In order to resolve the problem of the low utilization rate of magnesium slag and high requirement of dimension stability for modern concrete,orthogonal test scheme was designed to study the drying shrinkage characteristics of magnesium slag composite admixture concrete by experiment.The shrinkage model of concrete was established through the analysis of the role of law and the mechanism of admixture by micro structure.Results showed that the drying shrinkage of magnesium slag composite admixture concrete increases with time in a trend of hyperbolic curve,which has significant correlation.The significant level of fitting parameters model has high,good correlation with each factor.The drying shrinkage of concrete decreases with magnesium slag dosage and admixture replacement rate,increases with powder composite rate.The order of importance is magnesium slag dosage,admixture replacement rate and powder composite rate.The effect of magnesium slag on drying shrinkage of concrete increases gradually with time,tends to be stable at 90 d.In this period,there is only shrinkage,no expansion and expandable harm in concrete.So it is feasible to add proper amount of magnesium slag to compensate the shrinkage of concrete.
