Exploring mechanical and fracture properties in geopolymer concrete with ternary precursor waste materials through laboratory investigations and statistical analysis

Abstract

The prevalent excessive utilization of cement concrete, characterized by energy-intensive processes and notable carbon dioxide emissions, necessitates a shift towards sustainable construction materials. This study addresses the environmental challenges posed by conventional cement concrete by investigating the potential of recycled precursor geopolymer concrete as an environmentally friendly alternative. The research delves into the mechanical and fracture characteristics of ternary blend geopolymer (TBG) concrete incorporating an industrial by-product, red mud (RM), through comprehensive laboratory testing and statistical analysis. The investigation focuses on assessing the impact of varying RM replacement levels (0 %, 8 %, 15 %, 23 %, and 30 %) on mechanical properties and fracture behaviour in both Mode I and Mode II, utilizing semi-circular bend (SCB) specimens for fracture tests. Statistical methodologies, including Weibull fracture failure probability modelling and analysis of variance (ANOVA), were employed to interpret the results derived from 180 SCB test specimens. Furthermore, microstructural analysis through FTIR, SEM, and EDX testing was conducted on the diverse mixes. The outcomes revealed that the incorporation of RM in geopolymer concrete consistently diminished the compressive strength and flexural strength of the geopolymer concrete as the incorporation levels increased. For instance, the compressive strength decreases from approximately 40 MPa in the RM-free sample to about 25 MPa in the sample with 30 % RM. However, statistical analysis revealed that up to 8 % RM inclusion does not significantly affect the compressive strength and, in some cases, may even slightly increase it, highlighting the subtle effect of RM dosage. Additionally, Weibull modelling revealed that the probability of failure for samples with 30 % RM is about five times higher than for samples without RM. The microstructural analysis also depicted that high RM content may lead to decreasing homogeneity and the formation of deep cracks, negatively impacting mechanical properties. Elevated Fe and Al concentrations with higher RM content suggest potential reactions forming stable geopolymer gels and the presence of minerals like katoite.