Performance Comparison of Hot-Mix and Warm-Mix Asphalts with Cashew Nut Shell Liquid

Abstract

Hot-mix asphalt (HMA) is the paving material conventionally used all over the world, but the production of HMA at high temperatures of 150–180°C emits large amounts of particulate matter and harmful gases. Warm-mix asphalt (WMA) has been developed with the objective of minimizing these harmful emissions to the atmosphere during the production and placement process. WMA performs like HMA at lower mixing temperature. In this paper, cashew nut shell liquid (CNSL) is added from 0.5% to 3.5% by weight of bitumen at an increment of 0.5% in bitumen as an organic additive. The optimum CNSL content is found to be 2% by weight of bitumen and the viscosity reduction is 30% at 135 °C. This modified bitumen is used for the preparation of dense bituminous macadam mix (DBM) using WMA technology, making the mixing and compaction process more eco-friendly. A comparison of the stability and rutting characteristics of both HMA and WMA mixtures are made. Stability values of both HMA and WMA are above the minimum requirements of dense bituminous macadam. There is a reduction of 79% in rutting depth with WMA technology. Dynamic shear rheometer (DSR) test results showed that the bitumen modified with 2% CNSL can prevent rutting failure up to a maximum temperature of 71.22 °C as compared to 68.11 °C in neat bitumen. The statistical analysis authenticates the experimental findings. ANOVA analysis for the Marshall quotient revealed that the characteristics of WMA were similar to HMA, and the result for rutting showed that the additive CSNL and temperature had significant effects on rutting potential and make the asphalt pavements more resistant to permanent deformation.