A design engineer specifies a concrete strength of 5500 psi. Determine the required average compressive strength to be used in a mix design for: A new concrete plant where s is unknown A plant where s = 500 psi for 22 test results A plant with an extensive history (>30 tests) of producing concrete with s = 400 psi A plant with an extensive history of producing concrete with s = 600 psi Solution Here fck= fck +2.3 s.

1. A design engineer specifies a concrete strength of 5500 psi. Determine the required average
compressive strength to be used in a mix design for:
A new concrete plant where s is unknown
A plant where s = 500 psi for 22 test results
A plant with an extensive history (>30 tests) of producing concrete with s = 400 psi
A plant with an extensive history of producing concrete with s = 600 psi
Solution
Here fck= fck +2.3 s