Concrete Specifications and Cover Standards

Concrete Specifications

• Allowable concrete temperature during delivery and placement should be a maximum of 32°C.
• Concrete specimens should be subjected to final curing with free water maintained on their surfaces at all times at a temperature of 23°C ± 2°C.
• The compression testing machine should be calibrated once in 12 months.
• When the extent of damaged coating exceeds 2% of the surface area of the coated steel reinforcing bar in any 0.3–m (1–ft) length, the coated bar should be rejected.
• Concrete should be discharged from the mixer within 90 minutes or 300 revolutions of the mixer from the time the mixing water was added.

Concrete Cover and Clear Distances

• Minimum concrete cover for permanently exposed concrete structures to earth (including foundations over a sub-slab), weather supporting process equipment foundations should be 75mm.
• Minimum clear distance from anchor bolts or sleeves to the edge of concrete should be 100mm.
• The minimum anchor bolt diameter should be 20mm unless specified by the vendor for small equipment or for the anchorage of small miscellaneous items, e.g., of base or sub-base.

Prime Coat Specifications

• Prime coat should only be applied when the surface to be treated is dry and the atmospheric temperature is 16°C or above.
• Prime coat should be applied uniformly to the surface of the base using a pressure distributor at a rate between 0.65 and 1.75 liters/m2.
• The prime coat should be applied at a temperature between 50°C and 80°C for MC-70.
• The prime coat should be applied at a temperature between 65°C and 105°C for MC-250.

Tack Coat Specifications

• Tack coat should be applied on paved surfaces and vertical surfaces which will be in contact with the asphalt paving by means of a bitumen distributor at a maximum rate of 0.25 liters/m2.
• Tack coats should not be placed during rain, on a moist surface when the air or surface temperature is below 16°C.
• If application of the surface course is delayed by more than 3 days or if dirt, sand, or other impurities have contaminated the tack coat, a new tack coat should be applied after the original one has been swept clean.

Core Measurements and General Requirements

• Measurement of any cores should not be less than 10mm or 15% of the design thickness, whichever is less.
• Core compaction requirements should be equal to or greater than 96% of Marshall density (ASTM D-2726/ASTM D1559) using samples taken at the road site.
• Minimum Compressive Strength of pre-packaged cement-based grout at 28 days should be 5,000 psi.
• Standard temperature of mix should be 23°C ± 2°C when test cubes are cast.
• The compressive strength of the grout should be a minimum of 3,500 psi at 7 days of age.
• Grout should be given a continuous water cure (covered by wet burlap and 0.15 mm polyethylene) for a minimum of 7 days.
• Grout placement should be within 30 minutes at 32°C minimum working time, after mixing.

Public Sewer Specifications

• The maximum distance between manholes for public sewers should be 15m.
• Public sewers that are parallel to potable water lines should be separated from such lines by a minimum distance of 2m and shall be located below the potable water lines.

Underground Piping and Drainage

• Minimum pressure rating of valves should be 12.1 bar.
• For trenches deeper than 1.5 m, RTR pipe should be assembled in the trench.
• The minimum diameter of a storm drain pipe (except building connections) or road crossing culvert should be 300 mm.
• Storm drain manholes should have a minimum inside diameter of 1.0 m for straight run manholes with a pipe diameter size of 600 mm or less.

Cable Trench Specifications

• A minimum of 150 mm of dry sand should be installed from the bottom of the trench to the bottom of the cable or conduit as a cushion.
• A minimum of 300 mm of dry sand cover should be installed on top of the cable or conduit as a cushion.

Gypsum Board Specifications

• Gypsum board width should be 1220 mm to 1370 mm with a tolerance of -2 mm under the specified width.
• Gypsum board corners should be square with a tolerance of ± 2° over the full width of the board.
• Wood supports for lath or gypsum board should not be less than 38 mm in least dimension.

Grout and Bolt Specifications

• The minimum thickness of grout should be 25 mm.
• The minimum thickness of grout between the foundation and base plates should be 25 mm.
• Steel shims and packings should be provided.
• In bolted connections, the minimum size of high-strength bolts that should be used is 20 mm.
• The minimum thickness of gusset and stiffener plates should be 10 mm.

