General Construction Specifications
PART 1 - GENERAL
01 WORK INCLUDED
A. All work specified in this section shall comply with the provisions of Section 15010.
B. Types of concrete for mechanical work specified in this section include the following:
1. Lean concrete backfill to support mechanical work.
2. Encasement of mechanical work.
3. Underground structural concrete to accommodate mechanical work.
4. Tanks and vaults of mechanical work.
5. Basins and curbs for mechanical equipment.
6. Mechanical foundations and housekeeping pads.
7. Inertia bases for isolation of mechanical work.
8. Rough grouting in and around mechanical work.
9. Patching concrete cut to accommodate mechanical work.
10. Cooling tower sumps.
B. Quality control testing for concrete work is required as work of this section.
1.02 QUALITY ASSURANCE
A. Comply with governing regulations and, where not otherwise indicated, comply with the following industry standards, whichever is the most stringent in its application to work in each instance:
1. ACI 301 "Specifications for Structural Concrete for Buildings".
2. ACI 311 "Recommended Practice for Concrete Inspection".
3. ACI 318 "Building Code Requirements for Reinforced Concrete".
4. ACI 347 "Recommended Practice for Concrete Formwork".
5. ACI 304 "Recommended Practice for Measuring, Mixing,
Transporting and Placing Concrete".
6. Concrete Reinforcing Steel Institute, "Manual of Standard Practice".
1.03 SUBMITTALS
A. Submit shop drawings to Architect for approval in accordance with Section 15010.
PART 2 - PRODUCTS
02 FORM MATERIALS AND CONSTRUCTION
A. Forms for Exposed Concrete: Plywood, smooth metal or other smooth panel type material; sized for minimum joint exposure, and reinforced to prevent visible deflections resulting from pressure of placed concrete; sufficiently heavy for construction to prevent leakage which would be harmful to either structural or visual quality of concrete.
1. Plywood: PS-1 "BB (Concrete Form) Plywood", Class I, Exterior Grade, mill-oiled and edge sealed.
B. Forms for Unexposed Concrete: Smooth lumber, plywood or other easy-release material; reinforced to prevent excessive deflection or the possibility of failure during placement of concrete; sufficiently heavy for construction to prevent leakage which would be harmful to structural quality of concrete.
C. Form Ties: For exposed concrete surfaces, provide snap-off type ties designed to snap off 1-1/2" below surface.
D. Exposed-Corner Chamfer Strips: Provide wood, metal, plastic or rubber chamfer strips in forms at exposed external corners of concrete work.
E. Form-Coating Compound: Commercially formulated compound which will prevent bond of concrete to forms. Provide compound recommended by manufacturer for application indicated, and which will not stain concrete or interfere with moisture curing of concrete or subsequent painting of exposed surfaces.
03 REINFORCING MATERIALS
A. Reinforcing Bars: Except as otherwise indicated, provide ANSI/ASTM A 615, deformed, Grade 40 for size numbers 3 through 18; ANSI/ASTM A 675, plain, Grade 60, for size number 2; sizes as shown.
B. Steel Wire: ANSI/ASTM A 82, plain, cold-drawn.
C. Welded Wire Fabric: ANSI/ASTM A 185; sizes and spacings of wires as shown; 6" x 6" x No. 10 x No. 10 where not otherwise indicated.
D. Reinforcement Supports: Provide supports for reinforcement including bolsters, chairs, spacers and other devices for spacing, supporting and fastening reinforcing bars and welded wire fabric in place. Provide wire bar type supports complying with CRSI recommendations, unless otherwise indicated.
1. For on-grade work, provide supports with sand plates or horizontal runners.
2. At exposed surfaces, provide supports with legs that are stainless steel protected (CRSI, Class 2), or plastic protected (CRSI, Class 1)
04 CONCRETE MATERIALS
A. Portland Cement: ANSI/ASTM C 150, Type I, except as otherwise indicated.
B. Aggregates: ANSI/ASTM C 33, except as otherwise indicated.
1. Local aggregates not complying with ANSI/ASTM C 33 but which have shown by special test or actual service to produce concrete of adequate strength and durability may be used.
