混杂纤维增强水泥基复合材料的力学性能

研究了化学改性聚丙烯（PP）纤维以及掺加聚丙烯纤维和芳纶纤维混杂比例和混杂效应对水泥基复合材料力学性能的影响,并构建了纤维增强水泥砂浆界面层的物理模型,描述了纤维对水泥砂浆的增强机制。实验表明,聚丙烯纤维经改性后使水泥砂浆前期抗折强度明显提高,聚丙烯纤维和芳纶纤维的混杂使水泥砂浆的后期抗折强度显著提高。改性聚丙烯纤维掺加体积分数为0.56%,芳纶纤维的体积分数为0.24%时,混杂纤维增强水泥砂浆试样较空白试样,3天、28天抗折强度分别提高了18.48%、31.17%,3天、28天抗压强度分别提高了7.16%、5.19%。     

玄武岩纤维对水泥砂浆性能及水泥石微观结构的影响

以聚丙烯纤维为对比研究了新型材料玄武岩纤维（BF）对水泥砂浆的抗压、抗折强度和干缩的影响,并采用XRD、SEM及MIP现代检测技术对纤维微观作用机理进行了分析。结果表明：玄武岩连续纤维具有替代聚丙烯纤维的可行性;BF的加入提高了水泥砂浆的早期强度,但使28d强度有所降低;对早期砂浆的收缩有明显的改善效果,但28d以后对砂浆收缩的影响作用不显著;微观分析显示早期水化浆体中由于纤维-水泥石界面结合紧密和纤维乱向作用阻止了裂缝的引发与扩展,提高了水泥基材料早期力学性能。28d掺加纤维的水泥浆体在纤维-水泥石界面上产生弱界面,界面的弱化与总空隙率增加的共同作用导致掺加纤维水泥砂浆的长期力学性能下降。     

PVA及玄武岩纤维对水泥基复合材料力学性能的影响

在水泥基复合材料中掺入适量纤维可显著改善其物理力学性能,但有机-无机混杂纤维对水泥材料性能的影响目前研究不多。进行了单掺PVA纤维、单掺玄武岩纤维以及复掺两种纤维的水泥基复合材料力学性能实验。结果表明,单掺1.6%(体积分数)的短PVA纤维时,水泥基复合材料的抗折强度降低7%、抗压强度提升31%、折压比降低24%;单掺0.3%(体积分数)的短玄武岩纤维时,水泥基复合材料的抗折强度降低8%、抗压强度提升15.7%、折压比降低20%;掺0.3%(体积分数)短玄武岩纤维和0.5%(体积分数)短PVA纤维时,水泥基复合材料的抗折强度几乎无影响,抗压强度显著提升,折压比相对减少,其综合性能最优。     

短切玄武岩纤维混凝土力学性能试验与分析

为了研究短切玄武岩纤维掺量变化对混凝土基本力学性能的影响,对6种不同体积掺量的短切玄武岩纤维混凝土(BFRC)分别进行立方体抗压、轴心抗压、劈裂抗拉、抗折试验;基于试验结果,通过BP(Back Propagation)神经网路强度预测模型的构建,对附加纤维掺量的混凝土进行强度训练及预测。试验实测数据表明:掺入短切玄武岩纤维对混凝土早期抗压强度的发展有着延缓作用;当纤维掺量为0.1%时,抗压强度达到峰值。随着纤维掺量的增加,劈拉强度增幅较大,抗折强度保持上升趋势。通过BP神经网络的训练及发展趋势预测,结果表明:当纤维体积掺量为0.1%时,抗压强度达到最大值;劈拉强度与抗折强度则随着纤维掺量的增加而持续增大。基于试验数据及预测结果,得出短切玄武岩纤维的最佳体积掺量。     

微胶囊-玄武岩纤维/水泥复合材料的力学性能

以水泥、玄武岩纤维和脲醛/环氧树脂微胶囊为主要材料,制备水泥基复合材料标准试样,研究纤维掺量、纤维长度、微胶囊质量分数、水灰质量比和养护龄期对复合材料抗折强度和抗压强度的影响,利用正交实验确定微胶囊-玄武岩纤维/水泥自修复复合材料力学性能的最优配比。实验结果表明：抗折强度随着纤维掺量的增加而增加,抗压强度随着纤维掺量增加而减小;随着纤维长度的增加,抗折强度略有增加,抗压强度略有降低;抗折强度随着微胶囊质量分数的增加呈现出先增加后减小的趋势,而抗压强度则呈现下降趋势;抗折强度与抗压强度随养护龄期的增加而呈增加的趋势;材料经损伤后修复,抗折强度修复率为117%,恢复率为103%,抗压强度修复率为71%,恢复率为97%。     

