A project specifies a concrete strength of 24.1 MPa. Materials engineers will design the mix for a strength higher than that to account for variables. a. Calculate the required average compressive strength of the mix design if the mixing plant has a standard deviation of s = 3.8 MPa. b. Using the ACI code equation, estimate what would be the modulus of elasticity of this concrete at the required compressive strength. What is your recommendation for the maximum size of coarse aggregate for the following situation? A continuously reinforced concrete pavement cross section contains a layer of No. 6 reinforcing bars at 6-in. centers, such that the steel is just above mid-depth of a 10-in. thick slab. Cover over the top of the steel is therefore about 4 in