非洲干旱地区天然火山灰高性能混凝土内养护技术研究

发布时间：2018-04-23 01:41

本文选题：内养护 + 火山灰　；参考：《北京交通大学》2017年硕士论文

【摘要】：肯尼亚蒙-内铁路是东非铁路网的第一段,也是国际上第一条采用中国标准修建的国际现代化铁路。按照中国铁路标准有关要求,需要在混凝土中掺加矿物掺合料以提高其耐久性。然而东非地区普遍缺乏粉煤灰、矿粉等矿物掺合料,当地储量丰富的天然火山渣就成为一个合理的技术选择,所以本文采用肯尼亚当地的磨细火山渣作为矿物掺合料配制耐久性良好的高性能混凝土。由于高性能混凝土普遍存在早期收缩大、易开裂的问题,在非洲这样的干燥环境中,因得不到充分的外部养护,其收缩开裂问题更加不容忽视。基于此,内养护技术对天然火山灰高性能混凝土早期收缩开裂的改善是一个非常值得研究的课题。本文选取工程现场常用的两个强度等级高性能混凝土:HPC40、HPC60;采用两种内养护材料:火山渣、高吸水树脂(简称SAP);研究了两种内养护技术对天然火山灰高性能混凝土工作性能、力学性能、收缩性能及耐久性能的影响规律;并结合化学结合水、混凝土内部相对湿度、水分损失率,分析了内养护对火山灰混凝土性能的作用机理。主要工作和研究结果如下:(1)以流动性(坍落度和坍落扩展度)、粘聚性、保水性作为工作性能指标,研究了 SAP掺量、附加水胶比、不同拌合工艺对火山灰混凝土工作性能的影响规律;得出了 SAP在天然火山灰混凝土中的理论吸水倍率和适于SAP内养护的火山灰混凝土的拌合工艺。(2)以不同龄期的抗压强度作为力学性能指标,研究了两种内养护技术对火山灰混凝土力学性能的影响规律;得出了火山灰混凝土的抗压强度与内养护水胶比的关系;通过测定化学结合水的变化证明了内养护对胶凝材料水化的促进作用,并结合孔结构分析了内养护技术对强度的影响机理。(3)以自收缩和干燥收缩作为收缩性能指标,研究了两种内养护技术对火山灰混凝土收缩性能的影响规律;得出了内养护减缩率与内养护水胶比的关系以及干燥收缩开始产生的临界水分损失率,并结合内部相对湿度证明了内养护对干燥环境中火山灰混凝土良好的养护效果。(4)以电通量和碳化深度作为耐久性能的指标,研究了 SAP内养护对火山灰混凝土耐久性能的影响规律;采用显微镜观察了掺加SAP后净浆断面微观结构的变化情况;探讨了 SAP内养护对混凝土耐久性能的影响机理。
[Abstract]:Kenya's Mongol-Inner Railway is the first section of the East African railway network and the first international modern railway to be built to Chinese standards. According to the requirements of Chinese railway standards, mineral admixtures should be added to concrete to improve its durability. However, there is a general lack of coal ash, mineral powder and other mineral admixtures in East Africa, so the rich natural volcanic slag in the region has become a reasonable technical choice. In this paper, high performance concrete (HPC) with good durability is prepared by using the grinding slag of Kenya as mineral admixture. High performance concrete (HPC) generally has the problem of large early shrinkage and easy cracking. In dry environment such as Africa, the shrinkage cracking problem can not be ignored because of insufficient external curing. Based on this, the improvement of early shrinkage cracking of natural pozzolanic high performance concrete by internal curing technology is a subject worth studying. In this paper, two kinds of strength grade high performance concrete, 1: HPC40 / HPC60, which are commonly used in engineering site, are selected. Two kinds of internal curing materials are adopted: volcanic slag, super absorbent resin (abbreviated as SAP). The working performance of two internal curing techniques for natural pozzolanic high performance concrete is studied. The effect of internal curing on the performance of pozzolanic concrete was analyzed by combining with chemically bonded water, relative humidity of concrete and water loss rate. The main work and results are as follows: (1) taking fluidity (slump and collapse extension, cohesion, water retention) as the working performance index, the content of SAP and the ratio of additional water to binder are studied. The influence of different mixing processes on the performance of pozzolanic concrete; The theoretical water absorption rate of SAP in natural pozzolanic concrete and the mixing process of pozzolanic concrete suitable for curing in SAP are obtained. The compressive strength of different ages is taken as the mechanical performance index. The influence of two internal curing techniques on the mechanical properties of pozzolanic concrete was studied, and the relationship between the compressive strength of pozzolanic concrete and the water-binder ratio of internal curing was obtained. The effect of internal curing on the hydration of cementitious materials was proved by measuring the change of chemically bound water, and the mechanism of influence of internal curing technology on strength was analyzed in combination with pore structure. The effects of two internal curing techniques on the shrinkage properties of pozzolanic concrete are studied, and the relationship between internal curing shrinkage rate and internal curing water-binder ratio and the critical water loss rate at the beginning of drying shrinkage are obtained. Combined with internal relative humidity, it is proved that internal curing has good curing effect on pozzolanic concrete in dry environment. The influence of curing in SAP on durability of pozzolanic concrete was studied. The microstructure of clean slurry section with SAP was observed by microscope, and the mechanism of influence of curing in SAP on durability of concrete was discussed.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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