聚丙烯纤维水泥稳定碎石抗压强度试验研究

在大量试验研究的基础上,对试件养护龄期、聚丙烯纤维体积掺量以及水泥掺量的变化对聚丙烯纤维水泥稳定碎石抗压强度的影响进行分析。结果表明:聚丙烯纤维的掺加对水泥稳定碎石抗压强度有一定的增加;随着试验龄期的增长,抗压强度不断增长;在聚丙烯纤维掺量体积分数小于1‰的范围内,随着纤维体积分数的增加,水泥稳定碎石抗压强度和抗拉强度均有增加的趋势;随着水泥掺量的增加,聚丙烯纤维水泥稳定碎石抗压强度基本呈线性增加。     

掺氧化镁和纤维对混凝土抗拉强度的影响

为了探索复掺氧化镁(MgO)和聚丙烯纤维对面板混凝土抗拉强度的影响,通过不同的复掺MgO和聚丙烯纤维的掺量对混凝土抗拉强度的试验研究,揭示二者在混凝土复掺中的作用机理。结果表明,复掺MgO和聚丙烯纤维对混凝土的抗拉强度有明显影响,且随两者掺量的增加而越明显,但当两者掺量过大时,混凝土抗拉强度明显减小,所以从试验的角度揭示了混凝土的抗裂效应在复掺MgO和聚丙烯纤维适当的掺量下可以得到有效改善。     

钢纤维和聚丙烯纤维高性能混凝土力学性能试验研究

研究了钢纤维和聚丙烯纤维掺量对高性能混凝土抗压强度和劈裂抗拉强度的影响,并对影响机理进行了分析。结果表明,合理的纤维掺量对高性能混凝土抗压强度和劈裂抗拉强度均有一定的提高效果,对劈裂抗拉强度提高效果尤为显著。根据试验结果给出了掺钢纤维和聚丙烯纤维高性能混凝土抗压和劈裂抗拉强度的计算公式。     

聚丙烯纤维掺量影响卵石混凝土力学性能的研究

通过将聚丙烯纤维掺入卵石混凝土的方法,进行了力学性能试验,研究了聚丙烯纤维掺量、水胶比、龄期对混凝土立方体抗压强度、劈裂抗拉强度、抗弯强度、轴心抗压强度、静力弹性模量的影响,并分析了各力学性能之间的关系。     

新型增强纤维混凝土抗拉性能试验研究

针对最新引进的日产棒状X型聚丙烯纤维,对不同纤维掺量、不同强度等级的混凝土抗拉强度进行了试验研究,试验结果显示：①对于普通强度C30混凝土,随着X型聚丙烯纤维掺量增大,混凝土抗拉强度呈现出先逐渐增大而后又有所下降的趋势;对于高强C50混凝土,随着X型聚丙烯纤维掺量增大,混凝土抗拉强度则呈现出逐渐增大的趋势。②当纤维体积掺量控制在0.5%以内,纤维混凝土抗拉强度明显高于基准混凝土抗拉强度;且相同纤维掺量的C30混凝土抗拉强度增大幅度高于C50混凝土抗拉强度增大幅度。     

硅灰和聚丙烯纤维净浆界面剂对新老混凝土粘结力学性能的影响研究

通过测试新老混凝土粘结的劈拉强度、抗弯强度、抗剪强度,研究了硅灰和聚丙烯纤维单掺、复掺对新老混凝土粘结性能的影响,分析了硅灰和聚丙烯纤维对新老混凝土粘结性能的作用机理。结果表明,硅灰掺量为胶凝材料质量的9%,聚丙烯纤维掺量为0.6 kg/m3,28 d龄期时,新老混凝土粘结效果最好,粘结劈裂抗拉强度为2.36 MPa、抗弯强度为5.79 MPa、抗剪强度为5.11MPa。硅灰聚丙烯纤维净浆界面剂适用于混凝土结构修补。     

