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.     

再生沥青混合料的黏弹性动态响应及疲劳性能

为了分析废旧沥青路面材料(RAP)对热拌沥青混合料的黏弹性动态响应及疲劳性能的影响,设计了不同RAP掺量(10%、20%、30%)及不同级配(AC-13和AC-16)的沥青混合料,采用沥青混合料性能试验仪(AMPT)在不同温度和加载频率下的动态模量,之后采用时间-温度等效原理,确定了不同沥青混合料的动态模量主曲线;并对不同沥青混合料进行了单轴拉伸疲劳试验,通过简化的黏弹性连续损伤模型(S-VECD),确定了不同级配、不同RAP含量的沥青混合料的损伤特征曲线(C-S),及基于能量的疲劳失效标准与疲劳加载次数之间的关系(GR-Nf).结果表明:沥青混合料的动态模量随着温度的升高、加载频率的降低而降低,温度越低、频率越高,沥青混合料越接近弹性体,反之越接近黏性体;从不同级配的沥青混合料的动态模量主曲线中可以看出,RAP含量越高,其动态模量越高,但总体来看相差不大.疲劳试验及分析表明:RAP含量较高时,其疲劳性能较低,表明其应力松弛能力较差,因此应更加关注再生沥青混合料的抗疲劳性能.     

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.     

应力吸收层沥青混合料的力学性能评价

为评价应力吸收层沥青混合料的力学性能,在室内试验测定沥青材料技术性能的基础上,基于马歇尔设计法,针对齐鲁70#沥青、稳定型橡胶改性沥青及应力吸收沥青设计了三种砂粒式应力吸收层沥青混合料。通过基本性能试验系统测定应力吸收层沥青混合料的动态模量,并建立动态模量和相位角的主曲线,主要探索了以齐鲁70#、稳定型橡胶改性沥青及应力吸收沥青作为胶结料的应力吸收层沥青混合料的力学特性。结果表明,稳定型橡胶改性沥青和应力吸收沥青作为胶结料用于应力吸收层均有良好的力学性能。     

纤维对沥青混合料稳定性的影响研究

纤维在沥青混合料中的作用效果一直受到人们的关注,文中针对这一问题选用了四类纤维,分别采用普通沥青和改性沥青,选用沥青混合料AC-16I型,客观的分析了纤维沥青混合料的高温稳定性、低温稳定性、水稳定性和抗疲劳性能等路用性能。研究表明:纤维加入后,最佳沥青用量、空隙率、矿料间隙率、稳定度和流值均有不同程度增加,而密度下降;高温稳定性、低温抗裂性能、抗疲劳性能和耐水害性能等路用性能均有一定改善;其中高温和抗疲劳性能的改善最为显著,并且添加纤维的普通沥青混合料性能达到甚至超过改性沥青的性能,改性沥青再添加纤维性能将更好。     

Experimental Study on Young′s Modulus of Concrete

Ｃｏｎｃｒｅｔｅｃｏｍｐｏｎｅｎｔｉｓｗｉｄｅｌｙｕｓｅｄｉｎｉｎｄｕｓｔｒｉａｌａｎｄｃｉｖｉｌｃｏｎｓｔｒｕｃｔｉｏｎｓ .Ｙｏｕｎｇ′ｓｍｏｄｕｌｕｓｉｓａｂｏｕｔｉｔｓｂａｓｉｃｍｅｃｈａｎｉｃｓｃｈａｒａｃｔｅｒｉｓｔｉｃ ,ｗｈｉｃｈｉｓｉｎｄｉｓｐｅｎｓａｂｌｅａｎｄｉｍ ｐｏｒｔａｎｔｆｏｒｓｔｕｄｙｓｕｃｈｐｒｏｂｌｅｍｓａｓｄｅｆｏｒｍａｔｉｏｎ ,ｅｘｐｌｏｓｉｖｅｗａｖｅａｎｄｅａｒｔｈｑｕａｋｅｗａｖｅ .ＴｈｅｒｅｌａｔｉｏｎｂｅｔｗｅｅｎＹｏｕｎｇ′ｓｍｏｄｕｌｕｓａｎｄｔ…     

