Study On The Properties Of Calcium Sulphosilicate-Calcium Sulphoaluminate Cement

Sulphoaluminate cement(SAC)has great advantages in low carbon emission and low energy consumption,and the cement has high early strength,corrosion resistance,low expansion and other characteristics,which make it widely used in various special projects.However,due to the form of belite(C2S)in cement is mainly β-C2S,and its hydration activity is low,which makes the development of cement’s late strength is slow.Research has shown that a kind of transitional mineral,calcium sulphosilicate(C5S2S),will be formed in the process of SAC firing,which has a higher activity than C2S in the presence of calcium sulphoaluminate(C4A3S).Therefore,this article will introduce C5S2S into SAC,to preparate calcium sulphosilicate-calcium sulphoaluminate cement.And based on the early research results of the research group,this paper will further study on the factors that affect the performance of this cement,in order to form a kind of excellent performance of calcium sulphosilicate-calcium sulphoaluminate cement,which has important theoretical significance and application value for the development of new low carbon cement.At first,this paper studies the effect of C5S2S mineral content on the performance of calcium sulphosilicate-calcium sulphoaluminate cement.The experimental results show that the actual mineral composition of cement clinker is basically consistent with the theoretical mineral composition.The increase of C5S2S content makes the setting time of cement clinker extended significantly.Increasing the content of C5S2S in a certain range is beneficial to improve the compressive strength of cement and reduce the expansion rate of cement mortar.The increase of C5S2S content is beneficial to the formation of AFt.The effect of added gypsum on the setting time of cement with different content of C5S2S is different.Within a certain range,with the increase of added gypsum content,the compressive strength of cement increases gradually.Excessive added gypsum will suppress the dissolution and hydration of C5S2S mineral.Then,the effect of curing condition on the properties of calcium sulphosilicate-calcium sulphoaluminate cement is studied.The test results show that the increase of curing temperature can significantly improve the compressive strength of cement,and will not destroy the volume stability of cement mortar.The change of curing humidity has a great influence on the development of cement strength.The compressive strength of cement under air curing condition is significantly lower than that under water curing condition.With the increase of curing temperature and humidity,the hydration of C4A3S mineral and C5S2S mineral has quickened significantly.Finally,the mineral composition of calcium sulphosilicate-calcium sulphoaluminate cement is optimized to further reduce the production cost and improve the mechanical properties of cement.The results found that the increase of C4A3S content is beneficial to increase the compressive strength of cement,which suitable content range is 30%～40%.With the content of C4A3S unchanged,increasing C5S2S content can obviously improve the compressive strength of cement,and its suitable content range is 40%～55%.When the amount of SO3 introduced is equal,anhydrite improves the compressive strength of cement better than natural gypsum,and which suitable content is 8%.The final cement mineral composition determined by the test is 35%C4A3S,40%～55%C5S2S,and it is advisable to use anhydrite as added gypsum,which dosage is appropriate to 8%.