For high-strength concrete, a cement should produce a minimum 7-days mortar-cube strength of approximately ___ MPa.

For high-strength concrete, a cement should produce a minimum 7-days m

1.	For high-strength concrete, a cement should produce a minimum 7-days mortar-cube strength of approximately ___ MPa.
A.	10
B.	20
C.	30
D.	40
Answer» D. 40