from the copyright proprietors.
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2
REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
4.3-Power plant tailrace damage, p. 7
4.4-Navigation lock damage, p. 8
4.5-Tunnel lining damage, p. 8
4.6-Hydraulic jacking, p. 8
CHAPTER 5-EROSION BY CHEMICAL ATTACK,
p. 9
5.!-Sources of external chemical attack, p. 9
5.2-Erosion by mineral-free water, p. 9
5.3-Erosion by miscellaneous causes, p. 9
CHAPTER 6-CONTROL O F CAVITATION
EROSION, p. 1 0
6.1-Hydraulic design principles, p . 10
Example 1, p. 10
6.2-Cavitation indexes for damage and construction
tolerances, p. 11
Example 2, p. 11
6.3....:U
:... sing aeration to control damage, p. 12
6.4....::...Materials, p. 13
6.5-l.Materials testing, p. 14
6.6 Construction practices, p. 14
T
CHAPTER 7-CONTROL O F ABR ASION EROSION,
p. 15
concrete deteriorates for a variety of reasons, this report is
concerned with specific factors that influence these three
areas of erosion: 1) cavitation-erosion resulting from the
collapse of vapor bubbles formed by pressure changes
within a high-velocity water flow; 2) abrasion-erosion of
concrete in hydraulic structures caused by water-transported
silt, sand, gravel, ice, debris, or hydraulic jacking; and 3)
chemical action-disintegration of the concrete in hydraulic
structures by chemical attack.
Concrete in properly designed, constructed, used, and
maintained hydraulic structures can provide 30 to 50 years
of erosion-free service (Liu and Wang 2000). However,
for reasons including inadequate design or construction, or
operational and environmental changes, erosion does occur
in hydraulic structures.
1.2-Scope
Concrete erosion in hydraulic structures caused by cavi­
tation, abrasion, and chemical attack are included in this
report. Options available to the designer and user to control
concrete erosion in hydraulic structures are discussed, along
with information on the inspection and evaluation of erosion
problems. This report includes repair techniques, as well as
a brief guide to methods and materials for repair. Other types
of concrete deterioration are outside the scope of this report.
7.!-Hydraulic considerations, p. 15
7.2-Materials evaluation, p. 16
7.3-Materials, p. 16
CHAPTER 2- NOTATION
2.1-Notation
CHEMICAL ATTACK, p. 1 7
F
l
8.1-Control of erosion by mineral-free water, p. 17
8.2-Control of erosion from acid attack due to bacterial
action, p. 18
8.3-Control of erosion by miscellaneous chemical
causes, p. 18
p
p0
Pc
Pv
CHAPTER 8-CONTROL O F EROSION BY
CHAPTER 9-PERIO DIC INSPECTIONS AND
CORRECTIVE ACTION, p. 19
9.1-General, p. 19
9.2-Inspection program, p. 19
9.3-Inspection procedures, p. 19
9.4-Reporting and evaluation, p. 19
qa
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CHAPTER 10-REPA IR METHO DS AN D
Zo
MATERIALS, p. 2 0
Zc
10.1-Design considerations, p. 20
10.2-Methods and materials, p. 20
CHAPTER 11-RE FERENCES, p. 22
Authored documents, p. 23
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CHAPTER 1-INTRO DUCTION AN D SCOPE
(J
1.1- lntroduction
Erosion is the progressive disintegration of a solid by:
1) cavitation; 2) abrasion; or 3) chemical action. Although
force
length of air space between the jet and the spillway
floor, l (l = length)
water pressure at a given point, Fll2
absolute pressure at a given Point 0, F!l2
absolute pressure at a given Point c, F!l2
vapor pressure of water, Fll2
volume rate of air entrainment per unit width of jet,
l31T
amount of air a turbulent jet will entrain along its
lower surface, l3IT
time
average jet velocity at midpoint of trajectory, liT
average velocity at Section 0, liT
offset into the flow, l
elevation at Centerline Of pipe, l
elevation of the vapor bubble, l
width of jet coefficient based on turbulent intensity
of the jet
change in pressure between two points, F!l2
specific weight of water, F!l3 (62.4 lb/ft3 [9.81 kN/
m3], temperature-dependent
mass density of water, FT2fe4 (1.94 lb·s2fft4 [1000
kg/m3], temperature-dependent)
cavitation index
value of cavitation index at which cavitation
initiates
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
CHAPTER 3-EROSION BY CAVITATION
/Vapor CaVItieS
4�/
�
.
3.1- Mechanism of cavitation
Cavitation is the formation of bubbles or cav1t1es in a
liquid. In hydraulic structures, the liquid is water, and the
cavities are filled with water vapor and air. The cavities form
where the local pressure drops to a value that will cause
the water to vaporize at the prevailing fluid temperature.
Figure 3.1a shows examples of concrete surface irregulari­
ties that can trigger formation of these cavities. The pressure
drop caused by these irregularities is generally abrupt and
is caused by local high velocities and curved streamlines.
Cavities often begin to form near curves or offsets in a flow
boundary or at the centers of vortexes.
When the geometry of flow boundaries causes streamlines
to curve or converge, the pressure may drop in the direc­
tion toward the center of curvature or in the direction along
the converging streamlines. For example, Fig. 3.1b shows a
tunnel contraction in which a cloud of cavities could start to
form at Point (c) and then collapse at Point (d). The velocity
near Point (c) is much higher than the average velocity in
the tunnel upstream, and the streamlines near Point (c) are
curved. Thus, for proper values of flow rate and tunnel pres­
sure at Point (0), the local pressure near Point (c) drops to the
vapor pressure of water and cavities will occur. Cavitation
damage is produced when the vapor cavities collapse. The
collapses that occur near Point (d) produce high instanta­
neous pressures that impact on the boundary surfaces and
cause pitting, noise, and vibration. Pitting by cavitation is
readily distinguished from the worn appearance caused by
abrasion because cavitation pits cut around the harder coarse
aggregate particles and have irregular and rough edges.
3.2-Cavitation index
The cavitation index is a dimensionless measure used
to characterize the susceptibility of a system to cavitate.
Figure 3.2 illustrates the design principle of the cavitation
index in a tunnel contraction. In such a system, the critical
location (or point) for cavitation is at Point (c) (Fig. 3.1 b).
The static fluid pressure, where the velocity is essentially
the same as the approach velocity, at Point (1) will be
P1 =Pc + y(zc- zo)
A.
OFFSET
INTO FLOW
(3.2a)
(3.2b)
where p0 is the static pressure at Point (0).
The cavitation index normalizes this pressure drop to
the dynamic pressure. Dynamic pressure is the difference
between the total pressure (pressure at the point of stagna­
tion) and the static pressure, 1/2pv02 (Eq. (3.2b )).
.. . ·.
B. OFFSET AWAY FROM FLOW
.
C.
ABRUPT
·.'• ',
CURVATURE
AWAY FROM
D.
FLOW
ABRUPT
S L OPE
AWAY FROM
FLOW
Vapor cavities
E. VOID
�
OR TR A NSVERSE
F.
ROUGHEN ED SURFACE
GROOVE
t;es
G.
PROT RUDING JOINT
Fig. 3.1a-Cavitation situations at surface irregularities
(Falvey 1990).
(c)
� (O) --,----
---
(d)
(1}-t---
Fig. 3.1b-Tunnel contraction.
=
P o - [Pc + y( zc -Zo)J
1!2pvo 2
(3.2c)
where p is the density of the fluid (mass per unit volume),
and v0 is the fluid velocity at Point (0).
Readers familiar with the field of fluid mechanics may
recognize the cavitation index as a special form of the Euler
number or pressure coefficient, a matter discussed in Rouse
(1978).
If cavitation is just beginning and there is a bubble of vapor
at Point (c), the pressure in the fluid adjacent to the bubble is
approximately the pressure within the bubble, which is the
vapor pressure Pv of the fluid at the fluid's temperature.
Therefore, the pressure drop along the flow from Point (0)
to (1) required to produce cavitation at the crown is
!J.p
American Concrete Institute
Provided by IHS Markit under license with ACI
No reproduction or networking permitted without license from IHS
.
Vapor cavities
(j
where Pc is the absolute static pressure at Point (c); y is the
specific weight of the fluid (weight per unit volume); Zc is
the elevation at Point (c); and z0 is the elevation at Point (0).
The pressure drop in the fluid as it moves along a stream­
line from the reference Point (0) to Point (1) will be
!J.p =Po- [pc + y(zc- zo)]
3
=
Pv- [pc + y(zc- zo)]
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
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Fig. 3.2-Cavitation erosion experience in spillways (Falvey 1990). (Note: 1 m/s
and the cavitation index at the condition of incipient cavita­
tion is
cr
c
=Po-Pv + y(zc -zo)
1/2pv�
(3.2d)
It can be deduced from fluid mechanics considerations
(Knapp et a!. 1970), and confirmed experimentally, that in a
given system, cavitation will begin at a specific ac, no matter
which combination of pressure and velocity yields that ac.
If the system operates at a a above ac, the system does not
cavitate. If a is below ac, the lower the value of a, the more
severe the cavitation action in a given system. Therefore, the
designer should ensure that the operating a is safely above ac
for the system's critical location (refer to Chapter 6).
Actual values of ac for different systems differ mark­
edly, depending on the shape of flow passages, the shape of
objects fixed in the flow, and the location where reference
pressure and velocity are measured.
For a smooth surface with slight changes of slope in the
direction of flow, the value of ac can be below 0.2. For
systems that produce strong vortexes, ac could exceed 10.
Values of ac for various geometries are given in Chapter 6.
Falvey (1982) provides additional information on predicting
cavitation in spillways.
A system having a given geometry will have a certain
ac; despite differences in scale, ac is a useful concept in
model studies. Tullis (1981) describes modeling of cavita­
tion in closed circuit flow. Cavitation considerations (such
as ,surface tension) in scaling from model to prototype are
discussed in Knapp et a!. (1970) and Arndt (1981).
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3.3-Cavitation damage
Cavitation bubbles will grow and travel with the flowing
water to an area where the pressure field will cause bubbles
to collapse. Cavitation damage can begin at that point. When
a cavitation bubble collapses or implodes close to or against
a solid surface, a high pressure is generated, which acts
on an infinitesimal area of the surface for a short time. A
succession of these high-energy impacts will damage almost
any solid material. Tests on soft metal show initial cavita­
tion damage in the form of tiny craters. Advanced stages of
damage show a rough honeycomb texture with some holes
that penetrate the thickness of the metal. This type of pitting
often occurs in pump impellers and marine propellers.
The progression of cavitation erosion in concrete is not as
well documented as it is in metals. Work by Falvey (1990),
however, indicates that the rate at which damage progresses
from minor to major is dependent on the cavitation index.
The time to major cavitation damage can be approximated
by summing the rate of progression over time for all opera­
tions. The time of operation to major cavitation damage
depends on the cavitation index and can vary from hours
to years. It may be possible to adjust flows to avoid condi­
tions leading to rapid cavitation damage. For both concrete
and metals, however, the erosion progresses rapidly after
an initial period of cavitation exposure slightly roughens
the surface with tiny craters or pits. Figure 3.3b shows a
tendency for the erosion to follow the mortar matrix and
undermine the aggregate.
Roughness does not necessarily have to be caused by cavi­
tation. The presence of increased roughness by whatever
cause is enough to accelerate cavitation damage. At Glen
Canyon Dam, Arizona, the cavitation damage initiated at
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
5
Fig. 3.3b-Concrete test slab featuring cavitation producing
devices.
Fig. 3.3a-Christmas tree configuration of cavitation
damage on a high-head tunnel surface, Glen Canyon Dam,
Arizona (U.S. Bureau of Reclamation 2015).
locations where there was a buildup of calcite or other flaws
in the concrete surface. When significant roughness exists,
it may shorten the time to major damage as if the operation
time to minor damage had already passed. Severe cavita­
tion damage will typically form a Christmas tree configura­
tion on spillway chute surfaces downstream from the point
of origin, as shown in the damage pattern of Glen Canyon
Dam left spillway tunnel in 1983 (Fig. 3.3a) (U.S. Bureau of
Reclamation 20 15).
Once erosion has begun, its rate may be expected to
increase because protruding pieces of aggregate and other
damage caused by the initial cavitation become new gener­
ators of vapor cavities. In fact, a cavitation cloud often is
caused by the change in direction of the boundary at the
downstream rim of an eroded depression. Collapse of this
cloud farther downstream starts a new depression, as indi­
cated in Fig. 3.3a.
Microcracks in the interfacial transition zone (ITZ),
the region between the mortar and coarse aggregate, are
believed to contribute to cavitation damage. Compression
waves in the water that fills such interstices can produce
tensile stresses that cause microcracks to propagate. Subse­
quent compression waves can then loosen pieces of the
material. The simultaneous collapse of all cavities in a large
cloud, or the supposedly slower collapse of a large vortex, is
capable of exerting more than 100 atmospheres of pressure.