2. For rough grouting, provide aggregate which is well graded and 100 percent passing through 3/8" sieve.
C. Water: Clean and free of substances harmful to concrete.
D. Air-Entraining Admixture: ANSI/ASTM C 260.
E. Water-Reducing Admixture: ANSI/ASTM C 494, Type A (normal range) and Type F (high-range, super plasticizer).
F. Set-Control Admixtures: ANSI/ASTM C 494, as follows:
1. Type B, Retarding.
2. Type C, Accelerating.
3. Type D, Water-reducing and Retarding.
4. Type E, Water-reducing and Accelerating.
5. Type G, High-Range Water-Reducing and Retarding (Super- plasticizer).
B. Calcium Chloride: Use not permitted.
2.02 DESIGN AND PROPORTIONING OF MIXES
A. General: Design mechanical work concrete as follows, for each 28-day compressive strength class:
1. 4000 psi Class: 565 lbs. of cement per cu. yd. (6.0 sacks), and 0.35 water/cement ratio.
2. 3000 psi Class: 500 lbs. of cement per cu. yd. (5.25 sacks), and 0.46 water/cement ratio.
3. 2500 psi Class: 450 lbs of cement per cu. yd. (4.75 sacks), and 0.54 water/cement ratio.
4. Backfill Class (Lean Concrete): 375 lbs. of cement per cu. yd., (4.0 sacks), and 0.60 water/cement ratio.
5. Rough Grouting Class: 565 lbs. of cement per cu. yd. (6.0 sacks), and 0.60 water/cement ratio.
B. Admixtures: Except as otherwise indicated, use is at Contractor's option. Comply in each instance with admixture manufacturer's recommendations and suggested limitations for required quality of concrete. Use water-reducing admixture (normal or high-range in all concrete).
C. Comply with the following limitations for resulting air entrainment:
1. Concrete Above Grade: Not less than 2% nor more than 4%.
2. Concrete Below Grade: Not less than 2% nor more than 4%, except up to 6% where maximum aggregate size must be 3/4" or less.
3. Rough Grout Concrete: Not less than 4% nor more than 8%.
4. Backfill Concrete: Not more than 7%.
D. Slump Limitations: Limit water content in design mixes to produce the following slumps at point of placement (but do not exceed specified water/cement ratios). Concrete containing high-range water-reducing admixture may have slump limit up to 8".
1. Reinforced Structural Concrete: For concrete which is reinforced (with more than shrinkage crack protection), or in strength class of 3000 psi and above, limit slump to range of 1" to 3".
2. Plain Concrete: For concrete which is not reinforced or reinforced only for shrinkage crack protection, and in strength class below 3000 psi, limit slump to range of 2" to 5".
3. Rough Grout Concrete: Limit slump to range of 3" to 7".
4. Backfill Concrete: Limit slump to 5".
E. Mix for Patching: Where mechanical work requires patching of exposed concrete work which has been cut to accommodate mechanical work, provide concrete patching mix which is identical with mix of work being patched (same cement, aggregates, admixtures and proportioning).
2.03 CONCRETE MIXING
A. Job-Site Mixing: Mix materials for concrete in drum-type batch machine mixer. For mixers of 1.0 cu. yd., or smaller capacity, continue mixing at least 1-1/2 minutes, but not more than 5 minutes after all ingredients are in mixer, before any part of batch is released. For mixers of capacity larger than 1.0 cu. yd., increase mixing time by 15 seconds for each additional cu. yd., or fraction thereof.
1. Prepare and submit batch ticket for each batch discharged and used in work.
B. Ready-Mix Concrete: Comply with requirements of ANSI/ASTM C 94, except as otherwise indicated.
1. Delete references for allowing additional water to be added to batch for material with insufficient slump. Addition of water to batch will not be permitted.
2. During hot weather, or under conditions contributing to rapid setting of concrete, mix each load for shorter period of time than specified in ANSI/ASTM C 94. When air temperature is between 85 and 90 degrees F (29.4 and 32.2 degrees C), reduce mixing and delivery time from 1-1/2 hours to 75 minutes, and when air temperature is above 90 degrees F (32.2 degrees C), reduce mixing and delivery time to 60 minutes.
PART 3 - EXECUTION
05 INSTALLATION OF FORMWORK
A. Design, construct and maintain formwork to support vertical and lateral loads including pressure of cast-in-place concrete. Construct formwork so that formed concrete will be required size and shape and in required location. Construct with joints which will not leak cement paste. Form sides and bottoms of concrete work, except where clearly indicated to be cast directly in excavation or against other construction, or on grade or prepared subgrade. Design and construct forms for easy removal without damage to concrete and other work.
