Mechanical properties - Compressive strength - Drilled cores

Three cores drilled from the small blocks were used to determine the compressive strength (EN 12504-1) of the concretes at 28 days of maturity. The results are shown below.

The three fly ash concretes (mix B, C and D) and the high w/c-ratio concrete (mix H) have the lowest strength at 28 day of maturity, whereas the non air entrained concrete G and the low w/c-ratio (mix I) have the highest strength. This was true both for the actual measurements as well as after normalising the strengths to fixed air content (4 %) using the rule of thumb that one percentage point increase of air content results in a decrease of 4 % in strength.