(2) The saturation-drying weighing method was conducted to test porosity of cement mortar specimens with different fiber content at four kinds of flowing rate, and the variation of porosity with leaching duration of each specimen was obtained. The result also shows that, compared with the fiber reinforced cement mortar specimens, the porosity of the cement mortar specimens with no fiber content is smaller, and the density is better. The incorporation of fibers has not improved the leaching resistance of cement mortar.

(3) The concentration of calcium ion in the corrosion solution was measured regularly by using ethylenediaminetetraacetic acid (EDTA) titration method, and quantity of dissolved calcium ion of sample in leaching process was obtained. Result shows that, quantity of dissolved calcium ion of cement mortar with no fiber is smaller than that of fiber reinforced mortar. This result is consistent with the test result of calcium leaching process which is characterized by porosity.

(4) A device with larger stiffness for testing stress-strain curve of concrete was designed to test stress-strain curves of fiber reinforced cement mortar specimens with different leaching time. Result shows that, the device can be able to measure stress-strain curves of corroded samples. It can be obtained from curves that fiber reinforced cement mortar has better ductility than that of cement mortar with no fiber.

(5)According to Fick’s law and Gerard’s solid-liquid equilibrium equation, calcium ion transport equation and its numerical solution method of cement-based cylindrical specimen were established. A calculation and analysis program was compiled by MATLAB program to analyze the temporal and spatial variation of dissolution parameters such as porosity, corrosion depth, leaching time in the condition of immersion corrosion of 6m ammonium chloride solution. The relationship of model is verified by comparing calculated values with experimental results.

Keywords  calcium leaching, polyvinyl alcohol, fiber reinforced concrete, porosity, corrosion depth, compressive strength, model

目   次

1 引言1

1.1  研究背景1

1.1.1  钙溶蚀研究背景1

1.1.2  纤维混凝土的发展历程3

1.1.3  纤维混凝土的增强原理3

1.1.4  纤维混凝土的工程应用3

1.2  国内外研究现状4

1.2.1  钙溶蚀研究现状4

1.2.2  纤维混凝土研究现状7

1.3  本文研究内容9

2  实验10

2.1  原材料10

2.1.1  水泥10

2.1.2  砂子10

2.1.3  PVA纤维10

2.1.4  拌合水10

2.1.5  环氧树脂10

2.1.6  氯化铵溶液11

2.1.7  无水乙醇11

2.1.8  酚酞指示剂11

2.2  试样制备11

2.2.1  试件配合比11

2.2.2  试件成型与养护11

2.3  测试方法13

2.3.1  称重法测试孔隙率13

2.3.2  酚酞溶液滴定溶蚀深度14

2.3.3  EDTA滴定法测钙离子14

2.3.4  应力-应变曲线测试16

2.3.5  压力传感器标定17

2.3.6  微观形貌测试18

2.4  实验装置19

3  钙离子传输模型21

3.1  传输方程21

3.2  水泥水化程度22

3.3  水泥中可溶钙含量的确定22

3.4  初始孔隙率23

3.5  扩散系数23

3.6  边界条件24

3.7  固液平衡曲线24

3.8  有限差分法25

4  测试结果与分析29

4.1  钙离子溶出量29

4.2  溶蚀深度30

4.2.1  纤维对溶蚀深度的影响32

4.2.2  输水流速对溶蚀深度的影响32