Reinforcement effect of fiber and deoiled asphalt on high viscosity rubber/SBS modified asphalt mortar

In this paper we investigate the reinforcement mechanism of high viscosity rubber/SBS modified asphalt mortar mixed with fiber （mineral, lignin or carbon fiber） and deoiled asphalt （DOA）. The softening point, penetration and viscosity tests were conducted to characterize the engineering properties of asphalt-fiber mortar. The microstructure of fiber was observed using scanning electron microscopy （SEM）, and the results indicated that fiber can effectively improve the toughness of asphalt matrix through forming a spatial network structure, and then adhesion and stabilization of asphalt binder. The cone penetration test was designed to study the rheological property of fiber modified asphalt. The results indicated that the reinforcement effect increased with fibers and DOA fraction increasing to a certain threshold, and the optimal fiber content was dependent on the fiber type and its length. Fiber content and filler-asphalt ratio had significant effects on the softening point, penetration, viscosity and cone penetration of asphalt mortar.

Effects of Fibers on the Dynamic Properties of Asphalt Mixtures

The dynamic characteristics of fiber-modified asphalt mixture were investigated. Cellulose fiber, polyester fiber and mineral fiber were used as additives for asphalt mixture, and the dosage was 0.3%, 0.3%, 0.4%, respectively. Dynamic modulus test using SuperPave simple performance tester （SPT） was conducted to study the dynamic modulus （E＇） and phase angle （δ） for the control asphalt mixture and fiber-modified ones at various temperatures and frequencies. Experimental results show that all fiber-modified asphalt mixtures have higher dynamic modulus compared with control mixture. The dynamic modulus master curves of each type of asphalt mixtures are determined based on nonlinear least square regression in accordance with the time- temperature superposition theory at a control temperature （21.1℃）. The fatigue parameter E^＊×sinδ and rutting parameter E^＊/sinδ of asphalt mixture are adopted to study the fatigue and rutting-resistance properties, and experimental results indicate that such properties can be improved by fiber additives.

Stabilizing and reinforcing effects of different fibers on asphalt mortar performance

Physical properties of different fibers （mineral, cellulose, or carbon fiber） and their stabilizing and reinforcing effects on asphalt mortar performance were studied. Scanning electron microscopy was used to study the effect of fiber＇s microstructure on asphalt mortar＇s performance. Laboratory tests of mesh-basket draindown and oven heating were designed and performed to evaluate the fibers＇ asphalt absorption and thermostability. A cone penetration test was used to study the flow resistance of fiber-modified asphalt mortar. Results showed that fiber can form a three-dimensional network structure in asphalt, and this network can be retained at high temperature. This network of fibers favors the formation of a thick coating of mastic without asphalt draining down. Cellulose fiber possessed a greater effect on asphalt absorption and sta- bilization than did the other fibers （mineral and carbon fiber）. A dynamic shear rheometer was used to evaluate their rheological properties and rut resistance. Results indicated that fiber can effectively improve the rut and flow resistance of asphalt mortar. However, the bending beam rheometer results demonstrated that the addition of fiber had negative effects on the creep stiffness and creep rate of asphalt mortar.

Rheological Behavior of Basalt Fiber Reinforced Asphalt Mastic

The characters of basalt fiber are analyzed and compared with commonly used fibers. The rheological behaviors of the basalt fiber reinforced asphalt mastic are investigated by the dynamic shear rheological tests and the repeated creep tests. The results show that basalt fiber has excellent reinforced performances, such as high asphalt absorption ratio, low water absorption ratio, high tensile strength, high elastic modulus and high temperature stability. The rutting factor of the fiber reinforced asphalt mastic is higher than the plain asphalt mastic and the reinforced effects are more remarkable under high temperature. The rheological performances of the asphalt mastic demonstrate a good linear relationship between different temperature and loading frequency. The creep stiffness modulus of the asphalt mastic at different loading time can be expressed by power function. Improved Burgers model is used to represent the rheological behaviors of the asphalt mastic with basalt fiber and the model parameters are estimated.

