Strength Requirements

Example $1.$ The design engineer specifies a concrete strength of $4500$ psi $.$ Determine the required average compressive strength for:

i$)$ a new plant for which $s$ is unknown

ii$)$ a plant for which $s=520$ psi for $17$ test results

iii$)$ a plant with extensive history of producing concrete with $s=350$

iv$)$ a plant with extensive history of producing concrete with $s=550$