Assessing the impact of recycled mortar powder on the strength, durability and microstructural characteristics of geopolymer concrete

The recycling of concrete waste and its utilization in new concrete production can be a great contribution to a sustainable environment. In the present study, the impact of recycled mortar powder (RMP) was accessed on fly ash (FA) based geopolymer concrete (GC). The RMP was substituted with FA in the range of 0-50%. The durability properties such as capillary suction test (CST), initial surface absorption test (ISAT) and acid attack test were accessed and strength property was also evaluated in terms of compressive strength at ambient curing. Further, the ultrasonic pulse velocity (UPV) test and electrical resistivity test were also conducted for all GC mixes. The present study outcome shows that the overall properties of GC improved with the addition of RMP up to 30%. Moreover, the addition of RMP provides the early activation of GC due to calcium (Ca) compounds present in RMP. The microstructural characteristics of GC mixes were analyzed using field emission scanning electronic microscopy (FESEM) along with Fourier transform infrared (FTIR) spectroscopy and it revealed that the presence of Ca compound in RMP form additional nucleation sites i.e., calcium/sodium alumina-silicate hydrate gel with a polymeric chain which enhance the overall properties of the GC.