Mechanical properties of layered steel fiber and hybrid fiber reinforced concrete

To explore a new structure form of fiber reinforced concrete, namely, the layered steel fiber and layered hybrid fiber reinforced concrete （LSFRC and LHFRC）, the mechanical properties of LSFRC and LHFRC, such as compressive strength, tensile strength, flexural strength, fatigue and durability were focused on. The experimental results show that LSFRC and LHFRC can improve the flexural strength of concrete by 20%-50%. In the aspect of improving the flexural strength of concrete, adulterant rate has more obvious effect than length/diameter ratio. Double logarithmic fatigue equation considered liveability was founded. The impermeability of LHFRC is superior to LSFRC and plain concrete （C）. However, the porosity of LHFRC is lower than LSFRC and C. The shrinkage of LHFRC at every age is obviously lower than C. The antifreeze durability of LHFRC is also better than C.     

Mechanical Properties of Layered Hybrid Fiber Reinforced Concrete

1　IntroductionManyexpertsandscholarshavebeentryingtoim provethepropertiesofconcrete (mainlyimprovetensilestrengthandtoughness)foralongtime .Fiberreinforcedconcrete,akindofcompositematerialmadeofconcreteandreinforcingmaterials ,bymetalfibers ,inorganicfi bers ,organicfibersetc ,hasbeenstudiedandappliedlargelyasaneffectivewaytostrengthenconcrete .General lyspeaking ,highmodulusfiber (suchassteelfiber)cannotablyimprovethestrengthandtoughnessofconcrete ,butitscostishigh ;whilelowmodulusfiber (suc…     

层布式钢纤维混凝土路面板弯曲疲劳性能研究

通过70根层布式钢纤维混凝土小梁的弯曲疲劳试验,用双参数Weibull分布分析了其疲劳寿命,并进一步回归出不同失效概率下的单对数疲劳方程式,与国家现行纤维混凝土规范中的疲劳公式进行了衔接.试验结果表明:这种分层掺入少量钢纤维形成的混凝土,其抗弯疲劳性能较普通混凝土有大幅提高,且优于整体掺配钢纤维混凝土.     

尾矿砂聚合物钢纤维混凝土的基本力学性能

针对尾矿砂聚合物钢纤维混凝土的基本力学性能,通过设置不同掺量组合,采用标准方法进行试验.结果表明,当尾矿砂替代率为50%、钢纤维掺量为1. 5%、聚灰比为10%时,尾矿砂聚合物钢纤维混凝土基本力学性能达到相对较高水平,抗压强度较素混凝土提高约15. 45%,抗折强度提高约36. 17%.该新型混凝土在加强混凝土抗压、抗拉和抗剪等力学性能,抗腐蚀和抗碳化等耐久性能的同时,有效解决了铁矿石在加工之后产生的废料所造成的环境污染问题,是一种高效环保的混凝土.     

Flexural Fatigue Behavior of Layered Hybrid Fiber Reinforced Concrete

In order to obtain the fatigue life of layered hybrid fiber reinforced concrete （LHFRC） at different stress levels, flexural fatigue tests were carried out on specimens. The relation between fatigue lives and stress levels was simulated using the two-parameter Weibull distribution. Furthermore, both single- logarithmic and double-logarithmic regressive equations of various reliabilities were derived. It is evident that LHFRC gets the advantage of longer fatigue life over common concrete.     

Fatigue Defect of Layer Steel Fiber Reinforced Concrete

1　ＩｎｔｒｏｄｕｃｔｉｏｎＳｔｅｅｌｆｉｂｅｒｒｅｉｎｆｏｒｃｅｄｃｏｎｃｒｅｔｅ (ＳＦＲＣ) ,ａｎｅｗｔｙｐｅｏｆｃｏｍｐｏｓｉｔｅｗｉｔｈｓａｔｉｓｆａｃｔｏｒｙｐｒｏｐｅｒｔｉｅｓａｎｄｗｉｄｅａｐｐｌｉｃａ ｔｉｏｎｓ ,ｉｓａｋｉｎｄｏｆｒｅｉｎｆｏｒｃｅｄｃｏｎｃｒｅｔｅｗｉｔｈｎｏｎ ｄｉｒｅｃｔｉｏｎａｌｓｔｅｅｌｆｉｂｅｒｓｓｃａｔｔｅｒｅｄ .Ｒｅｃｅｎｔｌｙ ,ｔｈｅａｐｐｌｉｃａｔｉｏｎｓｏｆＳＦＲＣｈａｖｅｐｅｒｍｅａｔｅｄａｌｌｆｉｅｌｄｓｏｆｃｉｖｉｌｅｎｇｉｎｅｅｒｉｎｇ…     

层布式纤维混凝土弯曲疲劳性能研究

研究了在相同的混凝土配合比情况下,对选用相同的钢纤维的层布式钢纤维混凝土和层布式混杂纤维混凝土的小梁进行弯曲疲劳试验,比较了两者各级应力水平下的平均疲劳寿命;并通过对试验结果进行统计分析,运用两参数威布尔分布拟合不同应力水平下两者的疲劳寿命,得出其特点和规律,回归出不同存活率的双对数疲劳方程.     

