General Construction Specifications
SECTION 03300
CONCRETE
PART 1 GENERAL
1.01 Scope
This section covers the description of materials used in concrete construction and the installation of such materials.
1.02 Reference Specifications
The following reference specifications shall govern, where applicable, work covered here:
A. ACI-211, Recommended Practice for Selecting Proportions or Concrete.
B. ACI-301, Specifications for Structural Concrete for Buildings
C. ACI-304, Recommended Practice for Measuring, Mixing, Transporting, and Placing Concrete.
D. ACI-308, Recommended Practice for Curing Concrete.
E. ACI-315, Manual of Standard Practice for Detailing Reinforced Concrete Structures.
F. ACI-318, Building Code Requirements for Reinforced Concrete.
G. ACI-347, Recommended Practice for Concrete Formwork.
H. CRSI, Recommended Practice for Placing Reinforcing Bars.
PART 2 MATERIALS
2.01 Form Liners
A. Forms for exposed concrete shall be faced with clean, smooth plywood. Expose concrete includes surfaces of beams, columns, and slabs; interior and exterior walls; tank, chamber, and tunnel walls, except those in contact with earth.
B. Unlined steel forms may be used where concrete will not be exposed for view.
2.02 Coatings
A. The inside of forms shall be coated with non-staining mineral oil or other Engineer approved release agent applied according to manufacturer's recommendations before setting reinforced steel. The release agent shall not affect the finish of the concrete.
2.03 Form Ties
A. Form ties shall be commercially manufactured steel rods capable of withstanding applied pressures. Wire ties are not acceptable.
2.04 Expansion Joints
A. Joint filler shall be pre-molded self-expanding cork, "Servicised" No. 4324 as manufactured by W. R. Grace and Company, "Sealtight" Type 6 by W. R. Meadows, Inc., or equal and comply with ASTM D1752 Type III.
B. Exposed edges of joint filler shall be capped with a gray polysulfide joint sealer, "Hornflex" as manufactured by A.C. Horn, Inc., "Thiotok" by Toch Brothers Corp., or equal, applied in accordance with manufacturer's recommendation.
2.05 Concrete Reinforcement
A. Steel Bar Reinforcing, ASTM A615, Grade 60. Use weldable grade where necessary.
B. Cold Drawn Steel Wire, ASTM A82.
C. Welded Steel Wire Fabric, ASTM A185.
D. Steel Bar or Rod Mats, ASTM A184.
E. Stressing Tendons, Wire ASTM A421, Strand ASTM A416.
F. Reinforcement Supports
1. Plain, wired or doweled precast concrete block reinforcement supports conforming to CRSI may be used where concrete is poured on ground. Required concrete cover of reinforcement must be maintained.
2. Where concrete is not exposed to view, bright basic conforming to CRSI Class 3 may be used.
2.06 Cast-in-Place Concrete
A. Concrete Materials
1. Cement - Portland Type II, ASTM C150 for all concrete unless otherwise noted.
2. Fine Aggregate - Standard fine aggregate, natural sand, ASTM C33.
3. Coarse Aggregate - Aggregate for Standard weight concrete shall consist of gravel, crushed gravel or crushed stone conforming to ASTM C33.
4. Water - Water shall be clean, fresh, potable and free from injurous amounts of mineral and organic substances.
5. Admixtures
a. Type - A, a water reducing admixture of the hydroxylated carboxylic acid or the hydroxylated polymer types, conforming to ASTM C494.
b. Type - D, a water reducing and retarding admixture conforming to ASTM C494.
c. Type - E, a water reducing and accelerating admixture conforming to ASTM C494.
d. Type - F, an air entraining admixture, "Darex AEA" as manufactured by W.R. Grace and Co., "Sika-AER" by Sika Chemical Corp., or equal.
e. Manufacturer's descriptive details of admixtures shall be submitted for approval.
B. Classes of Concrete
1. Class A - concrete cast against earth in slabs and footings and where used as a topping.
2. Class B - concrete in supported slabs, beams, columns and walls.
3. Class C - concrete in fillets, cradles, and where used to fill voids or for backfilling operations.
4. Class D - concrete at location specifically designated on the contract drawings.
C. Grout and Bonding Agents
1. Type I - general purpose grout, composed of two parts sand and one part cement with sufficient water for required consistency. Grout shall have a minimum compressive strength of 3,500 psi at seven days.
