SECTION CAST-IN-PLACE CONCRETE

Transcription

1 SECTION CAST-IN-PLACE CONCRETE PART 1 GENERAL 1.01 SECTION INCLUDES A. The Contractor shall furnish all work and materials, including cement, sand and coarse aggregate, water, admixtures, curing compound, reinforcement, form work and other materials that may form an integral part of the concrete construction. B. Reinforced concrete for retaining walls and the like subjected to increased environmental forces or as directed by the Engineer, shall be in accordance to Section Structural Concrete. C. The size and configuration of the various components shall be as indicated herein, in the Standard Details, and in the approved Improvement Plans, if any. D. All materials and installation shall be in accordance with the standards and specifications of the Solano Irrigation District, latest revisions RELATED SECTIONS A. Section General Requirements B. Section Miscellaneous Metalwork 1.03 SUBMITTALS A. Shop Drawings in accordance with Section B. Concrete mix design TESTING A. Slump test, air entrainment test and compressive test cylinders will be made by the Engineer or as directed by the Engineer, and such tests shall conform to the latest ASTM procedures MEASUREMENT AND PAYMENT A. The quantity of concrete will be measured to the neat lines shown on the Drawings, unless otherwise noted. Payment will be made at the unit price bid per cubic yard in the Bid Schedule for the specified reinforced Concrete work. The unit price shall include furnishing and placing all concrete materials, reinforcement, excavation, backfill and water Approved: July 18, 2012 Page 1 of 6

2 B. The cost of the reinforced concrete for pipe support pads will be included in the cost of piping. Therefore no separate payment for this item will be made in the Bid Schedule for reinforced concrete work. PART 2 MATERIALS 2.01 CEMENT A. All cement shall be Portland Cement, Type II, conforming to ASTM Designation C-150. All cement shall be free of lumps and properly aged AGGREGATES A. Fine and coarse aggregates shall conform to the requirements of ASTM C-33. The maximum nominal size of coarse aggregate shall be three quarters of an inch (¾ ) WATER A. Water shall be clean and free from oils, acids, salts and other damaging substances. Raw water is not approved AIR ENTRAINING AGENT A. The Contractor may use an air entraining agent conforming to the requirements of ASTM Designation C-260 in all concrete. The amount of air entraining agent, if used, shall be such as will affect the entrainment of four to six percent (4% - 6%) of air, by volume of the concrete at the time of discharge from the mixer REINFORCEMENT A. Reinforcing steel shall conform to ASTM A-615 Grade 40, or as indicated in the Drawings, for deformed and plain billet steel bars for concrete reinforcement MEMBRANE CURING COMPOUND A. Membrane curing compound shall be a non-waxy white pigmented sealing compound conforming to ASTM C-309. PART 3 EXECUTION 3.01 FORMWORK A. Forms shall conform to the shape, line, grade and dimensions of structures as shown on the Drawings. B. Forms shall have sufficient strength to withstand the pressure resulting from placement and vibration of the concrete and shall be maintained rigidly in position. Embedded wire ties for holding forms will not be permitted. Bolts and Page 2 of Approved: TBD

3 rods used for form ties shall be so arranged that when the forms are removed, no metal shall be within 1 of any surface. C. Wood forms shall be of sound lumber, free from loose knots or other defects, and of such quality that when treated or coated, there will be no chemical deterioration or discoloration of the formed concrete surface. All form lumber shall be surfaced lumber in narrow and uniform widths closely matched, except that plywood of adequate stiffness shall be used on all surfaces exposed to air or water. D. Lumber reused in forms shall be cleaned, repaired and plugged. All nails shall be withdrawn from lumber prior to reuse. E. The form sheathing or lining shall be so placed that the joint marks on the concrete surfaces will be in general alignment, both horizontally and vertically. Forms shall be sufficiently tight to prevent loss of mortar from the concrete. F. Three-quarter inch (¾ ) chamfer strips shall be placed in the corners and at the top-of-wall line of the forms so as to produce beveled edges on permanently exposed concrete edges. Interior angles on such surfaces and edges of formed joints will not require beveling, except where shown on the drawings. G. Forms shall be removed as soon as practical after the concrete is placed, but not until the concrete has attained the necessary strength to support all live and dead loads during the construction period. Forms shall be removed in such a manner as to prevent damage to the concrete. Immediately after the forms are removed, all defects in the concrete, including the rod holes, rock pockets, and other unconsolidated areas, shall be repaired by the drypack method, and the total exposed area with sealing compound. H. Before the concrete is placed, the forms shall be coated with a non-staining commercial form releasing agent TOLERANCES A. Variations from level, grade, alignment or plumb for any portion of a structure shall not exceed one-half inch (½ ), unless a more restrictive tolerance is shown on the Drawings PLACING REINFORCEMENT A. Before concrete reinforcing bars are placed, the surfaces of the bars and the surfaces of any metal supports for reinforcing bars shall be cleaned of heavy flaky rust, loose mill scale, dirt, grease and other foreign substances. Heavy flaky rust that can be removed by rubbing with burlap or equivalent treatment is considered objectionable. After being placed, the reinforcing bars shall be maintained in a clean condition until they are completely embedded in the concrete. B. Reinforcing bars shall be accurately placed and secured in position so that they Approved: July 18, 2012 Page 3 of 6