Loud noise and structural vibration attest to the violence of
collapsing cavitation bubbles. The elastic rebounds from
continuous collapsing over time could initiate and propagate
cracks, causing chunks of material to break loose.
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Fig. 3.3c-Cavitation erosion pattern after 47 hours of
testing at a 240 ft (7 3 m) velocity head.
Figure 3.3b shows the progress of erosion of concrete
downstream from two protruding bolts used to generate
cavitation in a test slab. The tests were made at a test facility
located at Detroit Dam in Oregon (Houghton et a!. 1978).
Figure 3.3c shows cavitation damage on test panels after 47
hours of exposure to high-velocity flows in excess of 100 ft/s
(30 m/s). A large amount of cavitation erosion caused by a
small offset at the upstream edge of the test slab is evident.
Figure 3.3d shows severe cavitation damage that occurred
to the flip bucket and training walls of an outlet structure at
Lucky Peak Dam, Idaho. In this case, water velocities of 120
ft/s (37 m/s) passed through a gate structure into an open
outlet manifold (Jansen 1988). Figure 3.3e shows cavita­
tion damage to the side of a baffle block and the floor in
the stilling basin at Yellowtail Afterbay Dam, Montana (U.S.
Bureau of Reclamation 1981).
Once cavitation damage has substantially altered the
flow regime, other forces then begin to act on the surface,
causing fatigue due to vibrations of the element. High water
velocities striking the irregular surface can lead to mechan­
ical failure due to vibrating reinforcing steel. Significant
amounts of material could be removed by these added forces,
thereby accelerating failure of the structure. This sequence
of ca�itati?n da111age f�llowed by high-impact damage from
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
6
Fig. 3.3d-Cavitation erosion of discharge outlet training
wall and flip bucket at Lucky Peak Dam, Idaho.
Fig. 4.1a-Abrasion damage to concrete baffle blocks and
l
f oor area in Yellowtail Diversion Dam sluiceway, Montana
(U.S.Bureau of Reclamation 1981).
Fig. 3.3e-Cavitation erosion of baffle block and floor in
stilling basin (U.S.Bureau of Reclamation 1981).
the moving water was evident in the 1983 spillway tunnel
failure at Glen Canyon Dam, Arizona (Burgi et al. 1984).
CHAPTER 4-EROSION BY ABRASION
4.1-General
Abrasion erosion damage results from the abrasive
effects of waterborne silt, sand, gravel, rocks, ice, and other
debris impinging on a concrete surface during operation
of a hydraulic structure. These particles move around in a
cascading motion, then impact the concrete surface, similar to
the ball-milling action seen in mechanical grinders. Abrasion
erosion is readily recognized by the smooth, worn-appearing
concrete surface, which is distinguished from the small holes
and pits formed by cavitation erosion, as can be compared
in Fig. 3.3e, 4.1a, and 4.1b. Spillway aprons, stilling basins,
sluiceways, drainage conduits or culverts, and tunnel linings
are particularly susceptible to abrasion erosion.
The rate of erosion is dependent on many factors, including
size, shape, quantity, and hardness of particles being trans­
ported; water velocity; and concrete quality. While high­
quality concrete can resist high water velocities for many
years with little or no damage, concrete cannot withstand the
abrasive action of debris grinding or repeatedly impacting on
its surface. In such cases, abrasion erosion ranging in depth
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Fig.4.1b-Close-up of the abrasion damage to invert of the
Hoover Dam, Nevada Spillway (Falvey 1990).
from a few inches (millimeters) to several feet (meters)
could result, depending on flow conditions. An erosion and
sedimentation manual by the U.S. Bureau of Reclamation
(2006) is a good reference for evaluating bed movement and
sediment transport in hydraulic structures.
4.2-Stilling basin damage
A typical stilling basin design includes a downstream sill
from 3 to 20 ft (1 to 6 m) high intended to create a perma­
nent pool to aid in energy dissipation of high-velocity flows.
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
7
Fig. 4.2b-Stilling basing abrasion damage from recircu­
lating flows (Hanna 20 10).
Fig.4.2a-Typical debris resulting from abrasion erosion of
concrete.
Unfortunately, in many cases, these pools also trap rocks
and debris (Fig. 4.2a) (Hanna 2010). Material that becomes
trapped in the stilling basin is typically sand, gravel, cobbles,
or boulders. Figure 4.2b shows recirculating flow patterns
produced over the basin end sill create a turbulent flow
that continually moves the materials against the concrete
surfaces. This ball mill-type action causes severe damage
due to a repetitive grinding process. Flows during normal
operation of a hydraulic jump energy dissipation basin are
not capable of washing the particles out of the basin.
The stilling basins at Libby and Dworshak Dams-high­
head hydroelectric structures-were eroded to maximum
depths of approximately 6 and 10 ft (2 and 3 m), respectively
(Schrader and Tatro 1987). In the latter case, nearly 2000
yd3 (1530 m3) of concrete and bedrock were eroded from the
stilling basin (Fig. 4.2c). This was also a problem at Grand
Coulee Dam, Washington, that resulted in a massive cleanup
of the river channel to remove loose material. Impact forces
associated with turbulent flows carrying large rocks and
boulders at high velocity contribute to the surface damage of
concrete (Price 1947).
There are many cases where the concrete in outlet works
stilling basins of low-head structures also exhibited abra­
sion erosion. Chute blocks and baffles within the basin are
particularly susceptible to abrasion erosion by direct impact
of waterborne materials. There also have been several cases
where baffle blocks connected to the basin training walls
have generated eddy currents behind these baffles, resulting
in significant localized damage to the stilling basin walls and
floor slab of Nolin Dam, as shown in Fig. 4.2d (McDonald
and Liu 1987).
In most cases, abrasion erosion damage in stilling basins
has been the result of one or more of the following:
a) Construction diversion flows through constricted
portions of the stilling basin
b) Eddy currents created by diversion flows or power­
house discharges adjacent to the basin
c) Construction activities in the vicinity of the basin,
particularly those involving cofferdams
d) Nonsymmetrical discharges into the basin
American Concrete Institute
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.
Fig. 4.2c-Erosion of stilling basin floor slab, Dworshak
Dam, Idaho (Schrader and Kaden 197 6b).
e) Separation of flow and eddy action within the basin
sufficient to transport riprap from the exit channel into the
basin
f) Recirculating flow in hydraulic jump stilling basins
(ball milling)
g) Failure to clean basins after completion of construction
work
h) Topography of the outflow channel
i) Rockfall from canyon walls above (McDonald 1980).
Unlike cavitation damage, abrasion damage in stilling
basins is generally slow to develop. Damage generally
requires several flood events or long sustained operations
with materials present such as rocks that can cause damage.
Regular inspection and cleaning can help minimize damage.
4.3-Power plant tailrace damage
Abrasion erosion damage can also occur in the tailrace
of a power plant where water is discharged into the river
channel. At the Buffalo Bill Powerplant in Wyoming, the
draft tubes exit the plant at a lower elevation than the river
channel. At high flow rates through the powerplant, river
water is pulled back into the tailrace, trapping bed material
and riprap from the river and upstream dike. Erosion holes
were found occupied by large boulders that closely match
the size and shape of the hole. Beneath the boulder, smaller
rounded rocks were supporting much of the weight of the
boulder (Fig. 4.3), resulting in point loads that greatly accel­
erate the erosion process (Bartojay 2011).
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
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Fig.4.2d-Abrasion erosion damage to stilling basin, Nolin
Dam (McDonald and Liu 1987).
Fig. 4.4-Abrasion erosion damage to discharge lateral,
Upper St.Anthony Falls Lock, Minnesota.
Reinforcing steel
)
Bulkheod seol with
rounded edges
·
·_.
o
..
·_
.
0
.
. ..
Exposed onchor
..:·()" � .· .
. .. .
:o.
.
.
·
.· o
.
.·
·.
:
.
'?
•
o
.. .
o
- ·o
·
•
0
•
.
·
.
l·.o W
-·1
_.11·..
...
I.
Jl .
0 -
-
·1o· l l
. J . 1J
'?
Fig.4.3-Abrasion erosion damage in tailrace, Buffalo Bill
Powerplant, Wj;oming (Bartojay 2011).
Fig 4.6a-Initial damage due to uplift generally occurs at
the construction joints (Frizell 2007).
4.4-Navigation lock damage
Hydraulic structures other than spillways are also subject
to abrasion erosion damage. When the Upper St. Anthony
Falls Lock, Minnesota, was unwatered to repair a damaged
miter gate, an examination of the filling and emptying
laterals and discharge laterals revealed considerable abrasion
erosion (Fig. 4.4) (McDonald and Liu 1987). This erosion of
the concrete to maximum depths of 23 in. (580 mm) was
caused by rocks up to 18 in. (460 mm) in diameter that had
entered the laterals, apparently during discharge of the flood
of record through the lock chamber. Subsequent filling and
emptying of the lock during normal operation agitated those
rocks, causing them to erode the concrete by grinding.
4.5- Tunnel lining damage
Concrete tunnel linings are susceptible to abrasion erosion
damage, particularly when the water carries large quan­
titi�s of sand, gravel, rocks, and other debris. There have
been many instances where the concrete in both temporary
and permanent diversion tunnels has experienced abrasion
erdsion damage. Generally, the tunnel floor or invert is the
mo,st heavily damaged. The diversion tunnels of the Glen
Canyon Dam in Arizona experienced moderate abrasion
damage (less than I ft [800 mm]) of the invert of the tunnels
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during construction, after passing almost 3 million acre-ft
of water (3.7 billion cubic meters). The exposed aggregate,
concrete matrix, and exposed reinforcing steel bars had a
smooth, worn appearance (Wagner 1967).
4.6-Hydraulic jacking
Typically, the stability of reinforced-concrete-lined
chutes in spillways depends on the overall concrete design,
including joint and waterstop details; reinforcement;
anchorage; and a functioning, filtered underdrain system.
Damage resulting from hydrodynamic uplift on slabs can
begin at a joint, where offsets or spalling has occurred (Fig.
4.6a). Spillway flows over these offsets can introduce water
into the foundation, which can lead to structural damage due
to uplift or erosion of the foundation material. If the leading
edge has a crack or begins to separate, this creates a stagna­
tion point where jacking pressures can be induced (Frizell
2007). Hepler and Johnson (1988) described typical analysis
of spillway failures due to uplift and discussed case studies.
Frizell (2007) determined that a considerable flow is
possible to induce through the gap into the subsurface
drainage system. Most drainage designs are not meant to
provide for this amount of inflow and could be undersized
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
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5.2-Erosion by mineral-free water
Fig 4.6b-Structural collapse when enough undermining
has occurred to cause loss of support (Frizell 2007).
and pressurized by the incoming flow. This can result in
elevated uplift pressure, undermining of the foundation, and
structural collapse (Fig. 4.6b).
CHAPTER 5-EROSION BY CHEMICAL ATTACK
5.3-Erosion by miscellaneous causes
5.1-Sources of external chemical attack
The compounds present in hardened portland cement are
attacked by water and many salt and acid solutions. Fortu­
nately, in most hydraulic structures, the deleterious action
on a mass of hardened portland-cement concrete with a
low permeability is so slow that it is not a concern. There
are, however, situations where chemical attack can become
serious, accelerating deterioration and concrete erosion.
Acidic environments can cause the deterioration of
exposed concrete surfaces. The acidic environments can
range from low acid concentrations found in mineral­
free water to high acid concentrations found in many
processing plants. One example is the Spring Creek Debris
Dam in California that was designed to control the flow
of acid mine drainage into the Sacramento River. Before
treatment of water flowing into the reservoir began, the
reservoir water had a pH typically between 2 and 3 (acid),
which attacked the cement paste in the exposed concrete.
However, after 30 years of this exposure, the reinforced
concrete in the outlet works intake structure was mostly
intact with only approximately 112 to 1 in. (10 to 25 mm)
concrete loss (Smoak 1997).
Soil or groundwater conditions can also cause concrete
deterioration. In the presence of moisture, alkali soils or
water-containing sulfates of magnesium, sodium, calcium,
potassium, or ammonium can attack concrete, forming
chemical compounds that imbibe water and swell, causing
concrete damage (Mehta and Monteiro 2006).
Hydrogen sulfide corrosion, a form of acid attack, is
common in septic sanitary systems. Under certain condi­
tions, this corrosion can be severe and cause early failure of
a sanitary system.
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Hydrated lime is one of the compounds formed when
cement and water combine. It is readily dissolved by water
and more aggressively dissolved by pure, mineral-free water,
found in some mountain streams and desalinization plants
and other facilities using demineralized (distilled) water.
