Study On Structure And Properties Of Calcined Wollastonite

Wollastonite is a kind of calcium metasilicate mineral and the theoretical chemical composition?mass fraction?CaO48.3%,SiO₂51.7%.Naturally produced wollastonite is usually needle-shaped,radial,fibrous aggregates,and the like.Wollastonite is widely distributed on the earth and is mainly distributed in China,the United States,India,and Finland.The mineral resources of wollastonite is quite rich in China which is mainly in Jilin and Jiangxi and it ranks first in the world in reserves.Moreover,China is also a major producer of wollastonite.With the continuous research on the properties of wollastonite,wollastonite has been more and more widely used in modern industry in recent years.It is not only used to improve various mechanical properties and physical properties of plastics,metallurgy,coatings,rubber and other materials.Wollastonite is also incorporated into cement-based materials to improve the tensile strength of cement-based materials.However,there are few studies on calcined wollastonite.The existing research on calcined wollastonite mainly studies its antistatic properties,but there is few research on the effect of calcined wollastonite on the performance of cement-based materials.Calcined wollastonite was made after calcination at 800^oC,900^oC,1000^oC,1100^oC for2h.This paper studies the effect of calcined wollastonite on the properties of cement-based materials and the self-gelling properties of calcined wollastonite.Furthermore,it is also concerned that the better way to stimulate the gelling properties as well as the application of wollastonite in high dielectric composites.The conclusions are as follows:Firstly,the chain of wollastonite has become shorter and the surface of wollastonite has become smooth.In the meanwhile,it starts the crystal transform from?-CaSiO₃ to?-CaSiO₃.The amount of wollastonite is increasing with the increase of calcination temperature.Secondly,the self-gelling property of calcined wollastonite was proved in the environment of pure water as a result of the existence of f-CaO in calcined wollatonite,and it was proved that sodium silicate can better stimulate the self-gelling property of calcined wollastonite.In addition,the compressive strength of calcined wollastonite at1000^oC after 28d curing reached 4Mpa.Thirdly,calcined wollastonite is more obviously involved in the hydration reaction at the later stage of cement hydration compared to uncalcined wollastonite,which means calcined wollastonite contribute more tensile strength than uncalcined wollastonite.Specially,the strength of calcined wollastonite at 1000^oC increased by6.56%while the value of uncalcined wollastonite is 3.97%.Fourthly,the dielectric properties and the dielectric loss have changed greatly before and after calcination.It can be used as a high-dielectric composite material in a certain temperature range.Through the research in this paper,calcined wollastonite has certain self-gelling properties compared to un-calcined wollastonite,and at the same time it has a good promoting effect on the tensile strength of cement-based materials,and calcined wollastonite can be used to prepare high dielectric composites.