Study On Sulphoaluminate Cement Based Self-leveling Mortar For Rapid Repair

Sulphoaluminate cement is a special kind of cement developed by our country.Because of its good performance including fast setting time,high early strength,high volume stability,good durability and low carbon emission in the process of production,the country has been listed as the key research and development of cement.At present,the research on sulphoaluminate cement is being deepening and its application is increasingly broader.To settle the existing problems of cement concrete materials,the advantages of sulphoaluminate cement in rapid repair and protection has been increasingly researched recently,and its application prospect will be more and more extension.Based on the effect of three kinds of admixtures,polycarboxylate superplasticizer,redispersible polymer and defoamer on mortar,this thesis studies the change regulation of their fluidity and strength.Based on this,the optimum dosage of self-leveling mortar for rapid repair is determined.On the basis of guaranteeing great fluidity and optimizing the mix ratio,the influence law of bond strength is discussed,and the self-leveling mortar with 1h super early strength for rapid repair is prepared.The effect of silica fume and nano SiO₂ content on the properties of mortar was studied and the optimum content was determined.The results showed that the properties of the mortar improved obviously.The main properties of cement based self-leveling mortar used for rapid repair are discussed,including water cement ratio,fluidity,setting time,shrinkage rate,strength,bond and engineering application.The research shows that the cement based self-leveling mortar used for rapid repair has many excellent properties:large flow degree,high strength,fast development,small shrinkage?good volume stability?,good matching property and high bond strength with ordinary portland cement base mortar.In the aspect of engineering application,the failure modes of different pavement surfaces are discussed,and a targeted rapid repair process is put forward.Finally,the mechanism of early hydration of sulphoaluminate cement was analyzed by means of X ray diffraction?XRD?and hydration heat release.Through XRD analysis,it is found that the main hydration products of sulphoaluminate cement are ettringite and hydrated calcium silicate,and the admixtures do not change the hydration products but affect the hydration rate.The curves of hydration heat shows that there are two exothermic peaks in sulphoaluminate cement,and different admixtures can change the intensity and time of the exothermic peak.In addition,the reaction mechanism of different admixtures and sulphoaluminate cement was theoretically analyzed through chemical reaction principle.