Dissolved carbon dioxide is contained in some fresh waters
in sufficient quantity to make the water slightly acidic and
add to its aggressiveness. It has been reported that serious
attacks by fresh water on exposed concrete surfaces has
led to deterioration (Popovics and McDonald 1989). In the
United States, there are many instances where the surface
of the concrete has been etched by fresh water flowing over
it, although serious damage from this cause is uncommon
(Holland et a!. 1980). This etching is particularly evident
at hydraulic structures carrying runoff from high mountain
streams in the Rocky Mountains and the Cascade Mountains
of the central and western United States. A survey (ICOLD
1951) of the chemical composition of raw water in many
reservoirs throughout the United States indicates a nearly
neutral acid-alkaline balance (pH) for most of these waters.
5.3.1 Acidic environments-Decaying vegetation is the
most frequent source of acidity in natural waters. Decompo­
sition of certain minerals may be a source of acidity in some
localities. Running water that has a pH as low as 6.5 will
leach lime from concrete, reducing its strength and making
it more porous and less resistant to freezing and thawing
and other chemical attack. The amount of lime leached from
concrete is a function of the area exposed and the volume of
concrete.
Waters flowing from peat beds may have a pH as low as
5. The presence of acid of this strength will result in severe
attack of concrete (Neville 2009). For this reason, when
conveyances for groundwater are being designed, the corro­
siveness of water should be determined using standard water
quality tests (pH, acidity, and ion composition) to determine
its aggressiveness on the concrete.
5.3.2 Bacterial action Most of the literature addressing
the problem of deterioration of concrete resulting from
bacterial action has evolved because of the great impact of
this corrosive mechanism on concrete sewer systems. This
is a serious problem that, as Rigdon and Beardsley (1958)
observed, occurs more readily in warm climates such as
California, Australia, and South Africa. This problem also
occurs at the terminus of long-pumped sewage force mains
in the northern climates (Pomeroy 1974).
Sulfur-reducing bacteria belong to the genus of bacteria
that derives the energy for its life processes from the reduc­
tion of some element other than carbon, such as nitrogen,
sulfur, or iron (Rigdon and Beardsley 1958). Some of these
bacteria reduce the sulfates that are present in natural waters
and produce hydrogen sulfide as a waste product. These
bacteria are anaerobic.
Another group of bacteria takes the reduced sulfur and
oxidizes it back so that sulfuric acid is formed. The genus
. Thiobacillus is the sulfur-oxidizing bacteria that is most
-
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REPORT O N THE EROSION O F CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
CHAPTER 6-CO NTROL OF CAVITAT IO N
EROSIO N
6.1-Hydraulic design principles
In 3.2, the cavitation index a was defined by Eq. (3.2b).
When the value of a at which cavitation begins (a ) is known,
a designer can calculate velocity and pressure combinations
that will minimize potential damage. The object of a safe
design is to assure that the actual operating pressures and
velocities will produce a value of a greater than the value at
which cavitation begins (Falvey 1990). Note this is where
cavitation begins; there is little, if any, information on when
actual damage begins. However, it is possible that damage
occurs at the inception of cavitation, but it is so minor as to
not be detected at first.
One good way to minimize cavitation erosion is to make a
large by keeping the pressure p0 high and the velocity v0 low.
For example, deeply submerged baffle blocks in a stilling
basin downstream from a spillway chute are unlikely to be
damaged by cavitation during normal operations if both
these conditions are satisfied. This situation is illustrated in
Fig. 6.1a. The following example illustrates how a is calcu­
lated for this case.
c
Fig. 5.3.2-Acid attack in crown of waste-water conduit
showing exposed reinforcement, Denver Metro Waste Water
Treatment Plant (photo courtesy of URS).
destructive to concrete. It has a remarkable tolerance to
acid. Concentrations of sulfuric acid as great as 5 percent by
volume do not completely inhibit its activity.
Sulfur-oxidizing bacteria are likely to be found wherever
wannth, moisture, and reduced compounds of sulfur are
present. Generally, a free water surface is required in combi­
nat\on with low dissolved oxygen in sewage and low veloci­
ties that permit the buildup of scum on the walls of a pipe
in which the anaerobic sulfur-reducing bacteria can thrive.
Certain conditions should prevail before the bacteria can
produce hydrogen sulfide from sulfate-rich water. Sufficient
moisture should be present to prevent the desiccation of the
bacteria. There should be adequate supplies of hydrogen
sulfide, carbon dioxide, nitrogen compounds, and oxygen. In
addition, soluble compounds of phosphorus, iron, and other
trace elements should be present in the moisture film.
Newly made concrete is strongly alkaline with a pH of
approximately 12. No species of sulfur bacteria can live in
such a strong alkaline environment. Therefore, the concrete
is temporarily free from bacterially-induced corrosion.
Natural carbonation of the free lime by the carbon dioxide
in the air slowly reduces the pH of the concrete surface to 9
or less. At this level of alkalinity, the sulfur bacteria Thio­
bacillus thioparus, using hydrogen sulfide as the substrate,
generate thiosulfuric and polythionic acid. The pH of the
surface moisture steadily declines, and at a pH of approxi­
mately 5, Thiobacillus concretivorus begins to proliferate
and produce high concentrations of sulfuric acid, dropping
the pH to a level of 2 or less. The destructive mechanism in
the corrosion of the concrete is the aggressive effect of the
sulfate ions on the calcium aluminates in the cement paste.
The main concrete corrosion problem in a sewer, there­
fore, is chemical attack by this sulfuric acid, which accu­
mulates in the crown of the sewer (Fig. 5.3.2). Information
is available that enables the designer to design, construct,
and operate a sewer that could reduce the development of
sulfuric acid (Pomeroy 1974; ASCE-WPCF Joint Task Force
1982; American Concrete Pipe Association 1980).
Example 1
From model studies, the following information is given:
a) The mean prototype velocity at Point (0), immediately
upstream from the baffle block, is 30 ft/s (9.1 m/s).
b) The minimum prototype gauge pressure, exceeded 90
percent of the time, is 7.1 psi (49 kPa).
c) The barometric pressure for the prototype location is
estimated to be 13.9 psi (95.8 kPa).
d) The vapor pressure of water (pv) is 0.3 psi (2.1 kPa) and
the density of water (p) = specific weight divided by gravity
(y/g) = 1.94 lb·s2fft4 (103 kg/m3), from standard tables at a
given temperature (Haynes 2016).
Therefore, the absolute pressure at Point (0), 6.6 ft (2.0 m)
above Point (1), becomes
Po = gauge pressure + barometric pressure + y(zc - z1), from
Eq. (3. 2a)
Po
=
7.1 lb/in.2 + 13.9 lb/in.2
+
62.4 lb/fe co - 6.6 ft)
(12 in./ft)2
18.1 lb/in.2
and because Points (c) and (0) are on the sample plane, zc =
z0 , it follows that
cr =
18.1 lb/in.2 - 0.3 lb/in.2
� ( 1�:2 )
1.94
(30 ft/s)
= 2.9
REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
cr
Structure or irregularity
Tunne l
Sudden expansion in tunne l
(01
777777
7/7/
(I)
/'lJ(
�6.6 ft
Gate and gate s l o t s
�:
Pressure
transducer
//
ck
3/4
of
in .
max .
0.6
1 25 kN/m2 , or 1 25 kPa
(125 kPa - 2. 1 kPa)( l OOO Pa/kPa)
1 /2(1 000 kg/m2)(9. 1 m/s)2
( 1977 1
Galperin et a l .
( 1977 1
Ball
( 1959 1
1 1 967 1
Ball
1 1976 1
0.2
( 19 7 6 1
( 19 7 7 )
Falvey ( 1 9 8 2 )
Ball
Arndt
0.2
1.0
�unusual definition of
=
a.
Fig. 6.1b-Values o f a a t beginning of cavitation.
= 2.9
because 1 Pa 1 kg/(m · s2),
This value of a is well above the a of 1 .4 and 2 . 3 for
beginning of cavitation for this baffle block with sharp edges
(Fig. 6. l b) (Galperin et a!. 1 977). Hence, cavitation damage
is unlikely in the prototype.
A second, equally effective procedure to minimize poten­
tial cavitation damage is to use boundary shapes and toler­
ances characterized by low values of a for incipient damage.
For example, a carefully designed gate slot, with an offset
and rounded downstream comer, may have damage at a
calculated a value of 0.2. Unfortunately, the lowest value of
a a designer can use may be fixed by unintentional surface
imperfections in concrete, the need for small abrupt expan­
sions in flow passages, or the likelihood that vortexes will be
generated by obstructions such as partially open sluice gates.
Boundary geometry and construction techniques influence
the potential for cavitation damage.
A third choice, often inevitable, is to expect cavities to
form at predetermined locations. In this case, the designer
can: a) supply air to the flow; or b) use damage-resistant
materials such as stainless steel or polymer concrete systems.
Using damage-resistant materials will not eliminate
damage, but could extend the useful life of a surface.
This alternative is particularly attractive, for example, for
constructing or repairing outlet works that will be used infre­
quently or abandoned after their purpose has been served.
In any case, values of a at which cavitation erosion begins
are needed for all sorts of boundary geometries. Sometimes
critical values of a can be estimated by theory, but they
usually come from model or prototype tests.
=
6.2-Cavitation indexes for damage and
construction tolerances
Figure 6 . 1 b lists values of a at which cavitation begins
and the references from which these values came. A designer
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No reproduction or networking permitted without license from IHS
Galperin e t al .
1.6
=
and because Points (c) and (0) are on the sample plane, Zc
z0, it follows that
0=
( 1967 1
( 19 6 6 1
Rouse and Jezdinsky
roughness
Po = 49 kPa + 95 . 8 kPa
+ 9.8 1 kN/m2 (0 - 2.0 m)
to
Russell and Ball
depth
_i..".o
OJ;;;;;;7_22](?))//?777
In SI units
0.2
3.0
&
( 19 8 1 1
Wagner
Abraded concrete
Fig.6. 1a-Baffle block downstream from a low spillway.
Tullis
1 . 0*
0 . 19
1.4
2 .3
Baffle blocks
{2 m)
77///
Reference
1.5
inlet
11
should not use these numbers without studying the refer­
ences. Some reasons for this are:
a) The exact geometry and test circumstances should be
understood.
b) Authors use different locations for determining the
reference parameters of Eq. (3.2b), although the general
form of Eq. (3 .2b) is accepted by practitioners in the field.
c) Uniformity in the model is difficult to achieve.
d) Smooth, uniform concrete surfaces may be difficult to
achieve, maintain, or both, in the field.
Many of the essential details involved in the original refer­
ences are explained in Hamilton ( 1 983a,b; 1 984). The values
of <Jc listed in Fig. 6. 1 b show the importance of good form­
work and concrete finishing.
Example 2
The following information is given:
a) A 1 /4 in. (6 mm) offset ( Yo) into the flow caused by
mismatched forms has a ac of 1 .6.
b) A 1 :40 chamfer has a <Jc of 0.2 (only one-eighth as large)
crchamfer -g a offsel
From Eq. (3.2d),
By the definition of <Jc, the allowable velocity past the
chamfer, if (p0 - Pv)ll l2p is constant, becomes
vchamfer
1
=
= 2.83 . voflset [
_1___ J8 . voflset
- · v2 et
8 offs
Thus, on a spillway or chute where p 0 - Pv might be 1 7.4
psi ( 1 20 kPa), cavitation would begin behind the offset when
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� OCi )
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the local velocity reached 40 ft/s ( 1 2 m/s), but the flow
past the chamfer would cause no trouble until the velocity
reached approximately 2.83 times 40 ft/s ( 1 2 m/s), which
equals 1 1 3 ft/s (35 m/s).
When forms are required, as on walls, ceilings, and steep
slopes, skilled workers may produce a nearly smooth and
only slightly wavy surface for which a may be as low as 0.4.
Whereas on plane, nearly horizontal surfaces using a stiff
screed controlled by steel wheels running on rails and hand
floating and troweling, a a value of 0.2 may be achieved.
Construction tolerances should be included in all contract
documents. These establish permissible variation in dimen­
sion and location giving both the designer and the contractor
parameters within which the work is to be performed.
ACI 1 1 7 provides guidance in establishing practical toler­
ances. It is sometimes necessary that the specifications
for concrete surfaces in high-velocity flow areas, or more
specifically, areas characterized by low values of a, be even
more demanding. However, achieving and maintaining more
restrictive tolerances for hydraulic surfaces than those recom­
mended by ACI 1 1 7 can become costly or even impractical.
The final specification requirements require judgment on the
part of the designer (Schrader 1 9 8 1 ).
The U.S. Bureau of Reclamation (20 1 4) specifies surface
roughness tolerances (Table 6.2) that define the limits of
allowable surface irregularity such as bulges, depressions,
and offsets as measured by the roughness slope ratio shown
in Fig. 6.2.
Joints can cause problems in meeting tolerances, even
with the best workmanship. Some designers prefer to saw
and break out areas where small offsets occur rather than to
grind the offsets that are greater than specified. The trough or
hole is then patched and hand-finished to produce a surface
more resistant to erosion than a ground surface would be.