2. Type II - grout for machinery bases and where non-shrink grout is needed shall be a thermosetting resinous grout composed of a liquid resinous binder, a graded silica aggregate, and a chemical hardening agent. All grout components shall be furnished by the grout manufacturer. Grout shall be Carter-Waters Corp. 604 Machine Bond, Ceilcote Co. Ceilcote 648, or equal. Mix components and apply according to manufacturer's recommendations. Manufacturer's descriptive details of grout shall be submitted for approval.
3. Type III - bonding agent for anchoring bolts and reinforcing dowels into drilled or precast holes in concrete and bonding new concrete to old shall be a component epoxy. "Thiokol LP" by Toch Brothers, "Epoxite Binder" by A.C. Horn, Inc., or equal. Mix and apply according to manufacturer's recommendations. Submit manufacturer's descriptive details of bonding agent for approval.
PART 3 EXECUTION
3.01 Proportioning Materials
A. Concrete proportions shall be based on laboratory trial batches.
1. Advance tests of each class of concrete shall be made by ASTM C39 requirements by an independent testing laboratory.
2. Four standard 6-inch compression cylinders, two tested at seven days and two at 28 days, made in accordance with ASTM C192, using the materials and proportions proposed. Aggregate tests may be combined with these tests if suitably referenced on the reports. Repeat tests if materials change or there are unsatisfactory results.
3. Class and Properties of Concrete
4. Each design mix proposed shall be approved in writing by the Engineer prior to its use in the work.
B. Aggregates
1. The ratio of sand to total aggregate shall be from 33 to 42 percent by weight based on surface dry material, unless Engineer authorized. Some minor changes in aggregate proportions may be needed to adjust for changes in aggregate gradations.
C. Admixtures
1. Type - A water reducing admixture may be used where Engineer approved. Type - D or Type - E, with Engineer's approval to provide retarding or accelerating characteristics.
2. Type - F entraining admixture shall be used for concrete work exposed to temperatures less than 40 degrees F.
3. Air content shall be three percent maximum for trowel finished concrete and 3-5 percent for other concrete.
4. The use of calcium chlorine in concrete is prohibited.
3.02 On-Site Material Storage
A. Cement shall be stored in a dry, weathertight, ventilated structure to prevent absorption of moisture.
B. Stored aggregate shall have good drainage, protection from foreign matter and kept according to gradation.
3.03 Batching and Mixing
A. Measure concrete and mortar as specified in ASTM C94.
B. Mixing Concrete
1. Mix in an approved batch mixer or in ready mix conforming to ASTM C94. Do not exceed mixers rated capacity.
2. Mix concrete until materials are uniformly distributed and discharge completely before recharging the mixer. Job mixed concrete shall be mixed at manufacturer's recommended speed for at least one minute after all materials have been added. An additional 15 seconds mixing time shall be added for each additional 1/2 cubic yard of mixer capacity.
C. Cold Weather Concrete
Use cold weather concreting procedures whenever temperature is below, or is forecast to be below, 40 degrees F. within 24 hours.
1. Heat concrete materials. Use water with a temperature of less than 140 degrees F.
2. Heat aggregates by Engineer approved method. Heat uniformly and sufficiently to eliminate lumps of ice, snow or aggregates. Cover aggregates with tarpaulins to maintain uniform heat distribution. Spot aggregate temperatures shall not exceed 212 degrees F and average temperature shall not exceed 140 degrees F.
3. The temperature of concrete when placed shall not be lower than 55 degrees F. Allow for heat loss during transit.
4. Do not add calcium chloride, salt, or other chemicals to prevent concrete from freezing.
D. Hot Weather Concrete
When high air temperature, low relative humidity and/or wind velocity create hot weather conditions that tend to impair the quality of fresh or hardened concrete any or all of the following precautions shall be taken:
1. Reduce concrete mix temperature.
a. Use cold mixing water. Refrigerate or mix with ice.
b. Substitute ice for all or part of the mixing water. Use crushed, shaved or chipped ice and mix until all ice is melted.
c. Shade aggregate to keep them cool. Coarse aggregates may be sprinkled or fog sprayed. Avoid excessive surface moisture that could affect uniformity of slump. Drain aggregates to avoid free moisture.
d. Use cement with a temperature lower than 170 degrees F.
e. Use retarding and water-reducing admixtures.
f. Reduce mixing and agitating to minimum practicable.
g. Paint mixer drums white and spray outside with water before batching.
h. Coordinate truck dispatch with rate of placement to avoid delays in delivery.
