Mechanical and time-dependent properties of high-volume fly ash concrete for structural use

A two-phase experimental study on the effect of simultaneous partial replacement of cement and fine aggregate with fly ash on the mechanical and time-dependent properties of high-volume fly ash concrete (HVFAC) is presented. The results of the first phase of the study show that it is possible to make structural grade HVFAC with 50% of cement and an additional 30% of fine aggregate replacement that has a similar compressive strength to that of the control cement concrete and with adequate workability. In the second phase of the study the mechanical and time-dependent properties of HVFAC with a mass of fly ash of 50-70% of the total mass of cementitious materials were tested. The results show that with the increase in fly ash content the compressive strength of HVFAC increased by 22% on average at all ages tested. With the exception of the early-age compressive strength, it was found that the European standard EN 1992-1-1:2004 provisions for ordinary cement concrete underestimate the mechanical properties and significantly overestimate the shrinkage and creep of HVFAC. Better correlation with experimental results was obtained using different coefficients developed for HVFAC