Research Of Calcium Sulposilicate On The Performance Of Sulphoaluminate Cement Based Materials

Sulphoaluminate cement has the characteristics of early strength,high strength,impermeability,corrosion resistance and micro-expansion.It is an energy-saving and low-carbon cement.Because the production of sulphoaluminate cement requires high alumina materials,the production cost of sulphoaluminate cement increases,and the strength of sulphoaluminate cement tends to shrink in the later period.Adding mineral admixtures into sulphoaluminate cement can not only reduce the production cost of cement,but also reduce the hydration heat,improve the workability of cement concrete and improve the resistance to chemical erosion.However,the strength of cement is generally reduced by the addition of mineral admixtures,and the content range is lower than that of ordinary Portland cement,which inhibits the application of mineral admixtures in sulphoaluminate cement.In the calcination process of sulphoaluminate cement clinker,besides some main minerals,some intermediate minerals are formed,such as calcium sulphosilicate(4CaO·2SiO2·CaSO4).In the hydration process of sulphoaluminate cement,the aluminium glue produced by the hydration of calcium sulphoaluminate can stimulate the activity of calcium sulphosilicate.In sulphoaluminate cement mixed with fly ash,the active aluminium in fly ash can also stimulate the activity of calcium sulphosilicate,and the gypsum released by calcium sulphosilicate in the hydration process can further stimulate the activity of fly ash.The activity of calcium sulphosilicate is higher than that of Belite,and calcium sulphosilicate has a positive effect on the improvement of the later strength of cement.Therefore,it is of great significance to study the activity of calcium sulphosilicate and its role in sulphoaluminate cement and fly ash cement system in order to improve the performance of cement system,which is of great significance for the popularization and application of sulphoaluminate cement.Firstly,the calcination system and hydration activity of calcium sulphosilicate minerals were studied.Different calcination temperatures(1100,1150,1200)and times(primary and secondary)were used.The results showed that the optimum calcination temperature of calcium sulphosilicate minerals was 1150 C,and the second calcination was adopted.The hydration process of calcium sulphosilicate minerals was very slow,and water would occur slowly in the later stage.Calcium sulphoaluminate and gypsum can promote the hydration activity of calcium sulphosilicate,and gypsum produced during the hydration process of calcium sulphosilicate can further promote the hydration of calcium sulphoaluminate and form and stabilize ettringite.Calcium sulphosilicate was introduced into sulphoaluminate cement to study its influence on mechanical properties and hydration process of sulphoaluminate cement.The results showed that the setting time of cement was shortened in varying degrees by adding different amounts of calcium sulphosilicate into sulphoaluminate cement.The effect of 5%calcium sulphosilicate on setting time of cement was most obvious in three curing methods.After 28 days of hydration,the compressive strength of calcium sulphosilicate system with 5%content is higher than that of blank group;calcium sulphosilicate has no obvious effect on the volume stability of cement system;from the analysis of hydration products,it can be seen that the type of hydration products has not changed when calcium sulphosilicate is added into cement,and the main type of hydration products is ettringite.In the later stage of cement hydration,gypsum released from calcium sulphosilicate hydration stabilized ettringite remarkably.Calcium sulphosilicate is added into fly ash-sulphoaluminate cement-based cementitious materials.The results show that the initial setting and final setting time of cement system decrease with the increase of the content of calcium sulphosilicate in fly ash cement system,and the compressive strength of cement system decreases with the increase of the content of fly ash in 0.5 water-cement ratio system,and is lower than that of 0.5 water-cement ratio system.Strength;The strength of fly ash cement system without calcium sulphosilicate decreases gradually with the increase of fly ash content.After 7 days of cement hydration,the strength of 5%and 10%calcium sulphosilicate cement system is higher than that of the blank group without calcium sulphosilicate content,and the effect of 10%calcium sulphosilicate content is most significant.From the analysis of hydration products,it can be seen that adding calcium sulphosilicate into fly ash cement system does not change the cement.The main hydration products are ettringite.With the increase of hydration age,the intensity of the diffraction peak of ettringite increases gradually,and the diffraction peak of calcium sulphoaluminate decreases significantly.This shows that the coexistence of calcium sulphosilicate and calcium sulphoaluminate promotes the hydration of cement to a certain extent.