混杂纤维沥青混合料低温抗裂性的研究

为提高沥青混凝土的低温性能,将聚酯纤维、聚丙烯腈纤维、木质素纤维复合掺入SMA沥青混合料中做正交分析,通过劈裂试验和小梁弯曲试验,对沥青混合料低温抗裂性能进行研究.试验表明:混杂纤维沥青混合料的低温性能明显高于仅加入木质素纤维;通过极差分析和方差分析,当聚丙烯腈纤维、聚酯纤维、木质素纤维掺量分别为0.2％,0.2％,0...     

Temperature dependency of dynamic mechanical properties of cement asphalt paste by DMTA method

We investigated the temperature dependency of the dynamic mechanical properties of cement asphalt paste by the dynamic mechanical thermal analysis(DMTA) method. The experimental results show that the dynamic mechanical properties of cement asphalt pastes are sensitive to temperature due to the inclusion of asphalt, and may go through different states within a temperature range of-40 ℃ to 60 ℃, which is different from that of pure cement and asphalt. As the temperature of the cement asphalt paste increases, a considerable change of dynamic mechanical properties, including storage modulus(E'), loss modulus(E') and loss factor(tand) is observed. Moreover, the influence of asphalt to cement(A/C) ratio on the temperature sensitivity of the dynamic mechanical properties of cement asphalt composites was investigated. The temperature dependency of cement asphalt composites is ascribed to the temperature dependency of the asphalt and its interaction with cement paste. A simple fractional model is proposed to describe the viscoelastic behavior of cement asphalt composites.     

海泡石/玄武岩纤维复合沥青混合料性能研究

从海泡石纤维和改性玄武岩纤维的微观结构特性出发，进行海泡石／玄武岩复合纤维增强沥青复合材料的制备．通过路用性能试验，研究了海泡石纤维和改性玄武岩纤维对沥青混合料性能的影响以及结合机理．结果表明，添加适当量海泡石和改性玄武岩纤维可以制备性能优良的纤维复合沥青混合料．海泡石纤维对沥青表现极强吸持能力，有效调节沥青质与胶浆的含量．改性玄武岩纤维在沥青中主要起加固和改善混合料的作用．两种纤维的添加，使沥青混合料的高温变形性、水稳定性、低温抗裂性和抗疲劳性等显著提高。     

硫磺改性沥青混合料基本性能的研究

为考察硫磺改性沥青混合料的路用性能,选取AC-13和AC-20两种混合料类型、4种不同的硫磺掺量（硫磺占硫磺改性沥青胶结料的质量百分比分别为0%、30%、35%、40%）作为对比,采用浸水马歇尔试验、冻融劈裂试验、汉堡车辙试验测试了其水稳定性能,采用车辙试验、三点小梁弯曲试验和Overlay Tester试验分别测试了其高温性能、低温性能与疲劳性能,采用动态模量试验获得了其力学参数. 结果表明: 添加质量分数为30%硫磺后,AC-13和AC-20沥青混合料动稳定度分别提高了18%和26%,疲劳开裂性能有所提高, 低温性能没有明显改变. 添加不同质量分数的硫磺,沥青混合料的水稳定性能明显降低,其中AC-13沥青混合料在添加40%硫磺时冻融劈裂强度比下降达22%. 动态模量测试表明硫磺改性沥青混合料与普通沥青混合料动态模量变化趋势相同,但-10 ℃~54 ℃温度区间较普通沥青混合料动态模量要高.     