4 will not be displaced during the placing of the concrete, and special care shall be exercised to prevent any disturbance of the reinforcing bars in concrete that has already been placed. C. Refer to Section Miscellaneous Metalwork for requirements for steel embedments and anchor bolts CONCRETE PROPORTIONING A. The Contractor shall furnish concrete which will develop a minimum compressive strength of 3,000 psi, and shall conform to the basic requirements set forth in these Specifications. B. The net water-cement ratio of the concrete (exclusive of water within or absorbed by the aggregates) shall not exceed 0.60 by weight. C. A minimum of 5½ sacks of cement per cubic yard shall be used. D. The slump shall not exceed 3 for slabs that are horizontal or nearly horizontal, and 4 for other work. The Engineer reserves the right to alter the required slump whenever, in the Engineer s judgement, the quality of the work will improve CONCRETE MIXING A. Mixing may be performed at the site of work or by transit-mix methods. B. Transit-mixed concrete shall conform to the standard specifications for readymixed concrete per ASTM C-94. The total volume of materials mixed per batch shall not exceed the rated capacity of the mixer as determined by the standard requirement of the Associated General Contractors of America. C. If a batch mixer is used, the concrete ingredients shall be mixed for not less than one and one half (1½) minutes after all of the ingredients, except for the full amount of water, are in the mixer. The mixing shall be increased if the charging and mixing operations fail to produce a concrete in which the ingredients are consistent and uniform throughout. Water shall be added prior to, during and following the mixer-charging operation. Excessive overmixing, requiring additional water to preserve the concrete consistency, will not be permitted. Any mixer that at any time produces unsatisfactory results shall be repaired or replaced CONCRETE PLACING, JOINTING, FINISHING AND CURING A. Preparation: 1. In preparation for placing of concrete, all water, sawdust, chips and other construction debris and extraneous matter shall be removed from the interior of the forms. Page 4 of Approved: TBD

5 2. Concrete shall not be placed around any metal reinforcement or embedments until the Engineer has approved the reinforcement or embedments placed within the forms. 3. The forms, subgrade and reinforcement shall be wetted immediately before placement of the concrete. B. Temperature Limits: 1. The temperature of concrete as mixed and placed shall not be less than 55 F, nor greater than 90 F. 2. If during day or night the ambient temperature falls below, or is predicted to fall below, 40 F, concrete shall be protected from freezing during placement and curing by means of heating of materials or other approved methods, as directed by the Engineer. The concrete mix for cold-weather placement shall be maintained at a minimum temperature of 55 F during placement, and this minimum temperature shall be maintained for the first 72 hours of curing. 3. At all times the maximum temperature of concrete as placed shall be less than 90 F. When the temperature of concrete as placed may be 90 F or higher, as may be reasonably predicted from current temperatures of materials and the likelihood of rises in weather temperatures, the Contractor shall employ effective means, such as precooling aggregates and mixing water, use of ice as a part of the mixing water, shading aggregates, or placing at night, as necessary, to maintain the temperature of concrete, as placed, below 90 F. C. Placing: The concrete in each integral part of the structure shall be placed continuously. The Contractor shall not be allowed to commence concrete placement in any integral part of the structure unless the inspected and approved forms, reinforcement, embedments and other materials on hand are sufficient to allow completing the part without interruption in the placing of the concrete. The concrete shall be placed as nearly as possible to its final position by means that avoid segregation of the materials and displacement of the reinforcement. Concrete shall not be permitted to fall from a height greater than six feet (6 ) without the use of adjustable length pipes or elephant trunks. D. Compaction: Concrete during and immediately after placing, shall be thoroughly compacted. The compaction shall be done with mechanical vibrators capable of transmitting vibration to the concrete at frequencies of not less than 4,000 cycles per minute. The location, manner and duration of the application of the vibrators shall be such as to secure maximum consolidation of the concrete. The vibrators shall not be attached to or held against the forms or the reinforcing steel. E. Joints: 1. Construction Joints: Construction joints placed in concrete structures to Approved: July 18, 2012 Page 5 of 6

6 facilitate construction must be approved by the Engineer. Bond is required at all construction joints. The surface of all joints shall be clean and damp when covered with fresh concrete or mortar. Cleaning shall consist of removal of all laitance, loose or defective concrete, coatings, sand, and other foreign material from the surface of the joint and exposed reinforcing steel. Mortar for bonding of joints shall be the same as that in the concrete with the coarse aggregate omitted. The mortar bond shall be approximately one half inch (½ ) thick and worked into the joint surface. 2. Contraction Joints: These joints are placed in structures or slabs to provide for movement between units, and shall have no bond across the joint. Units shall be separated by joint filler where indicated on the Drawings. F. Finishing: All horizontal surfaces on structures will have a light broom finish. G. Curing: Reinforced concrete shall be cured by membrane curing. Sealing compound shall be applied to the concrete surfaces by spraying in one coat to provide a continuous, uniform membrane over all areas. /// END OF SECTION Page 6 of Approved: TBD