Research On Properties Of Composite Cement-based Self-leveling Mortar

Thanks to its high performanceof self leveling,cementitious self-leveling mortar has the outstanding advantages of good fluidity and stability,simple construction,smooth,good resistance to acid and so on.Also has been effectively applied in supermarkets,shopping malls,workshop and other commercial or industrial buildings on the ground.However,the exist single system cementitious self-leveling mortar on the current market has poor coordination in all aspects of performance.Therefore,it is very important to develop cementitious self-leveling mortar which has high fluidity,high strength and good performance in other aspects.In this paper,we improve the property of traditional single system cementitious self-leveling mortar by adding aluminum(sulphoaluminate)cement and gypsum.First we make a contrastive study of portland cement and calcium aluminate cement compound system with portland cement and sulphoaluminate cement compound system to determine the mixture ratio of the mortar.On the basis of this,we study the effect of different kinds of gypsum on the performance of mortar through adding gypsum alone or synchronously orthogonal test.Then we can determine the mixture ratio of the composite cement based self-leveling mortar.Through the experiment,we get:(1)Aluminate cement and sulphoaluminate cement can significantly improve the mechanical properties of mortar,but will make the mortar fluidity decrease.Considering the performance and the cost,we choose portland cement-sulphoaluminate cement composite mortar,sulphoaluminate cement content is 5%.(2)Polycarboxylate superplasticizer could greatly improve the fluidity and early strength of mortar.When the content is 3.0%,the mortar fluidity could increase 180%.Fly ash can increase the mortar fluidity.At most,the initial fluidity can improve 21.43% and the 20 minutes after fluidity can improve 25.93%.The higher the percentage of cementitious materials,the worse the fluidity,the better the mechanical properties are.(3)Dihydrite gypsum reduces the mortar fluidity at least.At most,it can keep the initial fluidity unchanged and increase the 20 minutes after fluidity by 1.38%.Alpha-hemihydrite gypsum increase the mortar strength most.At most,it can be improved by 23.25%.And the gypsum content should not be too large,adding amount from 0 to 2% is more appropriate.(4)Orthogonal test results show that: the effect of anhydrite on the fluidity of mortar is the biggest,and the effect of dihydrite gypsum on the mechanical properties of mortar is the most.(5)The properties of the mortar can be comprehensively promoted with the redispersible powder.The bond strength increased significantly,up to 253.85%.The abrasion loss significantly reduced,up to 70%.And the shrinkage rate decreased significantly,up to 41.67%.Considering the performance of all aspects,the proper admixture quantity of the redispersible powder is 3%.