Properties and sustainability of treated crumb rubber concrete

The construction industry is geared towards the use of sustainable building materials to accrue related environmental and economic benefits. In the present study, waste crumb rubber (CR) particles were pretreated using NaOH, KMnO4, and cement and used to replace 2%, 8%, 16%, 24% and 40% of the sand in concrete. The effect of the selected treatment methods on the properties of crumb rubber concrete (CRC) was evaluated by measuring compressive strength, abrasion resistance, acoustic performance, and thermal resistance. Further, the reduction in CO2 emission due to the use of CR in concrete was estimated. The results indicated that the developed structural CRC (compressive strength of more than 30 MPa) can be produced with up to 16% CR. The compressive strength of structural CRC with 16% NaOH-, KMnO4- and cement-treated CR increased by 2%, 12% and 15%, respectively, while the compressive strength of non-structural CRC with 40% CR increased by 6%, 23% and 76%, respectively. The weight loss due to abrasion of structural NaOH-, KMnO4- and cement-treated CRC with 16% CR decreased by 37%, 48% and 52%, respectively, while the weight loss of non-structural CRC with 40% CR decreased by 23%, 54% and 58%, respectively. Image analysis indicated that the treated-CR particles exhibited higher resistance to pull out from the concrete matrix than the untreated-CR. Even though CRC with treated-CR exhibited inferior sound and thermal insulation compared to CRC with untreated-CR, the sound and thermal insulation of the developed mixtures was better than that of conventional concrete. Further, CRC with treated-CR exhibited a considerable reduction in energy and fuel consumption and CO2 emission compared to conventional concrete. The use of NaOH-, KMnO4- or cement-treated CR in load-bearing CRC walls will decrease the annual CO2 emission by 1.30, 1.23, and 1.21 times, respectively, compared to that of conventional load-bearing concrete walls. Further, the use of NaOH-, KMnO4- or cement-treated CR in non-load bearing CRC walls will decrease the annual CO2 emission by 1.97, 1.82, and 1.53 times compared to the conventional non-load bearing concrete walls.