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Environmental Engineering Concrete Structures
This document is issued by PED, SABIC E&PM, Jubail Industrial City, Kingdom of Saudi Arabia. The information contained
in this document is the confidential property of SABIC. It cannot be disclosed, copied or used for any purpose without
approval from SABIC. If you are not authorized to posses this document, please destroy it immediately.
Classification: General Business Use
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ENGINEERING STANDARD
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REV. NO.
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DATE
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PAGE
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CONTENTS
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
SCOPE ........................................................................................................... 2
REFERENCES ............................................................................................... 3
DEFINITION ................................................................................................... 4
GENERAL ....................................................................................................... 4
DESIGN CRITERIA ........................................................................................ 4
5.1 General ................................................................................................... 4
5.2 Design Loads .......................................................................................... 4
5.3 Load Combinations ................................................................................. 5
5.4 Buoyancy ................................................................................................ 6
5.5 Sliding and Overturning .......................................................................... 7
5.6 Crack Control .......................................................................................... 7
DESIGN CONSIDERATIONS ........................................................................ 8
6.1 Foundation System ................................................................................. 8
6.2 Bottom Slab............................................................................................. 8
6.3 Wall ......................................................................................................... 8
JOINTS ........................................................................................................... 9
7.1 General ................................................................................................... 9
7.2 Expansion Joints ..................................................................................... 9
7.3 Contraction Joints ................................................................................... 9
7.4 Construction Joints ............................................................................... 10
CONCRETE MIX REQUIREMENTS ............................................................ 10
PROTECTIVE LININGS AND COATINGS ................................................... 11
HYDRAULIC CONSIDERATIONS ............................................................... 11
CONSTRUCTION ......................................................................................... 11
TIGHTNESS TESTING................................................................................. 12
ENVIRONMENTALLY ENGINEERED CONCRETE SLABS ....................... 12
REVISION HISTORY.................................................................................... 13
TABLE
1.
Table I
Load Combinations ................................................................................. 6
Tabel II
Stability Factor ........................................................................................ 7
Tabel III
Maximum Allowable Crack for Various Exposure Conditions ................. 8
Scope
Classification: General Business Use
Environmental Engineering
Concrete Structures
NUMBER
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REV. NO.
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ENGINEERING STANDARD
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3 OF 13
This standard is for the design of environmental engineering concrete structures, for example waste
water holding basins, cooling tower basins, waste water treatment basins, sumps, API separators,
neutralization pits, manholes and similar structures.
2.
References
Reference is made in this standard to the following documents. The latest issues, amendments, and
supplements to these documents shall apply unless otherwise indicated.
Any conflict(s) between this standard, SES and industry standards, engineering drawings, and contract
documents shall be resolved at the discretion of SABIC.
SABIC Engineering Standards (SES)
B01-E01 Design Criteria for Concrete and Steel Structures
B51-S01 Cast-In-Place Reinforced Concrete
B52-E03 Sea Water Intake Structures
C04-E02 Containment for Storage Tanks, Lined Retention and Evaporation Ponds
American Concrete Institute (ACI)
318
Building Code Requirements for Structural Concrete and Commentary
350M
Code Requirements for Environmental Engineering Concrete Structures and Commentary
350.1M
Specification for Tightness Testing of Environmental Engineering Concrete Containment
Structures and Commentary
350.2R
Concrete Structures for Containment of Hazardous Materials
350.4R
Design Considerations for Environmental Engineering Concrete Structures
American Society of Civil Engineers (ASCE)
ASCE/SEI 7-10 Minimum Design Loads for Buildings and Other Structures
American Association of State of Highway Transportation Officials (AASHTO)
HB-17
Standard Specification for Highway Bridges
Portland Cement Association (PCA)
IS072
Circular Concrete Tanks Without Prestressing
Royal Commission for Jubail and Yanbu (RC)
Royal Commision Environmental Regulation (RCER)
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3.
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Definition
Environmental Engineering Concrete Structures. The concrete structures intended for conveying,
storing, or treating water, wastewater or other nonhazardous liquids and for the secondary containment
of hazardous liquids or solid waste.
4.
5.
General
4.1.
Due to potential environmental aspects, Environmental Engineering Concrete Structures create
concerns uncommon in other concrete structures in contact with water. When the environmental
aspects become a concern, serviceability in terms of limited deflections and cracking, durability,
and permeability shall become more critical.
