Study On Activation And Expansion Characteristics Of Natural Anhydrite

China is rich in natural anhydrite mineral resources with high grade and wide distribution,but its development and application are greatly limited by its dense structure,slow dissolution,low hydration activity and poor volume stability of products.Therefore,this paper takes the activity activation of anhydrite as the breakthrough point,and studies the influence of grinding activation,sulfate activation,slag and cement on the hydration hardening property and swelling property of anhydrite,and the development law of mechanical property and swelling property of anhydrite-based materials under different curing methods.The results show that:The specific surface area and activity of anhydrite increased with the milling time,and the particle morphology and crystal structure of hardened anhydrite were significantly improved.Combined with the grinding efficiency and other factors,the suitable specific surface area was 400～500m²/kg.Sulfate activator can effectively stimulate the hydration activity of anhydrite,shorten the setting time and improve the strength of the hardened anhydrite.The activation effect of calcined alum is better than that of Na₂SO₄,but as an activator,it has a negative effect on the volume stability of anhydrite,so the comprehensive performance is the best when the Na₂SO₄ content is 1%.Both slag and Cement can effectively improve the hydration activity of natural anhydrite,shorten the setting time of anhydrite,increase the hydration rate,and significantly improve the phase composition and crystal morphology of the hardened anhydrite,and increase the strength.At the same time,the expansion of anhydrite decreases or tends to be stable due to the addition of slag and cement.The Cement can stimulate the potential activity of the slag,and when the slag and the Cement are mixed together,the activation effect of the anhydrite is better,the hydration rate and the strength of the hardened anhydrite are significantly increased,and the late expansion of the hardened anhydrite is effectively inhibited,and the volume stability of the anhydrite is improved.The curing conditions have great influence on the hydration,hardening and expansion of anhydrite.With the increase of curing humidity,the hydration rate and strength of anhydrite stimulated by Na₂SO₄ increased.The hydration rate of anhydrite blinder increases,and the strength increases first and then decreases.However,the linear expansion rate of the two products increased significantly,and cracks appeared in the anhydrite blinder under high humidity environment,which had a serious impact on the flexural strength.Therefore,anhydrite-based materials should not be maintained under high humidity environment.Under the two cycle systems,anhydrite-based materials with different proportions showed better performance and could significantly inhibit the expansion under high humidity conditions,which could be used as an appropriate curing method for anhydrite-based materials,and anhydrite blinder was more suitable for curing under the dry-wet cycle system.