The effect of aggregate absorption on pore area at interfacial zone of lightweight concrete

An experimental program was carried out to study the effect of water absorption of lightweight aggregate on the pore size distribution at the interfacial zone of lightweight aggregate concrete. Properties of lightweight expanded clay aggregates with absorption of 8.9%, 9.4% and 11% were compared. In order to do the study, three lightweight concrete mixes of water to cement ratio of 0.4, 0.44 and 0.48 were batched. The pore area percentage and pore size distribution in the cement paste and at the interfacial zone of the concretes cured for 28 days were examined using a high resolution optical microscope and image analysis software. The findings indicated that the pore area percentage at the interfacial zone was much higher than that at the hardened cement paste. The effect of W/C ratio of concrete on the pore area percentage at the interfacial zone was not significant. The aggregate of larger water absorption produced greater pore area percentage at the interfacial zone of concrete. For aggregates with absorption ranging from 8.9% to 11%, the pore area percentage ranged between 14.4% and 21.7%.