钢-聚丙烯纤维高性能混凝土力学性能试验研究

进行了钢纤维与聚丙烯纤维掺量及其混杂对高性能混凝土抗压强度和劈拉强度的试验研究,探讨了不同混杂纤维组合对高性能混凝土基体力学性能的影响规律。结果表明,钢-聚丙烯纤维混凝土的抗压强度、劈裂抗拉强度及其纤维增强系数与钢纤维和聚丙烯纤维掺量及混杂比密切相关。钢纤维掺量较低时,抗压强度随聚丙烯纤维掺量增加先减小后增加;钢纤维掺量较大时,抗压强度随聚丙烯纤维掺量的增加一直增大;当钢纤维掺量一定时,劈裂抗拉强度随聚丙烯纤维掺量的增加先增大后减小。当钢纤维和聚丙烯纤维掺量分别为3%、0.3%时,混杂效应系数最大。     

利用粉煤灰和聚丙烯纤维配制渠道衬砌混凝土的试验研究

研究了水胶比、粉煤灰掺量、聚丙烯纤维掺量对混凝土抗压强度、抗折强度和劈裂抗拉强度的影响。结果发现,即使粉煤灰掺入量达到300 g/kg,混凝土的强度等级也在C30以上;纤维掺量对混凝土抗折强度和劈裂抗拉强度的影响规律基本一致,纤维掺量越大混凝土抗折、抗拉强度越大。这表明,在渠道衬砌混凝土中掺入适当比例的粉煤灰和聚丙烯纤维是可行的,能满足渠道衬砌对混凝土的强度要求。     

棉秆纤维对陶粒泡沫混凝土力学性能影响的研究

针对陶粒泡沫混凝土强度低、脆性大、易开裂等问题,研究在相同纤维掺量及纤维长度下,棉秆纤维、玻璃纤维和聚丙烯纤维对陶粒泡沫混凝土抗压及劈裂抗拉强度的增强效果;考虑棉秆纤维掺入量和纤维长度2个因素在不同水平下对陶粒泡沫混凝土抗压及劈裂抗拉强度的影响,确定棉秆纤维的最佳掺量和最优长度范围。结果表明:聚丙烯纤维对陶粒泡沫混凝土的增强效果最好,掺加棉秆纤维能有效提高陶粒泡沫混凝土强度;棉秆纤维最佳掺量为0.8%,此时抗压强度较同配比未掺纤维的试块提高25.0%,劈裂抗拉强度提高43.1%;长11~15 mm的棉秆纤维对陶粒泡沫混凝土的增强效果最明显。     

聚丙烯纤维水泥稳定碎石抗弯拉强度试验研究

根据试验结果,分析了试件养护龄期、聚丙烯纤维体积掺量以及水泥掺量的变化对聚丙烯纤维水泥稳定碎石抗弯拉强度的影响,结果表明,聚丙烯纤维的掺加能提高水泥稳定碎石抗弯拉强度;随着试验龄期的增长,抗弯拉强度不断增长;聚丙烯纤维体积掺量小于0.1%时,随着纤维体积掺量的增加,水泥稳定碎石抗弯拉强度有不断增加的趋势;随着水泥掺量的增加,聚丙烯纤维水泥稳定碎石抗弯拉强度基本呈线性增加。     

钢纤维增强粉煤灰自密实混凝土力学性能

采用粉煤灰取代40%水泥来制备粉煤灰自密实混凝土(SCC),研究其工作性、基本力学性能和轴压变形性能随钢纤维体积分数的变化规律.结果表明:粉煤灰SCC的工作性随钢纤维体积分数的增加而降低,当钢纤维体积分数大于0.75%时,粉煤灰SCC的工作性降幅最大;钢纤维体积分数对粉煤灰SCC抗压强度的影响不明显,但能够显著改善其劈裂抗拉强度和抗折强度,当钢纤维体积分数为1.00%时,劈裂抗拉强度和抗折强度较未掺钢纤维粉煤灰SCC分别提高了14%、12%;钢纤维能够显著改善粉煤灰SCC的轴压变形能力,当钢纤维体积分数为0.50%时,其极限应力、峰值应变、应变能和相对韧性与未掺钢纤维粉煤灰SCC相比,分别提高了3%、35%、53%和49%.     

