Mechanical properties - Compressive strength

The development of compressive strength (EN 12390-3), measured at 0.5, 1, 2, 3, 7, 28 and 56 days, of all concrete types is shown below as average of two measurements at each age.

One trend observed is that microsilica seems to increase strength development in the middle period, i.e. particularly from 3 until 28 days of maturity. There is no apparently "kick" in strength development from fly ash at later ages. The slag based concretes exhibits a slow early strength development followed by a period (2-28 days), where the rate of strength gain is significantly higher compared to Portland cement based concrete, before leveling off at strength comparable to that of the microsilica containing Portland cement based concretes. For the 3-powder concretes lowering the w/c-ratio from 0.40 to 0.35 results in higher strengths at all ages, while increasing the w/c-ratio from 0.40 to 0.45 results in lower strengths at all ages.