In some cases, grinding to achieve alignment and smooth­
ness is adequate. However, to help prevent the occurrence
of aggregate popouts, a general rule of thumb is to limit the
depth of grinding to one-half the maximum diameter of the
coarse aggregate. Ground surfaces can also be protected by
applying a low-viscosity, penetrating phenol epoxy-resin
sealer (Borden et a!. 1 97 1). However, the smooth, polished
texture of the ground surface or the smoothness of a resin
sealer creates a different boundary condition that could affect
the flow characteristics. Cavitation damage has been observed
downstream of such conditions in high-velocity flow areas
(in excess of 80 ft/s [24 m/s]) where there was no change in
geometry or shape (Popovics and McDonald 1 989).
The difficulty of achieving a near-perfect surface and the
doubt that such a surface would remain smooth during years
of use have led to designs that permit the introduction of air
into the water to cushion the collapse of cavities when low
pressures and high velocities prevail.
Table 6.2-Examples of surface roughness
tolerances
nC
A
t 1
p����c:d by�
r license with ACI
.
No reproduction��or mg perm1tted Without license
from IHS
·
AAJn
Abrupt offsets limits
Gradual offset limits
0 2 0. 5
< 1 /4 i n . (6 mm)
1 : 1 6 or flatter
:S 1 /4 in. (6 mm)
to :S 1 18 in. (3 mm)
1 1 6 to 1 :32 or flatter
0.5 > 0 > 0.2
Construct an aeration ramp or slot for existing
spillways
Redesign (realign) for new spillways.
0 ::: 0.2
Finished Surface
Roughness Slope Ratio= Roughness Height
Roughness Length
CASE I - Offset on the Surface
Roughness Length
J
�
Finished Surface
Roughness Depth
----:...
--"-
-
Roughness Slope Ratio= Roughness Depth
Roughness Length
CASE 2 - Offset into the Surface
Fig. 6.2-Measuring surface roughness of an offset.
6.3-Using aeration to control damage
Laboratory and field tests have shown that surface irregu­
larities will not cause cavitation damage if the air-water ratio
in the layers of water near the solid boundary is approxi­
mately 8 percent by volume (Peterka 1 953). The air. in
Cavitation index <J
H
the water should be distributed rather uniformly in small
bubbles.
When calculations show that flow without aeration is
likely to cause damage, or when damage to a structure has
occurred and aeration appears to be a remedy, the problem is
dual: 1 ) the air should be introduced into the flowing water;
and 2) a portion of that air should remain near the flow/
concrete boundary where it will be useful.
The migration of air bubbles involves two principles: I )
bubbles in water move in a direction of decreasing water
pressure; and 2) turbulence disperses bubbles from regions of
high air concentration toward regions of low concentration.
Attention should be paid to the motion of bubbles due to
pressure gradients. A flow of water surrounded by atmo­
spheric pressure is called a free jet. In a free jet, there are
no gradients except possibly weak local ones generated by
residual turbulence, and the bubbles move with the water.
There is no buoyant force. On a vertical curve that is convex,
the bubble motion may have a component toward the bottom.
In a flip bucket, which is concave, the bottom pressure is
large and the bubbles move rapidly toward the free surface.
When aeration is required, air usually should be introduced at
the bottom of the flow. These bubbles gradually move away
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
13
F l o w net
Q; 76,270 ft 3/s
12160 m 3/ol
13ft
(4 m l
. o
Fig. 6.3a-Aeration ramps at King Tala! Spillway, Jordan (Wei and DeFazio 1982).
Table 6.3-Examples of use of air to prevent
(6.3)
cavitation damage
Structure or description
References
Palisades Dam, Idaho outlet sluices
Beichley and King ( 1 975)
Yellowtail Dam, Montana spillway
tunnel
Borden et al. ( 1 97 1 ); Colgate
( 1 97 1 )
Glen Canyon Dam, Arizona
spillway tunnel
Burgi et al. ( 1 984)
Ust-IIimsk Dam, Russia spillway
Galperin et al. ( 1 977)
Bratsk Dam, Russia spillway
Semenkov and Lentyaev ( 1 973)
Foz do Areia, Brazil spillway
Pinto ( 1 982)
General
Galperin et al. ( 1 977)
Comprehensive
Hamilton ( 1 983a,b, 1 9 84);
Quintela ( 1 980)
from the floor despite the tendency for turbulent dispersion
to hold them down. At the point where insufficient air is in
the flow to protect the concrete from damage, a subsequent
source of bottom air should be provided.
Aeration data, shown in Table 6.3 and measured on
Bratsk Dam in Russia, which has a spillway approximately
295 ft (90 m) high and an aeration device, are discussed by
Semenkov and Lentyaev ( 1 973). Downstream from the aera­
tion ramp, measurements showed that the air-water ratio in
a 6 in. ( 1 50 mm) layer next to the concrete declined from
85 to 3 5 percent as the mixture flowed down the spillway
a distance of 1 74 ft (53 m). If an exponential type of decay
is assumed, the loss per 1 ft ( 1 /3 m) was a little less than 2
percent of the local air-water ratio.
It is usually not feasible to supply air to flowing water
by pumping or compressing the air because the volumes
involved are too large. Instead, the flow is proj ected from
a ramp or step as a free jet, and air is introduced at the air­
water interfaces. Then the turbulence within the jet disperses
the air entrained at the interfaces into the main body of the
jet. Figure 6.3a shows typical aeration ramps for introducing
air into the flow (Wei and DeFazio 1 982).
To judge whether sufficient air will remain adjacent to
the floor of a spillway, the amount of air that a turbulent jet
will entrain should be estimated. Equation (6.3) for entrain­
ment by the lower surface has been proposed (Hamilton
1 983a,b, 1 984)
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.
Model and prototype measurements indicate that the value
of the coefficient a lies between 0 . 0 1 and 0.04, depending on
velocity and upstream roughness.
The length of cavity, l (Fig. 6.3a), is difficult to measure
in prototypes and large models. Instead, the upper and lower
profiles of the nappe can be estimated from two-dimensional
irrotational flow theory. One method is to use a finite element
technique for calculating nappe traj ectories.
As indicated previously, ramps and down-steps are used
to induce the flow in a spillway or tunnel to spring free from
the floor. A ramp is a wedge anchored to, or integral with,
the floor and usually spans the tunnel or spillway bay. Wall
and corner wedges and wall offsets away from the flow also
are used to cause the water to leave the sides of a conduit.
The objective is to provide a sudden expansion of the solid
boundaries. Such devices, often referred to as aerators, are
schematically depicted in Fig. 6.3b and 6.3c. (Ball 1 959;
DeFazio and Wei 1 983 ; Vischer et a!. 1 982; Russell and Ball
1 967). Air is allowed to flow into a cavity beside or under
a jet by providing passages as simple as the layout of the
project will permit.
Although offsets, slots, and ramps in conduits can intro­
duce air into high-velocity flow to effectively control cavita­
tion, if improperly designed, they can accentuate the cavi­
tation problem. For this reason, it is advisable to conduct
physical hydraulic model studies to ensure the adequacy of a
proposed aeration device.
6.4-Materials
Proper material selection can increase the cavitation
resistance of concrete. However, the only effective solution
is to reduce or eliminate the factors that trigger cavitation,
because even the strongest materials cannot withstand the
forces of cavitation indefinitely. The difficulty is that in the
repair of damaged structures, the reduction or elimination
of cavitation may be difficult and costly. The next best solu­
tion is to replace the damaged concrete with more erosion­
resistant materials.
In areas of new design where cavitation is expected to
occur, designers may include the higher-quality materials
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� OCi J
14
REPORT O N THE EROSION O F CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
'
,-1
DUCT THROUGH SIDEWALL
I
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I
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I
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I
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Fig. 6.3c-Air supply to aerators (Falvey 1990).
Fig. 6.3b-Types of aerators ( Vischer et al. 1982).
during the initial construction or include provisions for
subsequent repairs in service. For example, in many instal­
lations, stainless steel liners are installed on the concrete
perimeter downstream of slide gates to resist the damaging
effects of cavitation. These liners, although quite durable,
could pit and eventually need to be replaced.
The cavitation resistance of concrete where abrasion is not
a factor can be increased by using a properly designed low
water-cementitious material ratio (w/c m ), higher-strength
concrete, placed and cured properly to reduce cracking.
Careful selection of aggregate size and gradation and the
use of water-reducing admixtures has proven benefic ial, as
has lowering the placement temperature to reduce thermal
cracking potential (ACI 207 . 1 R). Hard, dense aggregate and
good bond between aggregate and mortar are essential to
achieving increased cavitation resistance (May 1 987).
The use of polymer impregnation, steel fiber reinforce­
ment, and polymers as a matrix binder or a surface binder
has been found to substantially improve the cavitation resis­
tance of conventional concrete, but could be costly (Schrader
1 978, 1983 ; DePuy and Dikeou 1 973).
Some coatings, such as neoprene or polyurethane, have
effectively reduced cavitation damage to concrete, but
because near-perfect adhesion to the concrete is mandatory,
their use is not common. Once there is a tear or a chip in the
coating, the entire coating is soon peeled off.
6.5- Materials testing
Because of the massive size of most hydraulic structures,
full-scale prototype testing is usually not possible. Model
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~
DUCT UNDER OFFSET
testing can identify many potential problem areas, but deter­
mining the ultimate effect of hydraulic forces on the struc­
ture requires some judgment. In some cases, it is desirable to
evaluate a material after it has been subjected for a reason­
able time to flows of a magnitude approaching that expected
during operation of the facility.
The U.S. Army Corps of Engineers evaluated erosion resis­
tance of materials at the Detroit Dam in Oregon (Houghton
et al. 1 978). Erosion testing at the facility consisted of
preparing test slabs 2 1 in. (530 mm) wide by 1 0 ft (3 m) long
using the desired material, coating, or overlay. High-velocity
water exceeding velocities of 80 ft/s (24 m/s) was passed
over the slabs for various durations, and the performance
of the material evaluated. Cavitation erosion resistance was
studied by embedding small obstacles in the test slabs that
protrude into the flow (Fig. 3 .3b).
Materials and coating systems evaluated for repairs to
the Tarbela Dam in Pakistan were tested at the Detroit Dam
facility. They included various concrete mixtures, fiber­
reinforced concrete (FRC), roller-compacted concrete,
polymer-impregnated concrete, polymer-impregnated FRC,
and several concrete coatings (Houghton et al. 1 978). Figure
6.5 shows the performance of several of these materials
subjected to flows with velocities of 1 20 ft/s (37 m/s).
6.6-Construction practices
Construction practices are of paramount importance
when hydraulic surfaces may be exposed to high-velocity
flow, particularly if aeration devices are not incorporated in
design. Such surfaces should be as smooth as can be practi­
cally obtained (Schrader 1 983). Surface imperfections and
deficiencies have been known to cause cavitation damage at
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
15
0 TEST SLAB NO. 1 -- CONVENTI ONAL CONCRETE -- Cement 600 1b/yd 3 (356 kg(m3 J ; MSA 1 - 1 /2 in. (3B mm)
0 TEST SLAB NO. 2 - - STEEL FRC -- Cement 690 lb/yd 3 (409 kg/m 3 ) ; MSA 3/4 in. ( 1 9 mm)
e TEST SLAB NO. 3 - - POLYMERIZED CONVENTIONAL -- Cement 600 lb/yd 3 (356 kg/m 3 ) ; MSA 1 - 1 /2 in. (38 mm)
• TEST SLAB NO. 4 -- POLYMERIZED FRC -- Cement 690 lb/yd 3 (409 kg/m 3 ) ; MSA 3/4 in. ( 1 9 mm)
MSA-- Maximum size aggregate
100
75
E
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.,
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50
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40
60
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20 0
Test Time . h
Fig. 6. 5--Erosion depth versus time, Tarbela Dam, Pakistan concrete mixtures (Houghton
et al. 1978).
flow velocities as low as 26 ft/s (8 m/s). Offsets no greater
than 1/8 in. (3 mm) in height have been known to cause cavi­
tation damage at flow velocities as low as 82 ft/s (25 m/s).
Patching repairs improperly made at the time of construc­
tion have been known to fail under the stress of water flow,
thereby providing the surface imperfections that triggered
cavitation damage to the concrete farther downstream. This
phenomenon occurred in the high head spillway tunnel at
Yellowtail Dam in Montana, ultimately resulting in major
cavitation and structural damage to the concrete lining
(Borden et a!. 1 97 1 ; Colgate 1 97 1 ). Accordingly, good
construction practices, as recommended in ACI 1 1 7, 3 02. 1 R,
304R, 3 08 . 1 , 309R, and 347R should be maintained both for
new construction and repair. Formed and unformed surfaces
should be checked during each construction operation to
confirm that they are within specified tolerances.
