Positive synergy between steel-fibres and rubber aggregates: Effect on the resistance of cement-based mortars to shrinkage cracking

Cement-based materials suffer from their low tensile strength and their poor straining capacity: they are sensitive to cracking, particularly shrinkage cracking. Enhancing the cracking resistance of cementitious materials is the challenge of a broad ongoing research programme. In this regard, the aim of the present work was the design of a cement composite exhibiting a high straining capacity before macrocracking localisation. It was assumed that incorporation of aggregates with low elastic modulus could be a solution. Actually rubber aggregates obtained from shredded non-reusable tyres were used, conferring an environmental interest on the study.After a previous contribution focusing on the basic mechanical properties of rubberised mortar, the purpose of this paper is to present the influence of rubber aggregates on the load–deflection relationship of mortar in flexure. The synergy between rubber aggregate substitution and metal–fibre reinforcement was also investigated. Despite the low strength and high shrinkage length change of rubberised mortars, ring-tests showed that the composite materials exhibited an enhanced resistance to shrinkage cracking. In this regard, a positive synergy effect between rubber aggregates and steel-fibres was evidenced: shrinkage cracking was delayed and when it occurred, multiple cracking with thinner crack openings was observed.