1. Install chamfer strips at external corners of exposed concrete work.
2. Construct forms to retain anchor bolts in accurate locations during placement of reinforcing steel and concrete. Use templates furnished by manufacturers to locate anchor bolts or, where not furnished, locate by accurate measure from certified setting diagrams.
B. Form Coating: Coat concrete-contact surfaces of forms to be removed. Apply form-coating compound before reinforcement is placed. Apply in accordance with manufacturer's instructions and remove excess compound and spillage.
C. Cleaning and Tightening: Clean forms and adjacent surfaces to receive concrete just before concrete is placed. Retighten forms promptly during concrete placement where required to eliminate leakage of cement paste.
06 PLACING REINFORCEMENT
A. Comply with requirements and recommendations of specified standards, including "Placing Reinforcing Bars" by CRSI. Place bars where indicated and support to prevent displacement during concrete placement, using appropriate reinforcement supports, properly spaced and wire tied to reinforcing bars.
1. Place reinforcement to obtain at least minimum recommended coverages for concrete protection. Set wire ties so ends are directed into concrete, not toward exposed concrete surfaces.
B. Install welded wire fabric in as long lengths as practicable. Lap adjoining pieces at least one full mesh and lace splices with 16-gage wire. Offset end laps in adjacent widths to prevent continuous laps in either direction.
C. Clean reinforcement of loose rust and mill scale, earth, ice, and other materials which would reduce bond with concrete.
07 PLACING CONCRETE
A. Wet wooden forms which have been coated with compound, immediately before placing concrete, and remove excess water from forms.
B. Strength-Class Applications: Comply with compressive-strength-classes shown on drawings for each unit of mechanical concrete work or, if not shown, comply with the following general application requirements.
1. Backfill: Provide backfill class (lean concrete).
2. Plain Concrete Encasement: Provide 2500 psi class.
3. Reinforced Concrete Encasement: Provide 3000 psi class.
4. Underground Structural Concrete: Provide 3000 psi class.
5. Tanks and Vaults: Provide 4000 psi class.
6. Block Type Foundations: Where least dimension is not less than 0.2 x largest dimension, provide 3000 psi class.
7. Beam-Type Foundations: Where least dimension is less than 0.2 x largest dimension, provide 4000 psi class.
8. Miscellaneous Supported Work: Provide 3000 psi class for curbs, pads, inertia blocks and similar supported work.
9. Concrete Fill: Provide 2500 psi class for filling structural steel foundation frames and for filling similar large-volume units.
10. Concrete Grout: Provide rough grouting class for filling voids to be grouted which are too small to be filled effectively with 2500 psi class concrete.
11. Patching General Concrete Work: Match concrete being patched.
B. Deposit concrete continuously or in layers of thickness which will result in no concrete being placed on concrete which has hardened sufficiently to cause formation of seams or planes of weakness within section. If section cannot be placed continuously, provide construction joints. Deposit concrete as nearly as practicable in its final location, so as to avoid segregation due to rehandling or flowing.
C. Consolidate placed concrete by mechanical vibrating supplemented by hand-spading, rodding or tamping. Use and procedures complying with recommended practices of ACI 309; eliminate voids in work.
D. Bring horizontal surfaces to correct level with straightedge and strike off. Use bull floats or darbies to smooth surface, free of humps and hollows.
E. Cold Weather Placement: Comply with ACI 306. Do not use frozen materials or materials containing ice and snow. Do not place concrete on frozen subgrade or on subgrade containing frozen materials. When air temperature has fallen or is expected to fall below 40 degrees F (4.4 degrees C), heat water and aggregates uniformly before mixing, as required to obtain concrete mixture temperature of not less than 50 degrees F (10 degrees C), and not more than 80 degrees F (26.7 degrees C), at time of placement. Protect concrete work from physical damage and reduce strength resulting from frost, freezing actions, or low temperatures.
F. Hot Weather Placement: Comply with ACI 305 when hot weather conditions could impair work. Maintain concrete temperature below 90 degrees F (32.2 degrees C) at time of placement, by cooling ingredients. Mixing water may be chilled, or chopped ice may be used to control concrete temperature, provided water equivalent of ice is included in calculating compliance with water/cement ratio limitations. Cover reinforcing steel with water-soaked burlap as necessary to ensure that steel temperature will not exceed ambient air temperature immediately before embedment in concrete.