Experimental evaluation on high temperature rheological properties of various fiber modified asphalt binders

High temperature rheological properties of fiber modified asphalt binders and impact of the type and content on such properties were studied.Three types of fiber,including polyester(PET),polyacrylonitrile(PAN) and cellulose(CEL),a control content(0%) and four levels of fiber content(2%,4%,6% and 8% by total asphalt binder mass) were used with asphalt binders.The high temperature rheological properties,consisting of complex modulus(G*) and phase angle δ,were measured using SHRP's dynamic shear rheometer(DSR) between 46-82 ℃.Experimental results indicate that the changes of G* and tan δ of fiber modified asphalt binders with the increase of test temperature tend to slow down,and the temperature susceptibility is improved obviously compared to that of original asphalt binder.Fiber modification results in the increase of rutting parameter(G*/sin δ) at high temperatures,the decrease of temperature susceptibility,and further improved high temperature performance of asphalt binder.An excellent correlation exhibits between fiber content and high temperature performance of asphalt binder.Moreover,fiber type also has different influences on the improvement of G*/sin δ,G*/sin δ of PET and PAN fiber asphalt binders are both higher than that of CEL fiber,but G*/sin δ of CEL fiber is still higher than that of original asphalt.However,there is a critical fiber content when fibers start to interact with each other.Therefore,based on the critical fiber content and economic consideration,the optimum fiber contents for various fiber-modified asphalt binders are obtained.

Effect of fiber types on relevant properties of porous asphalt

The research was conducted to evaluate the effects of cellulose and polyester fibers on the properties of porous asphalt mixes, using the tests of draindown, abrasion, volumetric properties, rutting, and moisture damage. Images of scanning electron microscopy and X-ray computerized tomography were adopted to identify the microstructure of the fiber and inner stone skeleton of porous asphalt. The influence of rutting parameter (G*/sinδ) of asphalt modified by different fibers on the rutting resistance of the mixes was investigated. Based upon MOHR-COULOMB theory, the cohesion and the angle of internal friction of the mixes were derived from both indirect tension and unconfined compression strength. The experimental results indicate that fibers mainly stabilize asphalt binder and thicken asphalt film around aggregates. Furthermore, they result in the improved mechanical strength of porous asphalt mixes at high temperature slightly. From comparison analysis, cellulose fibers appear to perform better than polyester fibers in porous asphalt mixes.

Self-monitoring Application of Asphalt Concrete Containing Graphite and Carbon Fibers

The self-monitoring application of asphalt concrete containing graphite and carbon fibers using indirect tensile test and wheel rolling test were introduced. The experiment results indicate that this kind of pitch-based composite is effective for strain/stress self-monitoring. In the indirect tensile test, for a completely conductive asphalt concrete specimen, the piezoresistivity was very weak and slightly positive, which meant the resistivity increase with the increment of tensile strain at all stress/strain amplitudes, with the gage factor as high as 6. The strain self-sensing ability was superior in the case of higher graphite content. However, when the conductive concrete was embedded into common asphalt concrete specimen as a partial structure function, the piezoresistivity was positive at all stress/strain amplitudes and with the gage factor of 13, which was much higher than that of completely conductive specimen. Thus, the strain self-sensing ability was superior when conductive asphalt concrete was taken in as a partial structure function. In the wheel-rolling test, the piezoresistivity was highly positive. At any stress amplitude, the piezoresistivity was strong, with the gage factor as high as 100, which was higher for a stress amplitude of 0.7 MPa than that of 0.5 MPa.

Relationship between fatigue life of asphalt concrete and polypropylene/polyester fibers using artificial neural network and genetic algorithm

While various kinds of fibers are used to improve the hot mix asphalt(HMA) performance, a few works have been undertaken on the hybrid fiber-reinforced HMA. Therefore, the fatigue life of modified HMA samples using polypropylene and polyester fibers was evaluated and two models namely regression and artificial neural network(ANN) were used to predict the fatigue life based on the fibers parameters. As ANN contains many parameters such as the number of hidden layers which directly influence the prediction accuracy, genetic algorithm(GA) was used to solve optimization problem for ANN. Moreover, the trial and error method was used to optimize the GA parameters such as the population size. The comparison of the results obtained from regression and optimized ANN with GA shows that the two-hidden-layer ANN with two and five neurons in the first and second hidden layers, respectively, can predict the fatigue life of fiber-reinforced HMA with high accuracy(correlation coefficient of 0.96).