Moisture Content Determination

• The minimum time that a plastic sheet should be in place on a concrete surface to determine its moisture content by the plastic sheet method, ASTM D4263, is 16 hours.

Concrete Slab and Masonry Wall Specifications

• The minimum concrete slab thickness supported on the ground is 100 mm (4").
• A masonry wall should be cured for 7 days prior to grout pouring for high-lift grouted construction.

Fill Material Specifications

• The maximum particle size of fill material should be 1/2 lift thick.
• Fill material classified as "select fill" should contain 0 to 20% particles passing through #200 sieves.
• Fill materials should be placed in lifts or layers not exceeding 200 mm in loose depth.
• Free-draining soils or cohesionless material should be compacted to 70% relative density.

Concrete Strength and Paving Slab Specifications

• The minimum compressive strength of structural concrete at 28 days should be 25 MPa.
• Paving slabs subject to vehicular traffic should have a minimum thickness of 150 mm.
• Control or construction joints for concrete paving should be spaced at a maximum of 6.0 meters in both directions.

Concrete Placement and Grout Strength

• Concrete may be allowed to drop freely at a maximum height of 1 m.
• Cementations non-shrink grout should have a compressive strength of 5,000 psi.

Miscellaneous Steel Specifications

• End-lap for metal panels should not be less than 250 mm.
• A beam with a depth of 8 inches requires 2 rows of bolts.

Brittle Materials

• A material is brittle if, when subjected to stress, it breaks with little elastic deformation and without significant plastic deformation.
• Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Breaking is often accompanied by a snapping sound.
• Examples of brittle materials are: bone, cast iron, ceramic, and concrete.

Concrete Vibrator and Cracking

• We use vibrators to increase the workability and consolidation of concrete.
• Concrete cracking can be caused by dehydration and shrinkage.

Pozzolan Use and Concrete Placement

• Natural pozzolan should be used at 15% of the cement weight.
• Place concrete in layers not exceeding 150 mm in thickness and consolidate.

Base Class Material and Tack Coat Delay

• The laboratory California Bearing Ratio (CBR) per ASTM D1883 or AASHTO T-193 for base class material at 100% compaction DD1557 should conform to minimum 80%.
• Testing should be conducted at a rate of one test every 300 m of base or sub-base.

Gypsum Board Width and Masonry Wall Curing

• Gypsum board width should be 1220 mm to 1370 mm with a tolerance of -2 mm under the specified width.
• A masonry wall should be cured for 7 days prior to grout pouring for high-lift grouted construction.

Lightweight Aggregate and Reinforcement

• Lightweight aggregate should have a dry loose weight of 1600 kg/m3 or less.
• Reinforcement bars are used to resist shear and torsion stresses in a structural member.
• The minimum clear spacing between parallel bars in a layer should be the diameter of the larger bar + 25 mm.
• The minimum bend diameter for No. 16 bar commonly used for stirrups and ties should be 100 mm.

Moisture Content by Plastic Sheet Method

• The minimum time that a plastic sheet should be in place on a concrete surface to determine its moisture content by the plastic sheet method, ASTM D4263, is 16 hours.

Fill Material Compaction and Sand Cushion

• Fill material should be compacted to 95% of the maximum laboratory density.
• Dune sand or clean sand used as fill material requires a cap layer of cohesive material, 150 mm to 300 mm thick.
• The sand cushion used for underground cable shall be a minimum of 150 mm deep.

ACI and Sieve Requirements

• The American Concrete Institute (ACI) is a professional organization for concrete professionals.
• The amount of selected fill material passing #200 sieve should be 100%.

Compaction

• Compaction should begin only after the fill or backfill has been properly placed and the material to be compacted is at the proper moisture content, 95% to 105% of the optimum moisture content per ASTM D1557 or ASTM D698, whichever is applicable.
• Fill or backfill placed beneath footings, grade beams, mats, buildings, and process areas should be compacted to at least 95% of the maximum Modified Proctor density as determined by ASTM D1557.

Damaged Coating and Reinforcing

• When the extent of damaged coating exceeds 2% of the surface area of the coated steel reinforcing bar in any 0.3 m (1 ft) length, the coated bar should be rejected.