Effect of rubber crumb on the microstructural properties of concrete

Abstract

This study evaluates the effect of rubber crumb on the microstructural properties of concrete which was used to partially replace fine aggregate by 0, 4, 8, 12, and 16% proportion and designated as M₀, M₄, M₈, M₁₂, and M₁₆ respectively. The wet and hardened properties of concrete were investigated by conducting a slump test and a compressive strength test, and by measuring the concrete bulk density. The crack formed as a result of compressive strength was investigated using a digital microscope, while the micro-cracks formed in the concrete structure were investigated using a scanning electron microscope (SEM). The results showed that concrete slump for all the samples range between 25 and 10 mm, with M₀ and M₄ having the highest slump. The compressive strength and density of the concrete decreased as the amount of rubber crumb increased in the mixture, with M₀ having a compressive strength of 51.88 N/mm² and M₁₆ having the lowest compressive strength of 19.40 N/mm². The SEM analysis showed that there was a weak bond between the concrete paste and the rubber crumb, which resulted in to a weak adhesive force, and the development of micro-cracks which contributed to the week compressive strength in concrete with higher rubber crumb.

Keywords:

• rubber crumb
• concrete
• micro-cracks
• microstructure
• compressive strength

Acknowledgements

The authors acknowledge the assistance and support of the Applied Microscopy and Triboeletrochemical Research Laboratory, Tshwane University of Technology, Pretoria for performing the scanning electron microscopy experiments.