纳米碳纤维增强混凝土的介电特性

为研究纳米碳纤维增强混凝土的介电特性,发现纳米碳纤维增强混凝土对电磁波的反射与损耗规律,采用波导法测试纤维掺量为0、0.1%、0.2%、0.3%、0.5%的纳米碳纤维增强混凝土在1.7～2.6 GHz频率范围内的介电常数。分别从相对复介电常数实部、相对复介电常数虚部、损耗角正切等方面分析了纤维掺量、频率对纳米碳纤维增强混凝土介电特性的影响,并对比分析0.3%纤维掺量下纳米碳纤维和普通碳纤维对混凝土材料介电特性的影响。结果表明:纳米碳纤维的掺加提高了混凝土材料相对复介电常数实部和虚部、损耗角正切,增强了混凝土材料对电磁波的损耗能力;纤维掺量越大,纳米碳纤维增强混凝土介电特性越强,对电磁波的损耗能力越大;纳米碳纤维对混凝土材料介电特性的提高效果强于碳纤维。     

冻融下预湿方式对塑钢纤维轻骨料混凝土与钢筋粘结性能的影响

通过常压预湿和加压预湿两种方式对烧结页岩陶粒轻骨料进行处理,探究不同冻融循环次数下,塑钢纤维轻骨料混凝土与钢筋的粘结性能,着重分析了两种预湿方式下试件力学性能、粘结强度、荷载滑移曲线、粘结韧性的变化规律。试验结果表明：加压预湿试件的力学性能、极限粘结强度低于常压预湿试件,且加压预湿试件的破坏形态均为劈裂破坏;加压预湿试件的极限粘结韧性A_u随冻融循环次数增加而减小,残余粘结韧性A₈₀、A₆₀下降较为平缓,但常压预湿试件粘结韧性均高于加压预湿试件。建立了冻融环境下塑钢纤维轻骨料混凝土剩余粘结强度与抗压强度之间退化模型和粘结韧性退化模型,模型计算值与试验值吻合较好。     

Meso-mechanical interfacial behavior of elbow steel fiber reinforced concrete

The strain distributions near the interface when the elbow steel fiber is pulled out from the half-mould concrete matrix are directly measured using a combined method of single fiber pull-out test and digital image correlation. Meanwhile, the real-time processes of the bonding, debonding and sliding at the interface are observed. The micro-mechanism of the strain localization in the failure process of interface when debonding occurs and the strengthening mechanism at the imbedded fiber are discussed. The experimental results show that the meso-scale strain localization gives rise to the localization of shear damage near the fiber interface. This strain localization characterized by the debonding process near the interface occurs, develops and moves gradually at an apparently regular interval. At the elbow part of the imbedded fiber, the peak value of the shearing stress occurs. But the primary debonding does not occur at this place because the strength of the shear damage is increased at the local area of the elbow part in the concrete, displaying an apparent reinforced effect at the end of the fiber.     

钢纤维自应力混凝土压力管受力性能的有限元分析

利用大型通用软件ANSYS,对钢纤维自应力混凝土压力管的工作性能进行了分析,揭示钢纤维自应力混凝土压力管在内压力作用下的受力破坏过程,并与试验结果进行了比较.分析结果表明,配置在管道中的钢筋产生预应力,并且随着钢筋量的增加而增加;钢纤维的作用是延迟了钢纤维自应力混凝土压力管的开裂,提高了管道的抗裂性能.     

The Mechanical Properties of Polypropylene Fiber Reinforced Concrete

The compressive, shear strengths and abrasion-erosion resistance as well as flexural properties of two polypropyenc fiber reinforced concretes and the comparison with a steel fiber reinforced concrete were reported. The exprimental results show that a low content of polypropylene fiber (0.91 kg/m^3 of concrete ) slightly decreases the compressive and shear strengths, and appreciably increased the flexural strength, but obviously enhances the toughness index and fracture energy for the concrete with the same mix proportion, coasequently it plays a role of anti-cracking and improving toughness in concrete. Moreover, the polypropylene mesh fiber is better than the polypropylene monofilament fiber in improving flexaral strength and toughness of concrete, but the types of polypropylene fibers are inferior to steel fiber. All the polypropylene and steel fibers have no great beneficial effect on the abrasion-erosion resistance of concrete.     

