Assessment of the effect of rubber aggregates as a partial replacement for coarse aggregates on the properties of concrete.

Abstract

This report is a presentation of a study carried out to investigate the effect of using waste tyre rubber aggregates as a partial substitute for coarse aggregates on the concrete properties and the findings from the study on the properties like compressive strength, workability and unit strength are presented The use of rubber aggregates from waste tyres has been investigated by various researchers with a major aim of minimizing waste tyre accumulation due to its associated challenges by using it in concrete as other methods of reusing and recycling it are either not economical or environmentally viable. However, the use of waste tyre aggregates results into a decrease in the compressive strength. Some researchers have suggested different methods of treatment of the rubber aggregates for example the use of silica fume, sodium hydroxide in order to improve the bond between the rubber aggregates and the cement paste and in turn improving the compressive strength of the rubberized concrete. Others have suggested mechanical treatment of the rubber particles by making their surfaces rough still to improve the bond. This study particularly investigates the effect of different sizes of the rubber aggregates on the properties of concrete. Compressive strength tests, slump tests and unit weight tests were carried out on the concrete containing no rubber aggregates (control) and concrete containing different sizes of rubber aggregates that is 10mm, 20mm and a mix of the two sizes combined in a ratio of 1:1. The rubber aggregates were replacing coarse aggregates by 10% of their volume It was discovered that the 10mm tyre rubber aggregates give a lower strength reduction (52.92%) compared to the 20mm and 10&20mm rubber aggregates which give a value of 58.77%. 10mm rubber aggregates give concrete of a better workability among the rubberized concrete with a slump value of 23mm followed by 20mm rubber aggregates having a slump of 20mm and the 10&20mm rubber aggregates give the lowest slump value (12mm) hence lowest workability. The control concrete gives the highest value, hence coarse aggregates substitution with rubber aggregates from waste tyres results into a decrease in the concrete workability. Rubberized concrete has a poor strength gain compared to normal concrete and it is worst for the concrete containing the 20mm rubber aggregates