Internal curing of high performance concrete using cenospheres

This study explores a novel internal curing agent, perforated cenospheres. Cenospheres are hollow fly ash particles produced from coal burning power plants. The shell of the cenospheres is inherently porous that is sealed by a thin layer of glass-crystalline film. By removing this film through chemical etching, the pores on the shell can be exposed, perforating the cenospheres and providing paths for water propagating into the internal volume of cenospheres. The perforated cenosphere were found to have water absorption as high as 180 wt%. The loaded water can be readily released from the cenospheres under high relative humidity (95%). When incorporating saturated cenospheres into cement mortar for internal curing, the autogenous shrinkage of the mortar was almost eliminated. The internal curing also improved the compressive strength of the cement mortar. All these results suggest that perforated cenospheres can be used as an efficient internal curing agent for HPC.