混杂纤维对活性粉末混凝土性能影响的研究
发布时间：2019-04-13 19:50
【摘要】：采用优质细石英砂、极低的水胶比和高性能的硅灰等活性混合材制得的活性粉末混凝土具有很高的抗压抗折强度,极低的孔隙率和超高耐久性。但同时RPC也表现的更加硬脆,这在工程应用中的危害很大。为了提高RPC的抗折强度、断裂韧性等性能,改善RPC的硬脆特性,通常在RPC中加入镀铜细钢纤维。同时聚乙烯醇纤维能够显著改善普通混凝土弯曲韧性、拉伸变形等性能。本文拟将二者混掺以改善RPC的抗折强度、变形及韧性等性能。本课题主要研究了不同镀铜细钢纤维/PVA纤维混掺方案下RPC试件的抗压抗折强度、小梁弯曲性能、冲击韧性、盐冻性以及微观形貌分析、显微硬度等微观性能,结果表明:随着镀铜细钢纤维掺量由0%增加到2.0%的过程中,RPC试件的抗压抗折强度与弯曲性能均显著提高。冲击韧性和抗盐冻性能随着钢纤维掺量的增加表现出先提高后降低的趋势,在1.5%时最佳。钢纤维掺量对RPC的初裂次数影响较小,而终裂次数影响较大,在掺量为1.5%时终裂次数最高。镀铜细钢纤维周围水泥石的微观结构分布较均匀,钢纤维的显微硬度约为水泥石的3.5倍,其与水泥石的界面过渡区结构致密,在0~30μm内存在一个明显的强化区,其显微硬度高于水泥石。当镀铜细钢纤维掺量一定时,掺入三种不同规格的PVA纤维,在PVA纤维掺量由0.5%、1.0%到1.25%增加的过程中,抗折强度均随掺量的增加而增大,抗压强度均与单掺钢纤维组保持一致,小梁弯曲试验峰值均随掺量的增加而增大。荷载-挠度曲线的下降段也由陡变缓;当PVA纤维掺量增加到2.0%时,抗压抗折强度都有着明显的降低,小梁弯曲试验峰值荷载、峰值变形明显下降,下降段较缓。掺入三种PVA纤维均能延缓RPC的初裂,但较细的PVA-HT-12纤维组与PVA-HT-6纤维组的终裂次数均明显降低。较粗的PVA-ECC-12纤维组仅在掺量为1.25%时,初裂、终裂次数均明显优于单掺镀铜细钢纤维组。随着镀铜细钢纤维的掺量由0%增加到2.0%的过程中,PVA-HT-12纤维组早期的抗盐冻性高于单掺钢纤维组,但后期性能较差。短纤维组的盐冻性优于长纤维组。PVA-ECC-12纤维内部的显微硬度约为水泥石的1/4,其与水泥石的界面过渡区结构疏松,在0~30μm内存在一个明显的薄弱区,其显微硬度约为水泥石的1/2,这与超景深显微仪所观测到在PVA-ECC纤维与水泥石结合的界面处存在一个厚度约为30μm的界面过渡区一致。从综合性能角度考虑,本文最终给出的最佳混掺方案为:镀铜细钢纤维最佳掺量为1.5%,PVA纤维的最佳掺量为1.25%,其中较粗的PVA-ECC-12纤维的综合效果最佳。
[Abstract]:The active powder concrete made of high quality fine quartz sand, very low water-binder ratio and high performance silica fume has very high compressive flexural strength, extremely low porosity and ultra-high durability. But at the same time, RPC also shows more hard and brittle, which is a great harm in engineering applications. In order to improve the flexural strength and fracture toughness of RPC and improve the hard and brittle properties of RPC, copper-plated fine steel fibers are usually added to RPC. At the same time, polyvinyl alcohol fiber can significantly improve the flexural toughness, tensile deformation and other properties of ordinary concrete. In this paper, we propose to improve the flexural strength, deformation and toughness of RPC by mixing them. In this paper, the compressive flexural strength, beam bending property, impact toughness, salt freezing property, micro-morphology analysis, microhardness and other micro-properties of RPC specimens under different copper-plated fine steel fiber / PVA fiber mixing schemes were studied. The results show that the compressive flexural strength and bending properties of RPC specimens increase significantly with the increase of the content of copper-plated fine steel fibers from 0% to 2.0%. The impact toughness and salt-freezing resistance of the steel fiber increased first and then decreased with the increase of the content of steel fiber, which was the best when 1.5% of the steel fiber was added. The effect of steel fiber content on the initial crack number of RPC is small, but the final crack number is greater, and the final crack number is the highest when the content of steel fiber is 1.5%. The microhardness of the steel fiber is about 3.5 times of that of the cement stone. The structure of the interface transition zone between the steel fiber and the cement stone is dense, and there is an obvious strengthening zone in the range of 0 ~ 30 渭 m, and the microhardness of the steel fiber is about 3.5 times that of the cement stone. Its microhardness is higher than that of cement paste. When the content of copper plated fine steel fiber is constant, three kinds of PVA fibers of different specifications are added, and the flexural strength increases with the increase of the content of PVA fiber from 0.5%, 1.0% to 1.25%, when the content of the fiber is increased from 0.5%, 1.0% to 1.25%. The compressive strength is consistent with that of single steel fiber group, and the peak value of beam bending test increases with the increase of the content of steel fiber. When the content of PVA fiber increased to 2.0%, the compressive and flexural strength decreased obviously, and the peak load and the peak deformation of the beam bending test decreased obviously, and the descending segment was slower than that of the control group, but the load-deflection curve also decreased steeply, and when the content of the fiber increased to 2.0%, the compressive and flexural strength of the beams decreased obviously. The first crack of RPC was delayed by adding three kinds of PVA fibers, but the final crack times of the finer PVA-HT-12 fiber group and the PVA-HT-6 fiber group decreased obviously. When the content of PVA-ECC-12 fiber was 1.25%, the number of initial crack and final crack was obviously better than that of single copper-coated fine steel fiber group. In the process of increasing the content of copper-coated fine steel fiber from 0% to 2.0%, the salt-freezing resistance of the PVA-HT-12 fiber group was higher than that of the single steel fiber group, but the later performance was poor. The microhardness of the short fiber group is about 1? 4 of that of the cement stone, the structure of the interface transition zone between the short fiber group and the cement stone is loose, and there is an obvious weak area within 0 ~ 30 渭 m of the short fiber group, which is better than the long fiber group. The microhardness of the ECC-12 fiber is about 1% of that of the cement stone. The microhardness is about 1? 2 of that of cement stone, which is consistent with that observed by ultra-depth-of-field microscopy at the interface between PVA-ECC fiber and cement paste with a thickness of about 30 渭 m. From the point of view of comprehensive properties, the optimum mixing scheme given in this paper is as follows: the optimum content of copper-coated fine steel fiber is 1.5%, and the optimum content of PVA-ECC-12 fiber is 1.25%, among which the coarser PVA fiber has the best comprehensive effect.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU528
