The effect of curing relative humidity on the microstructure of self-compacting concrete

•The samples cured at 70% RH present more tetrahedrally coordinated aluminium.•More aluminium is taken up by the CSH gel in the samples cured at 70% RH.•The transformation of ettringite to AFm is promoted at 70% RH.•The samples cured at 98% RH present lower mean chain lengths of the CSH gel. A study was conducted to investigate the effect of the curing relative humidity on the microstructural properties of SCC with limestone filler. Two curing conditions were considered with humidities of 98% and 70%. Three microstructural techniques were employed to study the hydration: TGA, Micro-Raman spectroscopy and NMR. It was found that the samples cured at 70% humidity present more tetrahedrally coordinated aluminium since more aluminium is taken up by the CSH gel and the transformation of ettringite to AFm is promoted. The samples cured at 98% humidity are more hydrated but present lower mean chain lengths of the CSH gel.