论文总字数：29807字

摘 要

因孔隙水分蒸发或迁移而产生体积收缩变形是水泥基材料的一个基本特性。实际工程中，水泥基材料的收缩因受约束而导致裂缝的形成与扩展，从而降低了整体结构物的耐久性和使用寿命。目前，在水泥基材料中掺入氧化镁膨胀剂补偿水泥基材料收缩是一种有效的防裂措施。国内外关于氧化镁膨胀剂对水泥基材料收缩变形性能的研究取得了大量的成果，但绝大多数是在固定湿度环境湿度下测量试件中心轴向的变形情况。本研究以砂浆、混凝土为研究对象，拟采用过饱和盐溶液法建立不同的相对湿度环境，研究掺不同掺量、不同活度氧化镁膨胀剂的水泥基材料在不同相对湿度下的膨胀性能，探讨掺氧化镁膨胀剂的水泥基材料的抗干缩性能，为在实际工程中建立合理的养护制度和氧化镁膨胀剂的应用提供理论参考。

本文通过大量的试验研究，对比分析，得出如下主要结论：

（1）将相同配方的水泥浆体和水泥砂浆试件移至(20±1)℃，40% RH，60% RH和80%RH环境中养护时，在14d之前，湿度越大，膨胀率也越大。

（2）将不同活性，同掺量的水泥浆体和水泥砂浆试件移至(20±1)℃，相同湿度环境中养护时，在14d之前，反应活性越大，膨胀率越大。

（3）在将不同掺量同活性的水泥浆体和水泥砂浆试件移至(20±1)℃，相同湿度环境中养护时，在14d之前，掺量越大，膨胀率越大。

（4）在所有实验的水泥浆体和水泥砂浆试件中，在14d之前，膨胀率最大的在水中养护的掺10%，反应活性50s氧化镁膨胀剂的试件；膨胀率最小的是在40RH中养护的掺5%，反应活性200s氧化镁膨胀剂的试件。

关键词： 干燥收缩 氧化镁 湿度 膨胀率

ABSTRACT

Due to evaporation or migration of pore volume shrinkage generated by a cement-based material basic features. Practical engineering, cement-based materials due to shrinkage constraints caused cracks formation and expansion, thereby reducing the overall structure of the durability and longevity. At present, the incorporation of the cement-based material expansion agent shrinkage compensated cement based materials is an effective crack control measures. Domestic and international studies on expansion agent of cement based materials shrinkage performance made a lot of achievements, but the vast majority are in the center of the specimen measuring humidity fixed axial deformation of ambient humidity. In this study, mortar, concrete for the study, to be adopted over a saturated salt solution method to create different relative humidity, the researchers mixed different content, different activity expansion agent performance cement-based material expands at different relative humidity, Discussion on the anti-shrinkage properties of MgO expansive cement-based material to provide a theoretical reference for the establishment of reasonable conservation systems and expansion agent used in the actual project.

According to a large number of experimental studies in this paper, comparative analysis, the main conclusions are as follows:

1. The same formulation of cement paste and cement mortar specimens move (20 ± 1) ℃, 40% RH, at 60% RH and 80% RH environment conservation, before the 14d, humidity, the greater expansion greater.    

2. The different activities, with the content of the cement paste and cement mortar specimens move (20 ± 1) ℃, when the same humidity environment conservation, before the 14d, the greater the reactivity, the greater the expansion.    

3. In the same activity with different contents of cement paste and cement mortar specimens move (20 ± 1) ℃, when the same humidity environment conservation, before the 14d, the greater the dosage, the greater the expansion.    

4. In all experiments the cement paste and cement mortar specimens, before the 14d,

the largest expansion in the conservation of water mixed with 10%, the reactivity of the specimen 50s expansion agent; smallest expansion in 40RH in conservation doped 5%, reactive expansion agent 200s specimen.

Keywords: Drying shrinkage Magnesia Humidity Expansion

目 录

摘要.............................................................................................................I

ABSTRACT...............................................................................................II

1. 绪论..............................................................................................1

1.1概述.....................................................................................................1

1.2水泥基材料的干燥收缩..........................................................................2

1.3氧化镁膨胀剂的研究与应用...................................................................3

1.3.1 MgO膨胀剂的膨胀机理.................................................................4

1.3.2 MgO膨胀剂的应用现状与前景.......................................................5

1.4 湿度对水泥抗干缩性能的影响..............................................................6

1.5本课题的研究目的和意义.......................................................................6

1.6本课题研究的研究内容.........................................................................6

1.6.1本课题的主要研究内容.................................................................6

第二章 原材料与实验方法......................................................................8

2.1试验原材料...........................................................................................8

2.1.1氧化镁......................................................................................... 8

2.1.2水泥.............................................................................................8

2.2试验方法..............................................................................................9

2.2.1相对湿度条件的控制.....................................................................9

2.2.2 水泥浆体试件制备及养护............................................................10

2.2.3 水泥砂浆试件制备及养护............................................................12

2.3 仪器设备...........................................................................................13

第三章 湿度对氧化镁膨胀性能的影响................................................15

3.1湿度对水泥浆体中氧化镁膨胀性能的影响............................................15

3.1.1 40%RH养护................................................................................15

3.1.2 60%RH养护................................................................................16

3.1.3 80%RH养护................................................................................18

3.1.4 水中养护...................................................................................21

3.1.5 不同湿度下养护..........................................................................22

3.2湿度对水泥砂浆中氧化镁膨胀性能的影响............................................24

3.2.1 60%RH养护................................................................................24

3.2.2 80%RH养护................................................................................26

3.2.3 水中养护...................................................................................28

3.2.4不同湿度下养护..........................................................................30

3.3水泥净浆的热重分析...........................................................................32

3.4本章小结............................................................................................33

第四章 结论与展望................................................................................34

4.1结论...................................................................................................34

4.2展望...................................................................................................34

参考文献..................................................................................................35

致谢..........................................................................................................38

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