Taking into account the inclusions' size in lightweight concrete compressive strength prediction

This paper deals with the mix design and mechanical properties of very lightweight concrete (LWC) made of expanded polystyrene spheres (EPS) and very high performance matrix. To avoid the segregation of EPS spheres in the concrete, it is necessary to adjust the matrix threshold by modifying the superplasticizer dosage. Based on experimental data obtained on different EPS concrete, it is shown that the lower the inclusion size, the higher the compressive strength of the hardened concrete. An empirical model is proposed, to take into account these experimental results. Young's modulus was also measured, it was found that its evolution against strength followed usual physical models, like the well-known Hashin's sphere model, and not an empirical one. Finally, a simulation, based on criteria outlined in the paper, shows that quite new concretes can be proposed in a range of strength versus specific gravity not yet achieved.