稳定型橡胶改性沥青混合料动态模量研究

为研究稳定型橡胶改性沥青混合料的力学性能,利用基本性能试验系统进行了动态模量试验。文章分析了温度和加载频率对动态模量和相位角的影响规律,基于时间-温度置换原理确定了动态模量主曲线和移位因子,并采用修正的Witczak模型预估稳定型橡胶改性沥青混合料的动态模量。结果表明：稳定型橡胶改性沥青混合料具有更小的低温模量和更大的高温模量;修正的Witczak预估模型可以较好地预测稳定型橡胶改性沥青混合料的动态模量值。     

Modularized dry coal beneficiation technique based on gas-solid fluidized bed

A 40–60 t/h modularized dry coal beneficiation process with a novel method to control the bed was designed around a gas-solid fluidized bed separator. Furthermore, the hydrodynamics of medium-solids consisting of wide-size-range magnetite powder (0.3–0.06 mm) and <1 mm fine coal were numerically studied. The simulation results show that the fluidization performance of the wide-size-range medium-solid bed is good. The separation performance of the modularized system was then investigated in detail using a mixture of <0.3 mm magnetite powder (mass fraction of 0.3–0.06 mm particles is 91.38 %) and <1 mm fine coal as solid media. The experimental results show that at separation densities of 1.33 g/cm³ or 1.61 g/cm³, 50–6 mm coal can be separated effectively with probable error, E, values of 0.05 g/cm³ and 0.06 g/cm³, respectively. This technique is beneficial for saving water resources and for the clean utilization of coal.     

Effect of thermal crosslink conditions on dynamic mechanical behaviors of flexible epoxy

The dynamic mechanical behavior of a new kind of flexible epoxy FE-1,which was crosslinked under four different thermal crosslink conditions,was studied.Dynamic mechanical measurement was carried out from 10 ℃ to 120 ℃,and loss factor,tan δ and the storagemodulus as functions of temperature were presented under five different frequencies of 0.1 Hz, 1 Hz,5 Hz,50 Hz and 100 Hz. The experimental results show that temperature has dramatic effects on the dynamic mechanical behavior of flexible epoxy. Compared with other common available epoxy, the flexible epoxy has higher loss factor over broad frequency and common temperature range. Activation energy corresponding to glass transition process of FE-1 was calculated from the temperature corresponding to tan 8 rna~ values, obtained at different measurement frequencies. The maximum value of loss factor is 0.75 and the Tg varies from 6 ℃ to 50 ℃, indicating the flexible epoxy can be used as damping polymer materials at common temperature or frequency range.     

沥青混合料抗压回弹模量与动态模量比较分析

分析了动态模量和抗压回弹模量在反映沥青混合料行为特性方面的优缺点，并对SMA13、Superpave20和Superpav也53种沥青混合料进行了不同条件下的动态模量和抗压回弹模量试验。结果表明，动态模量能综合反映温度和频率的影响，能更合理地反映沥青混合料的特性。相同温度下，抗压回弹模量对应于频率较低时的动态模量，对应频率大约在0．01—0．1Hz之间。由于抗压回弹模量试验中会引起试件的破坏，而破坏特性受混合料类型和温度的影响，所以不能确定唯一的对应频率。     

Effect of Silicone Maintenance Materials on Thermal Aging Resistance of Asphalt Mixture

Early water damage of asphalt pavement is one of the major types of destruction,so taking maintenance on asphalt pavement at the proper time is necessary. Many new maintenance materials and methods are in use nowadays to prevent pavement from water damage and skidding. This paper aims to study the effects of the silicone maintenance materials on thermal aging resistance of asphalt mixture. After thermal aging,the asphalt mixture using silicone materials and the control mixture are evaluated through their engineering properties,including indirect tensile modulus,low-temperature performance and fatigue resistance. The results indicate that the silicone materials used as repairing material can improve low-temperature performance and fatigue resistance of asphalt mixture,and decrease the indirect tensile modulus ratio before and after thermal aging. Consequently,the silicone maintenance material has the ability to protect asphalt mixture from thermal aging.     

Viscoelastic properties of monodisperse spherical silica suspension

The viscoelastic properties of the suspension of monodisperse spherical silica produced by hydrolysis of tetraethoxysilane in alcohol solvent with ammonia as a catalyst in polyethylene glycol (PEG) were studied. The results show that the SiO2/PEG suspension possesses the reversible shear thinning and shear thickening behaviors. In the shear thinning region, the loss modulus (G″) almost remains unchanged, whereas the storage modulus (G′) decreases. In the shear thickening region, G″ and G′ increase for the formation of the "clusters". The larger G″ over G′ in all the stress studied shows that the system mainly possesses the viscous property, and that the energy dissipated(Ed) is larger than that stored. Ed of this suspension is proportional to the maximum strain (γmax) rising with the exponent of 1.92 under low shear stress; however, in the shear thickening region, Ed is proportional to γmax rising with the exponent of 5.00.     

