Particle size effect on EPS lightweight concrete compressive strength: Experimental investigation and modelling

It had been observed [Parant, E., Le Roy, R., 1999. Optimisation des b6tons de densit6 inferieure h l. Tech. rep., Laboratoire Central des Ponts et Chaussees, Paris, France; Le Roy, R., Parant, E., Boulay, C., 2005. Taking into account the inclusions' size in lightweight concrete compressive strength prediction. Cem. Concr. Res. 35 (4), 770-775; Ganesh Babu, K., Saradhi Babu, D., 2002. Behaviour of lightweight expanded polystyrene concrete containing silica fume. Cem. Concr. Res. 2249, 1-8; Laukaitis, A., Zurauskas, R., Keriene, J., 2005. The effect of foam polystyrene granules on cement composite properties. Cem. Concr. Compos. 27 (1), 41-47] that the compressive strength of expanded polystyrene (EPS) lightweight concrete increases significantly with a decrease in EPS bead size (0), for the same concrete (macro) porosity (P) (EPS volume fraction). To confirm that this scaling phenomenon is an intrinsic particle size effect which is related to the EPS bead size (phi) and not affected by a volume size effect related to the specimen size (D), compressive tests have been carried out on homothetic EPS concrete specimens containing homothetic EPS beads. Moreover, five concrete (macro) porosities ranging from 10% to 50% have been investigated. Compressive tests results have confirmed the presence of a particle size effect on the EPS concrete compressive strength. Further, it is observed that this size effect is very pronounced for low porosity concretes and becomes negligible for very high porosity concretes. Based on EPS concrete failure modes analysis, a phenomenological model has been proposed with a view to explaining the EPS concrete particle size effect and predicting its normalized compressive strength according to the concrete (macro) porosity (p) and to the ratio (phi/I(c)) where (I(c)) is the width of the EPS concrete matrix fracture process zone (FPZ). The model predictions have been then compared with experimental results, showing a good agreement. (c) 2006 Elsevier Ltd. All rights reserved.