ASTM C478-2018 pdf free download

ASTM C478-2018 pdf free download.Standard Specification for Circular Precast Reinforced Concrete Manhole Sections
5. Design
5.1 Design requirements for a product are prescribed in the specific Part II section for that product. 5.1.1 The minimum compressive strength of concrete man- hole products covered by this specification shall be 4000 psi unless specified otherwise in Part II of this specification. 5.2 Modified or Special Design 5.2.1 Manufacturers are not prohibited from submitting to the owner, for approval prior to manufacture, designs other than those prescribed in the specific section for a product. If such approval is obtained, then the product shall meet all the tests and performance requirements specified by the owner in accordance with the appropriate sections on manufacture and physical requirements. 5.2.2 If permitted by the owner, the manufacturer is not prohibited from requesting approval of designs of special sections, such as reducers, tees, and bases.
6. Reinforcement
6.1 This section presents requirements for reinforcement cover, continuity, laps, welds, and splices. Other reinforcement requirements are presented in Section 4, and any additional requirements are given in the Part II section for a specific product. 6.2 Cover—The exposure of the ends of reinforcement, stirrups or spacers used to position the reinforcement during placement of the concrete shall not be cause for rejection. 6.3 Continuity—The continuity of the circumferential rein- forcement shall not be destroyed during the manufacture of the product, except when lift holes or pipe openings are provided in the product. 6.4 Welded Steel Cage Laps, Welds, and Splices:6.4.1 If splices are not welded, the reinforcement shall be lapped not less than 20 diameters for deformed bars, and 40 diameters for plain bars and cold-drawn wire. In addition, where lapped cages of welded wire fabric are used without welding, the lap shall contain a longitudinal wire. 6.4.2 When splices are welded and are not lapped to the minimum requirements in 6.4.1, there shall be a minimum lap of 2 in. and a weld of sufficient length such that pull tests of representative specimens shall develop at least 50 % of the minimum specified tensile strength of the steel. For butt welded splices in bars or wire, permitted only with helically wound cages, pull tests of representative specimens shall develop at least 75 % ofthe minimum specified tensile strength of the steel. 6.5 Steel Hoop Splices—When splices are welded and are not lapped to the minimum requirements in 6.4.1, there shall be a minimum lap of2 in. and a weld ofsufficient length such that pull tests from representative specimens shall develop at least 50 % ofthe minimum specified tensile strength ofthe steel. For butt welded splices, pull tests from representative specimens shall develop at least 75 % of the minimum specified tensile strength of the steel.
7. Precast Concrete Manufacture
7.1 Mixture—The aggregates shall be sized, graded, proportioned, and mixed with such proportions ofcementitious materials and water as will produce a thoroughly-mixed concrete of such quality that the products will conform to the test and design requirements of this specification. All concrete shall have a water-cementitious ratio not exceeding 0.53 by weight. Cementitious materials shall be as specified in 4.1.2 and shall be added to the mix in a proportion not less than 470 lb/yd 3 , unless mix designs with a lower cementitious materials content demonstrate that the quality and performance of the product meet the requirements of this specification. 7.2 Curing—Concrete products shall be subjected to any one of the methods of curing prescribed in 7.2.1 – 7.2.4 or to any other method or combination of methods approved by the owner that will give satisfactory results. 7.2.1 Steam Curing—Concrete products are placed in a curing chamber, free of outside drafts, and cured in a moist atmosphere maintained by the injection of steam for such time and such temperatures as needed to enable the products to meet the strength requirements. The curing chamber shall be so constructed as to allow full circulation of the steam around the entire product. 7.2.2 Water Curing—Concrete products are water-cured by covering with water-saturated material, or by a system of perforated pipes, mechanical sprinklers, porous hose, or by any other approved method that will keep the products moist during the curing period.