Measurement and quantitative characterization of aging-induced gradient properties for the asphalt mixture is an important theoretical basis for the accurate mechanical behavior analysis and design of asphalt pavement. In this research, the composite specimen method is proposed to obtain asphalt binders at different depths inside the asphalt mixture. Aging-induced gradient properties have been measured by dynamic shear rheometer (DSR) tests to reveal the internal mechanism. G* master curves for asphalt binders in different depths have been constructed by a generalized logistic sigmoidal model (GLSM) to investigate the gradient aging effects in a wide range. It is found that the composite specimen method can restore the boundary conditions of asphalt binders through the process of specimen preparation, core drilling, core shifting, asphalt injecting, gradient aging test, and layered cutting. It is feasible to study gradient aging characteristics inside the asphalt mixture. Asphalt binder samples obtained from the surface of the composite specimen with the most serious aging degree have the maximum G* value and the minimum delta value. Under the same aging condition, the variation of G* of the asphalt binder along the depth is more pronounced than that of delta. The change behavior of G* and delta are generally the same, and there are only differences in G* and delta values and the depth range of gradient aging effects for different aging levels. At the same temperature and loading frequency, values for G* under the Aging-L3 condition are the largest, and values for delta are the smallest in this aging state. The aging influence depth range inside the composite specimens is about 3 cm, 4.5 cm, and 5.5 cm after oven aging at 85 degrees C for 5 days, 10 days, and 15 days, respectively. GLSM is well suited for constructing G* master curves of asphalt binders. The distinction between G* master curves is most obvious in the depth of 0 - 1 cm and changes the most from the depth of 0 - 1 cm to 1 - 2 cm. Under the condition of Aging-L3, G* master curves are most differentiated at different depths, indicating the most significant gradient aging state inside the asphalt mixture composite specimen.

The research and development of high-performance pavement materials has been intensified owing to the demand for long-life pavements. This study is performed to develop a novel pavement material using waste rubber powder, waste lubricating by-product (LBP), and asphalt. Subsequently, the aging properties and aging mechanism of activated waste rubber powder modified asphalt (ARMA) are investigated based on its rheological properties and micro-characterization. The rheological results show that, compared with waste rubber powder modified asphalt (RMA), ARMA offers a higher aging resistance and a longer fatigue life. A comparison and analysis of the rheological aging parameters of ARMA and RMA show that LBP activation diminishes the aging sensitivity of ARMA. The micro-characterization result shows that the aging of ARMA may be caused by the fact that LBP-activated waste rubber powder is more reactive and can form a dense colloidal structure with asphalt. Therefore, the evaporation loss of asphalt light components by heat and the damage to the colloidal structure by oxygen during the aging process are impeded, and the thermal-oxidative aging resistance of ARMA is improved.

The unique thermal stress environment of asphalt supporting layer (ASL) in the slab track system is critical to its service safety. The extra thermal load is responsible for causing large thermal stress in ASL. A new modified thermal stress restrained specimen test (TSRST) method was developed to measure the thermal stress develop-ment of ASL during the cooling process. The high density polyethylene (HDPE) blocks were assembled onto the asphalt mixture beam to provide extra thermal load automatically during the cooling process, the modified TSRST test were conducted on two types of asphalt mixture types comparing to the standard TSRST test. The tests results show that the extra thermal load accelerates the development of thermal stress in asphalt concrete and elevates the fracture temperature and transition temperature. The modified TSRST test was proved to charac-terize the effect of the extra thermal load effectively, and the test results have good repeatability.

为提高再生沥青混合料的抗裂特性，提出采用抗裂性能优良的新型SBS/橡胶复合改性沥青进行RAP料的再生。基于低温弯曲小梁蠕变、约束温度应力及四点弯曲疲劳试验对复合改性沥青、SBS改性沥青的再生混合料进行低温抗裂及疲劳开裂性能研究。结果表明：橡胶的加入可提高再生沥青混凝土的低温及中温抗裂性能，这可能与混合料开裂初期形成的微裂纹扩展至聚合物网络被吸收断裂能量，抑制微裂纹进一步发展有关。进一步分析断裂温度可知，复合改性沥青再生沥青混合料较普通SBS改性沥青的再生混合料可延伸路面的服役温度范围6℃左右，有利于再生沥青混合料在西北寒冷地区的推广应用。