4.2.
Sumps and manholes vary in size, shape, and depth. Floors of these structures are usually
sloped and may have a basin for cleanout purposes. These structures should be covered with
concrete slab or checkered plate depending on storage, process type and frequency of
maintenance etc.
Design Criteria
5.1
General
5.1.1 Environmental engineering concrete structures shall be designed and constructed in
accordance with ACI 350M, 350.2R, 350.4R and Royal Commission Environmental Regulations.
5.1.2 General hazardous material containment structures shall be designed according to ACI
350.2R.
5.1.3 Secondary containment with the provision of leak detection system shall be provided to
hazardous material containment structures as per Royal Commission Environmental
Regulations (RCER). Refer to SES C04-E02 and RCER for details.
5.1.4 For the design of circular concrete tanks, procedures and suggested details shall be as
per Portland Cement Association (PCA) IS072.
5.1.5 For the environmental structures supported on the piling, ACI 350M shall be referred
only for the applicable portion of the pile in contact with the water.
5.1.6 The environmental concrete structures shall be analyzed and designed with the
approved software.
5.1.7 For multicell fluid-containment structures, the effects of combinations of empty and full
cells shall be considered in the design.
5.2
Design Loads
5.2.1 The following loads shall be considered in the design of environmental engineering
concrete structures. Refer to ACI 350M, 350.4R, SES B01-E01 and ASCE 7-10 for the details.
a.
Dead Loads (D)
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b.
Live Loads (L)
c.
Loads due to Weight and Pressure of Fluids (F)
(refer to ACI 350.4R for the densities of chemicals)
d.
Loads due to Weight and Pressure of Soil, Water in Soil (H)
e.
Wind Load (W)
f.
Earthquake Load (E)
g.
Thermal Loads (T)
h.
Other Loads
(i) Traffic Loads
(ii) Impact and Vibration Loads
(iii) Loads at Pipe Penetrations, Gates and Clarifies
(iv) Internal Pressure and Vacuum
(v) Differential Settlement
Load Combinations
5.3.1 The basic load combinations for the analysis and design of environmental concrete
structures shall be as per Table I.
5.3.2
walls.
Internal hydrostatic pressure shall be checked without soil pressure acting on outside of
5.3.3 External earth and surcharge pressure and buoyancy shall be checked with pit empty
condition.
5.3.4 External water pressure is from high ground water conditions and floods. The upward
pressure of water or uplift, if exist, shall be taken as the full hydrostatic pressure over the entire
bottom slab and it shall be measured from the underside/ bottom of the slab.
5.3.5 Where the vehicles have access adjacent to walls, a surcharge load representing
vehicle and traffic load shall be considered in accordance with AASHTO HB-17.
5.3.6 Thermal loads shall be based on design atmospheric temperature range or fluid
temperature whichever is critical.
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Table I
Load Combinations
LOAD COMBINATION
LOAD
COMB.
NO.
DESCRIPTION
SERVICE LOADS 1
(Allowable Stress Design)
FACTORED LOADS 2, 3 4
(Strength Design)
1a
Dead Load + Fluid Pressure
D + F
1. 4(D + F)
1b
Dead Load + Soil Pressure
D + H
1. 2D + 1 .6 H
2a
Dead Load + Fluid Pressure +
Thermal Load + Live Load + Soil
Pressure
D +F + T + L +H
1. 2(D +F +T ) + 1.6(L+H)
2b
Dead Load + Fluid Pressure +
Thermal Load + Live Load
D + F + T + L
1. 2(D +F +T ) + 1.6L
3a
Dead Load + Fluid Pressure +
Soil Pressure + Live Load
D + F + H + L
1. 2(D + F) + 1 . 6H + L
3b
Dead Load + Fluid Pressure +
Live Load
D + F + L
1. 2(D + F) + L
3c
Dead Load + Live Load + Partial
Wind
D + L + 0. 3W
1. 2D + 1.6L + 0.5W
4a
Dead Load + Fluid Pressure +
D + F + H + 0. 6W + 0. 75 L
Soil Pressure + Wind + Live Load
1. 2( D + F) + 1 . 6 H + 1 .0 W + L
4b
Dead Load + Fluid Pressure +
Wind + Live Load
D + F + 0 . 6W + 0 .7 5 L
1. 2( D + F) + 1 . 0W + L
5a
Operation Weight + Soil Pressure
+ Live Load + Earthquake
D + F + H + L + 0. 7 E
1. 2(D + F) + 1 . 6H + L + 1. 0 E
5b
Dead Load + Fluid Pressure +
Live Load + Earthquake
D + F + 0 . 75 L + 0. 7 E
1. 2(D + F) + L + 1 .0 E
6a
Dead Load + Fluid Pressure +
Soil Pressure + Wind
0. 8 5D + F + H + 0 . 6W
0. 9D + 1 .2F + 1 .6 H + 1. 0W
6b
Dead Load + Fluid Pressure +
Wind
0. 8 5D + F + 0. 6W
0. 9D + 1 .2F + 1 .0W
7a
Dead Load + Fluid Pressure +
Soil Pressure + Earthquake
0. 8 5D + F + H + 0 . 7 E
0. 9D + 1. 2F + 1. 6H + 1 .0 E
7b
Dead Load + Fluid Pressure +
Earthquake
0. 8 5D + F + 0. 7 E
0. 9D + 1. 2F + 1. 0 E
Notes:
(1) Load combinations for allowable stress design shall be used in conjuction with Appendix I of ACI 350M.
