高温后纤维纳米混凝土性能及其计算方法

发布时间：2018-01-19 05:12

本文关键词： 纳米SiO2 纳米CaCO3 纤维混凝土力学性能高温强度计算模型超声回弹应力-应变曲线氯离子 SEM　出处：《郑州大学》2015年博士论文　论文类型：学位论文

【摘要】：本文是国家自然科学基金项目“纤维纳米混凝土及其高温中和高温后性能研究”(51178434)的主要内容之一。通过试验研究、理论分析以及扫描电镜SEM的微观观察,重点研究了高温后纤维纳米混凝土基本力学性能、高温后纤维纳米混凝土轴压应力-应变关系、高温后纤维纳米混凝土氯离子渗透性能以及微观增强机理,建立了相应的计算模型,主要内容如下:(1)通过294个边长150mm纤维纳米混凝土立方体试块在不同龄期的抗压和劈拉试验、147个100mm×100mm×400mm梁式试件的抗折试验以及工作性能试验和SEM微观分析,探讨了纤维体积率和纳米材料掺量对纤维纳米混凝土微观增强机理与物理力学性能的影响。结果表明:在混凝土中掺入适量的纤维和纳米材料,改善了混凝土的微观结构,增加了混凝土的密实性,提高了混凝土的物理力学性能。随钢纤维体积率从0增大到1.5%,纤维纳米混凝土拌合物坍落度从40mm逐渐减小到25mm,纤维纳米混凝土抗压、劈拉和抗折强度分别提高12%、32%和12.5%。随纳米Si O2(简称NS)掺量从0增大到2%,纤维纳米混凝土拌合物坍落度减小95mm,初凝终凝时间分别减小52.3%和35.9%,纤维纳米混凝土抗压、劈拉和抗折强度分别提高9%、24%和14.7%。随纳米Ca CO3(简称NC)掺量从0增大到2%,纤维纳米混凝土拌合物坍落度减小50mm,初凝终凝时间分别减小35.2%和3.8%,纤维纳米混凝土抗压、劈拉和抗折强度分别提高8%、20%和8.8%。根据复合力学理论,并结合对本文和相关文献试验结果的统计分析,分别建立了考虑纳米材料和纤维影响的纤维纳米混凝土抗压、劈拉和抗折强度计算方法。(2)通过观察150个边长150mm纤维纳米混凝土立方体试块高温前后宏观形貌和量测高温前后质量损失,研究了纤维纳米混凝土高温形貌特征变化以及质量损失率与温度的关系。结果表明:随温度从25℃升高到800℃,纤维纳米混凝土表观劣化程度加剧,质量损失率从1%增大约10%。基于对试验结果的分析,建立了高温后纤维纳米混凝土质量损失率与温度的关系式。(3)通过450个边长150mm纤维纳米混凝土立方体试块高温后的抗压和劈拉试验、300个100mm×100mm×400mm纤维纳米混凝土梁式试块高温后的抗折试验,研究了纤维、纳米材料和温度对纤维纳米混凝土高温后抗压强度、劈拉强度和劈拉荷载-横向变形曲线、抗折强度和弯曲荷载-挠度曲线的影响。结果表明:随钢纤维体积率从0增大到1.5%,高温后纤维纳米混凝土抗压、劈拉和抗折强度呈增大趋势;600℃高温后,钢纤维体积率1.0%时的纤维纳米混凝土残余抗压强度较不掺纤维时提高了43.97%,残余劈拉强度提高了216.38%,残余抗折强度提高了84.8%;劈拉横向变形、劈拉荷载-横向变形曲线下包面积逐渐增大;弯曲荷载-挠度曲线下包面积、峰值挠度、弯曲韧性指数和弯曲韧性比均呈增大趋势。纳米材料的掺入使高温后纤维纳米混凝土抗压、劈拉和抗折强度均有一定程度提高,600℃高温后,NS和NC掺量分别为1%时的纤维纳米混凝土残余抗压强度较不掺纳米材料时分别提高了45.5%和38.2%,残余劈拉强度分别提高了63.9%和28.1%,残余抗折强度分别提高了78.7%和46.3%;随纳米材料掺量增大,弯曲荷载-挠度曲线下包面积和弯曲韧性指数有一定程度提高。随温度从25℃升高到800℃,纤维纳米混凝土抗压、劈拉和抗折强度逐渐减小,劈拉荷载-横向变形曲线下包面积逐渐减小,弯曲荷载-挠度曲线逐渐趋于扁平,峰值荷载显著降低,峰值挠度逐渐增大。基于对试验结果的统计分析,分别建立了纤维纳米混凝土抗压、劈拉和抗折残余强度相对值与温度的关系式。(4)通过150个边长150mm纤维纳米混凝土立方体试块高温前后超声、回弹和抗压强度试验,探讨了钢纤维体积率、NS和NC掺量对高温前后超声波速和回弹值的影响以及纤维纳米混凝土抗压强度、经历最高温度与超声波速和回弹值的关系。结果表明:在混凝土中掺入纤维和纳米材料,改善了混凝土微观结构,使高温前后超声波速和回弹值均有一定程度提高,800℃高温后,钢纤维掺量1.0%的混凝土超声波速较不掺钢纤维时提高了45.32%,回弹值提高了36.28%;NS和NC掺量分别为1.0%的混凝土超声波速较不掺时分别提高了21.66%和22.25%,回弹值分别提高了45.77%和30.85%。纤维纳米混凝土高温后抗压强度与超声波速和回弹值具有良好的相关性,超声回弹综合法适用于推定纤维纳米混凝土高温抗压强度及经历最高温度。通过对试验数据的统计分析,建立了高温后纤维纳米混凝土超声回弹综合测强曲线及推定经历最高温度的公式。(5)通过306个150mm×150mm×300mm纤维纳米混凝土棱柱体试块在25-800℃后的单轴受压试验,探讨了钢纤维、纳米材料掺量和高温对纤维纳米混凝土轴压应力-应变曲线的影响。结果表明:纤维纳米混凝土轴压应力-应变曲线可分为弹性阶段、裂缝稳定发展阶段、裂缝失稳扩展阶段和破坏阶段;随钢纤维体积率和纳米材料掺量的增大,轴压应力-应变曲线逐渐饱满,峰值应力和峰值应变均有一定程度的提高,曲线下包面积逐渐增大;随温度升高,轴压应力-应变曲线趋于扁平,弹性段逐渐变短,峰值应力显著降低,峰值应变明显增大,轴压应力-应变曲线下包面积减小。通过对试验数据的综合分析,建立了考虑温度、纳米材料掺量和钢纤维含量特征参数影响的纤维纳米混凝土轴压应力-应变曲线数学模型。(6)通过150个100mm×100mm×200mm纤维纳米混凝土棱柱体试块高温前后氯盐溶液浸泡干湿循环试验,研究了钢纤维、纳米材料和温度对纤维纳米混凝土氯离子渗透性的影响。结果表明:随钢纤维体积率和纳米材料掺量增大,纤维纳米混凝土的氯离子含量呈减小趋势。800℃高温后,钢纤维体积率1%时,纤维纳米混凝土7.5mm深度的氯离子含量为不掺钢纤维时的64.2%;NS和NC掺量分别为1%时,纤维纳米混凝土7.5mm深度的氯离子含量分别为不掺纳米材料时的72.9%和68.1%。随温度的升高,纤维纳米混凝土的氯离子含量逐渐增大。基于对纤维纳米混凝土抗氯离子渗透机理的分析和对试验结果的统计分析,建立了考虑温度、纳米材料掺量和钢纤维含量特征参数影响的纤维纳米混凝土氯离子含量计算公式。(7)通过混凝土微观结构SEM观察,研究了纤维、纳米材料和温度对纤维纳米混凝土微观形貌及其对宏观力学性能的影响。结果表明:纳米材料增加了混凝土的密实度,改善了水泥石微观结构;聚丙烯纤维高温熔解大大降低混凝土的内部压力,防止混凝土高温爆裂;钢纤维降低了温度梯度,其桥接阻裂作用减轻了混凝土内部微缺陷的引发和扩展,缓解了混凝土高温劣化。在混凝土中掺入适量纤维和纳米材料,提高了常温时混凝土的力学性能,有效缓解了高温对混凝土的劣化作用,改善了高温后混凝土的力学性能。
