Rak-82-2121 Production Technology of Concrete Structures
(2015)
Special Concrete Works
20.11.2015
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Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
1
Learning Outcomes
• To acquaint the student with
special casting methods
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Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
2
Shotcrete
• Shotcrete is a special type
of concrete containing small
aggregates or just sand
(mortar) which is sprayed
under high pressures onto a
surface. The technology
was developed already in
1911 and since then the
basic principle remained the
same. Shotcrete can be
applied by dry, wet or semi
wet method.
http://www.gunform.com/images/Gunite%2
0Arch%20Lining.jpg
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
3
Dry-mix shotcrete
• Batch of concrete cement
and natural dry aggregates –
moisture 2..5%
• Transportation by
compressed air
• Addition of water
• Advantages: long
transportation 250-600 m (h0
50 to 150 m); water to
cement ratio 0.4 to 0.45;
workability of the dry mass
1,5 hours
• Drawbacks: transportation
rebound 15-30%; dust and
harmful clouds; continuous
spraying - thickness layer less
than 40mm
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
4
Half wet-mix shotcrete
• Finished got involved dry mix
concrete W/C= 0.42…0.48
• Transportation in the hose of
compresses air
• Possibly the addition of the
fluid accelerator in nozzle
• Benefits: it can be used thick
spraying floors; the bulk is
got involved in the power
mixer; water cement
relationship no varying
• Drawbacks: the hose is less
than 20 meters; fine aggregate
and maximum grain size less
than 16mm; cement content
less that 350 kg/m3
http://www.shotcretetechnologies.com/grap
hics/i_ecuador1_lg.jpg
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
5
Wet-mix shotcrete
• Plastic concrete w/c =
0.55…0.70; max aggregate
size 8 mm; compressed air
• Benefits: small dusting;
suitable for thick spraying
floors; appropriate for closed
and tight places; possibility to
use fibre
• Drawbacks: low strength; thin
layer less than 20 mm;
strength degrading with
acceleration
https://www.shotcrete.org/media/images/he
ader-wet-mix.jpg
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
6
Wet-mix shotcrete
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
7
Wet-mix shotcrete
• Used additives:
• High class of concrete: fast
accelerators –closing
movement 80 to 170 m/s; high stone
the water leaks; retards
ingredient decrease of elasticity;
- better quality; air
efficient vibration and tightening;
entraining agent compressive strength 30 to 70 MPa;
cohesion and frost
splitting strength 3,5 to 4,5 MPa;
resistance of concrete
adhesion and cutting strength 1-3MPa
can be improved; when • Weakness: shrinkage risk; rough and
spraying in wet method
uneven surface; act of the thick
• Reinforcement: welded
structures as floors; dry method –
reinforcement mesh
dust; high amount of waste concrete
more than 100 mm
due to splashing; higher price per
cubic meter
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
8
Execution of work
• Sprayed surface: no dirt, and
• Processing of the surface:
not grease; no segregation;
timber, steel and sponge
right moisture content –
grinding; as soon as possible
adhesion; not completely dry
after spraying; moist curing for
and not frozen
7…14 days
• Concrete: aggregate to
cement ratio 3...5; moisture
content 3...5%
• Spraying of concrete: distance
from nozzle to surface
http://www.tunnel0.5…1,2 meters;
online.info/imgs/27339742_2b62bfa025.jpg
perpendicular to surface
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
9
Execution of work
• Spraying technique
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Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
10
Applications of shotcrete and
economy
• Rock strengthening and
tightening
• Repair and rectification of
the concrete structures
• Rectification of the stone
structures
• Arcs and shells structures
• Suspended concrete
ceilings
• Fire and corrosion
protection of the steel
structures
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Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
11
Vacuum processed concretes
• Remove excess of water
• Vacuum concrete equipment:
and entrapped from
pump and compressor 0.8 …0.9
concrete before its
atm; vacuum pads; filters
hardening
installed on the pipes; concrete
equipment and surface grinding
• Additional dehydrating of
apparatus
concrete with the help of
vacuum reduces a water to
cement ratio and decreases
its porosity
• Usually finishing of the
surface is possible just after
vacuum processing
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
12
Vacuum processed concretes
• Vacuum pads: tight nylon filter cloth;
tight places synthetic mesh- network
suction canalization; withstands
vacuum up to 80…90 kN/m2
• Vacuum treatment of concrete:
1…5% of compaction; 20…25%
reduction of water; 1% reduction of
the cement amount (removed
together with water); after processing,
to the pores to remain underpressure
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
13
Vacuum processed concretes
• Properties of vacuum processed • Special requirements for
concretes: enhanced early
vacuum processed
strength development; shorter
concrete: fine aggregate
formworks circulation time; initial
amount must not be too
strength 0.1…0.15 MPa; allows
large; risk of filter blocking;
light traffic; compression strength
aggregates preferably
increases mainly near the
circular; not too fluid
vacuumed surface; increase of
consistency; the segregation
can occur already during
flexural strength; enhancement
transportation – 2..3 sVB;
of abrasion resistance; better
usage of fly-ash or blast
compaction; reduction of
furnace slag is not
shrinkage; increase of the
recommended
modulus of elasticity.
