The effect of compressive stress on thermal and hygric properties of Portland cement mortar in wide temperature and moisture ranges

Basic thermal and hygric parameters of cement mortar - namely, the thermal conductivity, the linear thermal and hygric expansion coefficients, moistur e diffusivity, and water vapor permeability - are determined in dependence on the applied mechanical load inducing compressive stress in the samples r anging from 0% to 90% of compressive strength. The measurements are perform ed in wide temperature and moisture ranges, from 20 degreesC to 1000 degree sC and from the dry state to the saturation water content. The measured res ults show that both thermal and hygric parameters of cement mortar are affe cted only by compressive stress of 90% of the compressive strength of the m aterial and higher, in a significant way. Scanning electron microscope imag es and porosimetric measurements reveal that the most probable reason for t he observed differences in thermal and hygric parameters is the appearance of cracks with a typical width of 1-2 mum. (C) 2000 Elsevier Science Ltd. A ll rights reserved.