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胶凝材料水化反应过程中收缩或膨胀体积变化是由其水化产物性质决定。水泥的收缩值随水化龄期的变化规律反应了水泥水化特点。研究活性MgO水泥浆体水化过程及水化产物,探索单掺MgO对水泥体系膨胀特性的影响。活性MgO由菱镁矿经700℃保温2.5h煅烧制备。单掺8%活性MgO水泥净浆的安定性合格,单掺质量分数12%活性MgO水泥净浆的安定性不合格。MgO掺量由4%增长到20%时,20℃水浸泡膨胀率由1.88‰增加到10.05‰。纯水泥浆体20℃水浸泡90d后的孔容为0.018cm3/g,活性MgO增大了水泥浆体的孔容。MgO质量掺量由8%增加至12%时,水化产物Mg(OH)2堵塞了孔径,浆体20℃水浸泡90d的孔容从0.079cm3/g减小到0.030cm3/g。12%MgO水泥浆体孔径分布范围比8%MgO水泥浆体广,主要分布在2～100nm之间,且孔径微分分布增大。根据MgO水化反应产物、形貌表征以及孔径分析、体积膨胀率的实验结果,解释单掺活性MgO导致水泥浆体安定性问题的原因。
The shrinkage or swelling volume change during the hydration reaction of a cementitious material is determined by the nature of its hydration product. The shrinkage value of cement reflects the characteristics of cement hydration with the variation of hydration age. The hydration process and hydration products of active MgO cement paste were studied, and the influence of single MgO on the expansion characteristics of cement system was explored. Active MgO by magnesite by 700 ℃ insulation 2.5h calcination preparation. The stability of single mixed with 8% active MgO cement paste was qualified, and the stability of single-doped 12% active MgO cement paste was unqualified. When the content of MgO increased from 4% to 20%, the swelling rate of water immersion at 20 ℃ increased from 1.88 ‰ to 10.05 ‰. The pore volume of pure cement slurry after immersion for 90 d at 20 ℃ was 0.018 cm3 / g, and the active MgO increased the pore volume of cement slurry. When the content of MgO increased from 8% to 12%, the pore size of the hydration product Mg (OH) 2 was blocked, and the pore volume of the slurry immersed in water at 20 ℃ for 90d decreased from 0.079cm3 / g to 0.030cm3 / g. The pore size distribution of 12% MgO cement paste is wider than that of 8% MgO cement paste, mainly distributed in the range of 2 ~ 100 nm, and the pore diameter distribution increases. According to the results of MgO hydration reaction products, morphology, pore size analysis and volume expansion, the reasons for the stability of cement slurry caused by single doped MgO are explained.