The effect of temperature on strength-porosity relationship for concrete

In this paper, the unsealed concrete samples are tested to determine the compressive strengths and porosities while hot at various temperatures ranging from 25 to 280 degreesC. All measurements have been carried out after cooling the of the material. Porosity of the same concrete was measured using high-pressure mercury porosimetry, performed on a set of small-drilled fragments (of the average volume 0.5 cm(3)) of hardened cement paste. While the concrete at the age of 90 days exhibits expected dependency between compressive strength S and porosity P (i.e., S to be a decreasing function of P), specimens at the age of 28 days behave exactly conversely in this sense. Consequently, it seems to be that for the latter case the porosity does not influence dominantly the strength of concrete. (C) 2004 Elsevier Ltd. All rights reserved.