Research Of Hydration Property Of Slag-cement Complex Binder At Low Temperature

Geographical cold regions of our country is vast, including 13 provinces, municipalities and autonomous regions of the "Three North" areas, accounting for over 50% of the national territory, winter lasted to 3 to 6 months, thus, in the winter the concrete construction technology research in cold regions is particularly important. The heat of hydration of Portland cement hydration behavior including heat release rate and heat release,which, especially has a great influence on durability of mass concrete. Under alkaline conditions, the hydration reaction of the slag can produce hydrated calcium silicate gel and zeolite-based products, the solid structure is formed compact. Proposal of cement hydration at negative temperature thermodynamic model provides theoretical support for the cold winter concrete construction. Therefore, the study on hydration rule of slag-cement composite binder system at low temperature is of great significance.This paper focuses on slag-cement composite cementitious material system at low temperature hydration of the rule. Research slag content, ambient temperature and other factors on composite cementitious material system hydration heat release rate, hydration heat release, non-evaporable water content, mechanical properties and microstructure. Slag-Cement with low temperature hydration system to calculate kinetic parameters, validate and build low temperature composite binder hydration system mathematical model.The results showed that with the increase of slag content and the decrease of hydration temperature, the hydration exothermic rate and hydration heat of the slag-cement composite binder system exhibited a downward trend. Hydration temperature of -10?, slag content of 0,10%,30%,50%,composite cementitious materials hydration system into the acceleration period of the time were:10.82h,11.10h,11.32h,11.49h. At this point the system of composite cementitious materials hydration exothermic rate were 0.00091mw/g,0.00066mw/g, 0.00065mw/g,0.00055mw/g. Comparison of pure Portland cement systems, composite cementitious material system into the acceleration period lagged time were 0.17h,0.43h,0.62h. Selecting acceleration period, hydration time for 20 h, at this point the systems of composite cementitious materials hydration exothermic rate were 0.00238mw/g?0.00196mw/g? 0.00146mw/g?0.00141mw/g. Comparison at the temperature of 5?,0? under the conditions of composite cementitious material system hydration heat rate,-10? under the conditions of composite cementitious material system hydration heat release rate were decreased by 0.00342mw/g,0.00344mw/g,0.00344mw/g,0.00279mw/g and 0.00061mw/g,0.00054mw/g, 0.00039mw/g,0.00023mw/g; With the increase of slag content, hydration temperature decreases, the composite cementitious material system mortar specimens of compressive and flexural strength performance decline. Select the hydration temperature of -10?, hydration time of 28d, different slag content composite cementitious material system mortar specimens of compressive and flexural strength were decreased by 12.96%,26.80%,34.58% and 8.52%,24.03%,36.43%; Composite cementitious materials system with non-evaporable water content decreases with increasing slag content, and increases with prolonging time of hydration time. Hydration temperature of-10?, hydration time of 28d composite cementitious material system with of the slag content increased,non-evaporable water content were decreased by 11.79%,16.64%, 45.38%. Hydration temperature of-10?, with the slag content of 30% of the composite binder system hydration time increases, the non-evaporable water content were increased by 83.87%, 145.16%,177.42%.Each phase obtained by Krstulovic-Dabic model calculated the reaction rate curve, can better simulate the calorimeter test segmentation obtained actual hydration of cementitious materials da/dt curve. Observe the relationship between the three stages, and then explain the composite cementitious materials system at low temperatures the hydration mechanism. And the establishment of a mathematical model compressive strength. Through the establishment of a linear regression equation can be seen not only significant regression equation, R2 values were greater than 99%, and, slag content on composite cementitious material system compressive strength of mortar specimens impact is very significant. Within a certain range, the model can be more accurately predict the composite cementitious materials systems mortar specimens of strength development.Spectrum analysis can be seen by SEM, in the pure cement paste, resulting in a large number of well-grown crystals of ettringite and complete shape; In cement paste with same hydration time and blending slag, ettringite crystals is short and slender, the shape is not complete, the sample microstructure is loose, resulting in lower compressive strength, which is macroscopic mechanical performance test results coincide.