，
本文编号：2457889
[Abstract]:The active powder concrete made of high quality fine quartz sand, very low water-binder ratio and high performance silica fume has very high compressive flexural strength, extremely low porosity and ultra-high durability. But at the same time, RPC also shows more hard and brittle, which is a great harm in engineering applications. In order to improve the flexural strength and fracture toughness of RPC and improve the hard and brittle properties of RPC, copper-plated fine steel fibers are usually added to RPC. At the same time, polyvinyl alcohol fiber can significantly improve the flexural toughness, tensile deformation and other properties of ordinary concrete. In this paper, we propose to improve the flexural strength, deformation and toughness of RPC by mixing them. In this paper, the compressive flexural strength, beam bending property, impact toughness, salt freezing property, micro-morphology analysis, microhardness and other micro-properties of RPC specimens under different copper-plated fine steel fiber / PVA fiber mixing schemes were studied. The results show that the compressive flexural strength and bending properties of RPC specimens increase significantly with the increase of the content of copper-plated fine steel fibers from 0% to 2.0%. The impact toughness and salt-freezing resistance of the steel fiber increased first and then decreased with the increase of the content of steel fiber, which was the best when 1.5% of the steel fiber was added. The effect of steel fiber content on the initial crack number of RPC is small, but the final crack number is greater, and the final crack number is the highest when the content of steel fiber is 1.5%. The microhardness of the steel fiber is about 3.5 times of that of the cement stone. The structure of the interface transition zone between the steel fiber and the cement stone is dense, and there is an obvious strengthening zone in the range of 0 ~ 30 渭 m, and the microhardness of the steel fiber is about 3.5 times that of the cement stone. Its microhardness is higher than that of cement paste. When the content of copper plated fine steel fiber is constant, three kinds of PVA fibers of different specifications are added, and the flexural strength increases with the increase of the content of PVA fiber from 0.5%, 1.0% to 1.25%, when the content of the fiber is increased from 0.5%, 1.0% to 1.25%. The compressive strength is consistent with that of single steel fiber group, and the peak value of beam bending test increases with the increase of the content of steel fiber. When the content of PVA fiber increased to 2.0%, the compressive and flexural strength decreased obviously, and the peak load and the peak deformation of the beam bending test decreased obviously, and the descending segment was slower than that of the control group, but the load-deflection curve also decreased steeply, and when the content of the fiber increased to 2.0%, the compressive and flexural strength of the beams decreased obviously. The first crack of RPC was delayed by adding three kinds of PVA fibers, but the final crack times of the finer PVA-HT-12 fiber group and the PVA-HT-6 fiber group decreased obviously. When the content of PVA-ECC-12 fiber was 1.25%, the number of initial crack and final crack was obviously better than that of single copper-coated fine steel fiber group. In the process of increasing the content of copper-coated fine steel fiber from 0% to 2.0%, the salt-freezing resistance of the PVA-HT-12 fiber group was higher than that of the single steel fiber group, but the later performance was poor. The microhardness of the short fiber group is about 1? 4 of that of the cement stone, the structure of the interface transition zone between the short fiber group and the cement stone is loose, and there is an obvious weak area within 0 ~ 30 渭 m of the short fiber group, which is better than the long fiber group. The microhardness of the ECC-12 fiber is about 1% of that of the cement stone. The microhardness is about 1? 2 of that of cement stone, which is consistent with that observed by ultra-depth-of-field microscopy at the interface between PVA-ECC fiber and cement paste with a thickness of about 30 渭 m. From the point of view of comprehensive properties, the optimum mixing scheme given in this paper is as follows: the optimum content of copper-coated fine steel fiber is 1.5%, and the optimum content of PVA-ECC-12 fiber is 1.25%, among which the coarser PVA fiber has the best comprehensive effect.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU528
，
本文编号：2457889
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