Investigation of the high-temperature resistance of sludge ceramsite concrete with recycled fine aggregates and GGBS and its application in hollow blocks

Sludge ceramsite recycled concrete (SCRC) is made from sludge ceramsite and recycled fine aggregate (RFA) and is expected to be an eco-efficient lightweight concrete. The SCRC in this study was produced by incorporating sludge ceramsite, RFA and ground granulated blast-furnace slag (GGBS) as a replacement for coarse natural aggregate, natural sand and cement, respectively. An experimental study was conducted to evaluate the surface characteristics, mass loss, failure mode, residual compressive strength and microstructure of the SCRC after exposure to elevated temperatures (25 degrees C, 200 degrees C, 400 degrees C, and 600 degrees C). In addition, a new hollow block was manufactured with SCRC, and the thermal resistance of the SCRC hollow block was examined. The results showed that the SCRC displayed a good resistance to high temperatures, and its strength retention rate was over 60% after exposure to 600 degrees C. There was a slight impact from the RFA on the strength retention rate of the SCRC under elevated temperatures. The incorporation of GGBS improved the resistance of SCRC at elevated temperatures. With increasing GGBS content, the residual compressive strength of the SCRC increased first and then decreased, and the suggested optimal GGBS content is 30%. The prepared SCRC hollow block showed excellent thermal insulation performance and exhibited good application prospects in lightweight insulation walls.