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Improvement on microstructure of concrete by polycarboxylate superplasticizer


The effect of PCE-type SP on zeta potential of particles, spread flow, hydration kinetics, setting time, autogenous

shrinkage and chemical shrinkage of UHPC pastes is investigated, as well as the spread flow,

slump life and early-age strength development of UHPC. Furthermore, the dispersing and fluidretaining

ability of SP, retardation effect of SP, physical and chemical process effects are analysed. The

results show that the dispersing ability of PCE-type SP is determined by its chemical structure, which

shows an exponential relationship between the flowability of pastes and SP dosages. The fluidretaining

abilities of UHPCs are sensitive to the water-to-powder ratio, while the further addition of SP

will not enhance the slump life after excessing the saturation dosage. Both the adsorbed PCE and the

PCE remaining in the aqueous phase contribute to retardation effect. A linear correlation between the

final setting time (tfinal) and the time of maximum heat flow rate (t €Q¼max) is derived. The types and dosages

of SP primarily influence the absolute chemical shrinkage of pastes within 1 day, but have a great effect

on the autogenous shrinkage due to different physical coagulation and chemical process