Impact of replacement of natural river sand with geopolymer fly ash sand on hardened properties of concrete

In this research, M-25 grade concrete was produced from geopolymer fly ash sand (GFS) manufactured using fly ash and an alkaline activator solution as an alternative material to the natural river sand (NRS). The alkaline activator with 4 Molar NaOH solution and Na2SiO3/NaOH = 2:1 was used for the preparation of GFS. The mechanical and the durability characteristics of geopolymer fly ash sand concrete such as compressive strength, flexural strength, split tensile strength, rapid chloride permeability test, rapid chloride migration test, accelerated carbonation test, drying shrinkage test and the microstructure of the concrete using scanning electron microscope were studied. The obtained results were compared with the conventional river sand concrete. It was observed that the geopolymer fly ash sand concrete exhibited a comparable mechanical strength when compared to the river sand concrete, while the improvement in terms of durability was observed with the usage of geopolymer fly ash sand in the concrete suggesting the use of geopolymer fly ash sand as a complete replacement material to the river sand in the construction activities. (C) 2019 Elsevier Ltd. All rights reserved.