Flexural strength of rigid pavement using recycled concrete aggregates improved by polyvinyl alcohol

Research on the utilization of recycled concrete aggregate (RCA) in civil engineering applications is gaining popularity worldwide due to the increased efforts to promote the preservation of the environment and sustainable development. Recycled concrete aggregate concrete is, however, presently still limited to nonstructural applications. Recycled concrete aggregate concrete can still be considered as a rigid pavement material when its flexural strength is improved adequately to sustain future traffic loads. In this study, polyvinyl alcohol (PVA), a water-soluble polymer, was used to improve the flexural strength of RCA concrete. Polyvinyl alcohol was found to retard the hydration process, resulting in the delay in initial and final setting times of cement-PVA paste, therefore reducing the compressive strength of RCA-PVA concrete. For all the w/c ratios tested, the flexural strength increased with increasing p/c ratios up to an optimum p/c ratio that provided the highest flexural strength, followed by a subsequent decrease beyond this peak value. The optimum p/c ratio tended to increase with an increase in w/c ratio, being 0.5, 0.5, 1.0, and 1.5 for w/c ratios of 0.3, 0.4, 0.5, and 0.6, respectively. Based on the requirements of the Department of Highways, Thailand, the p/c ≤ 1 at w/c ≤ 0.5 was found to be suitable for developing RCA-PVA concrete for rigid pavements.