Millions of tyres are discarded every year. Since rubber is durable and non-biodegradable, disposal is a major challenge. Burning rubber produces noxious carcinogens. And tyres in landfills trap methane, endangering health.
Waste rubber can be reused as fuel in cement kilns. It can also be used in athletic tracks, basketball courts or bathroom flooring. Recently, researchers from the Malaviya National Institute of Technology, Jaipur, came up with yet another use for waste rubber. They used crumb rubber – tyres that are mechanically ground – as substitute for the fine aggregate in concrete. Such concrete is resistant to acid attack, say the scientists.
The team mixed cement and crumb rubber at various concentrations and made concrete cubes and immersed them in a 3% sulphuric acid solution. They examined changes in weight, compressive strength and microstructure after 7, 28 and 90 days. In the first week and after 28 days of the experiment period, the results were not impressive. The scientists noticed significant changes only after 90 days.
“We saw that compressive strength and weight reduced after 90 days when concrete with crumb rubber was exposed to acid. This could be because crumb rubber reacts with sulphuric acid to impart adhesiveness,” says Kunal Bisht, Malaviya National Institute of Technology, Jaipur.
“‘Crumb rubber at 4%, as replacement for fine aggregate, is most suitable for acidic environments,” says P V Ramana, his colleague.
So here is a trick to make concrete less heavy and crumbly and, at the same time, reuse waste rubber.
Construction and Building Materials, 194: 276–286 (2019);
Sushmitha Baskar, IGNOU