Mechanical behaviour of rubberised geopolymer composites

In this research study, crumb rubber geopolymers (CRGs) were prepared to alleviate the brittleness and enhance the impact strength of a geopolymer matrix. Two different sizes of crumb rubber (CR), 0.86 ± 0.25 mm (20m-CR) and 0.32 ± 0.14 mm (40m-CR), were used to replace the geopolymer matrix at 5, 10, 15 and 20 wt%. With increasing CR content, the bulk density was found to decrease while the porosity increased. The compressive and flexural strengths of the composite progressively decreased with increasing CR content. The greatest decrease was found in the 40m-CRG series. The rubberised geopolymer under compression testing remained intact after failure, suggesting improved ductility, as expected. Although the fracture toughness was insignificantly influenced by the CR size, the impact of CR content remains unclear. The impact strength was observed to improve around three-fold in the CRGs with 20 wt% CR, regardless of the CR size. Due to its fragility and low impact strength, the use of geopolymer paste in some construction applications is limited. This promising impact strength improvement thus opens up an opportunity for geopolymer-based materials to be used in such areas.