2%

4%

6%

10%

affects only the early development of strength

affects only the ultimate strength

both [a] and [b]

does not affect the strength

remains constant

increases with richer mixes

decreases with richer mixes

none of the above

5%

10%

15%

20%

2.0 to 3.5

3.5 to 5.0

5.0 to 7.0

6.0 to 8.5