Laboratory evaluation of alternative cost-effective pavement materials

Abstract

The South African road network is severely impacted by the high costs associated with upgrading, maintaining and constructing road infrastructure in conjunction with the shortage of good quality construction materials. The Council for Scientific and Industrial Research (CSIR) has conducted extensive research on an innovative, cost-effective bituminous stabilising agent known as Nano-Organosilane Modified Emulsions (NMEs). These emulsions allow road engineers to design stabilised base and subbase layers using marginal materials which are normally considered unusable for road construction. For the purpose of determining the potential performance of NMEs, extensive advanced laboratory evaluations have since been conducted, most recently in the form of triaxial testing. This paper outlines the results and findings from both monotonic and dynamic triaxial testing conducted on NME materials, and draws correlations with Heavy Vehicle Simulator (HVS) test results. Compared to standard materials and designs, the initial results on the use of NMEs as a stabilising agent in road bases and subbases has since showed excellent performance and cost savings. The key results in this paper conclude that NME materials: • Exhibit strong-cohesion as observed from monotonic triaxial testing as well as from test-pit samples cored from HVS test-sections at Provincial Road D1884; • Have significant potential for improved long-term pavement performance, based on laboratory measured resilient moduli in conjunction with back-calculated field-moduli on NME test-sections; • Display very low susceptibility to Permanent Deformation (PD) including rutting; and • Justify being considered as a sustainable and environmentally friendly alternative to traditional pavement materials and designs.