In: Civil Engineering
Design a concrete mix for reinforced concrete beams of a structure. The structure is located in a locality wherein water has excess of chlorides in it. Required average compressive strength of concrete has been determined to be 4700 psi. Beams have cross-section of 9 in. x 21 in. reinforced with 4 # 6 bars. Reinforcement has a concrete cover of 1.25 in. and there is a clear space of 1.0 in. between form surface and steel bars. Fine aggregate has bulk specific gravity (SSD) of 2.63; absorption capacity of 1.25%; surface moisture of 3.0% and a fineness modulus of 2.75. Coarse aggregate has bulk specific gravity (SSD) of 2.70; absorption capacity of 2.50 %; surface moisture of 1.75% based on SSD state and dry-rodded unit weight of 110 lb/ft3. Design concrete mix following the step-by-step method of ACI 211.1-91 for the subject beams and tabulate the quantities of ingredient materials in lb/yd3, lb/ft3 and 1.5 lb/ft3. Provide reference of relevant ACI Tables in each step.