(2) Load combinations for strength design shall be used in conjunction with chapter 9 of ACI 350M.
(3) Both the full value and the zero value of L and F shall be used to determine most severe condition.
(4) Required strength (U) for other than compression controlled sections shall be multiplied by the environmental
durability factor (Sd). This durability factor shall not be used for designs using service loads and permissible
service load stresses (Allowable Stress Design). Refer to ACI 350M for details.
5.4
Buoyancy
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5.4.1 A minimum safety factor of 1.25 against flotation shall be used for pit empty condition.
Wall or slab thickness may be increased or an apron (toe) added to resist buoyant effects.
5.5
Sliding and Overturning
5.5.1 Sliding and overturning can occur to environmental structures and to individual
components of environmental structures due to the unbalanced soil conditions, unbalanced
liquid levels, or wind or earthquake effects.
5.5.2 The minimum safety factor against sliding, minimum base area to remain in
compression, and the bearing capacity safety factor shall be as per Table II.
Table II
Safety Factors for Stability
SAFETY FACTOR
AGAINST SLIDING
MINIMUM BASE
AREA in
COMPRESSION
MINIMUM FOUNDATION
SAFE BEARING
CAPACITY FACTOR
Usual 3
1.5
100%
Unusual 1, 3
1.33
75%
As Recommended in
Geotechnical Investigation
Report
Earthquake 2
1.10
LOADING
CONDITIONS
Resultant Within the
Base
1.0
Notes:
(1) The “unusual” condition includes temporary construction conditions and worst-case fluid levels.
(2) Low safety factor was established based on short term nature of earthquake load, the ability of soil
to resist higher short term loads, and rarity of sliding and overturning failures in earthquakes.
(3) Safety Factor in case of Wind Load shall be reduced to 1.0 in line with ASCE 7-10.
5.6
Crack Control
5.6.1 Provisions of ACI 318 and 350M shall be followed to achieve a crack controlled section.
The Table III should be taken as a reference if provisions that prevents direct exposure of
concrete with the aggressive environment are not taken and/or that project specific crack control
targets are not specified.
5.6.2 Concrete members shall be properly sized and reinforced to eliminate cracks occurring
as a result of drying shrinkage (volumetric change), direct or flexural stress. Drying shrinkage is
inherent in concrete but random cracking shall be controlled with proper joint design.
Table III
Maximum Allowable Crack for Various Exposure Conditions
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Exposure Conditions1
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Maximum Allowable Crack
Width (mm)
Chemical exposure
(Sulfate Exposure: S1, Corrosion Protection Exposure: C2)
Corrosive chemical and aggressive environment
(Sulfate Exposure: S2)
Seawater, seawater spray, alternate wetting and drying and (Sulfate
Exposure: S3)
Water-retaining structures and (pH < 4.5)
0.25
0.20
0.15
0.10
(1) Exposure conditions shall be as per ACI 318.
6.
Design Considerations
6.1
Foundation System
6.1.1 The combination of shallow foundation and deep foundation (i.e. piles) systems is not
allowed for environmental engineering concrete structures.
6.1.2 If the structure rests on more than one kind of soil, necessary provisions shall be made
to prevent differential settlement.
6.2
Bottom Slab
6.2.1
Bottom slab shall be a minimum of 300mm thick.
