Improvement of flexural strength of concrete pavements using natural rubber latex

•Evaluation of compressive and flexural strengths for NRL-concrete.•Evaluation of microstructure for NRL-concrete.•Suggestion of cost-effective mix design of NRL-concrete pavement. In this research study, natural rubber latex (NRL) was used as a “green” additive to improve the flexural strength properties of concrete pavements. The mechanical compressive and flexural strengths of NRL modified concrete were investigated, using various water-to-cement (w/c) and dry rubber content-to-cement (r/c) ratios and curing times. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analyses techniques were used to examine the mechanical strength development of modified concrete. The results indicated that the compressive strength of NRL-concrete decreased with increasing the r/c ratio at all w/c ratios and curing times, whilst the highest flexural strengths were found at the optimal r/c = 0.58%, 1.16%, and 1.73% for w/c = 0.3, 0.4, and 0.5, respectively. The w/c ≤ 0.4 and r/c ≤ 2.31 as well as w/c = 0.5 and r/c = 0.58 to 1.73 were found to be applicable to NRL-concrete pavements, as the compressive and flexural strengths met the minimum requirements specified by the Department of Highways, Thailand. A mix design chart was proposed for NRL-concrete pavements, to facilitate the determination of effective mix ingredient based on operation and material cost to meet both economical and engineering criteria.