The Moisture Resistance of Sustainable Asphalt Mixtures Modified with Silica Fume

The administration of waste from constructing-demolition and the reuse of industrial waste materials are the main focuses of the sustainability initiatives. There are economic and environmental benefits to using recycled concrete aggregates (RCA). Nevertheless, the RCA mixes’ poor performance necessitates the addition of more enhanced substances. This study investigated the moisture resistance of asphaltic mixes that included RCA and silica fume (SF). Coarse aggregates were replaced with RCA at three different percentages 15%, 30%, and 45%, which were pre-treated by immersing it in acid with a concentration of 0.1 mol. for a duration of 24 hours. Then the mixes containing RCA were incorporated with various amounts of SF, with 3%, 6%, and 9% of the binder’s weight. These mixes were used to measure the Marshall characteristics and evaluate moisture resistance using indirect tensile strength, compresive strength tests. A thermal camera was employed to assess the modified asphalt’s homogeneity. The thermal images demonstrated that after 30 minutes of mixing SF at 160°C, the asphalt cement has been uniformly distributed SF particles, as evident by the colour convergence. The findings revealed that the addition of RCA to the asphalt mix increased TSR and IRS levels by 6.68% and 8.93%, respectively, at RCA 30% compared to the original mixture. Additionally, the inclusion of silica fume led to a rise in TSR and IRS until 6%, after which there was a drop, but the levels remained above the original mix. The use of 30% RCA ratio with 6% silica fume resulted in the highest improvement in TSR and IRS, with a rise of 13.72% and 14.13%, respectively.