论文总字数：23664字

摘 要

硫酸盐侵蚀显著影响水泥混凝土服役寿命，镁离子存在的情况下破坏尤为严重。为了促进水泥行业绿色可持续发展，研究水泥基材料劣化过程与侵蚀机理十分必要。石灰石作为天然矿物掺合料因其具有良好的经济效应而被广泛的应用于水泥基材料之中，然而，石灰石粉作为水泥替代材料会显著劣化混凝土抗硫酸盐侵蚀性能，尤其是增加低温发生碳硫硅钙石型侵蚀的风险。白云石是石灰石的伴生矿物，同属碳酸盐岩。近年来白云石粉作为矿物掺合料亦被国内外学者广泛研究，然而其抗硫酸侵蚀方面研究尚不充分。

为探究白云石粉水泥硫酸盐侵蚀劣化过程与机理，以石灰石粉水泥为参照，研究不同掺量和侵蚀温度，两种碳酸盐岩微粉水泥在浓度为50g /L的MgSO₄中侵蚀差异。采用XRD表征水化产物与侵蚀产物，SEM观察侵蚀产物微观形貌，MIP分析孔隙率，用膨胀率、质量变化与强度测试表征抗硫酸盐侵蚀性能。结果表明：养护28 d后，PDC水泥孔隙率略大于PLC。不同侵蚀温度下，不论掺入白云石微粉还是石灰石微粉都会导致水泥基材料的抗硫酸镁侵蚀性能的降低，且随掺量的增加，降低的越多；不同掺量下，PDC膨胀率整体小于PLC。常温侵蚀下强度测试因龄期较短，故不能用于表征侵蚀性能。两种侵蚀温度试件表观均有少量硫酸镁结晶，浆体表面生成了一层致密的氢氧化镁，钙矾石的量随着侵蚀龄期的延长而增加，并伴随着单碳的减少以及石膏的生成，低温下PDC和PLC还生成了碳硫硅钙石。综合膨胀率、重量损失、强度测试等，白云石微粉水泥相较于石灰石粉具有更好的抗硫酸镁侵蚀性能。

关键词：白云石微粉 石灰石微粉 硫酸镁侵蚀 矿物掺合料

Degradation process and mechanism of dolomite powder cement under magnesium sulfate attack

Abstract

Sulfate attack significantly affects the service life of cement concrete, and the damage is particularly serious in the presence of magnesium ions. In order to promote the green sustainable development of the cement industry, it is necessary to study the deterioration process and erosion mechanism of cement-based materials. As a natural mineral admixture, limestone is widely used in cement-based materials because of its good economic effects. However, limestone powder as a substitute material for cement can significantly degrade the resistance of concrete to sulfate attack, especially increasing the risk of TSA at low temperatures. Dolomite is associated with limestone, which is also a carbonate rock. In recent years dolomite powder as a mineral admixture has been widely studied by scholars all over the world. However, its research on sulfuric acid corrosion resistance is still insufficient.

In order to explore the sulfate degradation process and mechanism of PDC, PLC was taken as a reference to study erosion difference of two carbonate powder cements in MgSO₄ at a concentration of 50 g/L with different dosages and erosion temperatures. The hydration and erosion products were characterized by XRD. The microstructure of erosion products was observed by SEM. The Porosity was analyzed by MIP. Resistance to sulfate attack was characterized by expansion, mass change and strength test. The results show the porosity of PDC was slightly larger than that of PLC after 28 days of curing. Dolomite and limestone powder will lead to the decrease of magnesium sulfate corrosion resistance of cement-based materials, and decrease with the increase of dosage. Under different dosages, the overall expansion of PDC is smaller than PLC. The strength test under normal temperature erosion is not used to characterize erosion performance due to its short age. At the two etching temperatures, the specimens showed a small amount of magnesium sulfate crystals, and a dense magnesium hydroxide was formed on the surface of the slurry. The amount of ettringite increased accompanied by the formation of monocarbonate and gypsum with the age of erosion. PDC and PLC also produced thaumasite at low temperature. Combined with expansion, mass change, strength test, etc., PDC has better resistance than PLC to magnesium sulfate corrosion.

Key Words: Dolomite powders；Limestone powder；Magnesium sulfate；Mineral admixture

目 录

摘 要 I

Abstract II

第一章 绪论 1

1.1 研究背景 1

1.2 硫酸盐侵蚀机理 1

1.2.1 钙矾石侵蚀(ESA) 2

1.2.2 石膏型侵蚀(GSA) 3

1.2.3 碳硫硅钙石型侵蚀(TSA) 3

1.3 硫酸盐侵蚀的影响因素 4

1.3.1. 内部因素 4

1.3.2 外部因素 5

1.3.3 硫酸盐侵蚀评价方法 6

1.4 石灰石粉对水泥抗硫酸盐侵蚀的影响 6

1.5 白云石粉对水泥抗硫酸盐侵蚀的影响 6

1.6 研究目标与内容 7

1.6.1 研究目标 7

1.6.2 研究内容 7

第二章 原材料与实验方法 8

2.1 实验原料 8

2.1.1 水泥 8

2.1.2 碳酸盐岩微粉 8

2.1.3 细集料 8

2.1.4 其他原料 8

2.2 实验方法 9

2.2.1 膨胀率 9

2.2.2 质量变化 9

2.2.3 强度 9

2.2.4 微观结构及产物组成 10

2.3 实验仪器 10

第三章 结果与讨论 12

3.1 不同侵蚀温度下碳酸盐微粉水泥宏观特性表征 12

3.1.1 PDC与PLC不同侵蚀温度下表观变化 12

3.1.2 PDC与PLC不同侵蚀温度下变形规律 14

3.1.3 20 ℃硫酸盐侵蚀碳酸盐微粉砂浆质量变化 14

3.2 20 ℃硫酸镁侵蚀碳酸盐微粉砂浆强度变化 15

3.3 预养护28 d碳酸盐微粉水泥孔隙率及水化产物 16

3.3.1 预养护28 d碳酸盐微粉水泥孔隙率 16

3.3.2 预养护28 d碳酸盐微粉水泥水化产物 17

3.4 不同侵蚀温度下碳酸盐微粉水泥侵蚀产物与形貌 17

3.4.1 不同侵蚀温度下碳酸盐微粉水泥侵蚀产物 17

3.4.2不同侵蚀温度下碳酸盐微粉水泥侵蚀后微观形貌 18

3.5 碳酸盐微粉水泥硫酸镁侵蚀机理讨论 21

第四章 结论 23

参考文献 24

致谢 27

第一章 绪论

1.1 研究背景

水泥基材料作为建筑材料原材料，有着巨大的需求空间。水泥生产“两磨一烧”消耗大量能源，并排放大量CO₂气体，不利于环保。如何推动水泥行业朝着绿色低碳、可持续的方向发展的问题迫在眉睫。然而，实际上大部分水泥混凝土在没有达到其预期的使用寿命便形成了破坏，这种破坏显著影响水泥混凝土耐久性,因此会带了巨大的经济损失。因我国酸雨作用范围广，土壤、地下水中含大量硫酸根，混凝土长期遭受硫酸盐侵蚀，耐久性被破坏，尤其是我国西部盐渍地区，建筑物出现了“一年粉化，三年坍塌”的现象^{[1, 2]}。

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