Effect of Sand Particle Size on the Thermal Effusivity of Clay-Admixed Cement Mortar Bricks

This work aim to study the effect of sand granulometry on the thermal effusivity of blocks made by cement mortar mixed with clay. Three granular classes of sand (\(\:{E}_{2}\)(0.08/0.5mm), \(\:{E}_{3}\) (0.5/1.6mm), \(\:{E}_{4}\) (1.6/2mm)) and clay are used. The chemical characterization of the clay and the particle size test of the clay and sand were carried out according to the standards NF P94-555-1 and NFP 94 − 041, respectively. In the mortar, the sand was substituted with clay at 0%, 10%, 20%, 30%, 40%, 50% and 60% of the total sand mass, for clay contents ranging from 0 to 45%. The concrete samples were cast in standard molds of 100x100x30mm ³ size. The thermal tests using the asymmetric hot plate and parallel hot wire methods were conducted on the 63 samples manufactured. The results revealed a progressive decrease in the thermal conductivity and thermal effusivity with increasing clay content, regardless of the sand particle size. For class\(\:{\:E}_{2}\), the effusivity decreases from 1 606 at 0% of clay to 1 311 J.kg ^− 1 .m ^− 2 .s ^1/2 at 60%, corresponding to an 18.37% reduction, accompanied by a decrease in thermal conductivity from 2.71 to 1.79 W.m ^− 1 .k ^− 1 , corresponding to a 33.9% reduction. For\(\:\:{E}_{3}\), the effusivity was reduced to 25.55% and the thermal conductivity was reduced to 43.6%. For \(\:{E}_{4},\) the effusivity reduction was 27.76% and 43.8% respectively for its thermal conductivity. It appears that the influence of the sand particle size remains marginal. These decreases are attributed to the low intrinsic conductivity of the clay minerals, increased porosity due to the loss on ignition, and the disruption of the thermal conduction pathways.