玄武岩纤维混凝土的动态力学性能

采用Φ100 mm分离式霍普金森压杆 (SHPB) 试验装置研究了不同纤维体积掺量的玄武岩纤维混凝土在不同应变率下的冲击压缩力学性能 , 并对试验的有效性进行了分析。结果表明: 玄武岩纤维混凝土的动态强度增长因子与平均应变率的对数近似呈线性关系 , 强度与变形能力随平均应变率的提高而线性增加 , 体现了很强的应变率相关性 ; 纤维体积掺量为 0. 1 %的玄武岩纤维混凝土较素混凝土的动态抗压强度提高了 26 % , 变形能力提高了 14 %; 纤维体积掺量分别为 0. 2 %、 0. 3 %的玄武岩纤维混凝土的动态抗压强度比素混凝土高出 25 %左右 , 而变形能力较素混凝土无明显优势 ; 在玄武岩纤维混凝土的 SHPB试验中 , 试件破坏时刻为 123. 3～239.μ45 s , 近似恒应变率加载时间比例约为 62 % , 且应变率曲线的波动范围控制在 23 %左右 , 能够较好地满足应力均匀分布及恒应变率加载要求 , 表明 SHPB试验结果可靠。      

纤维增强活性粉末混凝土高温力学性能的实验研究

研究了钢纤维、聚丙烯纤维和PVA纤维的不同掺量以及纤维复掺在90℃、200℃和400℃高温养护时活性粉末混凝土的力学性能和微观结构.结果表明,200℃高温养护,单掺钢纤维时,RPC的抗折强度与90℃的相近,但抗压强度提高,迭210.2MPa;单掺聚丙烯纤雏时,由于其高温熔解,形成三维网络结构,与RPC融为一体,抗压强度显著提高,当掺量为1.5%(体积分数)时,强度达242.6MPa.纤维复掺时抗折强度与钢纤维相近,但抗压强度有所提高,200℃养护时达265 MPa.400℃养护时,随水胶比降低,强度进一步增大,当水胶比为0.12时,抗压强度达333.4MPa.     

纤维对薄层砂浆早期塑性收缩的影响

提出了一种利用视频显微镜技术来测量薄层砂浆早期塑性收缩的新方法,研究了纤维种类、聚丙烯纤维掺量及长度、纤维几何形态对薄层砂浆早期塑性收缩的影响。结果表明随着聚丙烯纤维掺量的增加,砂浆的塑性收缩值有所减小,说明聚丙烯纤维的掺入可以有效地抑制砂浆的塑性收缩;3mm、12mm长的聚丙烯纤维较6mm、9mm长的聚丙烯纤维对砂浆塑性收缩的抑制作用大;在抑制砂浆收缩性能上圆形截面纤维优于Y形截面纤维;掺聚丙烯纤维试样的塑性收缩较掺玄武岩纤维试样小,但两者的差距不大。     

玄武岩纤维掺量对大空隙沥青混合料路用性能的影响

为研究掺加玄武岩纤维的大空隙沥青混合料的路用性能,通过析漏试验和马歇尔稳定度试验确定了0％ ～0.5％ 六种玄武岩纤维掺量的最佳油石比.研究发现,当纤维掺量0.3％、油石比为4.9％ 时对应的稳定度值最大,析漏损失最少;掺加玄武岩纤维可以有效的提高大空隙沥青混合料的高温性能、水稳定性、低温抗裂性能和抗压强度,且玄武岩纤维掺量为0.3％ 时,各项指标达到最优.     