[Abstract]:This paper is the study of properties of nano fiber concrete and high temperature and high temperature after the National Natural Science Fund Project "(51178434) one of the main content. Through experimental research, theoretical analysis and microscopic observation of scanning electron microscopy SEM, focuses on the research of nano fiber after high temperature mechanical mixing ability of concrete after high temperature nano fiber concrete axial compressive stress strain relationship of concrete after high temperature, chloride ion permeability and micro nano fiber reinforced mechanism, a corresponding model is established, the main contents are as follows: (1) through the 294 side of 150mm nano fiber concrete specimens in different age compressive strength and splitting tensile test, 147 100mm * 100mm * 400mm beam try bending test and performance test and SEM analysis, discusses the fiber volume ratio and nano material content on nano fiber concrete micro mechanism and physical force Effect of performance. The results show that the doped fiber and nano materials in concrete, improve the microstructure of concrete, increase the density of concrete, improve the physical and mechanical properties of concrete. The steel fiber volume ratio increases from 0 to 1.5%, nano fiber concrete mixture slump from 40mm decreased to 25mm, nano fiber concrete compressive, tensile and flexural strength were increased by 12%, 32% and 12.5%. with nano Si O2 (NS) content increased from 0 to 2%, the mixture of nano fiber concrete slump decreases 95mm, 52.3% and 35.9% respectively. Initialcoagulation finalcoagulation time, nano fiber concrete the compressive, tensile and flexural strength were increased by 9%, 24% and 14.7%. with nano Ca CO3 (NC) content increased from 0 to 2%, the mixture of nano fiber concrete slump decreases 50mm, initialcoagulation finalcoagulation time was reduced by 35.2% and 3.8%, nano fiber concrete The compressive, tensile and flexural strength were increased by 8%, 20% and 8.8%. according to the composite mechanics theory, and combined with the statistical analysis of this paper and the test results of literature, considering the influence of nano fiber concrete and fiber nano materials were established respectively, tensile and flexural strength calculation method. (2) through the observation of 150 a length of 150mm nano fiber concrete cube macro morphology and amount of block before and after high temperature high temperature before and after weight loss, the effects of fiber morphology of nano concrete high temperature change and the relationship between quality loss rate and temperature. The results showed that with temperature from 25 degrees rise to 800 DEG C, nano fiber concrete apparent deterioration degree aggravate, quality loss the rate of increase of about 10%. from 1% based on the analysis of test results, the relationship between fiber type nano concrete mass loss rate and temperature of high temperature was established. (3) by 450 150mm length fiber Vinami coagulation The soil test cube after high temperature compressive and splitting tensile test, 300 100mm * 100mm * 400mm nano fiber concrete beam test bending test piece after high temperature, the research of nano fiber, fiber concrete after high temperature compressive strength of nano materials and temperature, tensile strength and splitting tensile loading transverse deformation curves, influence the bending strength and bending load deflection curve. The results show that with steel fiber volume ratio increases from 0 to 1.5%, after high temperature nano fiber concrete compressive, tensile and