超高强混凝土的硬化过程
发布时间：2018-08-14 16:10
【摘要】：超高性能混凝土作为一种新型水泥基材料,具有强度高,耐久性优异的优点。超高性能混凝土的抗压强度高于150MPa,约是传统混凝土的3倍以上。超高性能混凝土具有优异的韧性和断裂能,和高性能混凝土相比,超高性能混凝土的韧性提高了300倍以上,和一些金属相当,使得混凝土结构在超载环境下或地震中具有更优异的结构可靠性。超高性能混凝土具有优异的耐久性能,延长了混凝土结构的使用寿命,降低了维修费用。超高性能混凝土几乎是不渗透性的,几乎无碳化,氯离子渗透和硫酸盐渗透也几乎为零。尽管超高性能混凝土拥有很多显著的优点,但也存在一些缺陷。超高性能混凝土的胶凝材料用量高达800-1000kg/m3,增大了水化热,产生收缩。制备超高性能混凝土的原材料通常为水泥、硅灰、石英砂、石英粉、钢纤维和超塑化剂等,生产成本是普通混凝土的数倍。为了提高超高性能混凝土中辅助性胶凝材料的活性,生产超高性能混凝土时往往采用蒸汽或蒸压养护,复杂的生产工艺限制了超高性能混凝土在实际工程中的应用。为了降低超高强混凝土的生产成本,简化其生产工艺,常温养护超高性能混凝土成为了一个研究热点。由于原材料和生产工艺的差异,采用常温养护超高性能混凝土的硬化过程和传统热养护超高性能混凝土可能存在较大差异,鉴于此,本文研究了常温养护超高性能混凝土的硬化过程。由于钢纤维对超高性能混凝土的硬化过程影响较小,本文将研究不掺钢纤维的超高强混凝土的硬化过程。当砂胶比为1.0时,使用天然石英砂配制超高强混凝土的抗压强度达到131.5MPa。当砂胶比为1.1时,使用机制石英砂配制超高强混凝土的抗压强度达到139.8MPa。尽管使用机制石英砂配制超高强混凝土的流动度和抗压强度均大于使用天然石英砂配制超高强混凝土的流动度和抗压强度,但使用天然石英砂也能配制出性能优异的超高强混凝土,当砂胶比为1.0时,使用天然石英砂配制超高强混凝土的抗压强度达到131.5MPa。综合考虑超高强混凝土的生产成本和性能,本文采用天然石英砂配制超高强混凝土,采用的砂胶比为1.0。通过三角形正交设计,设计了七组超高强混凝土的胶凝组分,并将胶凝组分和性能的关系表示为等值线图。研究结果表明,在适当掺量下,硅灰可以提高超高强混凝土的流动度和抗压强度,降低超高强混凝土的孔隙率和氢氧化钙含量。在一定用量下,矿粉减小了超高强混凝土的流动度、抗压强度、孔隙率和氢氧化钙含量。硅灰和矿粉对超高强混凝土的流动度和3d抗压强度有正的协同效应,但对超高强混凝土的总水化热、56d抗压强度、孔隙率和氢氧化钙含量有负的协同效应。通过三角形正交设计,设计了七组超高强混凝土的胶凝组分,并将胶凝组分和性能的关系表示为等值线图。研究结果表明,在适当掺量下,硅灰可以提高超高强混凝土的流动度和抗压强度,降低超高强混凝土的孔隙率和氢氧化钙含量,减小了水化加速期出现的时间。在一定用量下,粉煤灰增大了超高强混凝土的流动度和早期孔隙率,减小了超高强混凝土的早期抗压强度和氢氧化钙含量。硅灰和粉煤灰对超高强混凝土的流动度和抗压强度有正的协同效应,但对超高强混凝土的总水化热、孔隙率和氢氧化钙含量有负的协同效应。为了研究水泥-硅灰-矿粉-粉煤灰四组分水泥基超高强混凝土的硬化过程,选取水胶比,硅灰掺量,矿粉掺量和粉煤灰掺量四个因素及四水平,对超高强混凝土的配合比进行正交设计,并研究其硬化过程。随着水胶比的增大,超高强混凝土的流动度显著增大,抗压强度在不同龄期下均有所降低,孔隙率在不同龄期下均有所增大,氢氧化钙含量在不同龄期下均有所增大。随着硅灰掺量的增大,超高强混凝土的流动度显著减小,抗压强度先增大后降低,孔隙率在不同龄期下均有所减小,氢氧化钙含量在不同龄期下均有所减小。随着矿粉掺量的增大,超高强混凝土的流动度没有明显的变化,抗压强度先增大后减小,孔隙率在早期减小,后期反而增大,氢氧化钙含量在不同龄期下均有所减小。随着粉煤灰掺量的增大,超高强混凝土的流动度先增大后降低,早期抗压强度大幅度降低,后期抗压强度先增大后降低,早期孔隙率增大,后期对孔隙率影响不大,氢氧化钙含量在不同龄期下均有所减小。纳米二氧化硅和纳米碳酸钙均降低了超高强混凝土的流动度。掺入纳米二氧化硅后,超高强混凝土的水化放热速度不断增大,水化放热量先增大后降低。掺入纳米碳酸钙后,超高强混凝土的水化放热速度不断增大,水化放热量不断降低。随着纳米二氧化硅掺量的增大,超高强混凝土的抗压强度先增大后降低,随着纳米碳酸钙掺量的增大,超高强混凝土的抗压强度先增大后降低。随着纳米二氧化硅掺量的增大,超高强混凝土的孔隙率先减小后增大,随着纳米碳酸钙掺量的增大,超高强混凝土的孔隙率先减小后增大。随着纳米二氧化硅掺量的增大,超高强混凝土的氢氧化钙含量不断减小,随着纳米碳酸钙掺量的增大,超高强混凝土的氢氧化钙含量不断增大。
[Abstract]:As a new type of cement-based material, ultra-high performance concrete has the advantages of high strength and excellent durability. The compressive strength of ultra-high performance concrete is higher than 150 MPa, which is about three times higher than that of traditional concrete. Ultra-high performance concrete has excellent durability, prolongs the service life of concrete structures, and reduces maintenance costs. Ultra-high performance concrete is almost impermeable, almost without carbonization, chlorine. Ion permeation and sulfate permeation are almost zero. Although super-high performance concrete has many remarkable advantages, there are also some defects. The amount of cementitious materials used in super-high performance concrete is as high as 800-1000kg/m3, which increases the heat of hydration and produces shrinkage. The raw materials for preparing super-high performance concrete are usually cement, silica fume, quartz sand and quartz. In order to improve the activity of auxiliary cementitious materials in ultra-high performance concrete, steam or autoclave curing is often used in the production of ultra-high performance concrete. The complex production process limits the application of ultra-high performance concrete in practical engineering. Because of the difference of raw materials and production process, the hardening process of UHPC cured at room temperature may be quite different from that of traditional UHPC cured at normal temperature. In view of this, this paper studies the curing process of UHPC cured at room temperature. The hardening process of ultra-high performance concrete cured at room temperature is studied in this paper because steel fiber has little influence on the hardening process of ultra-high performance concrete. When the ratio of sand to binder is 1.0, the compressive strength of ultra-high strength concrete