Preparation Of Ettringite Whisker And Its Strengthening And Toughening Effect On Cement And Gypsum

Ettringite is a kind of fibrous mineral crystal,which widely exists in cementitious materials as the hydration product of cement.The fibrous structure of ettringite and its high content of water in crystal make it can be widely used in building materials and energy fields as a kind of whisker.Ettringite whiskers were prepared from sulphoaluminate cement clinker-gypsumlime ternary system,aluminium sulphate-lime binary system and iron sulphate-lime binary system.The growth process of ettringite whiskers was studied,and the effects of different aluminium raw materials,reaction temperature and water-solid ratio on the growth rate and morphology of ettringite whiskers were analysed.The preparation method of ettringite whiskers is preferred.Two kinds of ettringite whiskers,outerdoped ettringite whiskers and self-generated ettringite whiskers,were application in Portland cement and building gypsum.The effect of application of ettringite whiskers on material mechanical properties and fracture properties of Portland cement and building gypsum was studied.The results show that the morphology of ettringite whiskers prepared from different aluminium raw materials is quite different.Ettringite whiskers prepared from sulphoaluminate cement clinker have the largest size and the morphology is similar to wood;ettringite whiskers prepared from aluminum sulphate have the smallest size and the morphology is diverse;ettringite whiskers prepared from iron sulphate have layered structure.Increasing the reaction temperature and increasing the reaction water-solid ratio both promote the reaction and increase the size of the ettringite whiskers,and the effect of the reaction temperature is more significant.The application of ettringite whiskers in Portland cement and building gypsum can significantly improve the flexural strength and the ratio of flexural strength and compressive strength of materials.In Portland cement with outer-doped ettringite whiskers and Portland cement with selfgenerated ettringite whiskers,when the content of ettringite whiskers is 5%,the best flexural strength enhancement effect can be obtained.In building gypsum,the flexural strength enhancement effect of outer-doped ettringite whiskers is more significant than that of self-generated ettringite whiskers,the outer-doped ettringite whiskers and selfgenerated ettringite whiskers all can significantly improve the fracture energy of cement paste,and play the role of crack resistance and toughening improvement.In this paper,ettringite is studied as a kind of fibre material,which breaks through the limitation that ettringite is only present as a kind of product of cement hydration,and provides an idea and theoretical basis for innovation and optimization of cementitious materials.