镁渣混凝土自生收缩与强度特性研究

发布时间：2019-02-19 11:19

【摘要】：由于镁工业近年来发展迅速,镁渣排放量急剧增加,导致环境污染问题日益严重,同时限制了镁工业的进一步发展;为追求混凝土的高强度以及高流动性,往往在混凝土中大量掺加外加剂和掺合料,这就导致混凝土收缩问题日益严重;镁渣的化学成分与水泥相近,有一定的水化活性,所含MgO具有膨胀性,将镁渣作为混凝土掺合料,能提高混凝土的强度,对混凝土的自生收缩有潜在的补偿,且可以降低工程成本,减少环境污染,因此该课题具有较高的研究意义,研究得到国家自然科学基金项目的支持。以C30镁渣混凝土为研究对象,设计单因素试验方案和正交试验方案;采用趋势分析、极差分析、方差分析等数据分析方法,分析各矿物掺合料对镁渣混凝土自生收缩的作用规律,揭示镁渣对混凝土自生收缩的作用机理,并建立混凝土自生收缩率随龄期以及各矿物掺合料掺量变化的关系模型,研究得出如下结论:(1)随镁渣掺量的增加混凝土的自生收缩逐渐减少,镁渣掺量越高镁渣对自生收缩的抑制效应越大。镁渣可以提高混凝土的抗压强度,但随着镁渣掺量水平的增加,镁渣对抗压强度的增强效应逐渐降低。(2)掺入粉煤灰对混凝土的自生收缩有抑制作用,随着粉煤灰掺量的增加,混凝土自生收缩大致呈线性降低。混凝土 28d抗压强度随着粉煤灰掺量的增加而降低,28d抗压强度与粉煤灰掺量大致呈线性关系。(3)掺入矿粉会使混凝土的自生收缩率增大,在测量龄期的前三天,矿粉对混凝土的自生收缩表现为抑制作用,之后,矿粉会促进混凝土自生收缩的发展,矿粉可以提高混凝土强度,两者大致呈线性关系。(4)各矿物掺合料对混凝土自生收缩作用的重要性次序依次为:镁渣掺量粉煤灰取代率矿粉取代率。(5)混凝土自生收缩率随龄期的变化趋势符合双曲线关系,建立的双曲线关系显著性高,相关性好,能准确预测不同龄期的混凝土自生收缩值。
[Abstract]:Due to the rapid development of magnesium industry in recent years, the discharge of magnesium slag increases rapidly, which leads to the increasingly serious environmental pollution problem and restricts the further development of magnesium industry. In order to pursue the high strength and high fluidity of concrete, a large number of admixtures and admixtures are often added to the concrete, which leads to the increasingly serious shrinkage problem of concrete. The chemical composition of magnesium slag is similar to that of cement, and it has certain hydration activity. The MgO contained in magnesium slag has expansibility. If magnesium slag is used as admixture of concrete, the strength of concrete can be improved and the autogenous shrinkage of concrete can be compensated. And it can reduce the project cost and reduce the environmental pollution, so the research is of high significance, and the research is supported by the National Natural Science Foundation of China. Taking C30 magnesium slag concrete as the research object, the single factor test scheme and the orthogonal test scheme are designed. By means of trend analysis, range analysis and variance analysis, the effect of mineral admixtures on the autogenous shrinkage of magnesium slag concrete is analyzed, and the mechanism of the effect of magnesium slag on the autogenous shrinkage of concrete is revealed. The relationship model of the autogenous shrinkage rate of concrete with age and the amount of mineral admixture is established. The conclusions are as follows: (1) the autogenous shrinkage of concrete decreases with the increase of magnesium slag content. The higher the content of magnesium slag, the greater the inhibition effect of magnesium slag on autogenous shrinkage. Magnesium slag can improve the compressive strength of concrete, but with the increase of the content of magnesium slag, the enhancement effect of magnesium slag on compressive strength decreases gradually. (2) the addition of fly ash can inhibit the autogenous shrinkage of concrete. With the increase of fly ash content, the autogenous shrinkage of concrete decreases linearly. The compressive strength of concrete decreases with the increase of the amount of fly ash, and the compressive strength of 28 days has a linear relationship with the content of fly ash. (3) the autogenous shrinkage of concrete increases with the addition of mineral powder, which is three days before the measuring age. After that, the mineral powder can promote the development of the concrete autogenous shrinkage, and the mineral powder can improve the strength of concrete. (4) the order of importance of mineral admixtures to the autogenous shrinkage of concrete is as follows: the replacement rate of mineral powder with magnesium slag and fly ash. (5) the rate of autogenous shrinkage of concrete with age. The trend of change accords with the hyperbolic relation, The hyperbolic relation is significant and the correlation is good. It can accurately predict the autogenous shrinkage of concrete at different ages.
【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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