Influence of particle size distribution of slag, limestone and fly ash on early hydration of cement assessed by isothermal calorimetry

Supplementary cementitious materials (SCMs) enhance early hydration of cement through theprovision of nucleation sites for the precipitation of hydration products. This effect contrastswith the dilution effect of the mineral addition to the cementitious system. In fact, the neteffect on heat release during the first hours of hydration is the reduction of peak intensity.Then, only when the specific heat is evaluated in terms of cement weight the actual effect ofthe admixture on hydration may be assessed. In this sense, a clear difference may be expectedin accordance with the replacement ratio and fineness of the SCM. Increased specific surfacefavors nucleation and it therefore enhances hydration. In this paper, cement pastes admixedwith slag, limestone and fly ash in three different fineness levels and three replacing ratioswere investigated through isothermal calorimetry. The filler effect of each SCM was inrelation with the fineness and replacing ratio, with higher impact on the aluminate reactionthan on the silicate reaction of cement.Supplementary cementitious materials (SCMs) enhance early hydration of cement through theprovision of nucleation sites for the precipitation of hydration products. This effect contrastswith the dilution effect of the mineral addition to the cementitious system. In fact, the neteffect on heat release during the first hours of hydration is the reduction of peak intensity.Then, only when the specific heat is evaluated in terms of cement weight the actual effect ofthe admixture on hydration may be assessed. In this sense, a clear difference may be expectedin accordance with the replacement ratio and fineness of the SCM. Increased specific surfacefavors nucleation and it therefore enhances hydration. In this paper, cement pastes admixedwith slag, limestone and fly ash in three different fineness levels and three replacing ratioswere investigated through isothermal calorimetry. The filler effect of each SCM was inrelation with the fineness and replacing ratio, with higher impact on the aluminate reactionthan on the silicate reaction of cement.C