Study On Mechanical Properties Of Sulphoalummate Cement Concrete With Admixture

In recent years,with the rapid development of concrete and building materials,the production of cement industry has put forward further requirements.Sulphoaluminate cement,as the third series of cement independently developed in China,has been widely used in engineering with its advantages of fast setting,high early strength,frost resistance,low alkalinity,micro expansion,corrosion resistance,etc.,especially for hydraulic engineering,emergency repair and construction,winter construction and other special projects.In practical engineering,admixture is often used to replace part of sulphoaluminate cement.On the one hand,admixture complementary advantages are used to improve the performance of cement;on the other hand,in order to protect the environment,develop green concrete and reduce the discharge of industrial waste.The admixture of fly ash and silica fume in cementitious materials is in line with the development trend of modern concrete.In this paper,by adding different proportion of fly ash and silica fume in concrete,the influence mechanism of admixture on the hydration reaction of cementitious system is analyzed,and the compressive strength and splitting tensile strength of concrete with different admixtures are tested The superior performance of the concrete provides a theoretical basis for its popularization and application.In order to prepare early strength and low strength concrete,this paper substitutes 0,10%,20%,30%and 40%sulphoaluminate cement by adding fly ash and silica fume admixture in the concrete,in which fly ash:silica fume=3:1 and 2:1.Through the pressure test under the standard conditions of 1 day,3 days,7 days,28 days and 90 days,including the age of 7 days frozen from the young age and 90 days standard curing after freezing,the influence on the mechanical properties of the sulphoaluminate salt water mud concrete was studied,and compared with the ordinary Portland cement concrete,and the morphology of the hydration products was analyzed by using the electron scanning microscope.The results of mechanical tests show that the strength of sulphoaluminate cement concrete decreases with the increase of the substitution rate of admixtures.The best substitution rate of 3:1 and 2:1 admixtures is 10%～20%and 30%～40%,respectively.The compressive strength of the two admixtures replacing 10%sulphoaluminate cement is the highest in three days,and the compressive strength is the best in three days when 10%is added.When the concrete is in plastic state,it is not afraid to be frozen.The influence of young age frozen on the compressive strength is small.After frozen,it is cured for 90 days.The compressive strength of the concrete exceeds the value of the standard curing for 90 days.SEM test results show that the number,morphology and state of hydration products in each group are different after 7 days of hydration.The addition of fly ash and silica fume improved the internal structure of sulphoaluminate cement concrete,and the internal porosity decreased with the increase of substitution rate.After the young concrete was frozen for 7 days,the number of hydration products decreased significantly.Combined with the influence mechanism of fly ash and silica fume,the main design principle for the preparation of concrete with admixture is to determine the best mix proportion and dosage of concrete.Proper proportion of admixture can not only meet the strength requirements of concrete,but also improve the working performance of concrete to a certain extent,and finally meet the requirements of construction and production.Figure[34],table[8],reference[76]...