纤维增强轻骨料混凝土力学性能试验研究

选用钢纤维、聚丙烯纤维及二元混杂纤维轻骨料混凝土,系统研究了其抗压强度、弹性模量、轴心抗压强度及抗折强度等力学性能,试验结果体现了不同纤维种类、不同纤维掺量及纤维混杂比例对轻骨料混凝土力学性能的影响;当钢纤维以体积率1.0%与聚丙烯纤维0.6kg/m3混杂时,纤维轻骨料混凝土的各项力学性能达到优化.     

钢纤维和聚丙烯纤维水泥混凝土路用性能的对比研究

通过室内试验,研究了钢纤维和聚丙烯纤维对水泥混凝土路用性能的影响。试验结果表明,不同体积掺量的钢纤维、聚丙烯纤维均能改善混凝土的力学性能,其中,高弹模的钢纤维对混凝土抗折强度和压折比的改性程度优于聚丙烯纤维。最后分别探讨了两种纤维对混凝土的抗渗性和增强机理。     

聚丙烯纤维混凝土力学性能试验研究

试验研究了聚丙烯纤维混凝土的抗压强度、抗剪强度、抗冲磨强度及弯曲性能，并与钢纤维混凝土进行了对比。结果表明：在混凝土基体不变情况下，低掺量聚丙烯纤维(掺量为0．91kg／m^3)略微降低混凝土的抗压强度和抗剪强度，少许提高混凝土的抗弯强度，显著提高混凝土的弯曲韧性和断裂能，从而起到阻裂和增韧作用，而对混凝土的抗冲磨性能几乎没有改善。另外．网状聚丙烯纤维对混凝土抗弯强度和韧性的改善优于聚丙烯单丝纤维，但它们较钢纤维的增强增韧效果还有一定差距。     

单一纤维对道路混凝土力学性能影响

研究了钢纤维和聚丙烯纤维对道路混凝土力学性能的影响。试验中两种规格的钢纤维以1∶1加入混凝土,体积掺量为0.6%~1.2%,聚丙烯纤维体积掺量为0.1%~0.3%。研究表明,钢纤维的加入对混凝土的抗压强度、抗折强度和劈拉强度都有不同程度的提高,掺量为0.9%时,增强效果最为明显。掺入聚丙烯纤维对抗压强度无增强作用,对抗折强度和劈拉强度有一定影响,以0.1%的掺量最为合理。     

Comparative flexural behavior of Hybrid Ultra High Performance Fiber Reinforced Concrete with different macro fibers

The flexural performance of four Hybrid (H-) Ultra High Performance Fiber Reinforced Concretes (UHPFRCs) with different macro fibers was investigated according to ASTM standards C1018-97 and C 1609/C 1609M-05. Four macro fibers were long smooth (LS-) steel fiber, two types of hooked (HA- and HB-) steel fibers, and twisted (T-) steel fibers while one type of micro fiber, short smooth (SS-) steel fiber, was blended. The enhancements in modulus of rupture, deflection capacity and energy absorption capacity were different according to the types of macro fiber as the amount of micro fiber blended increased. The order of flexural performance of H-UHPFRC according to the types of macro fiber was as follows: HB- > T- > LS- > HA-fiber. The influence of strain capacity in tension on the flexural performance of H-UHPFRC was also examined. The deflection capacity and the ratio between flexural strength and tensile strength were dependent upon the strain capacity of H-UHPFRC.     

冻融环境下钢纤维对轻骨料混凝土力学性能的影响

以天然浮石为粗骨料,对钢纤维及钢纤维与聚炳烯纤维混合的不同掺量试件进行了25、50、75次慢冻试验,进行了抗压强度、抗折强度及弹性模量的试验,试验发现:随着冻融次数的增加,混凝土的强度损失率逐渐增大,弹性模量和抗折强度有所降低,但是聚炳烯纤维和钢纤维的混合掺入可以有效地在保持混凝土的强度基础上,改善混凝土的韧性.     

