Experimental Study and Investigation of Compressive Strengths of Bentonite Geopolymer Concrete

This work presents the experimental study and investigation of the compressive strengths of Bentonite Geopolymer Concrete (BGC). The materials used in this research were bentonite, water, cement, superplasticizer, sodium reagents (alkaline activators), river sand and granite chippings. The concrete was tested for compressive strength and durability in magnesium sulphate solution. The bentonite geopolymer concrete (BGC) and controlled ordinary Portland cement concrete (i.e. normal concrete), each of dimension, 150 x 150 x 150mm were produced using the following mix proportions: 1:2:4. 1:11 /2:3, 1:3:6 and 1:1:2. The concrete were cured for 7, 14 and 28 days respectively. The normal concrete cubes were cured in curing tank containing distilled water while BGC cubes were subjected to ambient curing. The compressive strengths of both BGC cubes and normal concrete cubes were tested for compression in the universal testing machine. The results showed that compressive strengths of BGC for all the mix ratios considered increased as the ambient curing ages increased. The maximum strengths of BGC occurred at 28-day curing. The maximum strengths of the concrete were found as 16.30 N/mm2 , 18.85 N/mm2 , 11.40 N/mm2 and 23.10 N/mm2 for 1:2:4, 1:11 /2:3, 1:3:6 and 1:1:2 mix ratios respectively. The static elastic modulus of the geopolymer concrete were computed and found to be within the acceptable limit recommended by BS 8110-2:1985. However, the compressive strengths of the controlled ordinary Portland cement concrete (i.e. normal concrete) were greater than the compressive strengths of BGC for the mix ratios considered. Furthermore, as the curing ages of BGC in the sulphate medium increased, the more resistant of BGC to sulphate attack. Also, as the quantities of bentonite used in the production of BGC increased, the more resistant of the concrete to sulphate attack. Consequently, 1:1:2 BGC has the least reduction in compressive strength in the sulphate medium, thus, more resistant to sulphate attack.