Possibility of Using Stabilized Recycled Aggregate With Geopolymer as Base and Sub-Base Materials

Abstract

The production of aggregates is not environmentally friendly, very costly, and consumes a lot of energy. Therefore, the use of recycled aggregates (RA) such as reclaimed or recycled concrete aggregate (RCA) and recycled asphalt pavement (RAP) in road pavement will not only protect natural aggregates but also reduce the negative environmental impacts of these materials. At the same time, protection will be provided for waste disposal areas. The biggest disadvantage of using recycled aggregate is quality control during production. With this study, the suitability of RCA samples taken from demolished old buildings and RAP samples taken from old demolished roads as road base and sub-base material was investigated. This study aimed to investigate the usability of RAP and RCA together with low calcium fly ash in the formation of geopolymer material as an eco-friendly binder material in improving the strength properties of low plasticity soil. In this investigation, a formed geopolymer by using low calcium fly ash (FA), sodium silicate, and sodium hydroxide was used and cured at ambient temperature. The Soil-RA-Geopolymer samples were prepared using Class F Fly ash mixed with Blast furnace slag (BFS), soil, RAP, RCA, and liquid alkalis that were used instead of the optimum water content. After that, the unconfined compressive strength (UCS) tests were performed on the prepared samples. According to the variance analysis (ANOVA), the major factors affecting significantly on the UCS are the alkaline ratio and slagged-fly ash ratio. When the ratio of the slagged fly ash increase the UCS value increase till reaching the optimum ratio then the UCS value slightly decrease. The use of RCA and RAP effect slightly the UCS value and the test results indicate the possibility of using treated RAP/RCA materials with geopolymer as a base and sub-base material.