Study On Hydration And Properties Of Calcium Sulphoaluminate-Ternesite-Dicalcium Silicate

Calcium sulphoaluminate-ternesite-dicalcium silicate clinker system is a new system with development prospect.The sintering temperature of this kind of clinker is about 200℃lower than that of Portland cement clinker,and the carbon dioxide emission and energy consumption are reduced by 25～35%and 10～15%respectively.Its sintering temperature is lower than that of sulphoaluminate clinker by more than100℃.The cement has not only the excellent long-term stability of Portland cement,but also the advantages of high early strength of sulphoaluminate cement,so it has a broad application prospect.The hydration activity of ternesite-dicalcium silicate composite mineral system with solid solution of 0.5wt%P⁵⁺、F^–、Na⁺、K⁺、Li⁺respectively and the hydration activity of calcium sulphoaluminate-ternesite-dicalcium silicate three-phase system and ternesite-dicalcium silicate composite mineral in deionized water,1mol/L NaAlO₂、0.02mol/L Li₂CO₃ and 1mol/L Mg SO₄ were studied.The effects of liquid environment and solid solution ions on the composition and microstructure of hydration products of calcium sulphoaluminate-ternesite-dicalcium silicate clinker system were studied by compressive strength test,scanning electron microscope,X-ray diffraction and comprehensive thermal analysis.At the same time,the influence mechanism of different liquid environment on hydration activity of calcium sulphoaluminate-ternesite-dicalcium silicate clinker system was discussed.It is found that the NaAlO₂ solution can react with ternesite to produce ettringite,which can promote the hydration of ternesite-calcium silicate composite minerals.Li₂CO₃ solution can form a dense hydration product protective film around the cement clinker particles,so it can inhibit the hydration of composite minerals.Mg SO₄ solution promoted the hydration of ternesite-calcium silicate composite minerals from 28d to56d,and inhibited hydration after 56d.The hydration of ternesite-calcium silicate composite minerals was inhibited by solid solution of 0.5wt%P⁵⁺、F^–、Na⁺、K⁺、Li⁺respectively,and the compressive strength of 90 days was lower than 50%of the hydration test block in deionized water.For the three-phase system of calcium sulphoaluminate-ternesite-dicalcium silicate,both NaAlO₂ solution and Li₂CO₃ solution promote the hydration before 28days,but inhibit the hydration at the later stage.These two solutions also inhibit the hydration of dicalcium silicate in system.Mg SO₄ solution reacts with ettringite to form Ca（OH）₂and Mg（OH）₂,resulting in the failure of the cement paste.