The influence of the age of concretes with FBC fly ash or metakaolinite additives on their strength properties

Abstract

An influence of the age of concretes modified with addition of activated fluidized bed combustion (FBC) fly ash (fluidal ash - FL) or metakaolinite (MK) on their compressive strength fc, fracture toughness KIcS and Young's modulus E is determined in the paper. The additives were used as equivalents of part of cement. The performance effectiveness of both additives as substitutes of part of concrete is compared. The investigations were conducted after 28, 90 and 180 days of concrete curing. The functions for calculation of investigated mechanical properties of concretes (fc, KIcS and E) after 28, 90 and 180 days of hardening are given. Statistically significant influence of the concrete age and the change of its composition on the investigated mechanical properties (fc, KIcS and E) was shown. An increase in all the investigated parameters values (fc, KIcS and E) with the decrease in the water/binder ratio and diversified influence of the additive content change with respect to the age of the concrete was observed. It was found that the biggest increment of the values of investigated parameters occurs after 28 days of curing in relation to the results of 90 and 180 days concrete. A model enabling prediction of compressive strength fc of the concrete modified by mechanically activated FCB fly ash or metakaolinite with respect to its composition and age, was created.