纤维沥青路面抗裂性能机理分析

针对沥青路面反射裂纹病害较为普遍的现状,以漯河市旧路改造项目,通过室内低温抗裂实验,结合平面应变有限单元法,验证了纤维材料对沥青路面抑制反射裂纹扩展的有效性。基于动力学,结合粘弹性力学理论,根据室内试验得出纤维沥青路面的本构关系,以动态应力强度因子为表征参量,探讨了纤维沥青路面在单周期垂直载荷和水平载荷共同作用下的动力特性,分析了车辆制动对纤维沥青路面工作性状的影响,研究了阻尼比,回弹模量的变化对动态应力强度因子影响。数值结果表明：掺加纤维后对沥青路面的工作性能有了较大改善,动态应力强度因子明显降低,对抑制沥青路面反射裂纹扩展起到了显著的作用。     

基于有机-无机改性的赤泥沥青混合料综合性能

聚焦赤泥的资源化利用与筑路材料紧缺问题,提出采用赤泥替代石灰岩矿粉制备沥青混合料。针对赤泥-沥青界面遇水强度衰减问题,提出无机粉体共混(水泥、消石灰)和有机偶联剂表面修饰(硅烷偶联剂KH-550、KH-560)的改性工艺,并研究改性前后的赤泥对沥青混合料性能的影响规律。通过动稳定度试验、马歇尔试验、汉堡车辙试验、动态模量试验和两点弯曲试验对改性前后的赤泥沥青混合料进行系统评价,发现普通赤泥可以提高沥青混合料的高温稳定性,但是对水稳定性、低温抗裂性与疲劳性能有不利影响。通过对赤泥改性处理,赤泥沥青混合料的高低温性能、水稳定性与长期耐久性均得到不同程度提高,而采用硅烷偶联剂表面修饰改性效果更好。证实了使用赤泥进行沥青混合料生产的可行性,为赤泥的资源化利用开拓了方向。     

重载沥青路面结构组合的抗车辙性能分析

为研究结构组合对沥青混合料抗车辙性能的影响,首先对所设计的7种沥青混合料进行动态模量及单层车辙试验,得到基本材料参数及抗车辙性能;然后对7种混合料组合而成的3种路面结构在重载条件下进行双层结构车辙试验,并与单层车辙试验结果进行对比分析;最后,应用光纤光栅智能测试技术对实际路面进行现场应变测试,根据不同路面结构三向应变测试结果评价实际重载沥青路面结构的抗车辙性能．结果表明,单层车辙试验难以准确反映路面结构的抗车辙性能,而双层车辙试验效果良好．在设计抗车辙路面时要考虑不同面层的模量组合,才能最大程度地发挥各层混合料的抗车辙性能．     

Experimental study on fatigue performance of Gussasphalt mixture

Four-point flexural fatigue test for Gussasphalt mixture specimen was carried out at a straincontrolled mode system. The results showed that the development of the tested stiffness modulus and phase angle of the mixtures with increasing load cycles exhibited three periods, initial generation, slow development and failure period. The fatigue crack generation zone formed in the third period, in which the macro mechanical properties were signifi cantly decreased. Moreover, we also analyzed the effects of asphalt content and mixing temperature on the fatigue life of the mixture. The results showed that the fi rst period when the specimen＇s initial stiffness modulus was reduced to 80% accounted for 5%-10% of the total fatigue life; the second period in which the reduction became slow and demonstrated a liner relationship with load cycles occupied 70%-85% of the fatigue life; and the third period was about 5%-10%. The results indicated that the lower the mixing temperature, the longer the fatigue life of Gussasphalt mixture. Besides, the increasing of asphalt content has a minor effect on the fatigue life of Gussasphalt mixture