6.2.2
Reinforcing shall be double layer and be placed continuously across the entire slab.
6.2.3 Minimum slab reinforcing shall be that required for shrinkage and temperature stresses
according to ACI 350.
6.2.4
6.3
Minimum bar size shall be 12 mm and maximum spacing shall be 250 mm.
Wall
6.3.1 Walls shall be designed for lateral earth pressure based on the at-rest (Ko) or active
state (Ka) condition depending on the likelihood of the wall to move. If the position of a wall is
fixed, the earth pressure will likely be a value similar to the at-rest earth pressure. Walls of pits
analyzed using 2-way bending typically use at-rest pressures, while cantilever walls are usually
designed using active pressures. Appropriate pressure coefficients shall be obtained from the
geotechnical report.
6.3.2 Reinforced concrete walls shall be a minimum of 200 mm thick with single layer of
reinforcement.
6.3.3
Minimum thickness of wall shall be 300mm for walls of height 3 m or more.
6.3.4
Walls 250 mm or thicker shall have reinforcement on each face.
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6.3.5 Minimum wall reinforcement, vertical and horizontal, shall be in accordance with ACI
350M.
6.3.6
Minimum bar size shall be 12 mm and maximum spacing shall be 250 mm.
6.3.7
Additional bars shall be placed around openings.
6.3.8 Reinforced bars shall be protected from corrosion either with epoxy coating or by
application of cathodic protection.
7.
Joints
7.1
General
7.1.1
Joints shall be designed in accordance with ACI 350.4R and 350M to prevent any leaks.
7.1.2 Waterstops shall be installed at the joint between the slab and the wall, and at
expansion, contraction and construction joints for liquid tightness.
7.1.3 Materials used for waterstops to stop flow of liquids or gases shall be able to sustain
movement deformations without failure and shall be resistant to temperature and chemical
effects.
7.1.4 Shear keys shall be provided as required at the joints, and between the slab and the wall
for water tightness.
7.1.5 Joints shall be sealed with an appropriate joint sealant, which is resistant to the
contained liquid or sludge, to prevent chemicals from reaching the reinforcing bars.
7.2
Expansion Joints
7.2.1
Expansion and isolation joints shall be designed in accordance with ACI 350.4R.
7.2.2 Expansion joints tend to have the most problems with long-term leakage in liquidcontainment structures. Where possible, their usage should be limited to very long structure over
45m in length or where abrupt changes in the structure configuration occur.
7.2.3 Temperature of contained liquid shall be taken in consideration when designing the
width and spacing of expansion joint.
7.3
Contraction Joints
7.3.1
Contraction joints shall be designed in accordance with ACI 350.4R.
7.3.2 Contraction joints are used to dissipate shrinkage stresses by inducing cracking at
preselected locations.
7.3.3 Walls and slabs shall be designed with contraction joints at minimum 6 m to maximum 9
m centers, but shall be less than 48 times the thickness of slab.
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7.4
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Construction Joints
7.4.1
Construction joints shall be designed in accordance with ACI 350.4R.
7.4.2
Construction joints provide stopping places during construction.
7.4.3 Construction joints should be avoided in environmental engineering concrete structures.
Where necessary, they shall be designed to prevent any leakages.
7.4.4 Construction joints shall be located to conform to the jointing pattern and align with
contraction or expansion joints. Reinforcing is continuous through construction joints.
8.
Concrete Mix Requirements
8.1
The cast-in-place concrete shall be in accordance with SES B51-S01 and ACI 350M.
8.2
The minimum concrete strength shall be 30Mpa.
8.3
Concrete for environmental structures shall be impervious of low permeability and good
durability to prevent seepage and cracking, and to provide adequate protection to the
reinforcing.
8.4
Concrete mix and admixtures shall demonstrate low permeability, acceptable durability,
workability, compactability, and finishability characteristics. The limits on the percentage of
admixtures for the durability of environmental structures need to be considered.
8.5
Trial mixes shall be made with the admixture and job materials at temperatures and humidity
anticipated on the job to determine the effects of the admixture on the properties of fresh and
hardened concrete.
8.6
Concrete slump shall be arrived from trial mix to produce a working slump range from 100 mm to
150 mm.
