【作者】 周璇；

【导师】 黄政宇；

【作者基本信息】 湖南大学 ， 结构工程， 2017， 硕士

【摘要】 超高性能注浆纤维水泥基材料(Ultra High Performance-Slurry Infiltrated Fiber Cementitious Composites,UHP-SIFCC)是一种兼具高韧性、高强度的新型纤维增强水泥基复合材料。其独特的制作工艺保证了高纤维率的实现,而这种高纤维率下的纤维联锁作用使得其性能较普通钢纤维水泥基材料有了更大的提高。在以往的研究当中,注浆纤维水泥基材料的基体材料大多采用的是普通水泥基浆体,为了进一步提高水泥基材料的各项性能,本文以超高性能水泥基材料(Ultra High Performance Cementitious Composites,UHPCC)为基体,与注浆纤维水泥基材料的成型工艺相结合。本文研究了对不同种类、不同掺量和不同长度的钢纤维对超高性能注浆纤维水泥基材料的力学性能的影响。并测定了不同养护方式和基体不同水灰比、不同水泥类型条件下试件的力学性能。通过弯拉荷载-挠度曲线对钢纤维的增强、增韧效果进行了研究。为此得出了以下结论:(1)高体积率钢纤维的掺入,能显著地改善UHPCC的破坏形态。素UHPCC构件在抗弯和抗压破坏之前没有任何的征兆,是典型的脆性破坏。掺入高体积率钢纤维后制成UHP-SIFCC试件,在加载过程中首先产生了裂缝,随着荷载增加,构件能够继续承载,直至破坏试件也能保持较好的完整性,抗弯试件并未断裂。抗弯和抗压峰值强度相比初裂强度有较大的提高。(2)纤维率对于UHP-SIFCC抗压强度影响明显,纤维率越高,抗压强度越高;同比条件下端勾纤维对UHPCC的增强效果要优于回收纤维,这是因为回收纤维长短不一,纤维形状弯曲复杂所带来的纤维联锁作用的增强效果没能弥补锚固长度不足的缺陷;而对于端勾纤维,25mm端勾纤维的增强效果要优于13mm端勾纤维,故在之后的UHP-SIFCC研究中,建议尽量采用长纤维。(3)使用强度等级为52.5的水泥制作的UHP-SIFCC试件抗压强度要高于42.5的水泥UHP-SIFCC试件抗压强度;随着UHPCC基体水胶比的增大,UHP-SIFCC试件抗压强度降低。(4)28d标准养护强度相比7d标准养护强度有很大提高,90度热水养护72h相比48h的提升效果较小,90度热水养护2-3d强度已趋于稳定;标准养护28d与90度热水养护2d的强度接近,且2d热水养护的强度要略高于28d标准养护。(5)随着纤维率的提高、纤维长度的增长,UHP-SIFCC抗弯强度逐渐提高;掺端勾纤维的UHP-SIFCC试件抗弯强度高于掺回收纤维的UHP-SIFCC试件;UHP-SIFCC试件抗弯强度在本文变量范围内的增长幅度要明显高于抗压强度。(6)用复合材料理论计算UHP-SIFCC的抗弯强度误差在30%之内,掺短纤维的UHP-SIFCC试件理论计算误差要小于掺长纤维的试件。(7)随着纤维率的提高和纤维长度的增长,UHP-SIFCC的弯曲韧性得到提高;不同纤维率的UHP-SIFCC试件弯曲耗能的差别主要体现在下降段;8%纤维率的UHP-SIFCC试件相比6%的UHP-SIFCC试件破坏耗能的增加幅度高于10%的UHP-SIFCC试件相比8%的UHP-SIFCC试件破坏耗能所增加的幅度,这是由于高的纤维率使得纤维间距急剧减小,而纤维间距对于纤维与基体间的粘结强度有较大影响,从而影响了试件的弯曲韧性。(8)UHP-SIFCC试件的荷载—挠度曲线属于应变硬化曲线,其破坏过程分为明显的三个阶段,即线弹性阶段、塑性上升段和下降段。该试件在破坏过程中未发生应力突变,下降段中随着应变增大应力缓慢下降,后期持荷能力较强,表现出了比较好的延性。(9)通过比较几种常用的弯曲韧性评价方法,得出ASTMC1018韧度指数法对本研究中的UHP-SIFCC材料来说,没能很好地反映下降段的差异。而PCER法和初始、残余弯曲韧度比法则能较好地弥补这一缺陷。总体来说,试件的弯曲韧性随着纤维率的上升而提高,随着纤维长度的增长而提高。更多还原

