Abstract:
The study investigated the effects of selected potential chemical activators on thermal resistivity
of calcined clay based cement mortars. 0.5 M Na2SO4 and 0.5 M NaOH were used as activator
solutions. The chemical composition of sampled clays was determined by use of X-Ray
Florescence (XRF) technique. Clays were incinerated at a temperature of 800 °C for 4 h. The
calcined clays obtained were blended with OPC at replacement level of 35 percent by mass of
the OPC to make the test cement labeled PCC35. The PCC35 mortar prisms measuring
40 mmx40mmx160mm were cast with activator solutions and cured in water. Compressive
strength was determined at the 28
th
day of curing. As a control, OPC and PCC35 were similarly
investigated without activator solutions. The 28 day cured mortars were exposed to a temperature
of 700 °C for 2 h then cooled in water to room temperature and their compressive strengths
determined. Chemically activated PCC35 and non-activated PCC35 exhibited lower loss in
weight than OPC after exposure to the elevated temperatures. Chemically activated PCC35 and
non-activated PCC35 exhibited higher residual compressive strength than OPC after exposure to
the said temperatures. Na2SO4 activated mortars showed higher thermal resistance than NaOH
activated mortars. Generally, chemically activated PCC35 exhibited the highest thermal
resistance compared to non-activated PCC35 and commercial OPC mortars.
