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Integrating quarry dust and industrial waste in producing eco-friendly hybrid geopolymer concrete
Summary
A hybrid geopolymer concrete incorporating industrial plastic waste (plastic shales, pellets) and quarry dust as aggregate substitutes showed comparable or superior mechanical performance to conventional cement concrete, with basalt or dolomite powder replacement increasing compressive strength by ~10%. This is relevant to microplastic research as it demonstrates a pathway to sequester plastic waste into construction materials, potentially reducing plastic fragmentation into environmental microplastics.
This paper proposes the production and testing of hybrid geopolymer concrete (HGC) as a sustainable substitute for the well-known traditional slag- and fly ash-based geopolymer concrete. A total of fourteen sustainable HGC were proposed with a variety of quarry dust materials such as granite powder (GP), basalt powder (BP), and dolomite powder (DP) as partial substitutes of fly ash (FA). Additionally, industry waste materials namely, plastic shales (PS), plastic pellets (PP), and crumb rubber (CR) were used as partial substitutes of sand in the proposed HGC. Several variables were investigated including geopolymer binder type, concrete curing methods, and mixing procedures. Heat followed by water (HW) and heat followed by air (HA) curing methods were applied on the proposed HGC. Workability, compressive strength (under ambient and high elevated temperature), splitting tensile strength, and flexural strength were the physical, and mechanical properties measured. The measured properties of HGC were also compared with those of equivalent cement-based concrete mix. Selected HGC mixes were further analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. The results indicated that the proposed HGC is a practical and eco-friendly substitute of both traditional geopolymer and cement-based concrete, as it showed similar or better performance. The compressive strength increased by about 10% when 15% of the FA was replaced by BP or DP. Exposing the proposed concrete to high elevated temperature of 300 °C for 2 h increased its compressive strength by 20.5% for the control mix, 29.9% for mix contained 15% GP, 2.6% for mix contained 15% BP, 3.4% for mix contained 15% DP, and by 2.4% for mix contained 25% CR. However, all mixes lost strength when exposed to 600 °C for 2 h. Except for the Control mix, GP mixes, and PP mixes, the HW curing method showed lower strength in all mixtures. All HGC mixes showed better performance than the cement-based concrete. Microstructural analyses showed a thick and even structure for the HGC mixes, supporting their relatively high strength. This study demonstrates the substantial potential of HGC as a revolutionary concrete type for construction that coincides with global sustainability goals and meets contemporary building demands.