Effect of Waste Tyre-Rubber Aggregate on the Strength Properties of Concrete

This research studied strength-characteristics of concrete using waste tyre-rubber as partial replacement for coarse aggregate in concrete construction and compares the results to those of conventional concrete. The specimens were produced with percentage replacements of the coarse aggregate by 5%, 10% and 15 % of rubber aggregate. A control mix with no replacement of the coarse aggregate was produced, to make a comparative analysis. The samples consisted of concrete cubes, cylinders and beams. Various tests (such as slump, compressive strength, splitting tensile strength and flexural strength tests), were conducted. Data-collection was mainly based on the results of the tests conducted on the specimens in the laboratory. The results show that there is a reduction in the compressive strength of the concrete, due to the inclusion of rubber aggregates. Compressive strength losses of 12.69%, 17.75% and 25.33% were noticed for 5%, 10%, 15% replacement of coarse aggregate, respectively; tensile strength losses of 13.01%, 20.12%, and 24.76% were observed, respectively, when 5%, 10%, 15% of the coarse aggregate was replaced, after 28 days of curing; -0.1%, -0.15% and 0.2% decrease in flexural strength was observed for 5%, 10% and 15% replacement, respectively, after curing for 28 days. Rubberised concrete was found to have some desirable characteristics (such as lower density, enhanced ductility, and a slight increase in flexural strength in the lower compressive strength concrete categories). The overall results show that it is possible to use recycled rubber tyres in concrete construction, as a partial replacement for coarse aggregates. Nevertheless, the percentage of replacement should be limited to 10% (which ensures the strength of the concrete is kept within the required range), and the application should be restricted to particular cases where the properties related to the replacement with the rubber aggregates clearly indicate an improvement on conventional concrete, and so are desirable.