Engineering behavior of ambient-cured geopolymer concrete activated by an alternative silicate from rice husk ash

Manufacturing of commercialized silicate is a highly polluting source in geopolymer production. To reduce these emissions, rice husk ash has been considered as an option for synthesizing alternative silicate. However, available research has been focused on the study of geopolymer pastes and mortars, but unknowns remain on its reliability to manufacture plain geopolymer concrete, motivating this research. Goals were synthesizing an unfiltered-alternative sodium silicate from rice husk ash at room conditions (21 degrees C - 65 +/- 5%RH - atmospheric pressure) for manufacturing plain ambient-cured geopolymer concrete and assess its engineering properties. Results shown that the proposed concrete reached 21 MPa, 17959 MPa, 0.183, and 2.13 MPa for 28-day compressive strength, modulus of elasticity, Poisson's ratio, and splitting tensile capacity, respectively. Results also portrayed that all these properties of the proposed concrete were comparable to those of geopolymer concrete with commercial silicate and traditional Portland-cement concrete. Its elasticity modulus was 44% higher than that of the geopolymer concrete with commercial silicate, which is considered as serviceability proxy. Based on the results, three equation models were developed to predict the engineering properties of the proposed concrete. Results demonstrate that the use of alternative silicate from rice husk ash provides an innovative-cheaper and eco-friendlier geopolymer concrete exhibiting suitable properties for structural applications.