Effects of CaO addition on lightweight aggregates produced from water reservoir sediment

► The lightweight aggregates from water reservoir sediment with added CaO meet the European Union regulation UNIEN 13055-1. ► The properties of the lightweight aggregate with 1% CaO by weight calcined at 1200°C achieve the performance of a commercial product. ► CaO addition can decrease water adsorption and compressive strength of lightweight aggregate. ► C–S–H gel did not form with CaO addition. Lightweight aggregates were produced from water reservoir sediment with various amounts of CaO at calcining temperatures of 1170°C–1230°C. It was found that C–S–H gel did not form with CaO addition. The bulk density and compressive strength of the lightweight aggregates meet the regulations for lightweight structural concrete. The properties of samples with 1% CaO by weight calcined at 1200°C match those of a commercial product. Water adsorption and compressive strength decreased with increasing CaO addition since more of the glassy phase formed, which sealed pores and led to few connections between pores.