2006 Volume 47 Issue 6 Pages 1599-1604
Shrinkage reducing admixtures (SRA) have been used for several years to reduce the shrinkage of concrete. However, because their prices are very expensive and their dosages are very large, it is not economical for their practical application. Another problem of SRA is the degradation of compressive strength of concrete with SRA. In order to solve the two problems, a new polycarboxylate based superplasticizer with shrinkage reducing function was developed and its mechanism was investigated. According to experimental results, the admixture named JM-PCA (IV) reduces shrinkage of concrete effectively and reduces water content effectively. JM-PCA (IV) at a dosage of 0.25% decreases the shrinkage of concrete by about 40 to 55 percent at 28 days and 60 days when compared with sulfonated naphthalene formaldehyde condensate superplasticizer at a dosage 0.74%. The possible reason is that a shrinkage reducing component (SRC) and long ethylene oxides(EO) side chain were introduced into the molecular structure. The adsorption-reduction of interface tension is thought to be its main action mechanism of the reduction of shrinkage of JM-PCA (IV).