G. Finishing Horizontal Surfaces: Float and trowel horizontal (top) surfaces to level, smooth, uniform textured, dense finish, where surface is to remain exposed or receive coating, membrane or other thin-set finish.
Otherwise, leave struckoff surface undisturbed; except scratch surfaces which are to received concrete or mortar topping or setting bed, by raking with a stiff broom.
1. Depress top of concrete backfill sufficiently so that supported work can be set in bed of mortar or sand as indicated.
H. Curbs: Provide monolithic finish on interior curbs by stripping forms while concrete is still green and steel-troweling surfaces to hard, dense finish with corners, intersections and terminations slightly rounded and coved.
3.02 FORM REMOVAL AND SURFACE REPAIRS
A. Form Removal: Remove forms as soon as concrete has set and gained sufficient strength to ensure that neither removal of forms nor stress introduced by removal of support contributed by forms will result in damage to concrete.
1. Retain forms on vertical surfaces of concrete for not less than 3 days after concrete is placed.
2. Retain forms supporting horizontal and angular bottom surfaces of concrete for not less than 14 days after concrete is placed, except where indicated for longer periods of support.
B. Unexposed Surfaces: Repair significantly damaged and honeycombed areas, and remove major projections and fins where forms have been removed.
C. Exposed Surfaces: On formed surfaces which are to be exposed, including those to be coated or covered with membrane or other thin-set applied finish, repair and patch form-tie holes and damaged and honeycombed areas, filling voids with grout and completely removing fins and other projections.
3.03 CONCRETE CURING AND PROTECTION
A. General: Protect freshly placed concrete from drying and excessively cold and hot temperatures, and maintain in moist condition at relatively constant temperature for period of time necessary for hydration of cement, proper hardening, and achievement of strength requirements as specified.
1. Start initial curing as soon as free water has disappeared from concrete surface after placing and finishing. Weather permitting, keep continuously moist for not less than 72 hours.
2. Begin final curing procedures immediately following initial curing and before concrete has dried. Continue curing for at least 7 days and in accordance with ACI 301 procedures. Avoid rapid drying at end of final curing period.
3. Subgrade concrete backfill may be excluded from final curing procedures where adjoining subsoil is sufficiently moist to maintain concrete in moist condition.
B. Curing Method: Perform final curing for each area of concrete work by one of the following methods (at Contractor's option), as appropriate for location and accommodation of adjacent construction work which must continue:
1. Continuous water emersion or fog spraying.
2. Covering with absorptive cover which is maintained in wet-to-fully saturated condition.
C. Covering with moisture retaining cover, with sealed joints and maintained without holes or openings as non-breathing membrane.
D. Coating with membrane-forming curing compound, applied in 2 coats and maintained in effective condition for cure period (replace if degraded by rain before reaching stable condition).
1. Do not use compound curing method where surface is to be painted, dampproofed, waterproofed, or covered with other finish requiring bond to concrete.
2. Do not use compound curing method where forms must be retained more than 3 days.
3.04 MISCELLANEOUS CONCRETE WORK
A. Concrete Grouting: Grout openings and recesses as indicated, in and around mechanical work and other work which penetrates or adjoins mechanical concrete work, using rough grouting class of concrete mix. Provide formwork where required, and tamp, screed and trowel surfaces. Cure grout as specified for concrete work.
B. Refer to individual sections of these specifications for fine-grouting of base plates on foundations (usually with non-shrinking grout), and similar grouting requirements not defined herein as concrete work.
3.05 QUALITY CONTROL TESTING
A. Owner will engage testing laboratory to take samples for slump, compression testing and other quality control procedures. Cooperate with personnel of required testing program. Respond as directed to indicated results of testing program.
B. Engage testing laboratory to take samples, perform tests, and prepare and submit reports for concrete as it is placed. Comply with quality control testing requirements specified in sections of Division 3 for work similar to mechanical concrete work, including sampling, curing, testing, reporting, intensified curing of below-strength concrete, additional in-place sampling and testing, and corrective procedures as directed.
1. Backfill Concrete: Quality control testing is not required for backfill concrete (lean concrete).
END OF SECTION
