Mix design development of fly ash-GGBS based recycled aggregate geopolymer concrete

Concrete is the most extensively used building material across the world. It can accommodate huge volumes of industrial waste by-products such as fly ash, ground granulated blast furnace slag, and construction and demolition waste which are generated in massive quantities from thermal power plants, steel plants, as a by-product, and construction waste debris respectively. Lots of fly ash, ground granulated blast furnace slag, and construction and demolition waste are discarded, creating environmental and storage issues. The manufacturing of recycled aggregate geopolymer concrete is one of the cost-effective ways to dispose vast amounts of debris. The use of recycled aggregate geopolymer concrete as structural concrete is not encouraged due to lack of appropriate mix design methodology. The current study aims to develop a new mix design methodology by using fly ash and ground granulated blast furnace slag with 100% recycle aggregate, which is simpler and more consistent than previous procedures. The suggested process has been further validated by developing a range of concretes with alkaline activate content to binder ratios ranging from 0.3 to 0.8. According to the present study, by using fly ash and ground granulated blast furnace slag along with recycled aggregate in concrete, compressive strength of an order of nearly 60 MPa can be obtained at the curing age of 28 days. SEM and XRD analysis were also carried out to evaluate the processes of polymerization. The results suggest that fly ash and ground granulated blast furnace slag have a superior synergetic influence on recycled aggregate geopolymer concrete performance.