【Abstract】 Ultra High Performance-Slurry Infiltrated Fiber Cementitious Composites(Ultra High Performance-Slurry Infiltrated Fiber Cementitious Composites,UHP-SIFCC)is a new type of fiber reinforced cementitious composite with high toughness and high strength.Its unique production process to ensure the realization of high fiber rate,and the high fiber ratio of the fiber interlock makes its performance have a greater improvement than the ordinary steel fiber cementitious composite.In the previous study,the Slurry Infiltrated Fiber Cementitious Composites is mostly used in ordinary cement slurry,in order to further improve the performance of cementitious composite,the article use the ultra high performance cementitious composite(Ultra-High Performance Cementitious Composites,UHPCC)as matrix material,combined with the forming process of Slurry Infiltrated Fiber Cementitious Composites.This paper studied the influence on mechanical properties of different types,different content and different length of steel fiber on Ultra High Performance-Slurry Infiltrated Fiber Cementitious Composites.And the mechanical properties of the specimens were measured under different curing conditions and different water cement ratio,different cement types.The strengthening and toughening effect of steel fiber was studied by means of bending load deflection curve.This drew the following conclusions:(1)The addition of high volume steel fiber can significantly improve the failure mode of UHPCC.The pure UHPCC has no signs of failure prior to bending and compression,and it has typical brittle failure.The incorporation of high volume ratio of steel fiber made of UHP-SIFCC specimens,the first step is cracking in the loading process,with the increase of the load the specimens can bearing load unceasingly,until the destruction of the specimen can maintain better integrity,and the bending specimen is not broken.The flexural strength and compressive strength are improved compared with the initial crack strength.(2)Fiber rate can significantly affect the compressive strength of UHP-SIFCC,the higher the fiber ratio,the higher the compressive strength.Under the same condition,the end hook fiber to enhance the UHPCC is better than recycled fiber.This is because the recycled fibers has different lengths,the interlocking effect of fibers on the bending of complex shapes can not make up for the lack of anchoring length.As for the end hook fiber,25mm end hook fiber reinforcement effect is better than the 13mm end hook fiber.Therefore,in the future UHP-SIFCC research,it is recommended to use long fiber.(3)The compressive strength of the UHP-SIFCC specimens made of cement with strength grade 52.5 is higher than that of the cement of 42.5.With the increase of the water binder ratio of UHPCC matrix,the compressive strength of UHP-SIFCC specimen decreases.(4)Compared with 7d standard,the curing strength of 28d standard is greatly improved.The lifting effect of strength of 90 degrees water curing 72h to 48h curing is small,the 90 degree hot water curing 2-3d intensity has stabilized.The strength of 28d normal temperature curing is close to the strength of 48h hot water curing,and the strength of 2d hot water curing is higher than the 28d standard curing.(5)The flexural strength of UHP-SIFCC increases with the increase of fiber ratio and fiber length.The flexural strength of the UHP-SIFCC specimen with the end hooked fiber is higher than that of the UHP-SIFCC specimen with the recycled fiber.The growth rate of flexural strength of UHP-SIFCC specimen is obviously higher than that of compressive strength,within the scope of this article.(6)The bending strength error of UHP-SIFCC calculated by composite material theory is within 30%,and the theoretical error of UHP-SIFCC specimen with short fiber is less than that of long fiber.(7)The flexural toughness of UHP-SIFCC was improved with the increase of fiber ratio and fiber length.The difference of bending energy consumption of UHP-SIFCC specimens with different fiber ratio is mainly reflected in the descending segment.The interval amplitude of damage energy with 8%and 6%fiber ratio is higher than the the growth rate of damage energy with 10%and 8%fiber ratio.This is because the high fiber rate makes the fiber spacing sharply reduced,and the fiber spacing has a greater impact on the bond strength between the fiber and the matrix,thereby affecting the flexural toughness of the specimen.(8)The load deflection curve of UHP-SIFCC specimen belongs to the strain hardening curve,and the failure process is divided into three distinct stages,that is,linear elastic stage,plastic rising stage and falling stage.There is no stress mutation during the failure process.In the falling section,the stress decreases slowly with the increase of strain.The specimens have better loading capacity at later stage and show excellent ductility.(9)By comparing several commonly flexural toughness evaluation methods,it is found that the ASTMC1018 toughness index method can not reflect the difference of the falling stage well for the UHP-SIFCC material.The PCER method and the initial and residual bending toughness ratio can well compensate for this defect.In general,the flexural toughness of specimens increases with the increase of fiber content and fiber length.更多还原