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Natural rocks of magmatic origin are alternative precursors in alkali-activated materials and provide opportunities in the search for more environmentally friendly binders compared to portland cement. The pumice is one of these rocks and its amorphous structure and chemical composition make it one of the candidates as a precursor in producing geopolymer binder when finely ground. Since the majority of the pumice reserves are located in Turkey increases its potential utilization in this area, even more. This paper evaluates the physical, mechanical, and microstructural properties of geopolymer pastes and mortars manufactured with pumice powder (PP) and ground granulated blast furnace slag (BFS) with the activating agents sodium hydroxide (NaOH), potassium hydroxide (KOH), and sodium silicate (SS) solution. The experimental results showed that the compressive strength of the geopolymer pastes was mainly affected by the activator concentration and the PP ratio, rather than the activator type, for single activator mixes. However, the incorporation of SS changed this trend as the KOH and SS combination resulted in higher compressive strength compared to the NaOH and SS. The gradual increase of the PP ratio in the mix design decreased the density and thermal conductivity, on the other hand, increased the water absorption values of the geopolymer mortars. However, the physical properties were insignificantly changed in geopolymer mortars incorporating 60, 70, and 80% of PP in the binder.

The aggregate makes up about 65–75% of the total volume of concrete and the use of artificial aggregates manufactured from waste and by-product materials, as an alternative to natural aggregate, has attracted considerable research interest. Washing aggregate sludge (WAS) is obtained as a waste during the process of washing the aggregates, which is disposed or used as landfill. The utilization of WAS as a major component to manufacture artificial aggregates remains unexplored. Therefore, the focus has been directed towards the production of cold-bonded and sintered aggregates using WAS and their incorporation in concrete. The fresh pellets were manufactured using WAS, ground granulated blast furnace slag (GGBFS) and ordinary Portland cement (OPC) and kept in the laboratory conditions at 20 ± 2 °C and 95 ± 5% relative humidity to obtain cold-bonded aggregates, whereas WAS and GGBFS were utilized to manufacture sintered aggregate by heating the fresh pellets up to 1150 °C. The manufactured aggregate properties were characterized through physical, mechanical, chemical, and microstructural analysis. Concrete specimens were also produced by introducing the artificial aggregates in replacement with the coarse aggregate. The results showed that the concrete containing artificial aggregates can be produced with lower oven-dry density and comparable mechanical properties to efficiently utilize WAS.