Improving Performance of Water-Reducing Admixtures by Modification of Quartz Sands with Electrolyte

Abstract

It is widely known that modern anionic surfactants are adsorbed at positively charged active centers of hydrate phases in portland cement that leads to floccules decomposition as well as a release of immobilized water, therefore increasing cement paste flowability. Normally, in cement based concrete such fine and coarse aggregates as quartz sand, granite, sandstone etc. are used. They contain negatively charged active centers, therefore, are inert to anionic water-reducing admixture and don’t affect fluidization of cement based concrete mixture. For instance, quartz sand with high concentration of fine particles as well as oxides and hydroxides of Al and Fe cations demonstrates a higher reactivity to anionic water-reducing admixtures. In order to increase the efficiency of anionic surfactants in concrete mixtures the treatment of aggregates with salts based on two-and three-valent cations was proposed. That provides a higher concentration of positively charged active centers on quartz sand surface leading to increase of flowability of concrete mixture.