Fatigue Property of Basalt Fiber-Modified Asphalt Mixture under Complicated Environment

The fatigue property of asphalt mixtures under complicated environment （low-temperature bending performance, chloride penetration, freezing-thawing cycle and their coupling effect） and the improvement effect for relevant property of basalt fiber-reinforcing asphalt mixture under complicated environment are studied. Two grading types of asphalt mixtures, AC-16I and AC-13I, are chosen, whose optimum asphalt-aggregate ratio and optimum dosage of basalt fiber are determined by the Marshall test. The standard specimens are made firstly, and then the low temperature bending tests of asphalt mixture and basalt fiber-reinforced asphalt mixture under the coupling effect of the chloride erosion and freezing-thawing cycle have been carried out. Finally, the fatigue property tests of asphalt mixture and basalt fiber-reinforced asphalt mixture under complex environment are performed on MTS material testing system. The results indicate that the tensile strength, the maximum curving tensile stress, the curving stiffness modulus, and fatigue properties of asphalt mixture are influenced by the coupling effect of the chloride erosion and freezing-thawing cycle. The low-temperature bending performance and fatigue property of asphalt mixtures under complicated environment can be greatly improved by adding moderate basalt fiber. The dense gradation asphalt mixture possesses stronger ability to resist adverse environmental effects under the same condition.

Rheological properties of asphalt mixtures containing various fibers

Rheological characteristics of fiber-modified asphalt mixture were investigated.Cellulous fiber,polyester fiber and mineral fiber were used as additives for asphalt mixture,and the dosages were 0.3%,0.3%,0.4%,respectively.Dynamic modulus test using superpave simple performance tester(SPT) was adopted to study the dynamic modulus and phase angle for the control mixture and fiber-modified ones at various temperatures and frequencies.Test results show that the rheological properties can be improved significantly by the addition of various fibers.The dynamic modulus increases with the increase of frequency,and the phase angle decreases with the increase of frequency.When various fibers are used,the dynamic modulus increases and phase angle decreases at each frequency.This indicates that the stiffness and the elastic portion of fiber-modified asphalt mixtures can be enhanced when various fibers are used,which results in the change of viscoelastic properties of mixtures.The creep test results show that the total strain and the permanent strain of asphalt mixtures during load-unload cycle can be significantly reduced,which results in the improvement of resistance to permanent deformation for asphalt mixtures containing various fiber additives.The Burgers model can be employed effectively to illustrate the rheological properties of fiber modified asphalt mixtures.

不同纤维增韧环氧沥青混合料性能

为探究不同种类纤维(玄武岩纤维、玻璃纤维和聚酯纤维)对环氧沥青混合料抗开裂和耐疲劳性能的提升效果,在混合料配比设计的基础上,采用车辙试验、低温小梁试验、浸水马歇尔试验以及冻融劈裂试验等对其进行路用性能测试。通过冲击试验,探究纤维对环氧沥青混合料的三种增韧效果:在环氧沥青混合料中添加纤维可以不同程度提高其路用性能;低温性能再加入纤维后,提升效果较为明显;添加玄武岩纤维路用性能优于玻璃纤维和聚酯纤维。

植物茎秆纤维结构及其沥青胶浆流变特性

本研究将棉秸秆、玉米秸秆、废竹、蔗渣制备出植物纤维。采用相关分析和试验评价各植物纤维沥青胶浆的物化特性。结果表明:在微米级结构层面上,棉秸秆纤维、玉米秸秆纤维和蔗渣纤维呈现出空腔管状结构,竹纤维、木质素纤维为实心结构;各纤维的化学成分存在差异,且影响其热解速率。掺入纤维后,沥青胶浆高温稳定性改善明显,在初始试验温度下各纤维沥青胶浆车辙因子提升了23.8%~75.7%,弹性恢复率提高了9.4%~18.5%。掺加纤维后,沥青胶浆低温抗裂性能略有下降,但植物纤维类型对其影响并不显著。