冲击载荷作用下钢纤维增强混凝土的数值模拟

为了验证混凝土试件的侧限效应和钢纤维的增强和增韧效应,该文采用实验得出的应力应变曲线,通过ANSYS/LS-DYNA软件对SHPB混凝土冲击压缩实验的数值模拟,定性地再现了实验过程.     

钢纤维混凝土的配合比优化设计

水泥基复合材料均为抗拉性能低的脆性物质.加入随机分布的纤维会显著提高其断裂强度.素混凝土在加入纤维后会破坏原有的颗粒状骨架并降低配合物的和易性，使纤维混凝土的施工产生困难.针对配合初始和硬化后两种状态，提出钢纤维混凝土全新的配合优化设计过程给出了考虑纤维、外加物、水及水泥用量后和易性与时间的关系.研究了根据该优化方法所制得的试件在受压和受弯下的力学性能，并证明它比Swamy法更为优越.     

钢纤维混凝土动载疲劳特性的试验研究

运用TAW-2000型微机伺服多功能材料试验机,对不同强度混凝土掺入不同含量的钢纤维进行疲劳破坏试验研究。结果表明:在钢纤维体积含量一定范围内,随钢纤维体积含量增加,钢纤维混凝土的疲劳极限抗压强度增长十分明显;随钢纤维体积含量提高,混凝土的抗疲劳能力显著增强;随时间增长,应力曲线的上升段更加陡峭,下降段更缓慢,即钢纤维混凝土的疲劳强度、韧度均得到显著增长。     

Experiment on mechanical properties of steel fiber reinforced concrete and application in deep underground engineering

Specimens of steel fiber reinforced concrete (SFRC) in volume ratios of 0%, 0.5%, 1% and 1.5% were prepared to study the supporting effect of SFRC at these different volume ratios in a deep soft rock tunnel. Experiments with mechanical properties of compressive strength in cubic specimens, cleave strength in cylindrical specimens and four-point flexure strength of sheet metal specimens were carried out. The experimental results indicate that SFRC in a volume ratio of 1% is superior in ranking to other volume ratios in terms of technique and economics. By means of a numerical simulation, given the characteristics of soft rock de-formation and damage at great depth, a new support substitution scheme of SFRC to replace plain concrete is proposed. The results of an industrial trial show that the support provided by SFRC can withstand large deformations of the surrounding rock. Good results have been obtained in a practical application.     

局部高密度钢纤维混凝土静态断裂性能研究

对局部高密度钢纤维混凝土（简称DHPFPC）缺口试件在静荷载作用下的断裂过程进行了力学分析,分析中重点考虑纤维庆力对裂尖奇异性的影响和纤维应力在断裂截面上产生桥架作用对承载力的影响等,确定了考虑纤维闭合力的模型,根据对局部高度钢纤维混凝土断裂过程各阶段的非线性分析,编制了计算分析程序,通过计算获得的P－CMOD关系曲线与试验结果相吻合,确定有关参数,为定量计算PHPFRC缺口试件的裂尖有效庆力强度因子K奠定了基础。     

钢筋钢纤维混凝土梁正截面抗裂计算方法

根据试验结果 ,分析了钢纤维含量特征值和钢纤维类型等因素对钢筋钢纤维混凝土梁正截面抗裂的影响规律 ,研究了钢纤维对混凝土抗拉强度的增强效应与钢纤维对梁正截面抗裂度的增强效应之间的一致性关系 .提出了钢筋钢纤维混凝土梁正截面抗裂计算的方法     

纺织废料再生纤维增强混凝土力学性能的研究

对纺织废地毯再生纤维增强混凝土的力学性能进行实验研究．结果表明，含量为2％的纺织废地毯再生纤维增强混凝土的抗压强力、抗剪切强力和抗弯曲强力等力学性能较普通混凝土有所提高；干燥收缩性以及由此引起的韧性及能量吸收性较普通混凝土均有较大改善．这种混凝土若能得到广泛使用，还可节约资源、保护环境．     

Experimental Study on Electric Properties of Carbon Fiber Reinforced Concrete

According to the phenomenon that the physical properties have,a great effect on the electric capability of carbon fiber reinforced concrete, the author researched the relationship between DC resistance of carbon fiber reinforced concrete and curing age using the two-probe method. Then the effect of insulative area, location and quantity on DC resistance of carbon fiber reinforced concrete was investigated at different curing age with analysis of hydration. The results suggest that DC resistance increases greatly with its curing age, which illustrates the relationship like Gaussian curve. In every curing ages the electric capability of carbon fiber reinforced concrete weakenes with the increase of insulative area. In same curing ages, section and insulative area, the more the quantity of insulation, the stronger the conductibility. The insulative location in optimal position can only result in optimal conductibility.