Criteria for Design & Construction Concrete – Civil QC Notes Part-2

This article is about Criteria for Design and construction concrete of concrete structures as per SAES-Q-001 or international codes and standards.

Criteria for Design & Construction Concrete [SAES-Q-001]

Following specifications and standards for designing and constructing concrete structures, particularly focusing on prestressed concrete, structural concrete, and non-structural concrete. Here’s a summarization of the key points:

1. Prestressed Concrete:

• Foundation: The Prestressed Concrete Institute (PCI) Design Handbook is the basis for the design and analysis of precast, prestressed concrete structures, with specific modifications highlighted below.
• Compressive Strength: The minimum 28-day design compressive strength is 28 MPa (4,000 psi), and the release strength for a prestressed unit is 24.1 MPa (3,500 psi). More than 4,000 psi compressive strength can be implemented in the design of precast concrete.
• Prestressing Tendons: Uncoated, 7-wire “low relaxation” strand should adhere to ASTM A416. Grade 250 is to be used unless Grade 270 is indicated.
• Strands: The use of epoxy-coated strands is prohibited for prestressed concrete.
• Camber and Deflection: Flexural members must be designed with adequate camber to counteract deflection under superimposed dead loads.
• Cement Content: A minimum of 350 Kg/CM of concrete is specified for precast concrete, with no maximum limit imposed.

2. Structural and Non-Structural Concrete:

• Structural Concrete: Pertains to all reinforced concrete including those with minimum reinforcement for temperature and shrinkage control, possessing a 28-day design compressive strength of 28 MPa (4000 psi) as per ASTM C39.
• Non-Structural Concrete: Refers to unreinforced concrete having no significant structural value, such as lean concrete for sub-slabs and concrete for duct banks. It has a minimum 28-day design compressive strength of 14 MPa (2000 psi).

3. Paving Slope and Structural Protrusion:

• The slope to the catch basins or trenches must not be less than 1:65 (1.5%), and the maximum drop to catch basins from the high point of paving is 200 mm.
• When foundations protrude through the paving, 12 mm diameter reinforcing bars, 800 mm long, are mandated to be placed diagonally in the paving at all interior corners.

These guidelines ensure that concrete structures are designed and constructed to meet specific durability, strength, and structural integrity standards, thereby fostering reliability and longevity in construction projects.

Table 1 – Exposures Types

Exposure	Cement Type	Steel	Description
I	I	FBE	Concrete members exposed to negligible sulfate SO4  (less than 0.1% by weight of soil and less than 150 ppm in ground water )¹ and any of the following: · Water with total dissolved solid more than 1000 PPM. · Chemicals. · Within 5 km from the shore lines. · Where water table is less than one meter below the bottom of the foundation. · Sewage treatment plant.
II	V	FBE	Sulfate content is more than or equals 0.1% by weight of soil or more than or equals 150 ppm in the ground water and the chloride content is less than what is specified in exposure III.²
III	I+Silica Fume³	FBE	· Water soluble sulfate content more than 0.1% and water soluble chloride more than 0.1% by weight of soil. · Sulfate more than 1500 ppm and chloride more than 500 ppm in the ground water.
IV	I+Silica Fume	Uncoated	Sulfur pits
V	I	Uncoated	With negligible sulfates and chlorides (less than 0.1% each) by weight of surrounding environment.  e. g., Interior roof slabs

1. Sulfates and Chlorides Determination:

• Sulfates and chlorides levels in concrete should be determined following AASHTO T290 and AASHTO T291 test methods or their equivalents.

2. Cement and Rebar Specifications:

• If sulfate content is below 1500 ppm and chloride is above 500 ppm, Type I cement and Fusion Bonded Epoxy (FBE) coated rebars must be used.
• In situations where there is an absence of geotechnical investigation reports or soil chemical analysis, it is advised to use epoxy coated reinforcement and Type V cement.

3. Exemptions and Limitations:

• Silica fume cement usage is confined to structural concrete members. Certain constructions like plant paving, sidewalks, erosion protection paving, and slabs reinforced with welded wire fabric are exempted from the use of silica fume.

Minimum Concrete Cover:

• Table 2 would be specifying the minimum concrete cover, measured from the outermost rebar (tie bar), to be provided for reinforcement in cast-in-place concrete structures.

• The specifications and decisions related to cement type and rebar coating are based on the geotechnical investigations as required by SAES-A-113 or the availability of prior reports indicating soil chemical composition.

