高性能煤矸石混凝土性能的研究

发布时间：2018-08-13 20:13

【摘要】：煤矸石是煤炭开采和煤炼油生产过程中的工业废弃物。长期积存和逐年排弃不仅占用了大量的土地,而且在一定条件下还会自燃,对大气及地下水造成严重的环境污染。这些煤矸石,虽然一种污染源,但又是一种可利用资源,只要合理利用,便可变废为宝。目前,部分煤矸石作为原料主要用来制备陶瓷、耐火材料及水泥等,但煤矸石的有效利用仍不足70%。随着社会经济、环境和资源的发展,煤矸石的无害化应用受到了广泛的关注,尤其是实现其显著的社会价值、环境价值和经济价值。煤矸石中含有Fe2O3, TiO2, K2O, Na2O及CaO等氧化物,其主要的矿物组成为高岭石。煤矸石的煅烧与自然导致高岭石的脱水和分解,使其具有火山灰活性,因此煤矸石可部分替代骨料来配制绿色高性能混凝土。本文首先研究了煤矸石作为粗骨料的物理特性,其中包括级配、表观密度、吸水率、压碎指标、含泥量等,并利用XRD分析了煤矸石的相组成。通过基础试验的研究,找出煤矸石的最佳取代范围和水胶比、减水剂掺量、硅灰掺量等因素的适宜范围。然后采用正交试验法得出了煤矸石混凝土的最佳配合比,研究了水胶比、煤矸石掺量、减水剂掺量和硅灰掺量四个影响因素对高性能煤矸石混凝土工作性、力学性能和抗氯离子渗透性、碳化性能等耐久性能的影响。最后利用SEM观察煤矸石混凝土的微观结构和形貌。试验研究表明：此煤矸石含泥量较大,是影响工作性的主要因素之一,使用前需进行处理。煤矸石表观密度及压碎指标与碎石相接近,配制C50混凝土,其28d平均强度达到54MPa。混凝土中煤矸石掺量在40%～60%力学性能最佳,该煤矸石经自燃后具有火山灰效应,参与进一步水化使抗压强度得到保证,在最优配比下配制的煤矸石混凝土抗压强度可达54.71MPa。煤矸石的吸水率较大,对工作性有一定影响,高水胶比和低硅灰掺量可以改善煤矸石混凝土的工作,在最优配比下配制的混凝土坍落度可达设计要求190mm。在选取的四个正交试验因素中,水胶比和硅灰掺量对氯离子渗透和碳化性能影响非常显著,煤矸石掺量次之,而减水剂掺量影响不大。在最优配比下配制的煤矸石混凝土6h电通量可达943.25C,与同配比下的普通混凝土具有相似的抗氯离子渗透性能。在最优配比下配制的煤矸石混凝土28d碳化深度可达4.1mm,与同配比下的普通混凝土碳化深度相接近。煤矸石的掺量对混凝土的收缩影响较为严重,在此试验中,煤矸石掺量在40%时,既保证了煤矸石混凝土的抗氯离子渗透性能和抗碳化性能,又把混凝土的收缩降低到最小。从SEM扫描电镜分析可以看出,煤矸石混凝土具有较为密实的结构,自燃煤矸石的火山灰效应参与水化反应,形成网络硅酸钙凝胶,对骨料之间的缝隙进行填充,使煤矸石混凝土整体结构更加密实,从而降低并减少了氯离子和CO2在煤矸石混凝土中的传输速度及传输通道,提高煤矸石混凝土的耐久性和抗压强度。
[Abstract]:Coal gangue is a kind of industrial waste in the process of coal mining and oil refining. It not only occupies a large amount of land but also spontaneously combusts under certain conditions, causing serious environmental pollution to the atmosphere and groundwater. At present, some coal gangue is mainly used as raw materials to prepare ceramics, refractories and cement, but the effective utilization of coal gangue is still less than 70%. With the development of social economy, environment and resources, the harmless application of coal gangue has been widely concerned, especially to realize its remarkable social value, environmental value and cement value. Coal gangue contains oxides such as Fe2O3, TiO2, K2O, Na2O and CaO, and its main mineral composition is kaolinite. Calcination and nature of coal gangue lead to the dehydration and decomposition of kaolinite, making it have pozzolanic activity, so coal gangue can partly replace aggregate to prepare green high performance concrete. The physical properties of coarse aggregate, including gradation, apparent density, water absorption, crushing index, mud content and so on, are analyzed by XRD. The optimum substitution range of coal gangue and the suitable range of water-binder ratio, water reducing agent dosage, silica fume dosage and other factors are found through the study of basic experiment. The optimum mixing ratio of gangue concrete is obtained. The effects of water binder ratio, gangue content, water reducing agent content and silica fume content on the workability, mechanical properties, chloride ion permeability and carbonation resistance of high performance gangue concrete are studied. Finally, the microstructure of gangue concrete is observed by SEM. The experimental results show that the coal gangue has a large mud content, which is one of the main factors affecting the workability. The apparent density and crushing index of the coal gangue are close to the crushed rock. The average strength of C50 concrete reaches 54 MPa in 28 days. The mechanical properties of the concrete with 40%-60% coal gangue are the best. The compressive strength of coal gangue concrete can reach 54.71 MPa under the optimum proportion. The water absorption rate of coal gangue is higher, which has certain influence on the workability. High water binder ratio and low silica fume content can improve the work of coal gangue concrete under the optimum ratio. The slump of the concrete can reach 190mm. Among the four orthogonal experimental factors, the water-binder ratio and silica fume content have remarkable influence on the chloride ion permeability and carbonization performance, followed by the coal gangue content, while the water reducer content has little effect. Under the optimum proportion, the electric flux of coal gangue concrete can reach 943.25C in 6 hours, and the same proportion. Under the optimum proportion, the carbonation depth of coal gangue concrete can reach 4.1 mm in 28d, which is close to the carbonation depth of ordinary concrete in the same proportion. The influence of coal gangue content on the shrinkage of concrete is more serious. In this experiment, when the coal gangue content is 40%, the concrete can not only be guaranteed. The chloride ion penetration resistance and carbonation resistance of gangue concrete are studied, and the shrinkage of concrete is reduced to the minimum. SEM analysis shows that gangue concrete has a relatively compact structure. The pozzolanic effect of spontaneous combustion gangue participates in hydration reaction, forming network calcium silicate gel and entering the gap between aggregates. Row filling can make the whole structure of gangue concrete more compact, thereby reducing and reducing the transmission speed and transmission channel of chloride ion and CO2 in gangue concrete, and improving the durability and compressive strength of gangue concrete.
【学位授予单位】：沈阳建筑大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU528

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