Formation and Conversion of Ettringite During Hydration of Portland Cement from 0 to 20

The formation and conversion of ettringite during the hydration of Portland cement cured at 0,5,10 and 20 ℃ were inves-tigated by X-ray diffraction and nuclear magnetic resonance,respectively.The results indicate that ettringite formed from 0 ℃ to 20 ℃ firstly increases and then decreases as the hydration time increases from 1 d to 180 d.The formation of ettringite varied with the curing temperatures.The content of ettringite formed reached a maximum either at 3 d at 10 ℃ and 20 ℃ or at 28 d at 0 ℃ and 5 ℃.For the curing age,however,the content of ettringite formed at 20 ℃(10.2%) exceeded that formed at other temperatures after 1 day,the content of ettringite formed at 10 ℃(12.1%) exceeded that formed at other temperatures after 3 d,and the content of ettringite formed at 0 ℃ from 3 d to 180 d was the highest.In addition,ettringite converted to monosulfate more slowly at lower temperatures.