现代混凝土的气体传输性能研究

论文总字数：40768字

摘 要

随经济全球化，世界各国基础设施建设总量不断增加，混凝土因廉价、来源广、工作性能良好等优点而被广泛应用。同时，混凝土面临海洋、盐土、大气、冻融等严峻环境考验，致其耐久性设计备受关注，作为混凝土耐久性重要指标的渗透性成为研究重点。为了实现混凝土渗透性表征多维化，气体渗透性应用而生。现代混凝土中气体传输特性，关系到钢筋锈蚀、混凝土碳化，影响其力学性能和长期性能，同时也为混凝土耐久性研究提供理论支撑。

本文基于多孔介质理论与复合材料理论，结合现代分析测试技术，采用围压密封方式和变压压力法，首先统一了混凝土气体渗透性测试参数，在考虑混凝土粗集料下沉作用下系统研究了进气压、围压和尺寸对气体渗透性的影响，获取了合理的气体渗透性测试推荐参数。同时考虑粉煤灰、矿渣及粗集料级配对现代混凝土气体渗透性的影响，结合孔隙特征分析，研究了各因素影响气体渗透性的过程、特征和规律。得到以下研究成果：

1. 现代混凝土气体渗透性测试参数

基于变压压力法，考虑混凝土粗集料下沉，分别研究了圆柱形混凝土试样上、中、下不同部位在不同进气压、围压条件下气体渗透性，结合尺寸影响，系统测试了不同高度混凝土气体渗透系数。结果表明，15~30bars进气压、50bars围压，100mm试样高度作为气体渗透性测试优选参数。

1. 现代混凝土气体渗透性影响因素

基于优选气体渗透性测试参数，考虑矿物掺合料种类及掺量、粗骨料级配对现代混凝土气体渗透性影响，研究了各因素影响气体渗透性的过程、特征和规律，获取了气体渗透系数和滑移因子。结果表明：粉煤灰和矿渣掺入降低了气体表观渗透系数，10%、30%、50%掺量粉煤灰和矿渣对气体渗透系数降低幅度分别为： 54.69%、51.49%、74.41%和62.85%、55.52%、61.11%。相对连续级配5-25mm，单一级配5-10mm、10-16mm、16-20mm、20-25mm粗集料均降低现代混凝土气体渗透性，降低幅度为：63.72%、47.57%、46.48%、61.52%。

关键词：现代混凝土；气体渗透性；滑移因子；孔隙特征；变压压力法

Abstract

With the globalization of the economy, infrastructure construction in all countries of the world has been increasing, and concrete has been widely used due to its advantages of low cost, wide source and good work performance. At the same time, the concrete faces the severe environmental test of ocean, salt soil, atmosphere, freezing and thawing, and its durability design has attracted much attention. As the important index of concrete durability, the permeability has become the research focus. In order to achieve multi-dimensional characterization of concrete permeability, gas permeability applications have emerged. The gas transmission characteristics of modern concrete are related to steel corrosion, concrete carbonization, affecting its mechanical properties and long-term performance, and also provide theoretical support for concrete durability research.

Based on the theory of porous media and composite material theory, combined with modern analytical testing technology, using the confining pressure sealing method and the variable pressure method, the concrete gas permeability test parameters are first unified, and the system is studied under the consideration of concrete coarse aggregate sinking. The effects of inlet air pressure, confining pressure and size on gas permeability have obtained reasonable parameters for gas permeability testing. At the same time, considering the influence of fly ash, slag and coarse aggregate grade on the permeability of modern concrete gas, combined with the analysis of pore characteristics, the process, characteristics and laws of various factors affecting gas permeability are studied. The following research results were obtained:

1. Modern concrete gas permeability test parameters

Based on the pressure swing method, considering the sinking of coarse aggregate of concrete, the gas permeability of the upper, middle and lower parts of the cylindrical concrete specimen under different inlet pressure and confining pressure conditions was studied, and the influence of the size was systematically tested. Concrete gas permeability coefficient at different heights. The results show that the inlet pressure of 15~30bars, the confining pressure of 50bars and the height of 100mm sample are the preferred parameters for the gas permeability test.

1. Factors affecting on gas permeability of modern concrete

Based on the preferred gas permeability test parameters, considering the type and amount of mineral admixture and the influence of coarse aggregate grade on the gas permeability of modern concrete, the process, characteristics and laws of various factors affecting gas permeability were studied, and gas permeation was obtained. Coefficient and slip factor. The results show that the fly ash and slag incorporation reduce the apparent gas permeability coefficient of modern concrete, and the 10%, 30%, 50% content of fly ash and slag reduce the gas permeability coefficient: 54.69%, 51.49%, 74.41% and 62.85%, 55.52%, 61.11%. Relative continuous grading 5-25mm, single grading 5-10mm, 10-16mm, 16-20mm, 20-25mm coarse aggregates reduce the gas permeability of modern concrete, the reduction is: 63.72%, 47.57%, 46.48% and 61.52%.

Key words: Modern concrete; Gas permeability; Slip factor; Pore characteristic; Variable pressure method

目 录

摘 要 I

Abstract II

第一章 绪论 1

1.1 引言 1

1.2 研究现状 1

1.2.1 研究理论 1

1.2.2 气体渗透性测试参数 2

1.2.3 气体渗透性影响因素 3

1.3 本章小结 4

第二章 试验材料与方法 5

2.1 试验原材料 5

2.1.1 水泥 5

2.1.2 粉煤灰 6

2.1.3 矿渣 8

2.1.4 集料 9

2.1.5 减水剂 10

2.2 试验配合比设计 10

2.3 混凝土性能测试 11

2.3.1 孔结构 11

2.3.1.1 MIP测试 11

2.3.1.2 连通孔隙率测试 12

2.3.2 力学性能 13

2.4 气体渗透性测试方法 14

2.4.1 试件准备 14

2.4.2 气体渗透性测试设备 14

2.5 本章小结 17

第三章 混凝土气体渗透性试验测试参数优化 18

3.1 材料和方法 18

3.1.1试样制备 18

3.1.2 渗透性装置和测量精度 18

3.1.3 气体扩散机理 20

3.2 结果与讨论 21

3.2.1围压与进气压影响 21

3.2.1.1 R45U在50bars围压下气体渗透性 21

3.2.1.2不同围压下R45U气体渗透性 22

3.2.1.3 R45U、R45M和R45B气体渗透性 23

3.2.1.4 R35与R55渗透性比较 24

3.2.2 试样尺寸影响 26

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