3.04 Placing Concrete
A. General
1. Before placing concrete, oil forms, fasten reinforcements in place, retighten form ties at construction joints, place and anchor embedments and openings.
2. Clear debris from area where concrete is to be placed.
3. Do not place concrete under adverse weather conditions.
B. Conveying
1. Use methods to convey concrete from mixer to final location that will prevent separation or material loss. Do not exceed three feet with free fall of concrete.
2. Clean delivery before use and clean at frequent intervals while placing concrete.
3. Use sufficient delivery to insure a practically continuous flow of concrete. Standby shall be available in case of failure. Do not use aluminum delivery in contact with concrete.
C. Depositing
1. Place concrete to avoid segregation. Tremies shall be used to avoid free falls of more than three feet and to keep concrete at a uniform depth during placement.
D. Consolidating
1. Spade and rod concrete to prevent pockets or honeycomb around reinforcements and fixtures. Carefully secure dense concrete around inserts.
2. Consolidate concrete with mechanical vibrating and provide standby equipment. Unless approved by the Engineer, apply vibration directly to concrete. Use sufficient vibration to cause flow or settlement of concrete into place. Apply vibration at point of deposit and in freshly placed concrete. The duration shall be sufficient to accomplish compaction and embedment of reinforcement and fixtures.
3. Fork or spade by hand in corners and angles of forms and along form surfaces while concrete is plastic under vibratory action. Do not allow vibrator bottom to ride the form supporting the slab. Lay the vibrator on the concrete to prevent marring forms.
E. Bonding
1. Roughen, clean and wet concrete surfaces where new concrete is to be placed for horizontal construction joints. Apply 1 - 1/2 inches of grout before placing new concrete. The grout shall be the same mixture as the concrete without coarse aggregates.
2. Work freshly placed concrete at vertical or sloping joints to assure adequate mortar at the joint.
3. Roughen and clean existing old concrete and apply Type III bonding agent before placing new concrete to form bond.
F. Hot Weather Placing
During hot weather take any or all of the following precautions:
1. Schedule concrete delivery so placement is prompt.
2. Have enough vibration to consolidate concrete quickly. Have standby available.
3. If possible, place flatwork on grade after walls are up or roof is on.
4. In arid, windy conditions erect temporary windbreakers and sunshields.
5. Moisten subgrade before pouring but avoid free standing water and soft spots on surface.
6. Use water fogging to avoid excess evaporation from flatwork.
7. Place concrete in shallow lifts to assure better vibration.
8. Provide shade for equipment, paint surfaces white or cover with damp burlap.
9. Schedule pavement in late afternoon or evening to avoid high daytime temperature.
10. Apply monomolecular film evaporation retardant to concrete surface immediately after concrete is screeded, while moisture is still on the surface. Reapply evaporation retardant after each finishing operation in severe drying conditions.
11. Fog spray or spread and remove polyethylene sheeting between finishing operations on flatwork.
G. Cold Weather Placing
1. Surfaces coming in contact with fresh concrete shall be above 35 degrees F. but not necessarily higher than that of the concrete placed.
2. Remove all snow, ice and frost from spaces to be filled with concrete.
3. Thaw frozen subgrade by covering with insulation and if necessary applying heat. Recompact thawed material, if necessary. Do not place concrete on frozen subgrade material.
3.05 Tests While Placing Concrete
A. Concrete Strength
1. For each mix of concrete, make and test four standard 6 inch concrete cylinders from the same sample.
2. Test two cylinders after seven days and two at twenty-eight days. Meet specifications:
a. Sampling concrete for test purposes, ASTM C172
b. Making and curing test cylinders, ASTM C31
c. Testing of Specimens, ASTM C39
B. Slump
1. To maintain desired consistency when 25 or more cubic yards of concrete are placed, make a slump test by ASTM C143. Test for each 50 CY of concrete placed at one operation and one on each sample of concrete used in test specimens.
C. Air Content
1. Test air content of samples used for test cylinders according to ASTM C231.
D. Additional Strength Tests
If test cylinders fail to meet strength requirements, additional compression tests shall be done on cored cylinders according to ASTM C42 or load tests by ACI 318, as required by Engineer. If concrete does not meet requirements according to Engineer, the defective concrete shall be removed and replaced. Cost for retesting shall be paid by Contractor.
