The improvement mechanism of the interfacial structure between Portland cement paste and quartz by polyblend addition was studied. The key factor that a huge amount of [HSiO 3] - and [SiO 3] 2- ions emerges on the quartz surface, may be the break of hydrated and dissociated reaction balance on the quartz surface because of net charge effect of the active groups of polymer molecular chains. The mechanism of the formation of adhesive interface between Portland cement paste and quartz may be the products of gelatinous binder such as hydrated calcium silicate formed on the quartz surface due to the interaction between the negative ions of [HSiO 3] - and [SiO 3] 2- , and the hydrated positive ions of cement.