The Research On Anti-Washout Admixture Of Non-Dispersive Underwater Concrete

The paper aims to find out the most appropriate Polyacrylamide (PAM) and its corresponding quantity of Anti-Washout Admixture (AWA) from four different molecular weights PAM, through experiments of cement paste rheological properties, mortar anti-washout property and concrete properties. And basing on this point, exploring the compositions of the admixture, and matching other auxiliary admixtures to develop the right AWA to meet the construction requirement. First of all, the paper introduces the history and researches of Non-dispersive Underwater Concrete (NDC), and summarize the NDC application technology also. Secondly, through the introduction and comparison of each flocculating agents, choosing four different molecular weights PAM (4million, 6million, 8million, 10million respectively) as the essential component, and planning to find out the most appropriate PAM among these. And also the paper chooses corresponding experiments methods, materials and equipments. In order to present effects of PAM on anti-washout property of NDC, the paper chooses fresh cement as subject investigated, mixing four different average molecular weights PAM under different quantities, and finds the effects of PAM on divergence and rheological properties of fresh cement. The results show that, with the increase of PAM quantity, divergence of the paste gets larger earlier and smaller later, the yield point stress keeps on increasing, and the plastic viscosity increases rapidly initially, drops latter, and increases smoothly. The article discusses the reason of this phenomenon, and establishes the model of the action between cement and PAM. Experiments of mortar anti-washout property are in order to choose the most appropriate PAM and its corresponding quantity. The results present that, the yield point stress and the plastic viscosity of cement paste influence the anti-washout property of mortar greatly. And if the yield point stress is high and the plastic viscosity is low, anti-washout property will be better, and the fluidity will better too. Otherwise, as one of the auxiliary admixtures, reducing agent not only can improves the fluidity of mortar, but also can reduces the water soakage of mortar. Finally, the article determines the most appropriate PAM and its corresponding quantity through the anti-washout properties experiments of mortar. With the results of rheological properties of fresh cement and anti-washout property of mortar, the paper determines the types and the corresponding quantities of other auxiliary admixtures in AWA, through experiments of NDC properties. Through a series of comparisons, the paper determines Triethanolamine and silicon fume as the other auxiliary admixtures. The results shows that the early stage stress of NDC increases greatly, if adding 5% silicon fume and 0.05% Triethanolamine in it. NDC with AWA of above materials can meet the demand of the Nation Code.