镁渣混凝土的早期收缩

发布时间：2019-03-16 20:50

【摘要】：随着工业的发展,现代混凝土对尺寸稳定性的要求越来越高,然而其早强,高强,低水胶比,高流动性的特点却加剧了收缩变形的发展,尤其是早期收缩变形,过大的早期收缩将会使混凝土开裂,降低结构的耐久性和安全性。介于此,对混凝土早期收缩的研究是未来混凝土收缩变形研究的重点。同时镁及镁合金产业近年来的快速发展,相应的产生了大量的还原废料——镁渣,这对周围环境造成严重污染,已有研究发现镁渣具有一定的水化活性和体积膨胀性。如果能利用镁渣的体积膨胀性补偿一部分混凝土的早期收缩,将对减少混凝土早期收缩具有积极意义。此外将镁渣作为混凝土的掺和料,还可以提高混凝土的强度,同时达到降低工程成本,减少镁渣对环境污染的目的,因此本课题具有较高的研究意义。以常用的C30混凝土为研究对象,以镁渣掺量、粉煤灰掺量、等为主要因素,设计正交试验。应用非接触法,通过测定混凝土初凝后3d内的早期收缩率,利用极差分析、方差分析等分析方法,探究混凝土早期收缩的特性,通过研究得出如下结论:(1)镁渣、粉煤灰和矿粉对混凝土的早期自缩具有抑制效应,镁渣和粉煤灰的抑制效应很显著,矿粉抑制效应的显著性一般。(2)混凝土的早期自缩主要发生在终凝前,12h完成早期自收缩总量的60.0%以上,24h完成早期自收缩总量的80.0%以上,之后发展变缓,但72h后仍有一定的增长趋势。(3)镁渣复合掺合料混凝土的早期自缩与时间呈相关性很好的双曲线关系,其参数模型的显著性水平高,与各因数的相关性好。(4)镁渣与粉煤灰、矿粉的复掺效应镁渣与粉煤灰的复掺效应镁渣与矿粉的复掺效应。
[Abstract]:With the development of industry, modern concrete requires more and more dimensional stability. However, the characteristics of early strength, high strength, low water-binder ratio and high fluidity aggravate the development of shrinkage deformation, especially the early shrinkage deformation. Excessive early shrinkage will make the concrete crack and reduce the durability and safety of the structure. In view of this, the research on early shrinkage of concrete is the focus of the future research on shrinkage and deformation of concrete. At the same time, with the rapid development of magnesium and magnesium alloy industry in recent years, a large amount of reduction waste-magnesium slag has been produced, which has caused serious pollution to the surrounding environment. It has been found that magnesium slag has certain hydration activity and volume expansibility. If the volume expansibility of magnesium slag can be used to compensate the early shrinkage of some concrete, it will be of positive significance to reduce the early shrinkage of concrete. In addition, using magnesium slag as admixture of concrete can also improve the strength of concrete, at the same time, it can reduce the engineering cost and reduce the environmental pollution of magnesium slag, so this subject has higher research significance. Taking C30 concrete as research object, taking magnesium slag content and fly ash content as main factors, the orthogonal test is designed. By means of non-contact method, the early shrinkage rate of concrete within 3 days after initial setting is measured, and the characteristics of early shrinkage of concrete are studied by means of analysis of extreme difference and variance analysis. The conclusions are as follows: (1) magnesium slag, The early self-shrinkage of concrete is inhibited by fly ash and mineral powder. The inhibition effect of magnesium slag and fly ash is remarkable. (2) the early self-shrinkage of concrete mainly occurs before final setting. More than 60.0% of the total early autogenous contraction was completed at 12h, over 80.0% of the early autogenous contraction was completed at 24h, and then the development slowed down. However, there is still a certain increasing trend after 72 hours. (3) the early self-shrinkage of magnesium slag composite admixture concrete has a good hyperbolic relationship with the time, and the significant level of its parameter model is high. (4) Co-doping effect of magnesium slag and fly ash, compound mixing effect of magnesium slag and fly ash, compound mixing effect of magnesium slag and ore powder.
【学位授予单位】：宁夏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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