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Protective Linings and Coatings
9.1
Environmental engineering concrete structures ,such as but not limited to the following, shall be
protected when exposed to chemical attack.
a. Water treatment plants,
b. Domestic and industrial wastewater treatment plants,
c. Storage tanks and reservoirs,
d. Water and wastewater pump stations,
e. Sewers, manholes, and junction chambers.
9.2
Protective linings and coatings shall be used to prevent deterioration of the concrete caused by
the various corrosive products and by products produced in petrochemical plants.Manufacturer’s
recommendations and application procedures shall be referred for each specific use.
9.3
Available linings and coatings and their degree of protection for a given commodity shall be
investigated through coordination between structural and process engineering disciplines.
9.4
Coating of concrete structures shall be as per SES T01-S01.
9.5
For severe corrosive environments and high temperatures, use of acid brick lining, fire brick
lining , acid resistant tiles or double wall pits shall be considered.
10. Hydraulic Considerations
10.1 Hydraulic factors unique to the particular function of the environmental engineering structures
shall be considered in the layout and design, which will usually be a joint effort of the Process,
Mechanical, and Civil/Structural engineering disciplines.
10.2 There are definite hydraulic factors to be considered in the design of a sump in order to prevent
turbulence in the sump pump. The ideal flow to a pump is a straight channel with no obstructions
or changes in direction. Water should not flow past one pump to reach another. Refer to SES
B52-E03 for hydraulic design guidelines.
11. Construction
11.1 Construction of environmental structures shall be in accordance with SES B51-S01 and ACI
350M.
11.2 Form ties with water stop collars shall be used in walls intended to be liquid-tight. The filling and
patching of tie holes is essential for long-term durability.
11.3 The concrete that will be in contact with water or wastewater shall have smooth surfaces to
minimize flow resistance.
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11.4 Concrete shall be properly and completely cured in accordance with SES B51-S01. Water based
curing is very important for these structures and should be strictly adopted. Where possible,
extended moist curing is recommended for lower permeability.
11.5 Provision shall be made during construction to prevent flotation of basins prior to backfilling.
Flotation may be prevented by the use of openings or check valves
12. Tightness Testing
12.1 Liquid-containment environmental engineering concrete structures shall be tested for liquidtightness before backfilling around the structure and application of any liners or coatings.
12.2 Tightness testing shall comply with ACI 350.1M.
13. Environmentally Engineered Concrete Slabs
13.1 An environmentally engineered concrete slab is a slab on grade containing or conveying any
substance or contaminated water that can potentially impair groundwater use.
13.2 Environmentally engineered concrete slabs shall comply with Appendix H of ACI 350M.
13.3 Special consideration shall be given to cracking, deflection, durability, permeability, and joints.
13.4 The joint material shall be compatible with the material being stored or contained in the
structure.
13.5 The minimum thickness shall be 150 mm for conventional cast-in-place environmental concrete
slabs.
13.6 The minimum ratios of shrinkage and temperature reinforcement shall be in accordance with ACI
350M. The amount of reinforcement that shall be provided is a function of the distances between
joints. In some cases, it may be more economical to use additional reinforcing and reduce the
number of joints.
13.7 A design that uses a shrinkage-compensating type (K) cement or post-tensioned reinforcement
can eliminate the need for joints in an operating area.
13.8 Proper sub-base selection and preparation are crucial to minimize cracking in environmentally
engineered concrete slabs. Requirements for large slabs on compressible soils shall be
calculated as if the slabs were beams and girders on elastic supports.
13.9 The concrete mix shall be proportioned to reduce permeability and meet coating requirements
as necessary. The most basic and least expensive way to reduce shrinkage and permeability is
to use the least amount of water and cement that will meet the requirements for compressive
strength and produce a consistent workable mix.
13.10 Concrete shall be properly and completely cured in accordance with SES B51-S01. Water based
curing is very important for these structures and shall be strictly adopted. Where possible,
extended moist curing is recommended for lower permeability.
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14. Revision History
Revision No.2,
June 2013
Restructured Completely
Major Revision as per ACI 350
Updated : References and Design Requirements.
Added
: Table I and II
Added
: Environmentally Engineered Concrete Structures
Deleted : Design Examples.
Revision No.3,
June 2017
Updated : References
Refined : Section 4 and 6.1
Added
: Clause 5.1.7 and Table III
Revised : Table I (Load Combinations and Notes)
Clause 6.2.4 (Maximum bar spacing)
Revision No.4,
March 2021
Updated: Table II