prepared with natural quartz sand reaches 131.5 MPa. When the ratio of sand to binder is 1.1 The compressive strength of ultra-high strength concrete prepared with machine-made quartz sand is 139.8 MPa. Although the fluidity and compressive strength of ultra-high strength concrete prepared with machine-made quartz sand are greater than those of ultra-high strength concrete prepared with natural quartz sand, the super-high performance concrete can be prepared with natural quartz sand. When the ratio of sand to binder is 1.0, the compressive strength of ultra-high strength concrete made of natural quartz sand reaches 131.5 MPa. Considering the production cost and performance of ultra-high strength concrete, this paper adopts natural quartz sand to prepare ultra-high strength concrete. The ratio of sand to binder is 1.0. The results show that silica fume can improve the fluidity and compressive strength of ultra-high strength concrete, reduce the porosity and calcium hydroxide content of ultra-high strength concrete, and reduce the flow of ultra-high strength concrete under certain dosage. Mobility, compressive strength, porosity and calcium hydroxide content. Silica fume and mineral powder have positive synergistic effects on the fluidity and 3D compressive strength of ultra-high strength concrete, but have negative synergistic effects on the total hydration heat, 56d compressive strength, porosity and calcium hydroxide content of ultra-high strength concrete. The results show that silica fume can improve the fluidity and compressive strength of ultra-high strength concrete, reduce the porosity and calcium hydroxide content of ultra-high strength concrete, and reduce the time of hydration acceleration. Fly ash increases the fluidity and early porosity of ultra-high strength concrete, and decreases the early compressive strength and calcium hydroxide content of ultra-high strength concrete. In order to study the hardening process of cement-silica fume-mineral Powder-Fly ash four-component cement-based ultra-high strength concrete, four factors and four levels were selected, i.e. water-binder ratio, silica fume content, mineral powder content and fly ash content. With the increase of silica fume content, the fluidity of ultra-high strength concrete decreases significantly, the compressive strength decreases at different ages, the porosity increases at different ages, and the content of calcium hydroxide increases at different ages. With the increase of mineral powder content, the fluidity of ultra-high strength concrete has no obvious change. The compressive strength increases first and then decreases. The porosity decreases at the early stage, but increases at the later stage. The content of calcium hydroxide decreases at different ages. With the increase of fly ash content, the fluidity of ultra-high strength concrete increases first and then decreases, the early compressive strength decreases greatly, the later compressive strength increases first and then decreases, the early porosity increases, the latter has little effect on the porosity, and the content of calcium hydroxide decreases at different ages. The hydration exothermic rate of super-high strength concrete increases and the hydration exothermic heat increases first and then decreases with the addition of nano-silica. The hydration exothermic rate of super-high strength concrete increases and the hydration exothermic heat decreases with the addition of nano-silica. The compressive strength of concrete increases first and then decreases with the increase of nano-calcium carbonate content, and then decreases with the increase of nano-silica content. With the increase of nano-silica content, the content of calcium hydroxide in super-high strength concrete decreases. With the increase of nano-calcium carbonate content, the content of calcium hydroxide in super-high strength concrete increases.
