The Application Of Viscosity-modifying Admixture To PVA Ultra Ductile Fiber Reinforced Cementitious Composites

According to the different processing routes of ECC material, Engineered Cementitious Composites(ECC) can be classified into four types: normal casting ECC, self-compacting casting ECC, spray ECC, extruded ECC. Viscosity-modifying admixture maintaining non-aggregation of the cement particle, which is indispensable to process self-compacting ECC and spray ECC with the high flowability. Through the experiments below, the influences of different viscosity-modifying admixture on the mechanical properties and the workability of PVA—ECC were discussed.(1) With adding Viscosity-modifying admixture and superplasticizer ,how to change of the workability of the matrix ;with adding PVA fiber ,how to change of the workability of the new paste;feeding sequence and mixing technology are described in paper. Based on a large number of tests.the optimal Viscosity-modifying admixture was used for the new paste of special workability.(2) Through the experiments on flexural strength,compress strength test of the specimens incorporating different Viscosity-modifying admixture and superplacticizer, the influences of different viscosity-modifying admixture on the mechanical properties and interface between PVA fiber and the cement composites were discussed.(3) Through the experiments on uniaxial direct tensile with well flowability, both the special workability and pseudo hardening stress-strain are completes with a suitable viscosity-modifying admixture and an optimal mix design.But,the mechanical properties is decreasing adding too much HPMC.The results show a suitable viscosity-modifying admixture and an optimal mix design will lead to both high workability and better mechanical properties. The results of this research can play a guiding role in processing ECC with high flowability.