Mechanical properties of fly ash-based geopolymer concrete with crumb rubber and steel fiber under ambient and sulfuric acid conditions

The fly ash-based geopolymer concrete is composed of alkali-activated aluminosilicate and aggregates. The removal of cement from concrete plays a significant role in reducing greenhouse gases. The industrial disposal of recycled tires is an environmental issue, and using them in concrete, while maintaining its mechanical properties and employing steel fiber to improve these properties, has received attention. Moreover, hydraulic structures, such as dams, piers, and canals, constitute a great portion of concrete structures in the world, and the mechanical properties of concrete in the acidic conditions of such environments should be evaluated. In previous studies, the geopolymer concrete with up to 20% of fly ash replaced with cement showed desirable results. In this research, the geopolymer concrete with up to 20% of fly ash replaced with cement, crumb rubber equal to an amount equal to 10% of the volume of fine grains, and steel fiber were made and then cured in dry conditions at the temperature of 60 degrees C. After 28 days, their mechanical properties were studied in the environment in contact with sulfuric acid. The results showed that the highest compressive and tensile strengths, being equal to 49 MPa and 4.7 MPa respectively, belonged to the geopolymer concrete containing crumb rubber and 1% fiber with 20% of fly ash replaced with cement. In contact with acid for 90 days, the concrete with 1% fiber and without cement had the highest compressive strength, equal to 34 MPa, showing the smallest reduction, equal to 26%. These results were evaluated with the analysis of the microstructure, along with XRF, ultrasonic, and XRD tests. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Geopolymer concrete, with 20% of fly ash replacing cement, incorporating crumb rubber and 1% steel fiber, exhibited excellent mechanical properties in high temperature and acidic environments.