Lightweight aggregates from water reservoir sediment with added sodium hydroxide

Lightweight aggregates were produced from a mixture of water reservoir sediment and sodium hydroxide at a temperature of 1045–1085 °C. The mixtures were also pre-cured at 120 °C to observe the effect of geopolymerization. The physical properties of dry and wet sediment samples were observed at a given NaOH concentration. The results showed that the obtained LWAs meet the European Union regulation UNIEN 13055-1, which requires the LWA bulk density to be lower than 2000 kg/m3. The performance of most of the obtained LWAs reached that of commercial products. When calcined at 1110 °C, the LWAs lost the properties of a geopolymer cement and bloated, which lowered their bulk density. The addition of NaOH promoted the formation of a glassy phase that vitrified the LWA surface, making the level of water adsorption below 5%. The mineral phases of LWAs were quartz, hematite, albite, and hercynite.