导电作用下碳纳米管-碳纤维沥青混合料的自愈合研究

针对沥青路面因车辆荷载、温度荷载等带来的裂缝扩展问题,采用碳纳米管-碳纤维制备导电沥青混合料,进行电-热愈合试验,分析沥青混合料裂缝愈合前后的电阻率值、断裂能、极限承载力和微观结构,研究导电作用下碳纳米管-碳纤维沥青混合料的自愈合水平。结果表明,碳纳米管掺量在0.5%,1.0%时可以显著提高沥青混合料的自愈合能力;导电沥青混合料的自愈合水平与愈合前、后电阻率比值存在Sine函数关系;在50℃、20 min环境下小梁试件的极限承载力和断裂应变能得到最大限度的恢复。

冻融循环下纤维增韧型环氧沥青混合料损伤演化

为了研究季冻区玄武岩纤维增韧型环氧沥青混合料的性能劣化规律,首先,通过沥青黏温曲线分析和直接拉伸性能测试,初步确定纤维长度和掺量,并对比纤维改性前后的环氧沥青混合料(EAC)的路用性能,进一步确定最佳纤维长度和掺量,形成玄武岩纤维增韧型环氧沥青混合料(FEAC)的设计流程。随后,进行低温弯曲试验,测试不同冻融损伤程度沥青混合料的弯拉强度、弯拉应变、弯曲劲度模量和弯曲应变能密度。研究结果表明:6%(质量分数)玄武岩纤维掺量的FEAC具有较好的高温性能和低温抗裂性,并保持了与EAC相当的水稳定性。随着冻融循环次数的增加,EAC和FEAC的弯拉强度、弯曲劲度模量和弯曲应变能密度逐渐降低,而弯拉应变的变化趋势则与之相反。相较于EAC,FEAC表现出更高的弯拉强度、弯拉应变和较低的弯曲劲度模量。FEAC和EAC的弯曲应变能密度冻融损伤变化均呈现明显的3段式性能下降。S形逻辑函数能够有效地描述冻融循环的损伤变化规律,其中模型参数a、k和x c显示出玄武岩纤维对延缓环氧沥青混合料冻融损伤增长具有积极作用。

玄武岩纤维对聚氨酯改性沥青混合料水稳定性提升研究

为解决聚氨酯改性沥青混合料水稳定性不良的缺陷,通过浸水马歇尔试验、冻融循环条件下的劈裂试验、低温弯曲试验,研究不同玄武岩纤维掺量下聚氨酯改性沥青混合料的抗水损害能力。结果表明:在冻融循环作用下,玄武岩纤维降低了沥青混合料水损作用造成的空隙率变化,增强了沥青间的粘附性,当纤维掺量为0.3%时,其提升作用最强,残留稳定度和劈裂强度比分别提升了10.9%、32.3%,有效降低了冻融循环引起的弯拉强度与弯拉应变的下降速率,增强沥青混合料之间的粘结力,聚氨酯沥青混合料的水稳定性能得到提高。

直流电下导电沥青混凝土非线性导电行为研究

导电沥青混凝土中非线性导电行为的导电机制尚不明确。基于实验室制备的碳纤维(CF)–碳纤维粉(CFP)导电沥青混凝土,通过测试外力场对导电沥青混凝土电阻率的关系,结合线性随机电阻网络模型、动态随机电阻网络模型和非线性随机动态电阻器模型,研究导电沥青混凝土非线性导电行为,明确非线性导电行为的导电机制。结果表明:随着碳纤维掺量、油石比和压力的增加,电阻率呈现明显且相似的非线性下降趋势,其中,碳纤维粉掺量的增加导致电阻率先下降后上升;不同掺量的导电沥青混凝土伏安特性曲线均呈现非线性特征;在强电场作用下,导电相材料本身的非线性导电行为和绝缘态部分载流子通道导通引起的非线性导电行为共同导致了碳纤维–碳纤维粉导电沥青混凝土的非线性导电行为,并证明在电场作用下导电沥青混凝土存在隧道效应。