flexural strength increased; the high temperature of 600 DEG C, Vinami fiber concrete compressive strength of steel fiber volume ratio of 1% is not doped fiber increased by 43.97%, the residual tensile strength increased by 216.38%, the residual flexural strength increased by 84.8%; the splitting of transverse deformation, splitting tensile loading transverse deformation curves under the area gradually increased; the bending load deflection curve area under the peak, deflection Degree of flexural toughness index and flexural toughness ratio increased. Nano material doped nano fiber concrete after high temperature compressive, tensile and flexural strength were increased to a certain extent, the high temperature of 600 DEG C, NS and NC content respectively. The residual compressive strength of nano fiber concrete 1% is not mixed with nano materials were increased by 45.5% and 38.2%, 63.9% and 28.1% increased residual splitting tensile strength, flexural strength were increased by 78.7% and 46.3%; with the increase of content of nano materials, the bending load deflection curve and the area under flexural toughness index to a certain extent increased. With the temperature from 25 degrees to 800 degrees. Nano fiber, concrete compressive strength, splitting tensile and flexural strength decreased, splitting tensile loading transverse deformation curves under the area gradually decreases and the bending load deflection curve tends to be flat, the peak load decreased significantly and the peak deflection increases gradually . statistical analysis of the test results based on the nano fiber concrete compression were established, and the relationship between flexural tensile type residual strength and temperature. The relative value (4) through the 150 side of 150mm nano fiber concrete specimens before and after high temperature ultrasonic rebound and compression strength test of steel fiber volume ratio. The influence of ultrasonic velocity and rebound value before and after high temperature and nano fiber concrete compressive strength of NS and NC content, experience the highest temperature and ultrasonic velocity and rebound value. The results show that the incorporation of fiber and nano materials in concrete, improve the microstructure of concrete, the temperature before and after ultrasonic velocity and rebound value to a certain extent improve the high temperature of 800 DEG C, ultrasonic concrete steel fiber content of 1% speed is not mixed with steel fiber increased by 45.32%, the rebound value increased by 36.28%; the content of NC and NS were 1% of the super concrete The acoustic velocity is not mixed were increased by 21.66% and 22.25%, the rebound value were increased by 45.77% and 30.85%. nano fiber concrete after high temperature compressive strength and ultrasonic velocity and rebound value have a good correlation, ultrasonic rebound method applied to the presumption of nano fiber concrete high temperature compressive strength and maximum temperature. Through statistical analysis of experimental data, built after high temperature nano fiber concrete ultrasonic rebound strength curve and the maximum temperature presumption formula. (5) by 306 150mm * 150mm * 300mm nano fiber concrete prism specimens under uniaxial compression test at 25-800 