EVALUATION OF STRENGTH CHARACTERISTICS OF GEOPOLYMER CONCRETE WITH FOUNDRY SAND AND RECYCLED COARSE AGGREGATE AS PARTIAL REPLACEMENTS
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Abstract
Reducing environmental pollution is one of the primary concerns for sustainable development, in which the construction industry is no exception. A clean construction revolution calls for less resource-consuming, more resource-efficient, less wasteful, and less polluting technologies that are still able to meet the pre-defined quality standards and regulatory requirements. Over the last decade or so, geopolymer concrete has caught the attention of the scientific community as a feasible green material that exhibits good mechanical performance and durability and is advantageous in terms of global warming potential compared with the standard Portland cement concrete. This work is meant to disclose the strength performance of a kind of geopolymer concrete where foundry sand (FS) and recycled coarse aggregate (RCA) agents are used as a partial replacement for natural fine and coarse aggregates, respectively. Foundry sand is an inevitable by-product of metal casting, while RCA is the product of the demolition of concrete buildings; thus, these materials reduce the waste generated by landfilling and play an active role in the circular construction economy. Geopolymer binder in this experiment was generated from a mixture of fly ash and ground granulated blast furnace slag (GGBFS) with an alkaline solution consisting of sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃). The reason for substituting natural sand with foundry sand at various percentages was to observe the mechanical performances in the case of a combination of both materials. The first research trial included compressive strength, split tensile strength, and flexural strength tests at ages of 7, 14, and 28 days of curing.
The author's experiment yielded data which demonstrated that the replacement of the controlled and optimized fine aggregates with foundry sand serves the purpose of densifying the packing and promotes the strengthening happening at the early ages. In an analogous fashion, partial substitution of natural coarse aggregates with RCA reveals excellent results with negligible decreases in properties of the material, if the replacement percentages do not go over the upper limits. Excessive percentages of FS and RCA, on the other hand, are likely to reduce the strength owing to inferior bonding, increased porosity, and higher water absorption, which are characteristics of recycled products. Thus, the research work enables the strength attainments of geopolymer concrete with FS and RCA to become at the same level as or even exceed those of traditional mixtures, which provide a feasible and environmentally friendly alternative solution that can be applied to structural and non-structural fields. It manifests how this research may serve as a call-to-action for the construction industry and, more generally, for the society, regarding the imperative usage of the industrial waste materials as ingredients in design formulations of the geopolymer concrete, thus continuing the chain of natural resource conservation, carbon emissions reduction, and the endurance of sustainable practices. Genuine concerns of study results, accordingly, are a source of invaluable information for urban planners, scientists, and industry professionals conducting in the field of infrastructure development, who are committed to solving the challenges of the materials' integration in the green transition of their contemporary work.