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
14
Vacuum processed concretes
• Disadvantages: higher demand for
manpower; application of expensive
devices
• Applications: slabs (vertical and
hollow-core); supports for bridges,
columns, walls; massive structures;
concrete elements; placing of
concrete of the inclined surfaces;
water tight structures; repairmen of
damaged concrete structures; to
the large industrial buildings, stores,
parking etc.; seamless floors
http://civilblog.org/wpcontent/uploads/2014/07/vacuum
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Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
15
Placing of concrete under water
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Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
16
Tremies
• Concrete properties: slump
1..3; max. aggregate size 32
mm; cement content more
than 350kg/m3; concrete can
not easy to segregation; in the
beginning the extra cement
50kg/m3; normally used
plasticizers and retarder;
difficult control of the
properties; no vibration; reason
to make 25% stronger concrete
than suggested by the loads
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
17
Tremies
• The reinforcement should not be used (not
recommended): casting climbing speed is less than 30
cm/h. in general 1m/hour or even 6..10m/hour; casting
breaks are under 30 min; the distance of the pipes from
the moulds below 2.5 m; distance of the pipes in the
case of several pipes is under 5 meter and max 2 times
thickness of the cast plate
• Concrete production and transportation capacity must
be calculated and be done carefully according to:
weather conditions; traffic; breaking equipment
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
18
Pumping
• Pumping of concrete
needs assistance of
scuba divers who does
the actual work.
• Furthermore, special
equipment and
monitoring is needed.
• In general very
expensive and
• problematic method
used in special
circumstances.
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
19
Horizontal casting with
transportation tube
• Similar to tremie method
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Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
20
Injection methods (Grouted preplaced aggregate)
• In this method the
formwork is filled with
aggregates and injection
of cement paste under
the water between
aggregates is done.
http://www.jfbrennan.com/Portals/123881/images/
Vinyl%20Sheet%20Piling%202-resized-600.jpg
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
21
Bag work
• In this method cement
and aggregates filled
fabric bags are
immersed in water.
• Used mostly for
repairs.
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Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
22
Progressing methods
• The method is
applicable to
maximum
depth of 0.5
m.
• In this method
new concrete
will is dropped
to the fresh
concrete
which is over
the water.
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
23
Self compacting concrete
• Self compacting concrete
was developed in the 80s
in Japan.
• The most characteristic
feature of these types of
concretes is its capability
flow and no need for any
kind of additional
vibration.
• The mix design is
characterized by
increased mounts of fines
and application of fillers.
• The most commonly used fillers
are fly ash, limestone filler and
quartz fillers.
• The strength and durability are
comparable with conventional
concretes
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
24
Pumped concrete
• Concrete pumps; a)
mechanical, b) squeezing
pump
• Hydraulic concrete pump
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
25
General
• Pumping of concrete is one
of the most commonly used
transportation methods for
concrete at the building
site.
• The most common
applications are foundation,
industrial structures,
tunnels and bridges, soil
structures, dams and
power plants and also
small size structures.
• Pumped concrete has to full
fill certain requirements
concerning workability,
cohesiveness which is crucial
for this type of transportation.
• There are three types of
pumps which are commonly
used; mechanical, hydraulic
and so called squeezing
pump.
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
26
General
• Truck and trailer mounted
concrete pumps
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
27
General
• One of the main
advantages of pumping
of concrete is the
efficiency.
• Theoretically it is
possible to pump 5060m3/h.
• In practice however, it is
usually between 20 and
45 m3/h.
• Normal range is more
than 20m vertically and
25 m horizontally.
• The possibility to pump concrete to
difficult inaccessible places.
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
28
Usage
• Initially some of the
cement paste is lost to
lubricate the pipes.
• Always at the
beginning of pumping
the range is the
biggest and decreases
with time.
• The pipes can be
cleaned
• using water with
rubber balls.
• The particle size distribution of
aggregates should be optimized
towards the higher packing density;
the lowest possible amount of voids
between them.
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
29
Usage
• Cement used for
pumped concrete
should not be too
fine due to
increasing
cohesiveness of the
mix resulting in
“sticky” consistence.
• If cement is too
coarse there might
persist problems
with flow ability.
• The optimum amount of cement varies
between 250-300 kg/m3
• Due to pumping the amount of air in
concrete might drop by up to 25%
• Pumping did not show any influence on
mechanical properties however,
shrinkage appeared to be slightly higher.
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
30
Learning Summary
• Shotcrete
• Vacuum processed
concretes
• Placing of concrete
under water
• Self compacting
concrete
• Pumped concrete
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/ideapark_oulu.jpg
Rak-82.2121 Production Technology of Concrete Structures (4 cr)
Fahim Al-Neshawy & Esko Sistonen
Autumn 2015
31