Compressive and cyclic flexural response of double-hooked-end steel fiber reinforced concrete

Recent developments on high-performance double-hooked-end steel fibers have enhanced the wide applications of steel fiber reinforced concrete (SFRC). This study presents the compressive properties and the cyclic flexural performance of the SFRC that were experimentally examined. Three different double-hooked-end steel fibers at 0.25%, 0.5%, 0.75%, and 1% volume fractions were considered. All fiber types had similar length to diameter ratios, while the first two fiber types had similar anchorage mechanisms (4D) and tensile strength and the third type had different anchorage mechanism (5D) and a higher tensile strength. The increased volumetric ratio of the fibers increased the post-peak compressive strain (ductility), the tensile strength, and the cyclic flexural strength and cumulative energy dissipation characteristics of the SFRC. Among the 4D fibers, the mixtures with the larger steel fibers showed higher flexural strength and more energy dissipation compared to the SFRCs with smaller size fibers. For 1% steel fiber dosage, 4D and 5D specimens showed similar cyclic flexural responses. Finally, a 3D finite element model that can predict the monotonic and cyclic flexural responses of the double-hooked-end SFRC was developed. The calibration process considered the results obtained from the inverse analysis to determine the tensile behavior of the SFRC.     

混杂纤维对道路混凝土力学性能影响

研究了混杂纤维(钢纤维和聚丙烯纤维)对道路混凝土力学性能的影响。钢纤维以体积掺量为0.6%~1.1%,聚丙烯纤维体积掺量为0.1%~0.2%。纤维总体积掺量分别为0.8%、1.0%和1.2%。研究表明,混杂纤维对混凝土的抗压强度、抗折强度和劈拉强度都有不同程度增强作用,其中对抗折强度增强作用最为明显,其次是劈拉强度和抗压强度。两种不同性质的纤维同时加入可以产生混杂效应,其增强作用优于掺入单一纤维时的增强作用。     

不同种类钢纤维在C30泵送混凝土中的应用试验研究

为探讨不同种类钢纤维及掺量对C30泵送混凝土工作性能及力学性能的影响,主要研究了钢纤维混凝土工作性能、抗压强度及弯曲韧性。研究表明:钢纤维的掺入会影响混凝土泵送施工性能,经配合比优化后剪切压痕型和哑铃型钢纤维混凝土泵送性能优良;同掺量钢纤维混凝土,峰值前韧度差异相对较小,不同类型钢纤维的增韧效果主要体现在峰值后韧度的提高上,其中端钩型效果最好,其次为高强微细平直型,哑铃型和剪切压痕型峰值后韧度相当;对于低强度等级C30泵送混凝土,钢纤维增韧效果的发挥不仅与钢纤维自身强度有关,同时与钢纤维异性化程度和掺量有关。     

Mechanical properties of hybrid fiber reinforced lightweight aggregate concrete made with natural pumice

The purpose of this study is to improve the ductility of pumice lightweight aggregate concrete by incorporating hybrid steel and polypropylene fibers. The changes in mechanical properties and also bulk density and workability of pumice lightweight aggregate concrete due to the addition of hybrid steel and polypropylene fibers have been studied. The properties were investigated include bulk density and workability of fresh concrete as well as compressive strength, flexural tensile strength, splitting tensile strength and toughness of hardened concrete. Nine concrete mixtures with different volume fractions of steel and polypropylene fibers were tested. A large increase in compressive and flexural ductility and energy absorption capacity due to the addition of steel fibers was observed. Polypropylene fibers, on the other hand, caused a minor change in mechanical properties of hardened concrete especially in the mixtures made with both steel and polypropylene fibers. These observations provide insight into the benefits of different fiber reinforcement systems to the mechanical performance of pumice lightweight aggregate concrete which is considered to be brittle. These results provide guidance for design of concrete materials with reduced density and enhanced ductility for different applications, including construction of high-rise, earthquake-resistant buildings.     

