Synergetic effect of a chemical activator and blast-furnace slag on enhancing recycled aggregate mortar

The inferiority of recycled fine aggregate mortar (RFAM) is a major obstacle to its utilisation and a method to enhance RFAM is thus necessary to scale up applications. The concept behind the method proposed in this paper involves using a calcium hydroxide solution to pre-coat the surface of recycled fine aggregates in order to activate blast-furnace slag incorporated in RFAM to enhance performance. The results of this experimental research showed that, compared with conventional RFAM, the synergistic effects of using a calcium hydroxide solution and blast-furnace slag in RFAM produced better workability, earlier setting time, higher compressive strength at early and later ages, higher flexural and splitting tensile strengths, a lower volume of permeable voids, a greater formation of hydration products, a lower water absorption by immersion and a lower rate of capillary absorption. The method was found to enhance the performance of RFAM remarkably and, in addition, is economically and environmentally feasible.