Proposed ACI Standard Minimum Requirements for Thin Section Precast Concrete Construction
ACI Committee 324
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These minimum requirements pertain to design and construction of precast concrete structural elements the thickness of which is less than that permitted by standard building codes for use in normal fire-resistant structures, but is in no case less than 1 in. The use of either normal, moderate sulfate-resisting, or high-early-strength cement is permitted. Special grading limits for coarse aggregate are cited, and specifications for reinforcement and admixtures are given. Concrete of 4000-psi strength is specified for protected locations not in contact with the ground; 5000-psi concrete for other locations. Limits for air content, water-cement ratio, and cement content are given. Accurate placing of reinforcement is emphasized, and the amount of cover is stated. Fabrication is discussed in provisions on mixing, molds, casting, curing, surface treatment, and tolerances of individual elements. Supervision and inspection during fabrication are stressed, with some requirements for acceptance. Method and sequence of erection are also treated, including connection devices, assembly tolerances, and weatherproofing of joints. Differences in certain requirements from those given for normal fire-resistant structures in ACI 318 and ACI 711 are pointed out and the reasons therefor explained.