Effect of admixtures on thermal and thermomechanical behavior of cement paste

A comparative study was conducted on the thermal and thermomechanical behavior of cement pastes containing various additives (silica fume, latex, methylcellulose, and short carbon fibers). The thermal conductivity was decreased by silica fume, methylcellulose, or latex by up to 46 percent. It was not increased by carbon fibers. The specific heat was increased by silica fume, latex, methylcellulose, or carbon fibers by up to 9 percent. The flexural storage modulus decreased reversibly with increasing temperature from 30 to 150 C, whereas the weight loss upon heating was irreversible. Silica fume gave higher modulus than methylcellulose or latex, which in turn gave higher modulus than the absence of any additive. The creep rate was lower for silica fume than methylcellulose or latex, for which the creep rate was lower than the absence of any additive. The apparent coefficient of thermal expansion was reduced by silica fume (but still positive), but was negative for methylcellulose or latex.