Mechanical and environmental performance of engineered geopolymer composites incorporating ternary solid waste

Abstract

In order to reduce the utilization of cement and promote the low-carbon development of construction materials, engineered geopolymer composites (EGC) offer an alternative to engineered cement composites (ECC). In this study, slag, fly ash and steel slag were innovatively combined as precursor materials to prepare EGC. The focus was laid on the influence of sodium silicate modulus (Ms) and alkali content on the mechanical and tensile properties of ternary solid waste based EGC. Four levels of Ms (1.2, 1.5, 1.8, and 2.1) and three groups of alkali content (6 %, 8 %, and 10 %) were designed in the experiments. The flowability, setting time, compressive strength, flexural strength, uniaxial-tensile performance, and carbon emissions were comprehensively studied. Results revealed that as the Ms decreased and the alkali content increased, the setting time and flowability showed a decreasing trend. With an increase in Ms, the compressive strength and flexural strength initially increased and then decreased, indicating an optimal dosage of sodium silicate modulus. Moreover, alkali content showed a positive correlation with compressive strength and flexural strength. At Ms 1.5 and alkali content 8 %, the 28-day compressive strength reached a maximum of 83.9 MPa, the 28-day flexural strength was 14.7 MPa, and the ultimate tensile strain reached 11.31 %. The environmental benefit analysis indicated that compared with high-ductility cement-based materials, EGCs had lower carbon emissions and energy consumption, and the carbon emissions of EGCs were approximately 50.6 % lower than that of ECC.