Thinner placements bonded to underlying substrate
concrete should be avoided. Thin concrete placements could
have different thermal and mechanical properties from the
substrate material if different aggregates or mixture propor­
tions are used, possibly causing them to debond during
normal temperature cycles. In addition, the bond surface
will typically be weaker than other regions, making the
interface more susceptible to damage, and stresses closer to
the surfaces may be larger. Any debonding or delamination
at the leading edge can be a source of further damage by
induced jacking pressures from high-velocity flow or damage
from standing water that freezes. Thicker repairs should be
constructed with similar aggregates and mixture proportions
with similar strengths for similar properties as the substrate
material. They should also be mechanically fastened to the
substrate material with reinforcement and anchors.
If the potential for cavitation damage exists, care should
be taken in placing the reinforcement. The bars closest to the
surface, if practical for structural purposes, should be placed
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parallel to the direction of flow to offer the least resistance
to flow if erosion reaches the depth of the reinforcement,
as well as to provide transverse crack control. Extensive
damage has been experienced where the reinforcement near
the surface is perpendicular to the direction of flow. Addi­
tionally, increasing the concrete cover should be evaluated
by design experts when erosion due to high flows or abrasive
material is a concern. Consideration should be made to the
potential for larger drying shrinkage cracks in the surface
of the concrete as a result of having the reinforcement at a
greater depth (U.S. Bureau of Reclamation 20 1 5).
Where possible, transverse joints in concrete conduits
or chutes should be minimized. Preplanned, more closely
spaced joints are generally preferable to uncontrolled
cracking. One construction technique that has proven
satisfactory in placement of reasonably smooth hydraulic
surfaces is the traveling slipform screed. This technique can
be applied to tunnel inverts and to spillway chute slabs but
requires a specialized or experienced contractor. Informa­
tion on the slipform screed is found in Hurd (2005). Proper
mixture design (Neville 1 999), construction techniques, and
curing of these surfaces is essential because the development
of surface hardness improves cavitation resistance.
CHAPTER 7--CONTROL O F ABRASION EROSIO N
7. 1 --Hydraulic considerations
Under appropriate flow conditions and transport of
debris, all the construction materials currently being used in
hydraulic structures are, to some degree, susceptible to abra­
sion. While improvements in materials should reduce the
rate of damage, these alone will not solve the problem. Until
the adverse hydraulic conditions, which can cause abrasion
erosion damage, are minimized or eliminated, it is difficult
for any current construction materials to perform without
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16
REPORT O N T H E EROSION O F CONCRETE I N HYDRAULIC STRUCTURES (ACI 207.6R-17)
damage. Before construction or repair of major structures,
conduct hydraulic model studies of the structure to identify
potential causes of erosion damage and evaluate the effec­
tiveness of various modifications in eliminating those unde­
sirable hydraulic conditions. If the model test results indi­
cate it is impractical to eliminate the undesirable hydraulic
conditions, provisions should be made in design to minimize
future damage. For example, good design practices should
consider the following measures in the construction or repair
of stilling basins:
a) Include provisions, such as debris traps or low division
walls, to minimize circulation of debris; design end sills and
chute blocks so that they do not create a back roller below
the flow, trapping debris in the area.
b) Design downstream materials for stability at the design
flows.
c) Use model tests for design and detailing of the terminus
of the stilling basin and the exit channel to maximize flushing
of the stilling basin and to minimize chances of debris from
the exit channel entering the basin.
d) For stilling basins less than 25 ft (7.6 m) wide, flow
deflectors should be installed over a stilling basin end sill,
as shown in Fig. 7. l a, to redirect the current responsible for
carrying abrasive materials into the still basin (Hanna 2 0 1 0).
Flow defectors were installed at Choke Canyon (Fig. 7. 1b)
and Mason Dams to improve flow conditions to minimize
the potential for carrying downstream materials back into
the basin. Hanna (20 1 0) shows that a single mobile deflector
or two stationary staggered deflectors, staggered in position
both vertically and horizontally, are effective at sites where
large ranges of operations need be considered. This does
not, however, prevent materials from entering from above or
increase the effectiveness of flushing material from the basin.
Balanced flows into the basins of existing structures should
be maintained using all gates to avoid discharge condi­
tions where flow separation and eddy action are prevalent.
Substantial discharges that can provide a good hydraulic
jump \vithout creating eddy action should be released peri­
odically in an attempt to flush debris from the stilling basin.
Guidance as to discharge and tailwater relations required
for fl�shing should be developed through model or proto­
type tests, or both. Periodic inspections should be required
to det¢rmine the presence of debris in the stilling basin and
the extent of erosion. If the debris cannot be removed by
flushing operations, water releases should be shut down and
the basin cleaned by other means.
In locations where abrasion damage cannot be avoided,
consider measures to avoid major damage leading to
failure of the structure. Some materials, as discussed in the
following, can slow the progress of abrasion. However, for
existing structures subject to abrasion damage, the cost of
repairs may be considerable. Expensive repairs could be
delayed or avoided if a program to regularly clean debris
from the surface is implemented along with one to periodi­
cally measure damage. Typically, ball-milling abrasion does
not lead to failure during a single event. Surface damage
increases over time with each subsequent event. While
there may be a range of flows that can move debris onto the
-
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tn r t;cense w;th ACt
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� � or mg permitted without license from 1HS
Fig. 7. 1a-Flow deflector and desired flow pattern produced
(Hanna 20 10).
Fig. 7.1b-Choke Canyon stilling basin deflectors (Hanna
20 10).
concrete surfaces, once there, other flows could continue the
ball-milling damage. By periodically removing debris accu­
mulations, the events that could cause ball-milling but that do
not move abrasive materials onto the concrete surfaces will
not cause damage with the debris removed. Periodic clearing
could also provide opportunity for periodic measurements of
surface damage. For example, if a stilling basin is pumped
dry to remove rocks, the surface damage should be surveyed
at the same time. Periodic surveys can help predict the rate
of damage, which is useful for approximating when damage
might reach a critical point that requires repair.
7.2-Materials evaluation
Materials, mixtures, and construction practices should be
evaluated prior to use in hydraulic structures subjected to
abrasion-erosion damage. ASTM C 1 1 3 8M covers a proce­
dure for determining the relative resistance of concrete to
abrasion under water. This procedure simulates the abrasive
action of waterborne particles (silt, sand, gravel, and other
solid objects). Development of the test procedure and data
from tests on a wide variety of materials and techniques have
been described by Liu ( 1 980) and Causey ( 1 985).
7.3-Materials
Many materials and techniques have been used in the
construction and repair of structures subjected to abra­
sion erosion damage, with varying degrees of success. The
degree of success is inversely proportional to the degree of
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17
REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
exposure to those conditions conducive t o erosion damage
(McDonald 1 980). No single material has shown consis­
tently superior performance when compared to others.
Improvements in materials are expected to reduce the rate of
concrete damage due to abrasion erosion.
Abrasion-resistant concrete should include the maximum
amount of the hardest available coarse aggregate and
the lowest practical w!cm . Concrete mixtures should be
designed for workability and the capability of consolidation
and finish to meet the required tolerances. Good placement
practices and curing are also key. In laboratory studies, a
small increase in abrasion-erosion resistance has been shown
when using larger aggregates ( 1 - 1/2 in. [38 mm] versus 3/4
in. [ 1 9 mm]) (White 20 1 1 ). The abrasion-erosion resistance
of concrete containing chert aggregate has been shown to be
approximately twice that of concrete containing limestone
(Fig. 7.3). Given a good, hard aggregate, any practice that
produces a stronger paste structure will increase abrasion­
erosion resistance. Loss due to abrasion is directly propor­
tional to w/cm (White 20 1 1 ). In some cases where hard
aggregate was not available, high-range water-reducing
admixtures and silica fume were used to develop a strong
concrete with high compressive strength-approximately
1 5 ,000 psi ( 1 00 MPa)-to overcome proble�s with unsa is­
factory aggregate (Holland 1 983). At these h1gh compress1ve
strengths, the hardened cement paste assumes a greater role in
resisting abrasion-erosion damage, and the aggregate quality
becomes correspondingly less important. However, thermal
and shrinkage stresses also will likely be higher, increasing
the risk of cracking from early temperatures and shrinkage.
Concrete, when produced with a shrinkage-reducing admix­
ture or concrete designed to have low shrinkage potential,
can be beneficial when properly proportioned and cured.
In laboratory tests, the abrasion loss of a range of steel fiber­
reinforced concrete (FRC) mixtures was consistently higher
than that of conventional concrete mixtures with the same w/
em and aggregate type (Liu and McDonald 1 98 1 ). However,
the improved impact strength of FRC (Schrader 1 9 8 1) can
be expected to reduce concrete spalling where large debris is
being transported by high-velocity flow (ACI 544. 1 R).
The abrasion-erosion resistance of vacuum-treated
concrete, polymer concrete, polymer-impregnated concrete,
and polymer-portland-cement concrete can be significantly
superior to that of comparable conventional concrete. This
is attributed to a stronger cement matrix. The increased costs
associated with materials, production, and placing ofthese and
any other special concretes in comparison with conventional
concrete should be considered during the evaluation process.
Several types of coatings have exhibited good abrasion­
erosion resistance in laboratory tests. These include polyure­
thanes, polyurea, ceramic-filled epoxy, epoxy-resin mortar,
furan-resin mortar, acrylic mortar, and iron-aggregate
toppings. Problems in field application of coatings have been
reported (McDonald 1 980). These have been due primarily
to improper surface preparation or thermal incompatibility
between coatings and concrete. More recently, formula­
tions have been developed that have coefficients of thermal
expansion more similar to that of the concrete substrate.
�
American Concrete Institute
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10
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0.3
0.4
--- LIMESTONE
- - QUARTZITE - - - TRAP ROCK
--- - CHERT
0.5
0.6
0.7
Water- Cement Ratio
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0.8
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0.9
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Fig. 7.3-Relationships between water-cement ratio (w/c)
and abrasion-erosion loss.
Substrate and surface preparation are important in ensuring
a long trouble-free coatings project. Concrete surfaces
should be clean and dry before coating to establish strongest
bond. Dirt, dust, oil, and all other contaminates should be
removed and concrete surfaces prepared in accordance with
ASTM D4258. Surface preparation should include abrasive
blast or the equivalent to remove laitance and other loose
concrete in accordance with ICRI 3 1 0.2.
CHAPTER 8-CO NTROL O F EROSIO N BY
CHEMICAL ATTACK
8. 1-Control of erosion by mineral-free water
Pure water from glacial runoff or from condensation, as
in a desalination plant, can dissolve the calcium hydroxide
in the cement matrix (Neville 2009). The mild acid attack
possible with pure water rarely develops into deterioration
that can cause severe structural damage. Generally, mineral­
free water will leach mortar on surfaces exposed to this
water. This can be seen on exposed surfaces and at j oints
and cracks in concrete sections. As the surface calcium is
leached from the concrete, coarse aggregate is exposed,
which naturally decreases the amount of mortar exposed.
With less mortar exposed, less leaching occurs, resulting in
less chance for maj or structural problems to occur. Rough­
ened surfaces, however, could lead up to problems associ­
ated with cavitation if they are at a critical location. The
gradual erosion of leached mortar is minimized by use 0f
aluminous cements; partial substitution of cement with slag
cement, fly ash, or both; or use of low-lime portland cements
with less tricalcium silicate than dicalcium silicate (Tuthill
1 966). Protective coatings can also be effective when applied
to concrete surfaces.
8.2-Control of erosion from acid attack due to
bacterial action
The process of sulfide generation in a sanitary sewer when
insufficient dissolved oxygen is present in the wastewater
has been discussed and illustrated by an ASCE-WPCF
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18
REPORT O N THE EROSION O F CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
Joint Task Force ( 1 982). This original work was performed
by Pomeroy ( 1 974). Continuing work by Pomeroy and
Parkhurst ( 1 977) produced a quantitative method for sulfide
prediction. Engineers involved with projects of this nature
would be wise to also review the recommendations set forth
in the American Concrete Pipe Association ( 1 980).
Concrete conduits have served in sewer systems for many
years without serious damage in systems that were properly
designed and operated. The minimum adequate velocity of
flow in the sewer for the strength and temperature of the
sewage is usually 2 ft/s (0.6 m/s). Providing this velocity
without excessive turbulence and proper ventilation of the
sewer will generally prevent erosion by bacterial action.
Avoid turbulence because it is an H2S-releasing mechanism.
Where conditions are such that generation of H2S cannot
be eliminated by the system design, apply other means,
including:
a) Using hydrogen peroxide or chlorine compounds that will
convert the H2S (Water Pollution Control Federation 1 979):
i. H202 + H2S ---> ---> 2H20 + S
ii.
( 1 ) Clz + H20 --->---> HOC! + W + CI(2) HOC! + H2S ---> ---> S + HCI + H20 (low pH)
2
(3) S - + 4Ciz + 80H- --->---> SOi- + 8Cl + 4H20 (high pH)
b) Introducing compressed air into the water to keep
sewage fresh and thereby preventing development of an
anaerobic environment
c) Using an acid-resistant pipe such as vitrified clay or
polyvinyl chloride (PVC) pipes
d) Using acid-resisting liners on the crown of sewers
e) Increasing the concrete section to allow a sacrificial
thickness based on predicted erosion rates, at the risk of
increased cracking
f) Using concrete with limestone aggregate in place of sili­
ceous aggregates to give the acid more material to dissolve,
slowing down the overall rate
Graphical methods have been published to determine
sulfide buildup in sanitary sewers using the Pomeroy­
Parkhurst equations (Kienow et a!. 1 982).