Comparison of compressive and splitting tensile strength of high-strength concrete with and without polypropylene fibers heated to high temperatures

This paper presents the results of an extensive experimental study on the compressive and splitting tensile strength of high-strength concrete with and without polypropylene (PP) fibers after heating to 600 °C. Mixtures were prepared with water to cementitious materials ratios of 0.40, 0.35, and 0.30 containing silica fume at 0%, 6%, and 10% cement replacement and polypropylene fibers content of 0, 1, 2, and 3 kg/m³. A severe strength loss was observed for all of the concretes after exposure to 600 °C, particularly the concretes containing silica fume despite their good mechanical properties at room temperature. The range of 300–600 °C was more critical for concrete having higher strength. The relative compressive strengths of concretes containing PP fibers were higher than those of concretes without PP fibers. The splitting tensile strength of concrete was more sensitive to high temperatures than the compressive strength. Furthermore, the presence of PP fibers was more effective for compressive strength than splitting tensile strength above 200 °C. Based on the test results, it can be concluded that the addition of 2 kg/m³ PP fibers can significantly promote the residual mechanical properties of HSC during heating.     

混凝土高温爆裂临界温度和防爆裂纤维掺量研究综述与分析

确定无纤维或低纤维掺量的不同强度等级混凝土的爆裂临界温度,以及防止火灾时不同强度混凝土爆裂所需聚丙烯（PP）纤维或钢纤维最小掺量,对混凝土结构抗火设计具有重要意义。为此,对国内外大量高温爆裂试验研究结果进行分析,获得了爆裂临界温度与混凝土抗压强度（23~238MPa）的关系曲线,发现混凝土抗压强度越高,爆裂临界温度越低。通过大量试验数据拟合得到了防爆裂PP纤维掺量、钢纤维掺量与混凝土抗压强度的关系曲线,发现随着混凝土抗压强度的提高,所需防爆裂PP纤维掺量呈线性增长,而所需防爆裂钢纤维掺量呈指数增长。按EN 1992-1-2:2004《欧洲混凝土抗火设计规范》建议值,PP纤维掺量为0.22%的防爆裂混凝土,火灾下仍可能发生爆裂;按所提出计算式计算的掺量,则可有效降低火灾下混凝土爆裂的风险。     

The effect of carbon nanotubes and polypropylene fibers on bond of reinforcing bars in strain resilient cementitious composites

Stress transfer between reinforcing bars and concrete is engaged through rib translation relative to concrete, and comprises longitudinal bond stresses and radial pressure. The radial pressure is equilibrated by hoop tension undertaken by the concrete cover. Owing to concrete’s poor tensile properties in terms of strength and deformability, the equilibrium is instantly released upon radial cracking of the cover along the anchorage with commensurate abrupt loss of the bond strength. Any improvement of the matrix tensile properties is expected to favorably affect bond in terms of strength, resilience to pullout slip, residual resistance and controlled slippage.The aim of this paper is to investigate the local bond of steel bars developed in adverse tensile stress conditions in the concrete cover. In the tests, the matrix comprises a novel, strain resilient cementitious composite (SRCC) reinforced with polypropylene fibers (PP) with the synergistic action of carbon nano-tubes (CNT). Local bond is developed over a short anchorage length occurring in the constant moment region of a four-point bending short beam. Parameters of investigation were the material structure (comprising a basic control mix, reinforced with CNTs and/or PP fibers) and the age of testing. Accompanying tests used to characterize the cementitious material were also conducted. The test results illustrate that all the benefits gained due to the synergy between PP fibers and CNTs in the matrix, namely the maintenance of the multi-cracking effect with time, the increased strength and deformability as well as the highly increased material toughness, were imparted in the recorded bond response. The local bond response curves thus obtained were marked by a resilient appearance exhibiting sustained strength up to large levels of controlled bar-slip; the elasto-plastic bond response envelope was a result of the confining synergistic effect of CNTs and the PP fibers, and it occurred even without bar yielding.     

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。     

基于细观本构模型的UHPC梁受弯全过程分析

为预测超高性能混凝土(UHPC)残余抗拉强度,通过细观力学分析,研究了纤维对UHPC残余抗拉强度贡献机理,提出了考虑纤维埋深、分布和取向的UHPC细观本构模型。基于UHPC细观本构、受力平衡方程和变形协调条件,建立了UHPC梁受弯分析模型和受弯承载力理论计算方法。经与8个UHPC梁试件受弯试验结果对比发现,文中提出的模型可以较好地预测UHPC梁受弯全过程响应和受弯承载力。基于基准试验梁的不同作用机制受弯贡献比例分析发现,纵筋配筋率从0增至2.5%时,受拉区混凝土对受弯承载力贡献从89.6%降至2.4%;纤维率从0增至3%时,受拉区混凝土对受弯承载力贡献从0增至22.1%。计算结果表明,对于低配筋UHPC结构,混凝土抗拉贡献应予以考虑。     