混杂纤维自密实混凝土的强度和抗弯韧性

在工作度试验研究的基础上,根据不同国际标准研究了不同类型纤维(钢纤维、聚丙烯纤维、混杂纤维)对自密实混凝土强度与抗弯韧性的影响．结果表明：混杂纤维可显著提高自密实混凝土的韧性并改善其破坏形态．     

纤维对自密实活性粉末混凝土强度的影响

研究了不同掺量钢纤维、聚丙烯纤维对自密实活性粉末混凝土(RPC)力学性能的影响.结果表明:钢纤维的掺入提高了自密实RPC的抗压和抗折强度,尤其对抗折强度的提高非常明显,7 d抗折强度最大可提高95%,28 d抗折强度最大可提高73%;聚丙烯纤维可以提高自密实RPC 7 d抗折强度,最大可提高13%,但对抗压强度以及28 d抗折强度却起削弱作用;混杂纤维主要能提高自密实RPC的7 d抗折强度,最大可提高82%;纤维的掺加大都能降低自密实RPC的压折比,并提高其峰值荷载变形和断裂变形.     

聚丙烯纤维增强水泥砂浆的性能研究

采用三种不同的聚丙烯纤维(普通聚丙烯纤维,改性处理聚丙烯纤维,Y形聚丙烯纤维)增强水泥砂浆,研究了在纤维低掺量情况下,不同形式的纤维对普通水泥砂浆的抗压、抗折和抗裂性能的影响,并分析了纤维在阻裂增强方面的作用机理。实验证明,在同水灰比条件下,普通水泥砂浆中加入一定量的Y形纤维比加入普通纤维的增强效果好。     

改性合成纤维混凝土弯曲及抗冲击试验

针对普通混凝土道面易开裂、使用寿命无法达到设计寿命的情况,在普通混凝土中加入合成聚丙烯纤维及聚丙烯腈纤维,以提高混凝土的抗弯拉开裂性能及冲击韧性。对改性合成聚丙烯纤维混凝土及聚丙烯腈纤维混凝土进行了四点弯曲试验,并采用自行设计的冲击试验装置进行了冲击试验及经冻融循环后冲击试验。试验结果表明:在几乎不影响抗压强度的情况下,长度20、40 mm的合成聚丙烯纤维可以显著提升混凝土的抗弯韧性和冲击次数,经冻融后合成聚丙烯纤维混凝土的冲击次数下降幅度明显低于普通混凝土; 在抗弯韧性及抗冲击性能方面,改性合成聚丙烯纤维改善效果最佳,聚丙烯腈纤维次之,而长度40 mm的合成聚丙烯纤维又略强于长度20 mm的合成聚丙烯纤维; 在抗弯韧性方面,掺有长度40 mm合成聚丙烯纤维混凝土相较素混凝土提升了60.09%～120.62%; 未经冻融前掺有长度40 mm合成聚丙烯纤维混凝土在冲击试验中的初裂冲击次数和破坏冲击次数均为最高,相较素混凝土分别提升了114.29%～157.14%和120%～306.67%,相较于掺有长度为20 mm合成聚丙烯纤维的混凝土分别提升了5.56%～23.53%和15.15%～35.90%,相较于掺有聚丙烯腈纤维的混凝土分别提升了5.56%～13.33%和36.36%～60.66%; 试验结果可为混凝土道面的建设提供参考依据。     

掺有纤维的高强混凝土劈拉性能试验研究

通过63个100mm×100mm×100mm和63个150mm×150mm×150mm高强混凝土和钢纤维、聚丙烯纤维高强混凝土试件的劈拉试验,探讨了纤维体积率(纤维掺量)及纤维类型对高强混凝土劈拉强度和变形性能的影响,提出了不同类型的钢纤维对高强混凝土劈拉强度的增强系数和劈拉强度的计算公式。     

改性聚丙烯纤维混凝土抗疲劳性能研究

通过试验,研究了改性聚丙烯纤维对混凝土静力强度及疲劳性能的影响,结果表明,改性聚丙烯纤维掺加在混凝土中,混凝土的抗压强度变化不大,该纤维在混凝土中形成的乱向分布支撑体系,减少了裂纹的产生,提高了混凝土的劈裂抗拉、抗折以及弯曲疲劳性能.     

