Abstract

Cemented materials have high compressive strength but low toughness and flexural strength. This research evaluated improvement of toughness and flexural strength of cemented materials with the addition of natural rubber (NR), based on the results from extensive testing of the cemented pastes. While mixing with cement (C), Sodium dodecyl sulfate (SDS) was used as a surfactant admixture to provide stability to the NR particles. The natural rubber modified cement (NRMC) pastes were prepared by varying the influence factors, namely: SDS/C ratio, SDS to dry rubber content (SDS/DRC) ratio, and DRC/C ratio at the same water to cement (W/C) ratio of 0.55. The DRC/C ratios were varied in the range of 0–50%. The role of the influence factors on bulk density, setting time, temperature of setting paste, compressive and flexural strengths, and toughness of NRCM pastes were also studied in this research. Scanning electron microscopy (SEM) images and energy dispersive spectrometry (EDS) were carried out on the NRCM pastes to confirm on the presence of NR films and air bubble in the NRMC pastes. The bulk density was found to decrease in proportion to the increases in the SDS/C and DRC/C ratios. The addition of NR latex was found to improve the flexural strength and toughness, whilst retarding the setting time and hydration. The flexural strength was found to be increased with increasing DRC/C, up to the optimal value. Beyond this optimal value, the flexural strength decreased but with higher flexural deflection. The optimum SDS/DRC ratio of 10% and DRC/C ratio of 10 provided the highest compressive and flexural strengths of NMPC paste. The knowledge gained from this study provides useful information for further research and practice in infrastructure engineering applications such as earthquake-resistant lightweight cement wall and impact-resistance products.