3.06 Curing
A. Keep concrete moist for seven days after placement. Cure by any of the following means, if approved by the Engineer.
1. Cure with burlap, cotton, or mats kept wet or keeping forms wet.
2. Use waterproof paper curing lapping four inches at seams and sealing with tape.
3. Membrane curing by power spraying with fugitive dye included. Not to be used where surfaces receive a finish treatment. Submit manufacturer's descriptive data of curing compounds for approval.
3.07 Weather Protection
A. Rain-Protect exposed surfaces from wash.
B. Cold Weather Protection
1. Use covers, insulation, enclosures, or heat to prevent concrete from freezing. Extra protection is needed at edges and corners.
2. Heat enclosures with steam, forced hot air or other Engineer approved method. Vent heater exhaust gas outside enclosure. Do not use open fire or Salamanders. Keep heat continuous.
3. When using hot air heaters, cover exposed concrete surfaces with impervious sheet material or curing compound according to ASTM C309 to prevent dehydration of concrete.
4. Maintain concrete temperature above 50 degrees F. at least 72 hours. Protect from freezing an additional 72 hours or as long as needed for proper curing.
5. Keep enclosures or covering in place a minimum of 24 hours after heating is discontinued. Allow concrete to slowly reach ambient temperature to avoid thermal cracking.
6. Protect slabs cast against earth, such as tank bottoms by covering with non-staining insulating material or by other Engineer approved means to prevent frost penetration into the subgrade.
7. Keep temperature records of concrete including when it was placed, data, weather conditions, outside air temperature and concrete temperature. Obtain a range of temperatures by different locations. Record maximum and minimum temperatures in each 24-hour periods and deliver copy of record to Engineer and Owner weekly.
C. Hot Weather Protection
1. Provide continuous water curing with saturated material in contact with concrete surface and kept wet with soaker hoses.
2. Methods and materials specified in ACI 308, Recommended Practice for Curing Concrete, are acceptable.
3.08 Concrete Finishes
A. Cast-in-Place Concrete
1. Walls
a. Rough finish shall be used on concrete surfaces below grade adjacent to earth and not exposed to view. Within 24 hours of removing forms, cut out honeycomb, aggregate pockets, voids over 1/2 inch in diameter, and holes left by form ties to solid concrete; throughly wet, brush on a neat cement coat of grout and fill with mortar of one part cement, two parts fine aggregate (passing a No. 16 sieve) and a minimum of water. Tamp mortar in place. Finish patchwork flush with adjacent surfaces and damp cure for 48 hours.
b. Smooth finish exterior concrete surfaces exposed in the finished work. Apply rough finish as above but then throughly wet and brush-coat surfaces with cement grout of one part cement to two parts fine aggregate (passing a No. 30 sieve) and mixed with water to consistency of thick paint. Fill all pits, air bubbles, and surface holes using a cork or wood float. Scrape off excess with a trowel and rub surface with burlap. Complete the finish of any area in the same day making limits at natural breaks in the surface. Exposed exterior walls of structures continue to one foot below finished grade.
2. Slabs
a. Slabs shall be true to grade with allowance of 1/8 inch/10 feet slope where drainage is required.
b. Floor surfaces exposed to view at completion shall be given a monolithic finish. Wood-float surface to a true, even plane with no coarse aggregate visible when concrete will support a man's weight. Use pressure to bring moisture to surface, then double steel trowel to produce a smooth surface.
Walks exterior platforms, stoops and treads shall be wood-floated to a true and even plane. Apply steel trowel and roughen surface by dragging burlap across the surface.
d. Apply three coats of floor hardener such as "Hornolith" by A.C. Horn, Inc., "Lapidolith" by Sonneborn-Contech, or equal to concrete floors, curbs or pads in buildings not receiving other finishes. Apply according to manufacturer's recommendations.
3.09 Testing Wet Well
Test new wet well as follows:
A. Clean interior of debris and sweep.
B. Fill unit with liquid to operating level before backfilling.
C. Establish rate of filling.
D. Do not test until compressive strength of concrete is equal to 3,000 psi by cylinder tests.
E. If leakage is evident or level drops more than 1/4 inch in 24 hours from leakage, dewater wet well and repair leaks.
F. Repeat test until results are satisfactory. Owner accrues no cost for retests.
G. When results are satisfactory, remove liquid and dispose of it without damaging construction, the site, adjacent areas or the operation of existing facilities.
END OF SECTION
