Research On Hydration Activity And Durability Of Natural Anhydrite

Natural anhydrite is rich in naturnal resources in our country,the ratio is about 42%-60%that natural anhydrite approximately composes total quantity of the gypsum resources,and gypsum is a major resource.However,its exploitation and utilization are limited enormously because of its compact structure,low activity,poor gelatinization property and the low strength of early phase and so on.It is an important technical measure to solve present situation of anhydrite application by improving the activity of anhydrite to produce various construction materials and products so as to improve utilization ratio.In this article,we study adaptability of active activators to natural anhydrite from different mines,when natural anhydrite has hydrated,through determining and analysing transformation ratio of gypsum,setting time,strength of hardened body, phase composition as well as external appearance and so on.And study the durability of anhydrite to hydrate and harden by menas of analysis of volume stability,water resistance,frost resistance hardened.The experiment indicates:â‘ The influence of curing temperature to hydration of natural anhydrite is obvious.Along with the temperature rising,the hydration ratio of anhydrite reduces obviously,and the anhydrite does not hydrate nearly at 50℃.Ambient temperature of anhydrite binder and products in the process of production should be controlled within 30℃.â‘¡Activators has certian adaptability to natural anhydrite from different producing area.And among sulphate activators,FeSO₄ put up good adaptability entirely to each natural anhydrite,univalent K₂SO₄ and(NH₄)₂SO₄ put up good adaptability to Longyuan and Hanshan anhydrite.Divalent CuSO₄ has good effect of excitation.Under the influence of four kinds of activators,the effect of Daye anhydrite hydration is the worst.Among alkalescent activators,NaOH and KOH put up good adaptability entirely to natural anhydrite from different producing area.â‘¢There is a good effect to enhance the durability of test specimen that mix into the cemnt and slag,but need a appropriate mixture ratio.When the content of slag surpasses a certain ration,the expansivity of anhydrite test specimen will increase,and frost resistance become bad.So the suitable way is mixed with cement 5%and the slag 15%.This research will guide the utilization of anhydrite.It makes the anhydrite industry production come to realize,and it will produce excellent socialand economical efficiency.There is a comprehensive appraisal to the durability of the anhydrite binder through the research of the anhydrite durability,and provide a certain technical support for applications of the material anhydrite-based.