Experimental and simulation study on capillary water absorption of modified crumb rubber concrete with steam-cured

Abstract

It is well known that the process of steam curing will cause micro-cracks in concrete, which will adversely affect its water absorption performance. In this study, rubber particles were added into steam-cured concrete to reduce its water absorption capacity. Three types of rubber contents and two rubber modification methods, namely, NaOH modification and silane coupling agent (SCA) modification, were considered herein. Compressive strength, capillary water absorption (CWA), contact angle test of concrete was tested, and Fourier-transform infrared spectroscopy, Mercury intrusion porosimetry were used to study microscopic evolution, and ABAQUS simulations, molecular dynamics simulations were performed to reveal mechanism. The results showed that rubber particles could prevent the decrease in strength and reduce capillary water absorption coefficient in steam-cured concrete. When the rubber content was 70 kg/m3, the CWA coefficient of the steam-cured rubber concrete RC70-steam was reduced by 62.3% compared with that of the steam-cured concrete RC0-steam. Both NaOH and SCA modification introduce new functional groups on the surface of the rubber particles and reduce their contact angles, increased the water molecule content, endowing the surface with improved hydrophilicity, resulting in a more dense bond between rubber particles and concrete, thereby reducing the capillary water absorption coefficient. The addition of rubber particles optimised the pore structure inside the steam-cured concrete, and the proportion of transition pores was reduced by 5%, which contributed to improving the CWA of the concrete. The ABAQUS simulation showed that the addition of rubber increased the distortion effect of the water transport and extended the water transport path. The molecular dynamics results showed that the surface functional groups of rubber were changed and the hydrophobicity of rubber was reduced, which improved the bonding property of the rubber-concrete interface.