Sub-zero Temperature Performance And Thermodynamic Modelling Of Hydration Of Sulphoaluminate Cement With Antifreezing Agent

The construction of winter concrete is restricted due to the cold weather in northern China.How to increase the early strength of concrete at negative temperature is one of the key problems of winter concrete construction technology.And the introduction of antifreeze can improve the mechanical properties of concrete at negative temperatures.The antifreeze is an effective agent to reduce the freezing point and improve the microstructure of the material significantly.Therefore,the mechanism of various types of antifreeze and their influence on the process of cement hydration and hardening were studied,and the effect on the negative temperature in cold areas of China was investigated.The development of concrete construction technology has important theoretical significance and engineering application value.This article first analyzes the effect of ambient temperature?5?30??and watercement ratio?0.4?0.6?on the hydration of Portland cement and Sulfoaluminate cement by thermodynamic software.It found that a decrease in temperature significantly reduced the hydration rate of the various mineral components of the cement.This reduces the content of cement hydration products and the degree of hydration at all ages.An increase in the water-cement ratio can improve the hydration of cement.Second,thermodynamic software was used to analyze the salts early strength/antifreeze?sodium chloride?NaCl?,lithium carbonate?Li₂CO₃?.Effect of sodium nitrite?Na NO2??on the hydration of Portland cement and Sulphuraluminate cement to obtain the effect of different admixtures on the cement mechanisms of hydration.The results show that the introduction of NaCl causes Portland cement to produce Friedel's salt,sulphuraluminate cement to produce Kuzel's salt and sodium zeolite?Natrolite?.The introduction of Li₂CO₃ results in the formation of calcium carbonate in the structure.?Ca CO3?.The introduction of Na NO2 will also lead to the production of Natrolite in sulphoaluminate cement.Finally,triethanolamine?TEA?explores the effect and mechanism of organic admixture triethanolamine?TEA?on the sub-zero temperature performance of sulfoaluminate cement through mechanical properties,setting time,freezing point,hydration product content and micropore structure.With the increase of TEA dosage,the setting time is gradually shortened,and the freezing point of the liquid phase is reduced.The sub-zero temperature compressive strength during the same age increases first and then decreases with the increase of the dosage.This is because the addition of a certain content of TEA promotes the formation of AFt at negative temperature.With the increase of the dosage,the conversion of AFt to AFm will appear earlier.It was also determined that the optimal amount of TEA in sulfoaluminate cement at-5? was 3%.