deg.c, discusses the steel fiber, and high temperature nano materials doped with nano fiber concrete axial compressive stress-strain curves. The results show that the stage can be divided into elastic stress-strain curve of nano fiber reinforced concrete under axial compression, the crack development stage, crack Crack instability expansion stage and failure stage; with the increase of volume ratio of steel fiber and nano materials, uniaxial compressive stress-strain curve became full, the peak stress and peak strain were improved to a certain extent, the area under curve increases; with the increase of temperature, axial compressive stress-strain curve tends to be flat the elastic segment, gradually shorter, the peak stress decreased significantly, the peak strain increases obviously and the axial compressive stress strain curve under the area decreased. Through comprehensive analysis of test data, considering temperature, fiber axis nano material content of nano concrete and steel fiber content characteristic parameters affecting the compressive stress - strain a mathematical model of curve. (6) by 150 100mm * 100mm * 200mm nano fiber concrete prism specimens before and after high temperature chlorine salt solution immersion dry wet cycle test, the effects of steel fiber, nano materials and nano fiber temperature of concrete chloride The sub permeability effect. The results show that with the amount of volume ratio of steel fiber and nano material increase, chloride ion content of nano fiber concrete was decreased after high temperature of.800 DEG C, steel fiber volume ratio of 1%, chloride ion content of nano fiber concrete 7.5mm depth for steel fiber is 64.2%; NS and NC the admixture of 1% respectively, chlorine ion content of nano fiber concrete 7.5mm depth were not doped nano materials at 72.9% and 68.1%. with the increase of temperature, chloride ion content of nano fiber concrete increases gradually. The fiber nano concrete anti chloride ion penetration mechanism analysis and the statistical analysis of the test results based on the established considering the temperature calculation formula of nano material content and content of the fiber characteristic parameters affecting fiber nano concrete chloride ion content. (7) through the concrete microstructure observation of SEM, study the fiber, nano materials And the temperature on the fiber morphology of nano concrete and its influence on macroscopic mechanical properties. The results showed that the nano material increases the compactness of concrete, improve the microstructure of cement stone; polypropylene fiber high temperature melting greatly reduce the internal pressure of concrete, to prevent concrete spalling; steel fiber can reduce the temperature gradient, the bridge crack resistance effect of reducing concrete micro defect initiation and propagation, alleviate the deterioration of concrete at high temperature. Adding fiber and nano materials in concrete, improve the mechanical properties of concrete at room temperature, effectively alleviate the bad effect of high temperature on concrete, the mechanical properties of concrete after high temperature is improved.

【学位授予单位】：郑州大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU528

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