Statistical Approach of Additive Effect on Volumetric Characteristics of Asphalt Mixtures

The use of additives in asphalt concrete has improved the performance of road pavements. Some additives include silica powder, fly ash, and crumb rubber. This study analyzed additive levels’ effect on the volumetric characteristics of asphalt mixtures using a statistical approach. This research uses aggregate gradation for asphalt concrete wearing a coarse layer to determine the effect of additive content on the volumetric of hot asphalt mixtures. Asphalt modification is used with silica powder at compositions of 0%, 2%, and 6%; fly ash with 0%, 2%, and 4%; and crumb rubber with 0%, 1%, and 1.25%. Samples were made and tested according to the Marshall test procedure. The volumetric characteristics of the asphalt mixture were subjected to correlation analysis with the Pearson and Spearman rank approaches and the ANOVA test. The Pearson and Spearman rank correlation analyses showed that fly ash and silica additives were suspected of having no correlation and influence on volumetric characteristics except for crumb rubber. The ANOVA test results show that the largest volumetric characteristics are significantly influenced by the crumb rubber additive on voids in mineral aggregates. In contrast, the silica and fly ash additives affect voids in mineral aggregates and Marshall stability. The difference in silica and fly ash additive content has shown different ANOVA test results even though they have the same size and composition of the forming elements.