改性水稻秸秆对水泥基材料性能影响研究

为了减少农作物纤维废弃造成的污染,研究了利用植物纤维制备建筑材料的工艺,首先采用碱煮法对植物纤维进行改性,然后将其分别与聚丙烯纤维按照不同的比例加入到水泥净浆中进行比较,结果表明:植物纤维在水泥净浆中的分散比加入聚丙烯纤维均匀,经过改性后的秸秆纤维对水泥凝结硬化时间无明显影响,随掺量增加,水泥净浆的抗折强度呈先增后减趋势,且在掺量为4.5%时最高,与未掺纤维的参照组相比抗折强度提高了11%,抗压强度降低了近24%。并将其掺入砂浆中,砂浆抗干缩性能得到改善,植物纤维掺量为6.0%时砂浆干燥收缩值比基准组下降了37%,在本研究掺量条件下,与加入聚丙烯纤维相比,加入秸秆纤维对水泥净浆的抗折强度和抗压强度影响较小,原因在于其分散性更好。     

Special manufacturing and characteristics of basalt fiber reinforced hybrid polypropylene composites: Mechanical properties and acoustic emission study

Basalt fiber reinforced, polypropylene matrix hybrid composites were manufactured in the process of carding, needle-punching and pressing. Hemp, glass and carbon fibers were applied besides basalt fiber in these composites. In order to achieve a sufficient interfacial adhesion, the fibers were treated with the reaction mixture of maleic acid anhydride and sunflower oil. The hybrid effect in these composites was examined as a function of fiber content and fiber combination. The strength properties of hybrid composites improved owing to surface treatment and this was proven by mechanical tests and microscopic analysis, as well. Acoustic emission methods revealed that there is a correlation between the physical parameters of sound waves that occurred during failure and the mechanical properties.     

Use of biochar-coated polypropylene fibers for carbon sequestration and physical improvement of mortar

Biochar is widely recognized as an effective material for sequestration of carbon dioxide. The possibility of using it as a coating material on polypropylene fibers to improve mechanical properties and permeability mortar is explored in this study. Effectiveness of two types of biochar – fresh biochar and biochar saturated with carbon dioxide prior to application as coating – on compressive and flexural strength, post-cracking behavior and permeability of mortar is studied. The biochar used was derived from mixed wood saw dust by pyrolysis at 300 °C. Experimental results show that application of fresh biochar coating offer significant improvement in compressive strength and flexural strength of mortar. Residual strength and post-cracking ductility of mortar with biochar coated fibers is found to be higher than control samples, although fresh biochar coating offers the best performance. Mortar with polypropylene fibers coated with fresh biochar shows higher impermeability, compared to reference samples and mortar with saturated biochar coated fibers. The findings suggest that biochar coating could be a potential solution to improve properties of fiber reinforced cementitious composites that also promotes waste recycling and carbon sequestration.     

纤维/高强混凝土抗冻性能试验

通过纤维/高强混凝土快速冻融循环试验,从试件外观损伤形态、相对动弹性模量、抗冻等级、抗冻耐久性指数角度,研究了不同纤维体积分数的玄武岩纤维、纤维素纤维和不同纤维长度的玄武岩纤维对C60高强混凝土抗冻性能的影响。结果表明,加入玄武岩或纤维素纤维可改善C60高强混凝土的外观剥落损伤程度。C60高强混凝土的抗冻性均随玄武岩纤维（长度为18 mm）和纤维素纤维体积分数的增大而提高,在体积分数0.10vol%~0.20vol%内,前者的提高程度远大于后者,玄武岩纤维/高强混凝土能在更严酷的寒冷环境中满足更久的使用时间。玄武岩纤维长度的改变对C60高强混凝土的抗冻性影响较大,相对于18 mm长度,6 mm和30 mm长度的玄武岩纤维对C60高强混凝土抗冻性能改善作用很有限。      

纤维早强混凝土不同龄期的动态力学性能

早强混凝土在抢修、抢建及特殊工况中应用较广,其早期动态力学性能对其正常使用、安全评估等具有重要意义。制备了纤维体积掺量为0%、0.1%、0.2%和0.3%的玄武岩纤维早强混凝土,利用Φ100mm分离式霍普金森压杆(SHPB)装置对其1d、7d和28d的动力学性能展开研究。结果表明:玄武岩纤维早强混凝土动态力学性能具有显著的应变率强化效应,动态压缩强度和比能量吸收均随着应变的升高而显著增强;随着龄期的增加,早强混凝土的动态抗压强度和比能量吸收均增大,且均表现出前期增长迅速,后期增长缓慢的规律,在对比欧洲混凝土协会(CEB)等给出的应变率增长因子(DIF)计算公式后,提出了基于龄期增长的DIF计算模型;掺入玄武岩纤维对早强混凝土不同龄期的动态抗压强度和吸能性能均有不同程度的提升,纤维掺量越大,性能改善越明显。     

