Evaluation of early-age thermal cracking resistance of high w/b, high volume fly ash (HVFA) concrete using temperature stress testing machine

Abstract

Fly ash (FA) is an environmentally hazardous industrial solid waste. High FA replacement levels on properties of concrete with low w/b have been widely investigated, however, studies on the thermal cracking behavior of HVFA concrete with high w/b are lacking. This paper investigated the effect of high volume fly ash (HVFA) on mechanical properties and thermal cracking resistance of concrete with a high w/b of 0.45 using temperature stress testing machine (TSTM). An adiabatic curing condition during the temperature rise stage and a rapid cooling during the temperature drop stage were applied on test specimens. The effectiveness of concrete with different FA replacement levels (0%, 20%, 50% and 80%) on the thermal cracking potential of concrete under a restraint degree of 100% has been addressed. Results showed that the mechanical properties of concrete mixture decreased with the increasing FA replacement level; the ratio of creep-to-free strain (i.e., relaxation behavior) of concrete mixture decreased when the FA replacement level reached 20%, and converted to increase for the FA replacement level ranging from 50% to 80%; FA replacement level with 50% showed a desirable effect on the thermal cracking resistance enhancement of high w/b concrete mixture regarding restrained cracking control.

Keywords

• High volume fly ash
• Mechanical properties
• Thermal cracking resistance
• High w/b
• Temperature stress testing machine