MgO对水泥熟料膨胀性能的影响
发布时间：2018-11-26 12:37
【摘要】：水泥熟料中方镁石水化膨胀是引起混凝土体积不稳定的重要因素之一,国家标准对水泥中MgO的含量有明确限制。但是,方镁石不仅具有膨胀破坏性,还具有补偿收缩性。MgO水化产生的体积膨胀可以有效补偿大体积混凝土因温度应力产生的收缩,大幅度减少了裂缝的产生。与此同时,使用高镁石灰石生产熟料还具有缓解高品质石灰石资源日益匮乏的作用。针对水泥产业面临的资源和环境问题,结合外掺MgO水泥研究成果,本课题研究了MgO对水泥熟料膨胀性能的影响,以期为高镁石灰石高效利用提供理论依据。使用不同MgO含量的熟料制备了多种水泥净浆和砂浆试件,然后将这些试样在不同水浴温度环境(20℃,50℃和80℃),不同空气温度环境(20℃,50℃和80℃)和不同地域自然环境(深圳,西安,乌鲁木齐)养护。借助X射线衍射(XRD),扫描电镜(SEM),热重分析(TGA)等检测方法来表征不同MgO含量熟料制备的水泥在不同养护条件下的水化产物和水化过程。测定了水泥砂浆试件在不同环境中的收缩特性,分析了MgO对水泥熟料中方镁石和主要矿物相的含量的影响,SO_3的掺杂对高镁水泥熟料中方镁石的含量的影响以及SO_3及H3BO3单独和共同掺杂对高镁熟料中B矿晶型影响。研究表明:(1)在给定温度空气中养护的砂浆试件,水泥熟料氧化镁含量高的试块其收缩相对比较小,养护温度的升高促进试件收缩的增加;养护在给定温度水浴的水泥试块,水泥熟料氧化镁含量高的水泥试块其膨相对比较大,温度的升高对水泥试块的膨胀具有促进作用。(2)熟料中的氧化镁含量越高,方镁石含量越高,熟料其易磨性越差。(3)氢氧化镁的脱水反应发生在340℃~410℃之间,出现脱水峰最大峰值的温度为360℃。温度越高,氧化镁的水化速率越快,水化产物氢氧化镁越多。(4)水泥净浆在80℃水浴养护至7 d,距离未水化的方镁石5μm左右的区域存在着含镁的铝硅酸盐物质。养护至130 d,高镁熟料中方镁石已几乎完全水化,生成Mg(OH)2,周围有C(M)-S-H的存在。(5)SO_3掺杂有效减小了高镁熟料中方镁石的含量。H3BO3掺杂能够稳定β型硅酸二钙,形成了白硅钙石Ca7MgSi4O16等晶体矿物,掺入SO_3后会导致Ca7MgSi4O16的MgO分解出来,形成方镁石。(6)当SO_3和H3BO3同时对含镁β-C2S进行稳固的时候,SO_3和H3BO3有一个最佳配比:SO_3掺量4%,H3BO3掺量0.5%。在这个比例下,物料的水化反应会达到最佳。
[Abstract]:The hydration expansion of periclase in cement clinker is one of the important factors that cause the volume instability of concrete. The content of MgO in cement is restricted by the national standard. However, periclase not only has expansion and destructiveness, but also compensates shrinkage. The volume expansion caused by MgO hydration can effectively compensate the shrinkage of mass concrete due to thermal stress, which greatly reduces the occurrence of cracks. At the same time, the use of high magnesium limestone to produce clinker can alleviate the shortage of high quality limestone resources. In view of the resource and environment problems faced by cement industry and combined with the research results of MgO cement, this paper studies the effect of MgO on the expansion performance of cement clinker, in order to provide theoretical basis for the efficient utilization of high magnesium limestone. A variety of cement mortar and mortar specimens were prepared by using clinker with different MgO content. The samples were then treated at different water bath temperatures (20 鈩，
本文编号：2358579
[Abstract]:The hydration expansion of periclase in cement clinker is one of the important factors that cause the volume instability of concrete. The content of MgO in cement is restricted by the national standard. However, periclase not only has expansion and destructiveness, but also compensates shrinkage. The volume expansion caused by MgO hydration can effectively compensate the shrinkage of mass concrete due to thermal stress, which greatly reduces the occurrence of cracks. At the same time, the use of high magnesium limestone to produce clinker can alleviate the shortage of high quality limestone resources. In view of the resource and environment problems faced by cement industry and combined with the research results of MgO cement, this paper studies the effect of MgO on the expansion performance of cement clinker, in order to provide theoretical basis for the efficient utilization of high magnesium limestone. A variety of cement mortar and mortar specimens were prepared by using clinker with different MgO content. The samples were then treated at different water bath temperatures (20 鈩，
本文编号：2358579
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