Application of nano-silica in rubber modified asphalt mix made with marginal aggregates

The Global Environmental alert service has mentioned that the global requirement of natural stones has exceeded 40 billion tons annually. In such a scenario, it has become obligatory to look for an alternate aggregate for construction purposes. The present study comes up with a locally available waste material called over-burnt brick, which can be used for pavement construction. However, the lower strength of bricks can cause the structural deterioration of the pavement, and hence the asphalt mix needs to be modified with supplementary materials. Among several additives like polymers, fibers, plastics, etc., this study uses natural rubber and nano-silica (NS). Although several studies are available with crumb rubber modified bitumen, the application of natural rubber latex (NRL) is relatively rare and the hybrid application of NRL and nano-silica is the key novelty of this research. The experimental tests reveal that the binder property is greatly enhanced by the addition of NRL and nano-silica. There is almost 39% and 26.5% increment in the penetration and softening point for the modified binders. The performance test results indicate that the stability of asphalt mixes can be increased by about 33% by the addition of 6% NRL and it can be further increased by about 22% by adding 3% nano-silica in the NRL modified bitumen. The drain-down test indicates that the binder drain-down can be controlled by about 45% and 74% when the bitumen is modified by 6% NRL and 6% NRL + 3% nano-silica. A cost analysis is carried out to check the influence of these additives in the cost requirements for the preparation of modified asphalt mix using brick as aggregate. The overall study indicates the feasibility of waste bricks as a replacement of natural aggregates, and also shows the improvements achieved by using NRL and nano-silica as modifying agents.