Effect of crumb rubber and steel slag on asphalt mixtures for a micropavement

The need to reuse waste materials is a fundamental aspect in sustainable development. Two types of materials, crushed rubber (CR) and steel slag (SS), were selected to analyze their effects on micro-paving asphalt mixtures. The methodology was carried out in two phases: first, the behavior of these materials in cold asphalt mixtures was analyzed and, in the second phase, the design of micro surfacing developed in three scenarios was analyzed under the requirements of the ISSA standard (the control mixture (MP), the mixture with SS as a 10% aggregate substitute and the mixture with the best performing percentages of CR and SS). Test specimens were prepared with the addition of 5%, 8%, 10% and 12% of CR and 5%, 10%, 15% and 20% of SS as a replacement for fine aggregate. Main tests such as wet track abrasion test (WTAT), loaded wheel test (LWT) and Schulze–Breuer and Ruck compatibility were developed. As favorable results, the first two scenarios of the second phase (the control mix and 10% SS) had better performances; however, the mix incorporating CR and SS in percentages of 5 and 10% did not meet the design requirements of the ISSA standard for the WTAT and LWT. It was concluded that the best alternative for micropavement design was the substitution of fine aggregate by SS, in effect, it had lower costs, good mechanical performance and sustainable design for cold climates.