Restrained shrinkage cracking in steel fibre reinforced and rubberised cement-based mortars

Abstract

The paper focuses on the combined effect of Steel Fibre Reinforcement and of Rubber aggregates on the resistance to restrained shrinkage cracking of cement-based mortars. The kinetics of restrained shrinkage cracking of a control mortar is compared both to the one incorporating a single fibre content as reinforcement and to the above fibre reinforcement combined to rubber aggregates substitution. Two rates of substitution were considered in the case of Steel Fibre Reinforced and Rubberized Mortar (SFRRM). The used rubber aggregates are obtained by grinding used tyres, a way that may address the demand for the conservation of a clean environment by recycling an industrial by-product. Fibre-reinforced mortar was based on the control mortar and one metal fibre content was studied: 40 kg/m3 (0.5% by volume). The used fibres have a high bond with the cementitious matrix. SFRRM composites were cast using two contents of rubber aggregates: 20 and 30% by volume replacing mineral aggregates and the one fibre content reported here above (40 kg/m3). Tests were conducted using ring type specimens to simulate restrained shrinkage cracking according to ASTM C 1581-04 standard. Additionally, after the cracking occurred, the development of the crack widths was measured by video-microscope. Ring tests demonstrated that the SFRRM exhibit high strain capacity prior to macro-cracking localization and the effectiveness of rubber aggregates along with their positive synergistic effect when combined with fibre reinforcement to improve resistance to shrinkage cracking. It is a promising solution to improve the durability of large surface area such as pavements and thin bonded cement-based overlays, whose durability is often limited by shrinkage cracking.