Research On Preparation And Properties Of Natural Anhydrite Based Self-leveling Mortar

China is rich in anhydrite resource. It accounts for 42-60% in proven reserve of gypsum resource in total. The national future reserve of anhydrite is nearly 30 billion tons in total, including 2 billion tons industrial reserve, the highest in the world. The structure of anhydrite is tight; dissolving rate is slow; hydration activity is very low; these are core and key problems restricting the resource utilization of anhydrite. Resolving and breakthroughing effectively these problems is the premise of anhydrite utilization.From saving energy and protecting environment angle, this paper improves firstly activity of natural anhydrite through various methods. And then prepares Natural anhydrite cementitious material characterized by fast coagulation and hardening, high strength, good durability. Based on natural anhydrite cementitious material, adding additives such as superplasticizer and stabilizer, natural anhydrite based self-leveling mortar with big fluidity, good workability and high strength is prepared. Eventually reach the purpose of natural anhydrite efficient resource utilization and expand the application technology and field of anhydrite resource. Conclusions are as follows:1. Sodium and calcined alum are efficient single activator in improving activity of anhydrite. The former can improve significantly the compressive strength of anhydrite and the latter can improve greatly the flexural strength of anhydrite. Homemade dual compound activator called homemade activator, has the best activating effect. Prepared natural anhydrite cementitious material 7d flexural strength can achieve 9MPa, compressive strength can achieve 30MPa, having fine volume stability, not exuding frost and splitting.2. Homemade activator accelerates the hydration process of anhydrite, improves greatly hydration rate of anhydrite, optimizes the crystallization direction of dihydrate gypsum, reduces the crystal size, refines crystallization, makes crystal grow crisscross and structure tight. Homemade activator changes the growth behavior of dihydrate gypsum, makes dihydrate gypsum grow along more faces, leading to the partial transformation of the crystal morphology from tabular to columnar.3. Based on anhydrite cementitious material prepared, Natural anhydrite based self-leveling mortar can be prepared by Adding 0.75%melamine-superplasticizer S and 0.07% stabilizer W. Its initial fluidity is 140mm above, fluidity losses is small, bleeding rate is low,7d flexural strength can achieve 6MPa, compressive strength can achieve 25MPa.4. The more the admixture of superplasticizer, the smaller the thixotropy of anhydrite based self-leveling mortar. The introduction of superplasticizer can reduce the viscosity of anhydrite based self-leveling mortar. Make the liquidity of anhydrite based self-leveling mortar better. But at the same time superplasticizer can cause the gravitational sedimentation of gypsum particles, leading to stability of anhydrite based self-leveling mortar worse.5. The more the admixture of stabilizer, the greater the yield stress of anhydrite based self-leveling mortar, the greater the viscosity, the greater the liquidity became worse. Considering both stability and liquidity of the system, stabilizer dosage of 0.03%-0.10% is advisable respectively. Anhydrite based self-leveling mortar presents Newton fluid state under the admixture, stability and liquidity good enough, within lh, the liquidity losses of anhydrite based self-leveling mortar is not serious, the anhydrite based self-leveling mortar standing for a long time can return to initial fluidity by fast stirring.