(A) Classes of concrete. Concrete used in the work shall be designated Class “A” or Class “B” on the basis of the minimum 28-day compressive strength developed when tested in accordance with ASTM C39. Class “A” concrete shall develop a minimum compressive strength of 4,000 pounds per square inch in 28 days. Class “B” concrete shall develop a minimum compressive strength of 3,000 pounds per square inch in 28 days. Class “A” concrete shall be used for all load bearing or structural concrete such as roads, drives, curbing and utility structures. Class “B” concrete shall be used on non-structural items such as sidewalks, thrustblocking and the like.
(B) Portland cement.
(1) Different kinds of brands of cement, or cement of the same brand from different mills, shall not be mixed on the same job.
(2) All cement used in concrete for structures which will contain or carry liquids after completion, such as tanks and pipes, shall be air-entraining portland cement, conforming with ASTM C150, Type IA or IIIA. Air entraining admixtures shall conform to ASTM C260.
(3) All other cement shall be portland cement, conforming to either ASTM C150, Type I or Type III.
(C) Aggregate. Concrete aggregate shall conform to Section 904 of the state’s Department of Transportation Standard Specifications, latest edition. All aggregate shall be stored in an approved manner, which will keep the aggregate clean and free from foreign substances.
(1) Fine aggregate. Shall be natural sand of clean, hard, durable particles and shall conform to the state’s Department of Transportation Standard Specifications, Size No. 23.
(2) Coarse aggregate. Shall be crushed stone or gravel of clean, sound, durable particles and shall conform to the state’s Department of Transportation Standard Specifications, Class A, Size No. 5 or No. 8.
(D) Water. Water used in mixing that is known to be potable quality need not be tested. Any other water used shall be clean, free of oil, salt, acid, alkali, sugar, vegetable or any other substance harmful to the finished product. Water will be tested in accordance to the requirements of AASHTO T26.
(E) Admixtures may be used in concrete as follows.
(1) Air-entraining admixture. Shall conform to the requirements of ASTM C260 and shall be added to the mix in the amount necessary to produce the specified air content. Air-entraining admixtures shall be Micro-Air by Master Builders, Darex or Airalon by W.R. Grace, or equal.
(2) Water-reducing admixture. Shall conform to ASTM C494, Type A or Type D (water reducing and retarding). Water reducing admixture shall be mixed separately from air-entraining admixtures in accordance with the manufacturer’s printed instructions. Water-reducing admixtures shall be Pozzolith 122-N or LL-960 by master Builders, WRD A with Hycol by W.R. Grace, or equal.
(3) Pozzalanic admixtures. Shall be flyash or raw or calcined material pozzolans meeting the requirement of ASTM C618 with the exception that the maximum loss of ignition should be less than 6%. Pozzalanic admixtures may be used as a cement substitute with a maximum 20% substitution rate on a pound for pound basis.
(F) Proportioning concrete mixes. All concrete shall be proportioned by the water-cement ratio, unless specifically approved otherwise by the Engineer. The water-cement ratio shall be interpreted as the ration of the total quantity of water, including surface water contained in the aggregate, in pounds, per pound of cement. Weight of water based on 62.4 pounds per cubic foot at 60°F.
(1) Concrete shall be proportioned to give the required workability without exceeding the maximum quantities of mixing water, as follows:
Lbs. of Cement | 28-Day | ||
Class of Water-Cement | Per Cu. Yd. Concrete Compressive | ||
Concrete | Ratio (Max.) | Minimum | Strength (psi) |
“A” | 0.45 | 564 | 4,000 |
“B” | 0.55 | 423 | 3,000 |
(2) All concrete placed in the work shall have a slump between three inches and five inches when tested in accordance with ASTM C143; except that, a maximum slump of six inches may be permitted by the Engineer for sections less than six inches thick.
(3) All concrete shall include entrained air of not less than 5%, nor greater than 1%. Air entraining admixtures shall be required unless air entrained concrete meeting the above requirements is used.
(4) Adjustment shall be made to the mix to appropriate the amount of over design as required by ACI 318 § 4.3.
(G) Related concrete materials.
(1) Curing compound. Shall be non-staining acrylic type curing compound conforming to ASTM C309, Type I, clear. Curing compound shall in no way be detrimental to the application of sealers, finishes or flooring materials as may be specified.
(2) Curing and sealing compound. Shall be non-staining acrylic type curing compound. Conform to ASTM C309, Type I, clear; Kure-N-Seal as manufactured by Sonneborn or equal as approved by Engineer.
(3) Joint filler. Filler for expansion joints shall be ASTM D1752, Type III, preformed, self-expanding, non-extruding strips formed from clean granulated cork particles securely bound together by a non-bitumen synthetic resin of an insoluble nature. Filler material shall be acid resistant and waterproof. Filler shall be W.R. Grace Code 4324 or equal.
(4) Joint sealant. Pourable two part polysulfide conforming to USAS A1 116.1 and Thiokol Building Trade Performance Specification Class A (self-leveling) Type II (35-45 Shore A). Sealant shall be W.R. Grace No-Trak or equal.
(2004 Code, Art. VI, § B, part 2)