木质素纤维增强型透水性沥青稳定碎石疲劳研究

为提高增强型透水性沥青稳定碎石(asphalt treated permeable base,ATPB)的抗裂性能和耐久性,以SBS改性沥青为胶结材料配制掺入木质素纤维的ATPB混合料——纤维增强型透水性沥青稳定碎石(fiber asphalt treated permeable base,FATPB),并制作不同木质素纤维掺量的FATPB-25梁式试件进行不同应力比下的四点弯曲疲劳试验。将木质素纤维掺量为0.3%的FATPB-25与普通的AC-25、ATB-25的疲劳性能进行对比分析,探究考虑失效概率的应力比与纤维掺量对疲劳寿命的影响。研究结果表明:纤维掺量为0.3%的FATPB-25的抗疲劳性能明显比普通的AC-25和ATB-25的高,可用作耐久型的透水性下面层或柔性基层;通过包含失效概率的双对数方程可以对FATPB-25的疲劳寿命进行预测。

玄武岩纤维直径对其沥青混合料性能的影响

为研究玄武岩纤维直径对其沥青混合料性能的影响,设计制备掺有7、16、25μm这3种直径玄武岩纤维的AC-13沥青混合料,采用车辙试验、单轴贯入试验、低温小梁试验、浸水马歇尔试验及冻融劈裂试验测试其路用性能,通过理想开裂试验、动态模量试验测试其力学性能。结果表明:玄武岩纤维直径对沥青混合料各项性能指标的改善效果影响较大,沥青混合料的最佳油石比随着玄武岩纤维直径的减小而略有升高;由于相同纤维掺量和纤维长度条件下,纤维直径越小,其根数越多,在沥青混合料中形成的筋体网络越丰富,故7μm直径玄武岩纤维对沥青混合料的高低频动态模量、中低温抗裂性能以及高温抗变形能力改善效果最为显著。研究结论可为沥青混合料用玄武岩纤维的精细化设计提供参考。

秸秆纤维沥青混合料路用性能研究进展

介绍了目前常用的几种秸秆预处理方式,总结了植物秸秆纤维沥青混合料在道路工程中的应用及研究进展,指出了秸秆纤维沥青混合料在应用过程中存在的现实问题,并对其应用前景进行了展望,为今后研究提供方向。对秸秆纤维沥青混合料的应用具有重要的实际意义。

KH-560处理时间对PAN基碳纤维沥青复合材料性能的影响

以硅烷偶联剂KH-560改性的PAN基碳纤维为添加材料,制备了不同KH-560处理时间的PAN基碳纤维沥青复合材料。通过车辙试验、冻融劈裂试验和间接拉伸疲劳试验等研究了KH-560处理时间对沥青复合材料高温稳定性、低温抗裂性、水稳定性、疲劳性能和吸声性能的影响。结果表明,经过KH-560处理后的PAN基碳纤维表面的粗糙度增加,当KH-560处理时间为2 h时,纤维凹槽较深,与沥青的作用面积增大,纤维在复合材料中形成了致密网状结构,增强了PAN基碳纤维复合材料的稳定性。当KH-560处理时间为2 h时,PAN基碳纤维沥青复合材料的高温性能、低温抗裂性能、水稳定性和疲劳性能均最佳,此时其45和60 min的变形量、破坏劲度模量达到最小值,分别为1.851和2.117 mm、2 201 MPa;动稳定度、劈裂抗拉强度和破坏拉伸应变达到最大值,分别为3 077次/mm、4.6 MPa和3479με。在250~1 000 Hz和1 000~1 600 Hz范围内,当KH-560处理时间为2 h时,沥青复合材料的平均吸声系数均达到最大值,分别为0.116和0.127,较未处理的沥青复合材料分别提高了39.76%和45.98%,吸声降噪性能提升显著。综上可知,KH-560的最佳处理时间为2 h。