Cracking is one of the main diseases of cement grouted asphalt mixture (CGAM). This paper aims to disclose the whole process failure characteristics of CGAM under different loads. Three types of tests under acoustic emission monitoring were designed to observe the performance of CGAM under indirect tension, bending tension and compression. Stone matrix asphalt (SMA) was used as the control group. The results show that the failure process of CGAM can be divided into three stages. Large damage will be produced in one or more short periods. The cracking of cement mesh is one of the main factors to form cracks in CGAM, and its brittleness leads to the proportion of macro cracks of CGAM in each stage being greater than that of SMA. The proportion of shear failure of CGAM is higher than that of SMA, so more attention should be paid to its shear resistance in material design. © 2023 Elsevier Ltd

为进一步提高无核密度仪检测精度,基于灰色关联理论,将无核密度仪的平均相对误差作为母序列,将空隙率、测点数量等7种精度影响因素作为子序列,通过数据处理得出了所有影响因子在每种误差水平下的关联系数,并对关联系数取均值,得出整体

Under the influence of continuous periodic changes of various meteorological factors, there will be an inhomogeneous temperature field inside the asphalt pavement, which will cause a continuous gradient viscoelasticity of asphalt concrete with depth. In order to perform the structural mechanics analysis accurately, the temperature field gradient effect and the temperature-induced gradient viscoelasticity distribution inside the asphalt pavement should be revealed first. In this research, based on the heat conduction theory, a temperature field finite element analysis (FEA) model of a semi-rigid base asphalt pavement was established to investigate the distribution behavior of the temperature gradient along the depth. Dynamic modulus tests were conducted to survey temperature effect on the viscoelastic parameters of asphalt concrete. Eventually, the intrinsic relationship between temperature, depth, and viscoelastic parameters was integrated, and the relaxation time shift method was proposed to quantitatively characterize the temperature-induced gradient viscoelasticity at different depths. It is found that the temperature varies in a cubic parabolic fashion along the depth under the most significant positive and negative temperature gradient conditions. The relaxation time shift method can be effectively used to characterize the distribution of the relaxation modulus and relaxation time spectrum of asphalt concrete under the influence of temperature. It is easy to be programmed to fully consider the inhomogeneous temperature field, and applicable to both traditional and gradient FEA. The change of parameters of generalized Maxwell model for asphalt concrete with temperature is essentially the result of relaxation spectrum shifting along the relaxation time axis at different temperatures. When the temperature is high, the viscosity decreases, the relaxation spectrum shifts to the direction of decreasing relaxation time, the relaxation modulus of asphalt concrete decreases, and vice versa.

The permeable pavement has good drainage capabilities, but the voids are easy to be clogged. Describing the internal flow and potential surface flow of permeable pavement is essential for pavement design and driving safe maintenance. In this paper, indexes including connected porosity, equivalent area of the voids channels, and the bending rate were selected to depict the permeable pavement internal flow when the voids decreased due to clogging. A simulation model was proposed based on Darcy's law by using the images from computer tomography (CT) scanning; then, the seepage flow inside the voids was obtained to evaluate the drainage of porous asphalt mixture. The potential surface flow situation including waterlogging, critical runoff depth and drainage time was calculated. Surface hydrodynamic pressure between the tires and pavement was also compared. Results showed that the connectivity of internal voids was crucial to quantify the voids clogging. The internal flow nearly disappeared when the porosity decreased by less than 15% due to the blockage. The drainage function was influenced by the porosity, thickness, and length of the drainage path. The surface layer's thickness should be determined according to the indexes such as the maximum runoff depth without water skiing, the drainage time, and the road facilities, among others. Surface hydrodynamic pressure distribution illustrated it might decrease by 33% for every 10 km/h deceleration. A short flow path length and a more considerable cross slope within a reasonable range could decline drainage time. It was suggested that all these factors might be considered when designing and maintaining the permeable pavement. (C) 2021 American Society of Civil Engineers.

Purpose–This study aims to investigate the service performances of a new full-section asphalt concrete waterproof sealing structure(FSACWSS)for the high-speed railway subgrade through on-site tracking,monitoring and