Question

Approximate ratio of the strength of the cement conc of 7 days to that of 28 days (2/3)?

(a) .75

(b) .85

(c) 1

(d) 1.15

Answer 1

Correct answer is (a) .75

The explanation: After the lab broke the seven-day cylinders, the cylinder from the pier with added water broke at 1980 psi. The other seven-day cylinders were as high as 2620 psi.