Parker ( 1 95 1 ) lists the following remedial measures for
the control of H2S attack in concrete sewers:
a) Reduction-potential-generation
i. Inflow reduction
ii. Partial purification
iii. Chemical dosage to raise oxidation (but addition of
nitrates is impracticable)
iv. Aeration
v. Chlorination
vi. Removal of slimes and silts
vii. Velocity increase
b) Emissions
i. Turbulence reduction
ii. Treatment with heavy metal salts (Cu, Fe, Zn)
iii. Treatment with alkalis
iv. Full flow in sewer
c) H2S fixation on concrete
i. Ventilation
ii. Periodic wetting
iii. Use of resistant concrete
iv. Ammoniation
v. Use of protective coatings
The designer faced with reducing bacterial action should
be aware that: 1 ) chlorination may, under certain circum­
stances, be in violation of local codes because it can produce
trihalomethane, a known carcinogen; and 2) it could also
be a violation of local codes to add heavy metal salts to
wastewater.
Lining concrete pipe, walls, and conduit with PVC sheets,
a plastic liner, or a chemical-resistant liquid-applied coating is
an effective method of protecting the concrete and reducing
surface roughness. This technique has been used commer­
cially for many years. The designer should carefully deter­
mine which system is appropriate for the exposure conditions
and structural requirements for each application. Further
information on remedial measures for sanitary sewer systems
is available (U.S. Environmental Protection Agency 1 985).
8.3-Control of erosion by miscellaneous
chemical causes
8.3.1 Acid environments-No portland-cement concrete,
regardless of its other ingredients, will withstand attack from
water of high acid concentration. Where strong acid corro­
sion is indicated, other construction materials or an appro­
priate surface covering or treatment should be used. This
includes applications of sulfur-concrete toppings, epoxy
coatings, polymer impregnation, linseed-oil treatments, or
other processes, each of which affects acid resistance differ­
ently. Replacement of a portion of the portland cement by a
suitable amount of slag cement or fly ash selected for that
property can improve the resistance of concrete to weak
acid attack. Also, limestone or dolomite aggregates have
been found to be beneficial in extending the life of structures
exposed to acid attack (Bicz6k 1 967).
Performance-based cements having reduced calcium, and
when meeting ASTM C 1 1 5 7/C 1 1 57M or ASTM C 1 600/
C 1 600M, have proven to slow deterioration and be more
resistant to acid attack. Some cements made primarily from
fly ash particles and additives have no significant calcium
and have been found to be denser and allow less acid past
the surface. Laboratory studies have shown that only a small
amount of material is lost initially when exposed to strong
sulfuric acid solutions, with little or no deterioration at later
ages (VanderWerf 20 1 1 ) .
In 1 994, laboratory and field evaluation o f acid-resistant
materials at Spring Creek Debris Dam, California, were
evaluated in a pH 1 .7 test tank just outside the Richmond
Mine portal. Ordinary portland-cement concrete, silica fume
concrete, a polymer concrete overlay, a flexible epoxy coating,
and a flexible polyurethane coating were tested (Smoak
1 997) . Findings showed that silica fume concrete offered no
improvement, and the concrete with the polyurethane coating
showed superior performance. However, it was noted that the
concrete coated with the epoxy and polymer overlay failed
due to holidays or defects in the coating system, leaving
access for acid attack to the underlying concrete. Additional
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
information on chemicals that attack concrete can be found in
Portland Cement Association (2007).
8.3.2
19
rope inspection, or the use of remotely operated vehicles
may be necessary.
Alkali-aggregate reaction and chloride admix­
tures-Deterioration of concrete caused by alkali-aggregate
reaction and by chloride admixtures in the concrete mixture
is not included in this discussion. Extensive information on
these topics can be found in ACI 22 1 . 1 R and ACI 2 1 2.3R.
8.3.3 Soils and groundwaters-Sulfates of sodium, magne­
sium, and calcium frequently encountered in the alkali soils
and groundwaters ofthe western United States attack concrete
aggressively. ACI 2 0 1 .2R discusses this in detail. Use ofType
V sulfate-resisting cement, which is low in tricalcium alumi­
nate (C3A), is recommended whenever the sulfate in the water
is within the ranges shown in ACI 3 1 8- 1 4 Table 19.3 . 1 . 1 . The
subject of designing a sulfate-resistant concrete mixture is
complex. It is generally agreed that limiting the C3A content of
the cement to the 3 to 5 percent range, as in a Type V cement,
is beneficial. Limits of C3A content also are established for
Types I and II cements (ASTM C 1 50/C 1 50M). Additional
issues are also important, including restricting the tetracal­
cium aluminoferrite content (C4AF) to 1 0 percent; providing
air entrainment (an air-entrained mixture using Type II
cement can be more sulfate resistant than a non-air-entrained
mixture using Type V cement); replacing 20 to 30 percent of
the cement content with a pozzolan or fly ash; and using a rich
mixture, with the w/cm restricted to a maximum of 0.45 . The
use of shrinkage-compensating cements, made with Type II
or Type V portland-cement clinker and adequately sulfated,
produces concrete having sulfate resistance equal to or greater
than portland cement made of the same type of clinker (Mehta
and Polivka 1 975).
CHAPTER 9-PERIO DIC INSPECTIONS AND
9.3-lnspection procedures
Before the on-site inspection, the team should thoroughly
evaluate all available records, reports, and other documenta­
tion on the condition of the structure and maintenance and
repair, and become familiar with previous recommendations.
Observations to make during an examination of hydraulic
facilities include:
a) Identifying structural cracking, spalling, and
displacements
b) Identifying surface irregularities where cavitation
potential is a concern
i. Offset into or away from flow (including at joints or
cracks)
ii. Abrupt curvature away from flow
iii. Abrupt slope away from flow
iv. Local slope changes along flow surface
v. Void or transverse groove
vi. Roughened or damaged surfaces that give evidence
of cavitation or abrasion erosion
vii. Structural imperfections and calcite deposits
viii. Cracking, spalling, and rust stains from reinforcement
c) Inspecting gate slots, sills, and seals, including identifi­
cation of offsets into the flow
d) Locating concrete erosion adj acent to embedded steel
frames and steel liners and in downstream water passages
e) Finding vibration of gates and valves during operation '.
f) Observing defective welded connections and the pitting,
cavitation, or both, of steel items
g) Observing equipment operation and maintenance
:
h) Making surveys and taking cross sections to determine :
The regular, periodic inspection of completed and oper­
ating hydraulic structures is important. Observance of
concrete erosion should be included in these inspections.
The frequency of inspections is usually a function of use
and evidence of distress. Inspections provide a means of
routinely examining structural features, as well as observing
and discussing problems requiring remedial action. ACI
20 1 . 1 R, ACI 207.3R, and EM- 1 1 1 0-2-2002 (U.S. Army
Corps of Engineers 1 995) provide detailed instructions for
conducting extensive investigations.
the extent of damage
.
i) Investigating the condition of concrete by nondestruc- '
tive methods or by core drilling and sampling, if distressed
conditions warrant
j) Noting the nature and extent of debris in water passages
Observed conditions, the extent of the distress, and recom­
mendations for action, should be recorded by the inspec­
tion team for future reference. High-quality photographs or
videos of deficiencies are beneficial and provide a permanent
record that will assist in identifying slow progressive fail­
ures. A report should be written for each inspection to record
the condition of the project and justify funding for repairs.
To-scale drawings should be created to show damaged areas.
9.2-lnspection program
9.4-Reporting and evaluation
The inspection program should be tailored to the specific
type of structure. Designers should provide input to the
program and identify items of primary and secondary impor­
tance. The inspection team should be composed of qualified
technical personnel who are experienced and can relate in
common terminology. Team size is usually dependent on
the number of technical disciplines required. The program
should be established and monitored by an engineer who
is experienced in design, construction, and operation of the
proj ect. The use of underwater dive inspections, climb team
The inspection report can vary from a formal publication
to a trip report or letter report. The report should include
the standard items: who, why, what, where, and when. A
pre-established outline is usually of value. An inspection
checklist of deficiencies and subsequent corrective actions
should be established from prior inspections. Any special
items of interest can be shown in sketches or photos. The
report should address existing and potential problems and
categorize deficiencies relative to the urgency of corrective
action, as well as identify the extent of damage, probable
CORRECTIVE ACTION
9.1-General
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
20
cause of damage, and probable extent of damage if imme­
diate repairs are not made. It is important that the owner or
agency distribute the report in accordance with applicable
U.S. federal or state safety regulations.
When the inspection report indicates that remedial action
is required, the next step is either a supplemental investiga­
tion or the actual corrective action. Deficiencies noted in the
inspection should be evaluated and categorized as to minor,
major, or potentially catastrophic. The scope of work should
be defined to establish reliable budget estimates. Design of
proper repair schemes sometimes requires model tests, rede­
sign of portions of the structure, and materials investiga­
tions. Each of these items requires funding by the owner.
The more details identified in the scope of work, the more
accurate the cost estimate. Wherever possible, it is important
to correct the probable cause so that the repairs will not have
to be repeated in the near future.
CHAPTER 10-REPA IR METHO DS AN D
MATERIALS
1 0.1- Design considerations
1 0.L1 General-Although it is always desirable to elimi­
nate the cause of erosion, it is not always possible; therefore,
a varie of materials and material combinations are used for
concrete repair. Some materials are better-suited for certain
repairs and the designer should use judgment in their proper
selecti<?n. Also, consider the time available to make repairs,
access points, logistics in material supply, ventilation, nature
of the work, available equipment, and skill and experience
of the local labor force. Underwater repair options can be
evaluated using ACI 546.2R. Detailed descriptions of repair
considerations and procedures are found in the Concrete
Repair Manual (American Concrete Institute 20 1 3).
1 0.1.2 Consideration of materials-A major factor that is
critical to the success of a repair is how well the repair mate­
rial matches the strength and thermal expansion properties of
the substrate concrete, as previously discussed. Adhesion of
the repair material to the substrate concrete is also critical for
a long-lasting repair. ICRI 2 1 0.3R discusses adequate bond
strength at the interface between concrete repairs. Some
specifiers allow acceptance of bond strengths for cementi­
tious materials as low as 100 psi (0.69 MPa) when tested in
accordance with ASTM C 1 583M.
Normal portland-cement concrete will generally match the
characteristics of in-place concrete with regard to tempera­
ture change. Thermal stresses that could result in a thicker
repair should be minimized. This can often be managed
by control of temperatures, replacement of cement with
supplementary cementitious materials, and precooling the
repair materials. Care should be taken to minimize drying
shrinkage.
ty
10.2-Methods and materials
1 0.2.1 Steel plating Installing stainless steel liner plates
on concrete surfaces subj ect to cavitation erosion has been
a generally successful method of protecting the concrete
against cavitation erosion. Colgate's ( 1 9 77) studies show
-
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stainless steel to be approximately four times more resistant
to cavitation damage than ordinary concrete. The currently
preferred stainless material is ASTM A240/A240M S30403,
from the standpoint of excellent corrosion and cavita­
tion resistance, and weldability. The steel plates should be
securely anchored in place and sufficiently stiff to minimize
the effects of vibration. Vibration of the liner plate can lead
to fracturing and eventual failure of the underlying concrete
or failure of the anchors. Grouting behind the plates to
prevent vibration is recommended. Unfortunately, the steel
plating could hide early signs of concrete distress. The tran­
sition from steel plating to concrete should also be designed
carefully so that the concrete surface does not cavitate due
to an offset.
This repair method, like many others, treats only the
symptom of erosion and eventually, if the cavitation is not
reduced or eliminated, the steel itself can become damaged
by pitting.
10.2.3 Fiber-reinforced concrete (FRC)- Laboratory
abrasion-erosion tests under conditions of low velocity
carrying small-size particles have concluded that FRC should
not be used for new construction or repair where abrasion­
erosion is of major concern (Liu and McDonald 1 98 1 ).
10.2.4 Epoxy resins Resins are natural or synthetic, solid
or semisolid organic materials of high molecular weight.
Epoxies are one type of resin. These materials are typically
used in preparation of special coatings or adhesives or as
binders in epoxy-resin mortars and concretes. Several vari­
eties of resin systems are routinely used for the repair of
concrete structures . ACI Committee 503 ( 1 973) describes
the properties, uses, preparations, mixtures, application, and
handling requirements for epoxy resin systems.
The most common use of epoxy compounds is in bonding
adhesives. Epoxies will bond to most building materials, with
the possible exception of some plastics. Typical applications
include the bonding of fresh concrete to existing concrete.
