A comparison of strength and elastic properties between conventional and lightweight structural concretes designed with expanded clay aggregates

Properties such as compressive strength, modulus of elasticity (MOE), Poisson's ratio and the ductility of lightweight aggregate concrete (LWAC) mixtures were investigated, and the results obtained were compared with conventional concrete (CC) mixtures with similar design characteristics. For this purpose, LWAC mixtures were casted using lightweight expanded clay (EC) aggregates with different unit weight properties. Dry unit weights of LWAC mixtures changed approximately between 1640 kg/m³ and 2050 kg/m³. To express the effect of matrix strength on the determined properties, concrete mixtures with different matrix strengths were designed by keeping the total aggregate volume constant. For this purpose, the water to cementitious material ratio and the amount of cementitious materials were changed. Results have shown that, depending on the unit weight of concrete, the compressive strength of LWAC mixtures varied between 20 MPa and 70 MPa. Compared with CC mixtures, the elastic properties and ductility of LWAC mixtures changed significantly. Within the same compressive strength range, LWAC mixtures showed remarkable reduction in MOE and more brittle behavior compared with CC mixtures. Poisson's ratios of the LWAC and CC mixtures, on the other hand, produced similar values. A new model for predicting the MOE of such concretes is also suggested.