STUDY ON BEHAVIOUR OF GEOPOLYMER CONCRETE

Abstract

Geopolymer concrete is an innovative, sustainable, cementless, and eco-friendly concrete that directly reduces carbon footprints due to the total replacement of the cement in the concrete. A very excessive amount of CO2 is produced in the production of cement. In the experimental investigation, fresh, chemical, and mechanical properties of various parameters were tested to find the optimum point, in which the GGBFS to flyash ratio by weight ranged from 00/100 to 75/25, liquid-to-binder ratios ranged from 0.4 to 0.7, superplasticisers content percentage ranged from 0.5% to 2.0%, molarity of sodium hydroxide ranged from 8M to 16M, sodium silicate to sodium hydroxide ratios ranged from 0.5, tests for the durability studies, in which they compared the effect of elevated temperatures up to 8000C, seawater condition, sulphate attack (both sodium sulphate and magnesium sulphate), acid attack, freeze-thaw condition, wetting-drying condition to the OPC concrete specimens In the experimental investigation, the workability was tested using slump, density, compressive strength, splitting tensile strength, flexural strength, poisons ratio, elastic modulus, rebound hammer strength, and ultrasonic pulse velocity as various parameters. In durability tests, to check the density, mass loss, compressive strength, residual compressive strength, ultrasonic pulse velocity, and visual inspection. The ambient-cured sample has less strength than the oven-cured samples, but in both cured samples, the 75/25 fly ash/GGBFS ratio gets the maximum engineering strength. The compressive strength, splitting tensile and flexural strength got the optimum point at the 0.60 liquid-to-binder ratios in the GPC mix design. The strength increases with the increment of the liquid-to-binder ratio, but it reduces randomly beyond the 0.60 ratios. 1% superplasticizer in the mix gets a higher strength compared to the other mixes with different percentages of superplasticiser. The compressive strength rises with the enlargement in molarity of NaOH in the mix design but beyond a point decreases the compressive strength in the oven-cured specimens. The highest compressive strength of oven cured 14M mix is 34.2N/mm2

at 56 days. The engineering strength enlarges with the increment of alkaline ratio in the mix design, but it decreases beyond 2.5 alkaline ratio in both curing condition samples. The GPC design mix's mechanical strength increases with the increment of the curing temperature, but it reduces beyond the 1000C curing temperature. The higher curing temperature increases the gain rate of the GPC samples. The GPC specimens have better stability against the elevated temperature compared to the OPC concrete specimens. The GPC specimens failed at an 8000C temperature, whereas the OPC specimens failed at 6000C. In seawater conditions, this initially increases the strength and density, but beyond 12 weeks, degradation occurs in both types of specimens. Both types of samples show a similar pattern in strength and mass loss. Both types of specimens show a similar pattern of strength and mass loss in the sulphate conditions, whereas the GPC specimens show better stability than OPC concrete specimens. In the freeze-thaw conditions, the OPC concrete specimens show better stability than the GPC specimens. The residual strength of GPC specimens was retained at 54% after 90 cycles, whereas the OPC concrete specimens retained 87% of the original.

Both concrete specimens strengthen the mass continuously with an increment of wetting- drying cycles up to 60 cycles, and it decreases slightly after that. Mass loss occurs beyond

60 cycles, but conventional concrete specimens show no mass loss.