Study On The Liquid Alkali-free Accelerator

With the application of wet shotcrete construction technology is used more and morewidely, more attention is payed on liquid accelerator research. At present, the most liquidaccelerator which is developed in domestic is alkaline. Although this type of acceleratingagent reduce the dust in the construction process, and reduce inadequate dispersion in the mixcompared with the powder accelerating agent, due to its strong alkali, it causes too much lossof late concrete strength, and it is harm to the constructors’ physical health. Therefore, a newresearch on low alkaline liquid accelerator research is very important.At first, this paper selected two inorganic components and two organic components,determined the best proportion of components though the orthogonal experiment design, andthen developed the LYaccelerator successfully. This accelerator is milk white in roomtemperature, its alkali content is less than2.0%, and its solid content is43.7%. When thedosage of the LY accelerator was9%, the initial setting time of cement paste was2.9min, andfinal set time is6.8min.This paper detected accelerating performance of LY accelerator, the effect on strength ofcement mortar and the effect on volume change of cement mortar, and discussed thecomprehensive performance of LY accelerator. The experimental results showed:（1） The LYaccelerator had good adaptability to different kinds of cement.（2） The LY accelerator canmaintain good coagulation effect during10to40℃temperature range.（3） With the increaseof mixing time, effect of the accelerator is gradually decreased.（4） When the dosage of theLY accelerator was9%,1d、3d and28d flexural strength of jidong cement mortar were2.9MPa,6.15MPa and6.15MPa,1d,7d and28d compressive strength were11.78MPa,45.92MPa and46.5MPa;1d、3d and28d flexural strength of qinling cement mortar were3.45MPa、6.17MPa、7.9MPa,1d,7d and28d compressive strength were20.16MPa、39.88MPa、54.2MPa.（5） After adding LY accelerator, cement mortar was shrunk, and with theincrease of the LY accelerator’s dosage, shrinkage rate increased gradually.This paper analysed cement sample of different hydration time and different dosage ofLY accelerator by means of XRD and SEM analysis, studied mechanism of the LYaccelerator. The results showed: the LY accelerator accelerated the hydration reaction of C₃A,shortened the induction period of C₃S, promoted the formation of early ettringite.