Adsorption of Shrinkage Reducing Admixture(SRA) and Superplasticizer on Solid Particle Surface of Cement and Supplementary Cementitious Materials

Shrinkage reducing admixture(SRA) is a novel chemical admixture which can significantly reduce the shrinkage of cement based materials.Most of researches mainly focused on the effect of SRA on macroscopic properties of cement based materials.There are,however,few reports on the adsorption of SRA on interface of cementitious materials-water.Thus,the existential state of SRA in cementitious materials is not well understood.In this study,the adsorptions of two SRA products on solid particle surface of cement,blast furnace slag and fly ash were investigated,comparing with those of two polycarboxylate(PC) superplasticizers under the same testing conditions.The results shown a significant difference of adsorption between SRA and PC on solid particles,and the adsorption of SRA was eight times as small as those of PC,which indicated that majority of SRA was dissolved into cement pore solution,rather than adsorbed onto the surface of solid particles.The IR spectrograms revealed that the main functional groups of SRA were as same as PC.Therefore,it is believed that there is no necessary connection between the adsorption and types of SRA's and PC's functional group,the difference of adsorption possibly resulted from the different molecular or chain structures of SRA and PC.