【学位授予单位】：湖南大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU528
本文编号：2183406
[Abstract]:As a new type of cement-based material, ultra-high performance concrete has the advantages of high strength and excellent durability. The compressive strength of ultra-high performance concrete is higher than 150 MPa, which is about three times higher than that of traditional concrete. Ultra-high performance concrete has excellent durability, prolongs the service life of concrete structures, and reduces maintenance costs. Ultra-high performance concrete is almost impermeable, almost without carbonization, chlorine. Ion permeation and sulfate permeation are almost zero. Although super-high performance concrete has many remarkable advantages, there are also some defects. The amount of cementitious materials used in super-high performance concrete is as high as 800-1000kg/m3, which increases the heat of hydration and produces shrinkage. The raw materials for preparing super-high performance concrete are usually cement, silica fume, quartz sand and quartz. In order to improve the activity of auxiliary cementitious materials in ultra-high performance concrete, steam or autoclave curing is often used in the production of ultra-high performance concrete. The complex production process limits the application of ultra-high performance concrete in practical engineering. Because of the difference of raw materials and production process, the hardening process of UHPC cured at room temperature may be quite different from that of traditional UHPC cured at normal temperature. In view of this, this paper studies the curing process of UHPC cured at room temperature. The hardening process of ultra-high performance concrete cured at room temperature is studied in this paper because steel fiber has little influence on the hardening process of ultra-high performance concrete. When the ratio of sand to binder is 1.0, the compressive strength of ultra-high strength concrete prepared with natural quartz sand reaches 131.5 MPa. When the ratio of sand to binder is 1.1 The compressive strength of ultra-high strength concrete prepared with machine-made quartz sand is 139.8 MPa. Although the fluidity and compressive strength of ultra-high strength concrete prepared with machine-made quartz sand are greater than those of ultra-high strength concrete prepared with natural quartz sand, the super-high performance concrete can be prepared with natural quartz sand. When the ratio of sand to binder is 1.0, the compressive strength of ultra-high strength concrete made of natural quartz sand reaches 131.5 MPa. Considering the production cost and performance of ultra-high strength concrete, this paper adopts natural quartz sand to prepare ultra-high strength concrete. The ratio of sand to binder is 1.0. The results show that silica fume can improve the fluidity and compressive strength of ultra-high strength concrete, reduce the porosity and calcium hydroxide content of ultra-high strength concrete, and reduce the flow of ultra-high strength concrete under certain dosage. Mobility, compressive strength, porosity and calcium hydroxide content. Silica fume and mineral powder have positive synergistic effects on the fluidity and 3D compressive strength of ultra-high strength concrete, but have negative synergistic effects on the total hydration heat, 56d compressive strength, porosity and calcium hydroxide content of ultra-high strength concrete. The results show that silica fume can improve the fluidity and compressive strength of ultra-high strength concrete, reduce the porosity and calcium hydroxide content of ultra-high strength concrete, and reduce the time of hydration acceleration. Fly ash increases the fluidity and early porosity of ultra-high strength concrete, and decreases the early compressive strength and calcium hydroxide content of ultra-high strength concrete. In order to study the hardening process of cement-silica fume-mineral Powder-Fly ash four-component cement-based ultra-high strength concrete, four factors and four levels were selected, i.e. water-binder ratio, silica fume content, mineral powder content and fly ash content. With the increase of silica fume content, the fluidity of ultra-high strength concrete decreases significantly, the compressive strength decreases at different ages, the porosity increases at different ages, and the content of calcium hydroxide increases at different ages. With the increase of mineral powder content, the fluidity of ultra-high strength concrete has no obvious change. The compressive strength increases first and then decreases. The porosity decreases at the early stage, but increases at the later stage. The content of calcium hydroxide decreases at different ages. With the increase of fly ash content, the fluidity of ultra-high strength concrete increases first and then decreases, the early compressive strength decreases greatly, the later compressive strength increases first and then decreases, the early porosity increases, the latter has little effect on the porosity, and the content of calcium hydroxide decreases at different ages. The hydration exothermic rate of super-high strength concrete increases and the hydration exothermic heat increases first and then decreases with the addition of nano-silica. The hydration exothermic rate of super-high strength concrete increases and the hydration exothermic heat decreases with the addition of nano-silica. The compressive strength of concrete increases first and then decreases with the increase of nano-calcium carbonate content, and then decreases with the increase of nano-silica content. With the increase of nano-silica content, the content of calcium hydroxide in super-high strength concrete decreases. With the increase of nano-calcium carbonate content, the content of calcium hydroxide in super-high strength concrete increases.
【学位授予单位】：湖南大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU528
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