• These guidelines are pivotal to ensure the longevity and structural integrity of the concrete structures by mitigating the potential adverse effects of chemical components and ensuring the structures are built with materials best suited to the specific environmental and soil conditions they are subjected to.

Table 2 – Minimum Concrete Cover

Concrete Structure	Minimum Cover (mm
Concrete cast against and permanently exposed to earth (including foundations over a sub-slab)	75
Formed concrete exposed to earth or weather. Supporting Process Equipment. Buildings, walkway platforms, stairs, AC pads.	75 50
Concrete not exposed to weather nor in contact with ground (which can be inspected from all sides): Beams, columns          Slabs, walls, joists	50 25
Concrete exposed to sea water, raw water or sewage	75
Between reinforcement and anchor flange/pipe within pipeline anchor blocks	100
Concrete slab over 50 mm sub-slab	50
Sidewalks, walkways, etc.	50

1. Embedded Items:

• Aluminum items, such as conduits and pipes, must be coated to prevent reactions with concrete when embedded in structural concrete.

2. Placing Concrete:

• Limitations are placed on the free drop of concrete to prevent segregation, especially around reinforcing materials. The free drop is restricted to less than 1 meter.

3. Curing:

• Concrete curing should adhere to specified standards, including continuous water curing until achieving 70% of the specified strength, following ACI 305R and ACI 308 recommendations, with some modifications. The use of steam curing for precast concrete is also allowed as per ACI 517.

4. Protection and Coating:

• A plasticized sheet vapor barrier, or alternatives like lean concrete or coatings like coal tar or bitumen, are required under and around concrete structures to prevent moisture intrusion and direct contact with earth. Exceptions and specific requirements based on the soil contamination level are noted.

5. Pumped Concrete:

• Slump and cylinder tests are mandated to be taken at specific points when concrete pumps are used to ensure the consistency and quality of the concrete mix.

6. Concrete for Underground Ducts:

• Specific coloring and standards are set for underground duct envelopes, adhering to SAES-T-911, SAES-P-104, ACI 212.3R section 6.6, and ASTM C979.

7. Testing and Inspection:

• Contractors are required to engage Saudi Aramco approved testing agencies for field and laboratory testing, including compressive tests, slump tests, unit weight, air content, and fresh concrete temperature, conforming to 09-SAMSS-097.

8. Implications:

• These standards and specifications are critical to ensure the durability, integrity, and longevity of the concrete structures. They are intended to mitigate the risk of structural failure and to ensure that the structures are resilient to environmental conditions and usage demands.

9. Commentary Note:

• Particular attention is given to coating and protection specifications to prevent deterioration due to contact with specific soil types or contaminants, and certain exemptions are made based on practical considerations.

10. Special Requirements:

• Special requirements, such as the prohibition of the use of APCS-10 where the soil is contaminated with hydrocarbons, are also noted to cater to specific environmental and structural needs.

Table B – Acceptance Criteria for Mixing Water

Test	Frequency of Test	Max.	Min.
TDS	Weekly	500 ppm	N/A
pH	Weekly	8.0	6.0

Truck Mixing and Concrete Discharge:

1. Timing & Revolutions:

• Concrete must be discharged within 90 minutes of mixing water introduction or before 300 revolutions of the drum.
• If not, discharge should be completed within three hours or before 600 revolutions after the introduction of cement to aggregates, whichever occurs first.

1. Temperature Control:

• Concrete delivered at a temperature exceeding 32°C or failing to maintain a temperature of 32°C until used shall be rejected.
• Replacement of the rejected concrete shall be at the expense of the Manufacturer.

1. Reporting & Documentation:

• The location of the Batch Plant and the Job Order (JO) Number for the Project must be documented.
• The time of leaving the Batch Plant must also be recorded.

Concrete Test Cylinders:

• Number & Age:
• 1 cylinder for 3 days.
• 1 cylinder for 7 days.
• 2 cylinders for 28 days.

Test Report:

• Required Data:
• Each test sample should be documented with the Name of Project and Job Order (JO) for the Project.
• Other necessary data include the slump in millimeters, ambient air temperature in ºC, concrete temperature in ºC, and % Air when air entrainment is used.

Implications:

• These stipulations help in maintaining the quality and integrity of the concrete by controlling the mixing and discharge conditions.
• Strict documentation and reporting of each batch ensure traceability and accountability.
• Regular testing and maintaining a record of concrete samples ensure compliance with quality standards and early detection of any discrepancies in the mix.

Application:

• These guidelines seem applicable in construction projects where high-quality control and precision are required in concrete preparation and placement, ensuring the long-term durability and integrity of the constructed structures.