Mechanical and Durability Studies of Fly Ash and Bottom Ash Based Geopolymer Concrete Using Potassium Based Alkaline Activator at Ambient Temperature

Abstract

Concrete is most widely used material on earth after the water. Ordinary Portland cement (OPC) is used as the primary binder to produced concrete. The production of OPC not only consumes significant amount of natural resources and energy but also releases substantial quantity of carbon dioxide to the atmosphere. Utilisation of the waste generated from thermal power stations such as fly ash and bottom ash is very less against the production and is dumped under the ground which causes the environmental pollution and health hazard for human beings. We can reduce the pollution and protect environment, by increasing the usage of industrial by-products in our construction industry. Geopolymer concrete is such a one and in the present study, to produce the geopolymer concrete the Portland cement is fully replaced with fly ash and bottom ash and alkaline liquids are used for the binding of materials. The alkaline liquids used in this study for the polymerization are the solutions of Potassium Hydroxide (KOH) and Potassium Silicate (K2SiO3). An attempt has been made to study performance of geopolymer concrete for various strength and durability tests and its comparison with Control Concrete. M25 grade of concrete was chosen for the study. Different molarities of Potassium Hydroxide (i.e. 8M, 10M, 12M) and fly ash and bottom ash percentage (i.e. 60:40, 50:50,40:60) were taken to prepare different mixes. Parameters such as Alkali liquid ratio, alkaline to cementitious material, dosage of admixture were also varied. The test specimens of 150 mm × 150 mm × 150 mm size cubes were prepared. Ambient curing was adopted in this study. The geopolymer concrete specimens were tested for their compressive strength at the age of 7, 14 and 28 days and comparison with control concrete was carried out. The geopolymer concrete specimens were also tested and compared with control concrete for durability properties by performing various tests like acid resistance, sulphate resistance, chloride resistance, water absorption, sorptivity test, rapid chloride permeability test, accelerated corrosion test and fire resistance test. The study shows that bottom ash and fly ash when used in equal proportion with suitable combination of Potassium based alkaline activators gives strength of M 25 grade concrete. Mechanical properties like split tensile strength and flexural strength were similar to that of OPC concrete and some durability properties were superior to that of OPC concrete like acid resistance. This indicates that geopolymer concrete with fly ash and bottom ash can be used cured at ambient curing and can be manufactured at field.