The spalling strength of ultra-fiber reinforced cement mortar

This is a research report about the effects of polypropylene fiber and wood fiber on mechanical properties of cement mortar. First, using advanced Hopkinson pressure bar (HPB) tests, it investigates the wave propagation in cement mortar comprised polypropylene fiber and wood fiber. Second, according to the experiment, the spallation position is recorded by high-speed camera. Thirdly, it analyzes the test data of ultra-fiber reinforced and common cement mortar by numerical method. Finally, it deduces the spalling strength of all kinds of cement mortar by integrating all experimental data above. The results indicate that, compared with the strength of common cement mortar, the dynamic spalling strength of ultra-fiber especially that of the polypropylene fiber reinforced cement mortar increases evidently. However, adding too much fibers will deteriorate the dynamic spalling strength of cement mortar specimen. So the results will provide a test basis for further optimizing performance of cement mortar.     

混杂比对碳纤维-玄武岩纤维混杂增强环氧树脂基复合材料弯曲性能的影响

将玄武岩纤维置于混杂铺层的压缩侧,研究了碳纤维-玄武岩纤维混杂增强环氧树脂基复合材料的弯曲性能及混杂比对其弯曲性能的影响。通过对试样进行三点弯曲试验得到了材料的弯曲性能,并通过扫描电子显微镜观察材料的失效模式。与纯碳纤维增强环氧树脂基复合材料相比,当混杂比为16.7%和33.3%时,混杂复合材料的弯曲强度明显提升,弯曲强度分别提高12.4%和15.2%,但是其弯曲模量随着混杂比的提升而降低。混杂后的材料及玄武岩纤维增强环氧树脂基复合材料的失效位移都高于碳纤维增强环氧树脂基复合材料,断裂韧性明显提升。从侧面观察可以发现不同铺层在压缩侧、拉伸侧和中间层有不同的失效形式。      

Thermo-mechanical properties of fiber reinforced raw perlite concrete

The effect of hooked steel, wavy steel and polypropylene fibers on the thermo-mechanical properties of raw perlite aggregate concrete was investigated. In order to determine the effect of fiber ratio on the thermo-mechanical properties of 100% raw perlite concrete, 0.25%, 0.75%, 1.25%, and 1.75% fiber ratios were used by volume of the sample and also, 350 kg/m³ cement dosage and 3 ± 1 cm slump were used. When compared to the control sample that contains no fiber, (1) with the increase of steel fiber ratio in the mixtures thermal conductivity (TC), unit weight, splitting-tensile strength, and flexural strength of concretes increased, (2) with the increase of steel fiber ratio in the mixtures compressive strength of concretes decreased, and (3) with the increase of polypropylene fiber ratio in the mixtures TC, unit weight, compressive strength, splitting-tensile strength, and flexural strength of concretes decreased.     

Analysis of the strain-rate behavior of a basalt fiber reinforced natural hydraulic mortar

Fiber reinforced inorganic materials, such as concrete or mortars are expected to present good mechanical properties under high dynamic loading conditions, such as those induced by earthquakes. Furthermore, basalt fibers, which are being increasingly investigated in structural applications, are also expected to present good performance under high strain-rate conditions.This paper presents the results of a dynamic characterization of a basalt fiber reinforced natural hydraulic mortar, in order to verify its capability to withstand high dynamic loading conditions. In particular, the reinforced mortar was morphologically characterized by SEM and mercury intrusion porosimetry; then, quasi-static flexural and tensile tests were conducted. Finally, dynamic tensile failure tests were carried out at medium and high strain-rates, using a Hydropneumatic machine and a Modified Hopkinson bar apparatus, respectively. The results were elaborated to derive Dynamic Increase Factors for the tensile strength.The fiber addition leads to a bridge action effect, and consequently to a more ductile behavior and higher toughness of the fiber reinforced mortar compared to a plain mortar. In addition, the fiber reinforced mortar appears to be highly strain-rate sensitive, as the tensile strength DIF increased up to 5.1, for a high strain-rate of about 10² s⁻¹.