A sustainable application of recycled tyre crumbs as insulator in lightweight cellular concrete

Abstract

End-of-life waste tyres are known to have negative economic and environmental impacts due to the difficulty associated with their disposal and recycling. The use of recycled tyre crumb (RTC) as a component of construction materials has emerged as a potentially sustainable solution to this environmental issue. There exists extensive research covering the use of RTC as a filler in conventional concrete. However, there are very limited studies focused on insulation properties of RTC in lightweight cellular concrete (LCC) as a sustainable application that can add value to the final product. This study investigates the effects of different RTC contents on compressive strength, porosity, thermal conductivity, sound insulation and water permeability of LCC as an insulator. A rather homogeneous distribution of tyre crumbs within LCC structure was achieved. It has been found that LCC samples containing RTC are suitable as insulators because the sound and thermal insulation are improved as rubber content is increased compared to the sample with similar density but without RTC. The insulation properties of this product also come with the same total porosity and a significant reduction in the rate of water permeability compared to the sample without RTC. 3D restructuring of micro-CT scan images of this composite revealed the effects of tyre crumb on the total and local porosity of this composite. Despite the fact that addition of tyre crumb reduced the strength, surface treatment of crumb rubber with sodium hydroxide solution exhibited significant improvement in the compressive strength of LCC as the result of better physical bonding with hydrated cement proven by scanning electron microscopy (SEM) images and energy dispersive spectroscopy (EDS) analysis.