Epoxies can also be used for bonding dry-pack material,
FRC, polymer concretes, and some latex-modified concretes
to hardened concrete. Epoxy formulations have been devel­
oped that will bond to damp concrete and even concrete
under water. There are case histories of successful uses of
these materials in hydraulic structures. To help assure proper
selection and use of materials, consultation with product
representatives is advised before an epoxy is specified or
procured. When using a bonding agent, the bonding agent
should not set before the concrete or mortar is applied; other­
wise, bond can be poor. ASTM C88 1 /C8 8 1 M is a specifica­
tion for epoxy bonding systems useful in concrete repairs,
and ACI 503.2 covers epoxy bonding in repair work.
Experience shows that the localized application of epoxies
can create serious problems in areas of high-velocity flow.
If the finished surface has a smooth or glassy texture, flow
at the boundary can be disrupted and may have the effect
of a geometric irregularity, which could trigger cavitation.
This texture problem is minimized by using special finishing
techniques, improving the surface texture of the patch with
sand, or both. Sometimes the patch can be too resistant to
damage, with the result that the abutting original material
-
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
erodes away, leaving an abrupt change in surface geometry
and developing a condition worse than the original damage.
Epoxy mortars and epoxy concretes use epoxy resins for
binder material instead of portland cement. These materials
are ideal for repair of normally submerged concrete, where
ambient temperatures are relatively constant. Beware that
they are different from traditional concrete. Epoxies can
generate more heat while hardening, are likely to have a
different coefficient of thermal expansion than the substrate
concrete, and hardened epoxies may soften when exposed
to elevated temperatures. Mixed results have been observed
in the epoxy-mortar repair of erosion of outlet surfaces,
dentates, and baffle blocks (McDonald 1 980). Depending on
the epoxy formulation, the presence of moisture, either on
the surface or absorbed in the concrete, can be an important
factor that affects the success of the repair. ACI 503.4 is a
specification for epoxy mortar in repair work.
The concept of improving concrete by incorporating
the epoxy directly into the mixture was encouraged by
the successful latex modification of concrete (Murray and
Schrader 1 979). Several commercial products have been
developed and research is continuing. The epoxies generally
enhance the concrete's resistance to freezing and thawing
spalling, chemical attack, and mechanical wear. Epoxy­
modified concrete (Christie et a!. 1 98 1 ) has a curing agent
that is retarded by the water in the mixture. As the water is
used up by cement hydration and drying, the epoxy resin
begins to gel. Accordingly, the mixture will not become
sticky until the portland cement begins to set, and this greatly
extends the pot life ofthe wet concrete. These materials have
had limited use in hydraulic structures.
1 0.2.5 Acrylics and other polymer systems- There are
three main ways in which polymers have been incorporated
into concrete to produce a material with improved properties
as compared to conventional portland cement concrete:
1 ) Polymer-impregnated concrete (PIC)
2) Polymer-portland-cement concrete (PPCC)
3) Polymer concrete (PC)
PIC is a hydrated portland-cement concrete that has been
impregnated with a monomer that is subsequently polym­
erized in place. By effectively case hardening the concrete
surface, impregnation protects structures against the forces
of cavitation (Schrader 1 978) and abrasion erosion (Liu
1980). The depth of monomer penetration depends on the
porosity of the concrete and the process and pressure under
which the monomer is applied. In addition to noting that
these materials are costly, the engineer is cautioned that
some monomer systems can be hazardous and that monomer
systems require care in handling and should be applied only
by skilled workers experienced in their use (DePuy 1 975).
Surface impregnation was used at Dworshak Dam in Idaho
in the repair of cavitation and abrasion erosion damage to
the regulating outlet tunnels (Schrader and Kaden 1 976a)
and stilling basin (McDonald 1 980; Schrader and Kaden
1 976b ). High-head erosion testing of PIC at Detroit Dam test
facility has shown excellent performance (U.S. Army Corps
of Engineers 1 977).
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21
PPCC is made by the addition of water-submersible poly­
mers directly into the wet concrete mixture. PPCC, compared
with conventional concrete, has higher strength, increased
flexibility, improved adhesion, superior abrasion and impact
resistance, and usually better freezing-and-thawing resis­
tance and improved durability. These properties can vary
considerably, depending on the type of polymer being used.
The most commonly used PPCC is latex-modified concrete.
Latex is a dispersion of organic polymer particles in water.
Typically, the fine aggregate and cement contents are higher
for PPCC than for normal concrete.
PC is a mixture offine and coarse aggregate with a polymer
used as the binder. This results in rapid-setting material with
good chemical resistance and exceptional bonding charac­
teristics. Polymer concrete has had limited use in large-scale
repair of hydraulic structures because of the expense of large
volumes of polymer for binder. Thermal compatibility with
the parent concrete should be considered before using these
materials.
Polymer concretes are finding application as concrete
repair materials for patches and overlays, and as precast
elements for repair of damaged surfaces (Fontana and
B artholomew 1 98 1 ; Scanlon 1 9 8 1 ; Kuhlmann 1 98 1 ; Bhar­
gava 1 98 1 ). Field test installations with precast PC have
been made on parapet walls at Deadwood Dam in Idaho, and
as a repair of cavitation and abrasion damage in the stilling
basin of American Falls Dam, also in Idaho.
ACI 548 . 1 R provides an overview of the properties and
use of polymers in concrete. Smoak ( 1 985) has described
polymer impregnation and polymer concrete repairs at
Grand Coulee Dam.
1 0.2.6 Silica fume concrete L aboratory tests have shown
that the addition of an appropriate amount of silica fume and
a high-range water-reducing admixture to a concrete mixture
will greatly increase compressive strength. This, in turn,
increases abrasion-erosion resistance (Holland 1 983 , 1 986b;
Holland et a!. 1 986). As a result of these tests, concretes
containing silica fume were used by the U.S. Army Corps of
Engineers to repair abrasion-erosion damage in the stilling
basin at Kinzua Dam in Pennsylvania (Holland 1 986a)
and in the concrete lining of the low-flow channel for the
Los Angeles River (Holland and Gutschow 1 98 7). Despite
adverse exposure conditions, particularly at Kinzua Dam,
the silica fume concrete continues to exhibit excellent resis­
tance to abrasion erosion.
Silica fume offers potential for improving many proper­
ties of concrete. However, the high compressive strength and
resulting increase in abrasion-erosion resistance are particu­
larly beneficial in repair of hydraulic structures. Silica fume
concrete should be considered in repair of abrasion-erosion­
susceptible locations, particularly in those areas where avail­
able aggregate might not otherwise be acceptable. However,
silica fume may not be the best option for thick placements
where the surface is too dense to let bleed water escape
(increasing the risk of plastic drying shrinkage), or cost­
prohibitive when the volume of materials is large. Silica
fume concrete also usually has a higher risk of cracking from
early hydration temperatures and drying shrinkage (NCHRP
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22
REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
2008 ; ACI 224R). Guidance on the use of silica fume in
concrete is given in ACI 234R.
10.2.10 Pipe inserts-For repair of small-diameter pipes,
many of the methods discussed in the previous sections of
A successful underwater repair of the stilling basing at
this report are not applicable. A common construction prac­
Canyon Ferry Dam in Montana was done with 1 2,000 psi
tice today is to obtain a jointless, structurally sound pipe­
(82 MPa) silica fume concrete (U. S . Bureau of Reclamation
inside-a-pipe without excavating the existing unsound pipe.
2005). A remotely operated hydro-demolition tool was used
One such method that has been used successfully is to insert
to remove concrete and exposed reinforcing steel bars at a
steel or plastic pipe inside the deteriorated concrete pipe and
water depth of 50 ft ( 1 5 m). From barges, divers assisted
then fill the annular space between the concrete and plastic
the installation of custom formwork and placement of self­
liner with grout. With the proper selection of material, a pipe
consolidating high-strength concrete having a 24 in. (600
insert can provide a sound, chemically-resistant lining (U.S.
mm) spread, which was pumped through a slickline.
Department of Housing and Urban Development 1 985 ; U.S.
Underwater abrasion testing has also shown that concrete
Army Corps of Engineers 1 995 ).
with ultra-fine Class F fly ash as a partial replacement for
Another popular method is the installation of a resin-satu­
cement performs as well as concrete with silica fume at the
rated fiberglass hose into the pipeline. The hose is inserted
same replacement rates (White 20 1 1 ).
into the pipeline using water pressure. After installation, the
1 0.2.7 Shotcretes-Shotcrete has been used extensively
in the repair of hydraulic structures. This method permits
replacing concrete without the use of formwork, and the
repair can be made in restricted areas. Shotcrete, also known
hose is filled with hot water to initiate the chemical reaction
of the resin. The hardened resin forms a rigid pipe lining.
1 0.2.11 Linings-Tunnels, conduits, and pipes that have
surface damage due to abrasion erosion, bacterial action, or
as pneumatically applied mortar, can be an economical alter­
chemical/acid attack can be protected from further damage
native to other, more conventional systems of repair. ACI
with a nonbonded, mechanically attached PVC lining.
506R provides guidance in the manufacture and application
Depending on the extent of the damage, some patching of
of shotcrete. In addition to conventional shotcrete, modi­
the concrete surface may be required before installation.
fied concretes such as fiber-reinforced shotcrete, polymer
Carbon fiber-reinforced polymer (CFRP) has also been
shotcrete, and silica fume shotcrete have been applied by
an effective method for lining tunnels, conduits, and pipes.
the air-blown or shotcrete method. In areas where cavita­
CFRP systems were initially implemented for structural
tion is possible, additional trowel finishing may be neces­
repair of pipelines in 1 997 (Sleeper 2 0 1 0). Various struc­
sary to achieve acceptable tolerances and smoothness of the
tural loading conditions can be designed for based on the
concrete.
direction and number of layers of CFRP applied. Labora­
Coatings-High-head erosion tests have been
tory studies have shown that some systems have excellent
conducted using both polyurethane and neoprene coatings
cavitation resistant (Fyfe Company 2008) . Inspection during
1 0.2.8
(Houghton et al. 1 97 8). Both coatings exhibited good resis­
installation is recommended to ensure that substrate prepa­
tance to abrasion and cavitation. The problem with flexible
ration is adequate to obtain a good bond between the CFRP
coatings like these is their bond to the concrete surfaces.
and the concrete.
Once an edge or a portion of the coating is tom from the
1 0.2.12 A eration slots-The installation of an aeration
surface, the entire coating can be peeled off rather quickly
slot is not only a consideration in the design of a new facility
by hydraulic force.
but often an appropriate remedial addition to a structure
1 0.2.9 Prep/aced-aggregate concrete-Preplaced-aggre­
experiencing cavitation erosion damage. Structural restora­
gate concrete, also referred to as prepacked concrete, is used
tion and the addition of aeration slots have been used in the
in the repair of large cavities and inaccessible areas. Clean,
repair of several structures . Refer to 6.3 for a more detailed
well-graded coarse aggregate, generally of 0.5 to 1 . 5 in. ( 1 2
discussion of this method. The addition of aeration slots will
to 3 8 mm) maximum size, i s placed in the form. Neat cement
likely reduce the flow capacity of the structure significantly
grout or a sanded grout, with or without admixtures, is then
because of the added volume of entrained air.
pumped into the aggregate matrix through openings in the
CHAPTER 11-RE FERENCES
bottom of the forms or through grout pipes embedded in
the aggregate. The grout is placed under pressure, and pres­
Committee documents are listed first by document number
sure is maintained until initial set. Concrete placed by this
and year of publication followed by authored documents
method has a low volume change because of the point-to­
listed alphabetically.
point contact of the aggregate; there is high bond strength
to top bars for the same reason. The use of pozzolans,
water-reducing admixtures, and low water content is recom­
mended to further reduce shrinkage and thermal volume
changes while maintaining the fluidity required for the grout
to completely fill the voids in the aggregate. Successful
A merican Concrete Institute
ACI
1 1 7- 1 0( 1 5)-Specification
for
Tolerances
ACI 20 1 . 1 R-08-Guide for Conducting a Visual Inspection of Concrete in Service
installation is often difficult, and a mockup is recommended
ACI 2 0 1 .2R- 1 6-Guide to Durable Concrete
before using. ACI Committee 706 (2005) provides details
ACI 207 . 1 R-05( 1 2)-Guide to Mass Concrete
and guidance for the use of prep laced-aggregate concrete.
for
Concrete Construction and Materials and Commentary
ACI 207.3R-94(08)-Practices for Evaluation of Concrete
·· in Existing·Massive Structures for Service Conditions
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
ACI 2 1 2.3R-1 6-Report on Chemical Admixtures for
A uthored documents
ACI Committee 503, 1 973, "Use of Epoxy Compounds
Concrete
ACI
23
22 1 . 1 R-98(0 8)-Report
on
Alkali-Aggregate
Reactivity
with Concrete," ACI Journal
Sept., pp. 6 1 4-648.
