Application of ground scrap tyre rubbers in asphalt concrete pavements

A laboratory scale evaluation of the feasibility of using ground rubber from scrap tyres in dry process hot-mix asphalt concrete used for road pavement was investigated. The rubber to asphalt ratio (by weight) of the specimens that was initially kept constant at 0.2 was subsequently varied from 0.1 to 0.5 using different rubber particle sizes. Some specimens were cured at ambient temperature, while others were soaked in water inside a curing tank, for a period of 28-days in the laboratory. The Marshall method was used to prepare both conventional and rubberized asphalt concrete specimens. The indirect tensile testing machine was used in the measurements of mechanical properties of all specimens. The results from the study show that the rubberized asphalt concrete mix has much better mechanical properties than the conventional one: the tensile strength of the specimens for example, increased from 1.82 × 103 to 2.04 × 103 kPa as the rubber to asphalt ratio increased from 0.1 to 0.3. Similar trends were observed in compressive and tensile moduli. The mechanical properties of rubberized specimens cured in air and those soaked in water were not significantly different (P>0.05). However, the conventional concrete especially those soaked in water showed inferior mechanical properties. The rubber particle size of 0.60 mm had the best mechanical properties while that of particle size 2.36 mm has the poorest mechanical properties.