Properties of high-performance cementitious composites containing recycled rubber crumb

Concrete containing rubber crumb from waste tyre has been investigated previously and enhancement of material performance, for example, energy absorbing, has been observed. However, at the same time, the degradation of compressive and flexural strength, as well as some other physical properties are also inevitable. In this study, physical, mechanical properties and durability of High Performance Cementitious Composites containing rubber crumb (HPCC-R) were assessed. Moreover, 2% volume fraction of micro steel fibres were added to form High Performance Fibre Reinforced Cementitious Composites (HPFRCC-R) to increase its integrity. Experimental results were then compared to those of the base material without rubber crumb. The impact of different mix design methodologies, grading of rubber particles, and different curing conditions were investigated. It was observed that the drying shrinkage is neglectable after hot water curing at either 90 °C or 60 °C for HPCC-R. Under normal curing condition, drying shrinkage development follows the similar trend as the base material but end up with approximately 20% higher shrinkage at 28 days’ age. The compressive strength and flexural strength of both HPCC-R and HPFRCC-R decrease significantly with the increase of the amount of rubber crumb. Applying hot water curing at 90 °C and pre-treatment of rubber crumb using Na(OH) were identified as effective approaches to compensate the compressive strength loss. However, it was observed that impacts of different curing conditions are insignificant on the flexural strength development. The rapid chloride permeability test (RCPT) results of HPFRCC-R material under different curing conditions were at the same level, and as good as that of the base material. Mixing scheme of using rubber crumb as filler material instead of replacement of fine sand lead to better material performance regarding its compressive strength versus density ratio at a relatively high replacement ratio of 40% by volume. It is recommended to use “Addition” mixing scheme when a large amount of rubber crumb being used in HPFRCC in the future.