ACI 224R-0 1 (08)-Control
of Cracking in Concrete
Proceedings , V. 70, No. 9,
ACI Committee 706, 2005, "RAP-9 : Spall Repair by the
Structures
Prep laced Aggregate Method," American Concrete Institute,
ACI 234R-06( 1 2)-Guide for the Use of Silica Fume in
Concrete
ACI 302. 1 R- 1 5-Guide for Concrete Floor and Slab
Construction
F armington Hills, MI.
American Concrete Institute, 2 0 1 3 , Concrete Repair
Manual, fourth edition, American Concrete Institute, Farm­
ington Hills, Ml, 2 3 63 pp.
ACI 304R-00(09)-Guide for Measuring, Mixing, Trans-
American Concrete Pipe Association,
1 980,
Concrete
Pipe Handbook, ACPA, Irving, TX.
porting, and Placing
Arndt, R. E. A., 1 9 8 1 , "Recent Advances in Cavitation
ACI 3 0 8 . 1 - 1 1 -Specification for Curing Concrete
ACI 3 09R-05-Guide for Consolidation of Concrete
Research," Advances in Hydroscience
ACI 3 1 8- 1 4-Building Code Requirements for Structural
New York, pp. 1 -78.
Concrete and Commentary
ASCE-WPCF Joint Task Force,
12, Academic Press,
1 982, "Gravity Sani­
ACI 347R- 1 4-Guide to Formwork for Concrete
tary Sewer Design and Construction," ASCE Manuals and
ACI 503 .2-92(03)-Standard Specification for Bonding
Reports on Engineering Practice No. 60, American Society
Plastic Concrete to Hardened Concrete with a Multi-Compo­
of Civil Engineers, New York, pp. 47-66.
nent Epoxy Adhesive
Ball, J., 1 959, "Hydraulic Characteristics of Gate Slots,"
ACI 503 .4-92(03)-Standard Specification for Repairing
Concrete with Epoxy Mortars
Journal of the Hy draulics Division, V. 85, No. 1 0, Oct., pp.
8 1 - 1 14.
Bartoj ay, K., 20 1 1 , "Buffalo Bill Powerplant Tailrace
ACI 506R- 1 6-Guide to Shotcrete
ACI 544. 1 R-96(09)-Report on Fiber Reinforced Concrete
and Draft Tube Repair - Feasibility Level Design Tech­
ACI 546.2R-1 0-Guide to Underwater Repair of Concrete
nical Memorandum," Technical Memorandum BBPP8 180-FEA-2001- 1 (MERL- 11-47), U . S . Bureau of Reclama­
ACI 548 . 1 R-09-Guide for Use of Polymers in Concrete
tion, Denver, CO.
Beichley, G. L., and King, D . L.,
ASTM International
ASTM
A240/A240M- 1 6-Standard
Specification
for
Chromium and Chromium-Nickel Stainless Steel Plate,
Sheet, and Strip for Pressure Vessels and for General
C 1 50/C 1 5 0M- 1 7-Standard
Specification
for
Specification
for
Bhargava, J. K., 1 98 1 , "Polymer-Modified Concrete for
cations of Polymer Concrete, SP-69, American Concrete
Institute, Farmington Hills, Ml, pp. 205-2 1 8 .
Portland Cement
ASTM
Hy draulics Division, V. 1 0 1 , No. 7, July, pp. 829-846.
Overlays: Strength and Deformation Characteristics," Appli­
Applications
ASTM
1 975, "Cavitation
Control of Aeration of High-Velocity Jets," Journal of the
C88 1 /C88 1 M- 1 5-Standard
Epoxy-Resin-Base Bonding Systems for Concrete
ASTM C 1 1 3 8M-1 2-Standard Test Method for Abrasion
Bicz6k, 1 967, Concrete Corrosion and Concrete Protec­
tion, Chemical Publishing Co., New York, 543 pp.
Borden, R. C.; Colgate, D . ; Legas, J.; and Selander, C. E.,
1 97 1 , "Documentation of Operation, Damage, Repair and
Resistance of Concrete (Underwater Method)
Testing ofYellowtail Dam Spillway," Report No.REC-ERC-
ASTM C 1 1 57/C 1 1 57M- 1 1 -Standard Performance Spec­
ification for Hydraulic Cement
71-2 3, U . S . Bureau of Reclamation, Denver, May, 809 pp.
ASTM C 1 5 83 M - 1 3-Standard Test Method for Tensile
Burgi, P. H.; Moyes, B. M.; and Gamble, T. W. , 1 984,
Strength of Concrete Surfaces and the Bond Strength or
"Operation
Tensile Strength of Concrete Repair and Overlay Materials
1 983," Water for Resource Development, American Society
by Direct Tension (Pulloff Method)
of Civil Engineers, New York.
ASTM C 1 600/C 1 600M- l l -Standard Specification for
of Glen Canyon Dam
Spillways-Summer
Causey, F. E., 1 9 8 5 , "Preliminary Evaluation of a Test
Method for Determining the Underwater Abrasion-Erosion
Rapid Hardening Hydraulic Cement
ASTM D4258-05(20 12)-Standard Practice for Surface
Resistance of Concrete," GR-84- 1 , U . S . Bureau of Reclama­
Cleaning Concrete for Coating
tion, Denver, CO.
International Concrete Repair Institute
1 98 1 , "Epoxy-Modified Portland Cement Concrete," Appli­
Christie III, S . H.; McClain, R. R.; and Melloan, J. H . ,
ICRI 2 1 0.3R- 1 3-Guide for Using In-Situ Tensile Pulloff
ICRI
3 1 0.2-97-Selecting
Concrete
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Specifying
cations of Polymer Concrete, SP-69, American Concrete
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Tests to Evaluate Bond of Concrete Surface Materials
REC-ERC- 7 1 -4 7, U.S. Bureau of Reclamation, Denver, CO,
Dec.
American Concrete Institute
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
Colgate, D . , 1 977, "Cavitation Damage in Hydraulic Struc­
Pennsylvania," Miscellaneous
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1 986a, "Abrasion-Erosion Evaluation
Devices on Hydraulic Structures," Frontiers in Hydraulic
of Concrete Mixtures for Repair of Low-Flow Channel ,
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L o s Angeles River," Miscellaneous Paper SL-86- 1 2 , U . S .
York, pp. 426-43 1 .
Army Engineer Waterways Experiment Station, Vicksburg,
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CO.
DePuy, G. W. , and Dikeou, J. T., 1 973, "Development of
Polymer-Impregnated Concrete as a Construction Material
for Engineering Projects," Polymers in
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American Concrete Institute, Farmington Hills, MI.
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Engineering Monograph No. 42, U . S . Bureau of Reclama­
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68 pp .
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1 9 86, "Use o f Silica-Fume Concrete t o Repair Erosion
Damage in the Kinzua Dam Stilling Basin," Fly Ash,
Silica Fume, Slag, and Natural Pozzolans in Concrete ,
SP-9 1 , V. 2 , American Concrete Institute, F armington
Hills, MI, pp. 8 4 1 -864.
Holland, T. C., and Gutschow, R. A., 1 987, "Erosion
Resistance with Silica-Fume Concrete," Concrete Interna­
tion, Denver, CO, 1 45 pp.
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Polymer Materials in the Transportation Industry," Applica­
tional, V. 9, No. 3, Mar., pp. 32-40.
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tions ofPolymer Concrete, SP-69, American Concrete Insti­
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nology Center, San Diego, CA.
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G.,
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Hy draulic Laboratory
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Modified Concrete
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American Co ete Ins
Provided by I ftQJn r license with ACI
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
Liu, T.
C.,
and McDonald, J.
E.,
1 9 8 1 , "Abrasion­
25
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Occurrence and Prevention," Technical Report No. SR 79,
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Structures," Technical Report No. C-78-4, U.S. Army Engi­
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tional, V. 9, No. 3 , Mar. , pp. 5 5 -6 1 .
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Microstructure, Properties, and Materials,
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Concrete,
Schrader, E . , 1 98 1 , "Impact Resistance and Test Proce­
third edition,
McGraw Hill, New York, 1 5 9 pp.
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dure for Concrete," ACI Journal Proceedings, V. 79, No. 2 ,
Mar.-Apr., p p . 1 4 1 - 1 46.
Expansive Cement Concretes," Durability of Concrete, SP-47,
Schrader, E., 1 9 8 3 , "Cavitation Resistance of Concrete
American Concrete Institute, Farmington Hills, pp. 367-379.
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Murray, M. A., and Schrader, E .
K.,
1 979,
"Epoxy
Concrete Overlays," T he Military Engineer, V. 7 1 , No. 462,
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to Resist Cavitation/Erosion Damage," Proceedings, 2nd
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NCHRP,
2008,
"Applications
International Congress on Polymers in Concrete, College
of Illuminated, Active,
In-Pavement Marker Systems, A Synthesis of Highway
Practice,"
NCHRP Synthesis 3 80, National Cooperative
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Repairs at Dworshak Dam," The Military Engineer, V. 68,
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at Dworshak Dam," T he Military Engineer, V. 68, No. 443 ,
pp. 254-259.
Pearson Education Limited, Edinburgh Gate, England.
by Hydrogen
of Engineering, University of Texas at Austin, Austin, TX,
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Highway Research Program, Washington, DC.
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Society of Civil Engineers, New York.
No. 444, July-Aug. , pp. 282-286.
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Sewage and Industrial
Wastes, V. 2 3 , No. 1 2, Dec., pp. 1 477- 1 4 8 5 .
Damage to Concrete in Dams," Concrete International, V. 8 ,
Peterka, A. J., 1 95 3 , "The Effect o n Entrained Air o n Cavi­
No. 3 , Mar., p p . 1 6-23 .
tation Pitting," Proceedings of the Joint Meeting of the IAHR
S emenkov, V. , and Lentyaev, L . , 1 97 3 , "Spillway Dam
and ASCE, Minneapolis, MN, Aug.
with Aeration of Overflow," Gidrotekhs Stroitel, No. 5 ,
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p p . 1 6-20.
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No. 2 , Feb., pp. 34-3 8; and No. 3 , Mar. 1 982, pp. 42-44.
(CFRP) As a Long Term Repair Solution," Pipelines 20 10:
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Control in Sanitary Sewerage Systems, EPA 625 - 1 -7-005
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Rehab, and Reinvest, pp. 1 1 3 3 - 1 1 42 .
and NTIS PB/260/479, Oct.
Smoak, W. G., 1 985, "Polymer Impregnation and Polymer
Pomeroy, R. D . , and Parkhurst, J. D . , 1 977, "The Fore­
Concrete Repairs at Grand Coulee Dam," Polymer Concrete:
casting of Sulfide Build-Up Rates in Sewers," Progress in
Uses, Materials, and Properties, SP-89, American Concrete
Water Technology, V. 9, pp. 62 1 -628.
Institute, Farmington Hills, MI, pp 43-50.
Popovics, S., and McDonald, W. E., 1 9 89, "Repair, Evalu­
Smoak, W. G., 1 997, "Tests of Acid Resistant Materials
ation, Maintenance, and Rehabilitation Research Program­
for Spring Creek Debris Dam," Memorandum to Principal
Inspection of the Engineering Condition of Underwater
Designer, Spring Creek Debris Dam Modification,
Concrete Structures," No. WES/TR/SL-REMR-CS-9, Army
Bureau o f Reclamation, Denver, C O .
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Skokie, IL.
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and Solids in Flowing Water," ACI Journal Proceedings, V.
43, No. 5 , May, pp. 1 009- 1 023 .
American Concrete Institute
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Significance of Tests and Properties of Concrete and
Concrete- Making Material, STP- 1 69A, ASTM Interna­
tional, West Conshohocken, PA, pp. 275-289.
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REPORT ON THE EROSION OF CONCRETE IN HYDRAULIC STRUCTU RES (ACI 207.6R-17)
26
U . S . Army Corps of Engineers, 1 977, "Investigation of
Cavitation-Erosion Resistance of Conventional Steel Fiber
and Polymer Impregnated Concrete for Tarbela Dam," North
Pacific Division Materials Laboratory, Troutdale, 29 pp.
U.S. Army Corps of Engineers, 1 995, "Evaluation and
Repair of Concrete Structures," EM- 1 1 1 0-2-2002, Wash­
Systems and Treatment Plants," EPA/62511 -85/0 1 8, Oct.,
Washington, DC.
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Cures," Inspectioneering Journal, Sept.-Oct., Inspection­
eering, LLC.
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1 982,
"Hydraulic Modelling ofAir Slots in Open Chute Spillways,"
ington, DC.
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eighth edition, U.S. Department of lnterior, Denver, CO.
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tion - Canyon Ferry Dam Spillway Stilling Basin Repair,
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tation Manual, U.S. Department of Interior, Denver, CO.
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mens," Technical Memorandum MERL- 1 1 -0 1 , U.S. Bureau
of Reclamation, Denver, CO.
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