Towards understanding cork concrete behaviour: Impact of considering cork absorption during mixing process

The main objective of this paper to examine the impact of varying the considered level of cork absorption during preparation of cork concrete. For this purpose, experiments were carried out on cork concretes considering three different levels of cork absorption, namely: (i) no water, (ii) water corresponding to 2 h of cork absorption and (iii) cork saturation water. For each level of absorption, three cork percentages (25, 50 and 75%) were studied. Concretes were tested in terms of consistency, density, microstructure and hygro-thermo-mechanical properties. Microstructure' results highlighted the impact of considering cork absorption on the porosity of concrete, its pore size distribution and the Interfacial Transition Zone (ITZ) between cork and matrix. By increasing the considered level of cork absorption, the hygric performance of cork concretes was substantially improved. For instance, by going from zero to a saturation level, an increase of 20% was recorded on Moisture Buffer Value (MBV) of concrete with 75% of cork. The best thermal conductivity was obtained for concretes incorporating water corresponding to 2 h of cork absorption. However, the highest specific heat (Cp), value that insure high thermal inertia, was recorded for concretes containing cork saturation water. Depending on water amount and cork percentage, thermal conductivity of concretes ranged between 140 and 1230 mW/(m.K). Notwithstanding the decrease of compressive strength with increasing cork absorption water, the produced concretes exhibited good performance for the use as non-structural materials.