混杂纤维增强轻骨料混凝土物理力学性能研究

选用钢纤维、聚丙烯纤维二元混杂纤维掺入轻骨料混凝土,系统研究其抗压强度、弹性模量、轴心抗压强度及抗折强度等力学性能,试验结果表明,纤维掺入对轻骨料混凝土物理力学性能的影响较大;掺入钢纤维具有较好的增强增韧效果,但表观密度相应增大;钢纤维和聚丙烯纤维混掺可以在不增加轻骨料表观密度,保证强度的基础上,有效地改善轻骨料混凝土的韧性。     

Pull-out behavior of prestressing strands in steel fiber reinforced concrete

This paper presents the results of an experimental study investigating the effects of steel fibers on the mechanical properties of concrete and the enhancement of bond strength of prestressing strands in steel fiber reinforced concrete (SFRC). The first part of the experimental program consisted of compression, tension and flexural tests on SFRC. Two types of steel fibers with 30 mm and 60 mm fiber lengths were used with five different fiber contents. The second part of the study consisted of simple pull-out tests on 12.7 mm and 15.2 mm diameter seven-wire untensioned prestressing strands embedded in concrete blocks. The pull-out tests were conducted with two different fiber lengths and five different fiber contents for each strand diameter. The steel fibers were observed to improve the pull-out resistance of strands by controlling the crack growth inside concrete blocks.     

仿钢丝聚丙烯长纤维对钢纤维混凝土力学性能影响

按照国际标准对新型仿钢丝聚丙烯合成长纤维增强高性能混凝土的工作度、含气量、强度及弯曲韧性进行了试验研究。其中对该纤维混凝土的弯曲韧性按照国际材料与结构联合会(RILEM)标准进行了研究,同时还对比了钢纤维混凝土及新型聚丙烯长纤维与钢纤维混杂时纤维混凝土的韧性,得出了不同纤维混凝土的能量吸收值和等效抗弯强度,探讨了新型聚丙烯长纤维部分取代钢纤维的可能性。试验表明,该纤维具有很好的增韧效果,可以部分取代钢纤维来达到增韧增强和降低成本的目的。     

纤维类型对混凝土抗压强度和弯曲韧性的增强效应及变异性的影响

为研究单掺钢纤维、聚丙烯纤维和纤维素纤维对混凝土抗压强度及弯曲韧性的影响,在不同体积掺量下进行了混凝土试块的抗压强度及弯曲韧性试验,并对试验结果进行了变异性分析。试验结果表明:3种纤维混凝土抗压强度较素混凝土平均提高26.7%、6.1%和11.1%;二次抗压强度保持率分别达77.0%、45.7%和58.0%;抗弯承载力最大分别提高31.6%、3.5%和14.0%;基于荷载挠度曲线、Newkumar法及弯拉应力应变曲线分别计算的弯曲韧性指数I_(20)、Newkumar指标PCS_m和韧度比R_x分别为素混凝土的4.2、3.1、2.6倍,19.9、9.8、6.9倍和4.0、3.4、2.7倍。变异性分析结果表明,掺入纤维后混凝土的抗压强度变异性小于弯曲韧性。同时,基于Newkumar法和应力应变曲线法算得的混凝土弯曲韧性指标变异系数小于荷载挠度曲线法。总体而言,钢纤维增强混凝土的抗压强度和弯曲韧性最为显著,且变异系数最小。纤维素纤维增强混凝土抗压强度及聚丙烯纤维增强混凝土弯曲韧性则相对较显著。