Effect of Natural Clay and M-Sand on the Strength and Chemical Attack of Fly Ash Geopolymer Concrete

This paper reports the achievements of using the stable form of the natural clay, locally available in Coimbatore, Tamilnadu, India, as a base material of geopolymer concrete with flyash. The laboratory and field study shows the strength development and acid resistant of Clay-Fly ash geopolymer mortar and concrete with dissimilar ingredients, specimen sizes and heating temperature. A silty natural clay without calcination is used as a pozzolanic component with low calcium Class F-flyash brought from Mettur Thermal Power Unit, Tamilnadu as well as fine aggregate with manufacturing sand in different combinations. The moisture content in the clay is adjusted with the total volume of liquid used for geopolymer manufacturing. The considered factors are FA/Clay ratio, Alkaline activator ratio, M-Sand/Clay ratio, molding moisture content, specimen sizes, curing temperature, rest period and NaOH concentration. Alkali solution for this study is prepared with the mixture of Sodium silicate and different molarities of Sodium hydroxide solution with the proportion ratio 1. The mortar test specimens were 70x70x70 mm cubes, 50x 100 mm cylinders and concrete test specimens were 150x150x150mm cubes, 100 x 300 mm cylinders heat cured at 600C/800C in an oven. The grades selected for the experimental investigation were M 25, M 30 and M 40 and the mixes were designed for the molarity of 8M, 10M and 12M.

This paper compares experimental reports about the behavior of clay-fly ash geopolymer mortar and concrete exposed to 5% acid solutions for up to 8 weeks with conventional concrete. The strength comparison between Geopolymer and Conventional mortar and concrete is also reported.

The changes in weight and strength of GPC & OPC over a period of 28 and 56 days are periodically assessed in acidic environment.

The test results show that the heat-cured clay-fly ash GPC has an excellent resistant to acid when compared to OPC. Thus we can conclude that the manufacturing of geopolymers have an excellent strength, higher volume stability and better durability.