大掺量粉煤灰混凝土铺装强度性能的试验研究

高粉煤灰在道路路面铺装用混凝土中的掺入量,对水泥取代率30%以上的大掺量粉煤灰混凝土的强度性能指标进行了测评。重点对影响道路铺装设计的基础参数,混凝土抗弯强度进行了长期检测分析。结果表明:混凝土在掺入了粉煤灰后,28 d后期抗弯强度较普通混凝土增长显著,截止一年期测试结束后仍有增加趋势;其抗弯强度增长率随着粉煤灰掺入量的增大而提高,且高于同种配合条件下粉煤灰混凝土抗压强度的增长率;大掺量粉煤灰混凝土满足材料抗弯强度要求,适用于道路路面铺装工程。     

Experimental study on mechanical properties of a novel micro-steel fiber reinforced magnesium phosphate cement-based concrete

Magnesium phosphate cement (MPC) received increased attention in recent years, but MPC-based concrete is rarely reported. The micro-steel fibers (MSF) were added to MPC-based concrete to enhance its ductility due to the high brittleness in tensile and flexural strength properties of MPC. This paper investigates the effect of MSF volume fraction on the mechanical properties of a new pattern of MPC-based concrete. The temperature development curve, fluidity, cubic compressive strength, modulus of elastic, axial compressive strength, and four-point flexural strength were experimentally studied with 192 specimens, and a scanning electron microscopy (SEM) test was carried out after the specimens were failed. Based on the test results, the correlations between the cubic compressive strength and curing age, the axial and cubic compressive strength of MPC-based concrete were proposed. The results showed that with the increase of MSF volume fraction, the fluidity of fresh MPC-based concrete decreased gradually. MSF had no apparent influence on the compressive strength, while it enhanced the four-point flexural strength of MPC-based concrete. The four-point flexural strength of specimens with MSF volume fraction from 0.25% to 0.75% were 12.3%, 21.1%, 24.6% higher than that of the specimens without MSF, respectively.     

Induction heating of electrically conductive porous asphalt concrete

In this research, an electrically conductive porous asphalt concrete, used for induction heating, was prepared by adding electrically conductive filler (steel fibers and steel wool) to the mixture. The main purpose of this paper is to examine the electrical conductivity and the indirect tensile strength of this conductive porous asphalt concrete and prove that it can be heated via induction heating. It was found that, to make porous asphalt concrete electrically conductive, long steel wool with small diameter is better than short steel fibers with bigger diameter. However, steel fibers with short length and big diameter have better strength reinforcement capability than steel wool with long length and small diameter. It was also proved that conductive porous asphalt concrete containing steel wool can be easily heated via induction heating. Finally, 10% (by volume of bitumen) of steel wool type 000 was proposed as an optimal content in porous asphalt concrete to obtain an optimal conductivity, a good induction heating rate and an acceptable indirect tensile strength. It is expected that the autogenous healing capacity of asphalt concrete will be enhanced with the increase of temperature during induction heating.     

钢纤维对高强混凝土弯曲性能影响的试验研究

选用工程中常用的铣削型、切断弓型、剪切波纹型钢纤维,以不超过2.0%的体积分数掺入高强混凝土中,通过2种尺寸小梁试件的弯曲强度和韧性试验,研究了钢纤维类型及掺量对高强混凝土弯曲强度及变形性能的影响.结果表明:当3种类型钢纤维分别以2.0%的体积分数掺入高强混凝土中时,可使高强混凝土抗裂能力分别提高72%,41%和42%,弯曲极限强度分别提高90%,84%和57%.钢纤维对高强混凝土试件的尺寸效应系数影响显著,试验时应考虑试件尺寸对试验结果的影响.钢纤维高强混凝土弯曲韧度指数及承载力变化系数均随钢纤维体积分数的增大而增大,并大于理想弹塑性材料的相应值.不同类型钢纤维对高强混凝土弯曲强度及弯曲韧性的改善效果不同,可通过改进钢纤维的加工工艺、表面形状等来提高钢纤维对高强混凝土的增强增韧效果.