Experimental Study And Mechanism Analysis Of Sulphoaluminate Cement-based Materials

Sulphoaluminate cement is the third series cement developed independently in China,the main mineral clinker is 3CA·CaSO₄-C₂S-CaSO₄·2H₂O,which has the advantages of early strength and high strength,short setting and hardening time,impermeability,frost resistance and corrosion resistance,the application and development prospects are very optimistic.The unit production cost of sulphoaluminate cement is higher than that of Portland cement,and the setting and hardening speed is faster,the addition of mineral admixture reduces its strength and impermeability,and limits its application and popularization.The paper regards mechanical strength and durability as the primary target of modification,in order to improve the working performance and reduce the unit cost of the composite cement,the low cost ordinary Portland cement was introduced to replace the sulphoaluminate cement.Based on the theory of the pozzolanic effect of silica fume and the cementation film effect of polymer cement powder,etc.The proper proportion of silica fume and rubber powder is chosen to solve the problems of low carbonization resistance and increased dry shrinkage caused by the addition of common silicon cement.The experimental results show that:1.Single doped silicon cement,the fluidity of sulphoaluminate cement decreases and the setting time becomes faster.The strength of the mortar mixed with two kinds of cement is not a simple combination of the two,but shows more complex characteristics.When the single-doped silica cement is 30%⁵0%,there is a tendency of rapid hardening and anti-carbonization of the composite cement.2.Fly ash has a positive effect on water demand of sulphoaluminate cement,whereas silica fume has an inhibitory effect.Compared with fly ash,silica fume has more obvious retarding effect on sulphoaluminate cement.After adding fly ash,the strength of sulphoaluminate cement decreased to a certain extent,and the effect of silica fume was better than that of fly ash.Compared with fly ash,silica fume can reduce the dry shrinkage of mortar more effectively.The carbonation resistance of sulphoaluminate cement was improved obviously by adding two kinds of admixtures.3.The fluidity of sulphoaluminate cement increases with the increase of the ratio of aggregate to cement,and the setting time increases first and then decreases.The strength value of cement mortar can be improved by adding 0.6%rubber powder,and the carbonation resistance of sulphoaluminate cement based material can be improved significantly by adding rubber powder because of the effect of polymer cementation film formation.When the ratio of polymer to cement was 0.9%,the frost resistance of mortar reached the best.4.With the addition of silica fume in sulphoaluminate cement with large amount of silicon cement,the water demand of composite cement is increased and the setting time is prolonged.When the cement mortar is mixed with 6%silica fume,the dry shrinkage of cement mortar reaches the minimum value,and its value is between 6%silica fume and 40%ordinary silica cement.Proper amount of silica fume can improve the strength and carbonation resistance of cement mortar in the middle and late stage,and the effect of adding 4%silica fume on the frost resistance of mortar is the best.5.The setting time of the composite cement increased with the addition of rubber powder in the sulphoaluminate cement with large amount of silicon cement.Compound rubber powder can improve the water demand,strength and dry shrinkage value of composite cement to some extent.The carbonation resistance of sulphoaluminate cement based material was improved by adding 0.6%rubber powder,when mixed with 0.9%rubber powder,its frost resistance is the best,and the effect of compound blending is better than that of single rubber powder.By SEM scanning test,the cementation of polymer film improved the toughness and strength of cement mortar and improved the durability of mortar.