Experimental and Environmental Analysis of High-Strength Geopolymer Based on Waste Bricks and Blast Furnace Slag

The rationalization of material flows, together with the utilization of waste raw materials for the production of alternative binders, became a very attractive topic during the last decades. However, the majority of designed materials can be used as a replacement for low-performance products. In this work, the waste materials (brick powder and blast furnace slag) are valorized through geopolymerization to design high-performance material as an alternative to high-performance concrete. Designed mixtures activated by sodium silicate and waste-originated alkali solution are characterized by the meaning of the chemical and mineralogical composition, evolution of hydration heat, and mechanical strength test. To contribute to the understanding of the environmental consequences and potential benefits, the carbon footprint and embodied energy analysis are provided. Obtained results highlight the potential of end-of-life bricks for the design of high-performance composites if mixed together with more reactive precursors. Here, even values over 60 MPa in compressive strength can be achieved with the dominant share of low-amorphous brick powder. The higher crystalline portion of brick powder may lead to the reduction of drying shrinkage and preservation of flexural strength to a greater extent compared to used slag. Performed environmental analysis confirmed the CO2 emission savings; however, the embodied energy analysis revealed a huge impact of using alkaline activators.

Automated summary

The rationalization of material flows and utilization of waste raw materials for alternative binders have gained attention in recent decades. This study focuses on the valorization of waste materials through geopolymerization to design high-performance materials as an alternative to high-performance concrete. The results highlight the potential of using end-of-life bricks mixed with reactive precursors to achieve compressive strength values over 60 MPa, with the low-amorphous brick powder dominating the mixture. Environmental analysis shows CO2 emission savings, but the embodied energy analysis reveals the significant impact of using alkaline activators.