Changfa Ai

State-of-the-art review of interface bond testing devices for pavement layers: toward the standardization procedure

Abstract During the past thirty years, interface bonding between pavement layers has been a topical subject worldwide to research. In this context, many researchers have developed and utilized their own devices to investigate the properties of pavement interfaces. In the absence of an international standard procedure for interface bonding, it is inevitable that testing results are not comparable in all cases. In addition, various conducted studies reveal that parameters such as temperature, loading conditions, materials and so on exert an influence on interface properties. This paper aims to deal with the matter effectively via a thorough and comprehensive review of interface bond testing to lay the groundwork for standardization procedure. For this purpose, first, a general overview of interface bond function and its impact on pavement performance is presented. Then, different types of interface bond test methods according to loading conditions are explained; furthermore, the configuration of various setups is discussed and their function is compared together. Finally, given the prior experiences, a framework for a methodical approach to a standard evaluation of pavement interfaces is presented.

Analysis of measured strain response of asphalt pavements and relevant prediction models

Abstract In order to investigate the actual strain response of asphalt pavement under real condition, three types of asphalt pavement sections with typical surface structures are built. The effects of axle configuration, axle load, speed and testing temperature on strain response of asphalt pavement were analysed through in situ dynamic loading. Experimental results indicate that the strain response at the bottom of the asphalt surface layer increases with increasing axle load and temperature, but decreases with the rise of speed. On the other hand, the temperature exerts different influence levels on pavement sections with different structures. It is also concluded that the tandem axle load could lead to a greater strain response than that of single axle load. Applying the analysis of variance, the effects of pavement surface temperature, axle load, speed and their double interactions are studied as well. Finally, the paper proposes prediction models of the strain response at the bottom of asphalt layer by means of multivariate regression analysis.

Characterization of Interface Bonding in Asphalt Pavement Layers Based on Direct Shear Tests with Vertical Loading

AbstractThe interface bonding condition between asphalt concrete layers is unquestioned as one of the significant factors influencing pavement performance. In order to research the interface charac...

Experimental study of a new modified waterproof asphalt concrete and its performance on bridge deck

The employment of asphalt concrete on the bridge surface paving has been widely used in long-span bridges owing to its merits such as light weight, seamless, good performance and simple maintenance. Currently, three types of asphalt materials – namely Guss asphalt , stone mastic asphalt and epoxy asphalt concrete – are principally applied in bridge deck pavement. However, these asphalt pavements have their own disadvantages. In order to further enhance the overall performance of asphalt concrete and its engineering applicability on bridge surface, in this research a new modified waterproof asphalt concrete is produced. The new modified asphalt from two aspects of the asphalt binder material and mixture were developed. To evaluate the performance of the new asphalt material and verify the feasibility of its application, a series of tests on bitumen and asphalt mixture were conducted. In addition, a comparative evaluation between the newly developed asphalt mixture and traditional ones was conducted. All in all, the results of this research could make a great contribution to the application of asphalt concrete technology on bridge surface paving.

High-Order Spectral Finite Elements in Analysis of Collinear Wave Mixing

Implementing collinear wave mixing techniques with numerical methods to detect acoustic nonlinearity due to damage and defects is of vital importance in nondestructive examination engineering. However, numerical simulations in existing literatures are often limited due to the compromise between computational efficiency and accuracy. In order to balance the contradiction, spectral finite element (abbreviated as SFE) with 3 × 3 and 8 × 6 nodes is developed to simulate collinear wave mixing for 1D and 2D cases in this study. The comparisons among analytical solutions, experiments, finite element method (FEM), and spectral finite element method are presented to validate the feasibility, efficiency, and accuracy of the proposed SFEs. The results demonstrate that the proposed SFEs are capable of increasing computational efficiency by as much as 14 times while maintaining the same accuracy in comparison with FEM. In addition, five 3 × 3 nodes’ SFEs or one 8 × 6 nodes’ SFE per the shortest wavelength is sufficient to capture mixing waves. Finally, the proposed 8 × 6 nodes’ SFE is recommended for collinear wave mixing to detect damage, which can offer more accuracy with similar efficiency compared to 3 × 3 nodes’ SFE.

Study of Strength Forming Mechanism and Influencing Factors of Half-Warm Mix Asphalt

In order to study the strength forming mechanism and influencing factors of half-warm mix asphalt (HWMA), the stability of Marshall samples is tested under different test conditions such as gradations, asphalt quantities, forming methods, number of compaction passes, maintenance period, and forms of maintenance. The results show that (1) the suspension dense gradation is satisfactory for early strength of HWMA, and its strength varies with asphalt quantity; (2) the number of compaction passes and maintenance period are two major external factors influencing strength forming, and the increase in strength reduces significantly when the number of compaction passes on both sides increases above 130. (The Marshall samples acquire final strength in 49 days of maintenance.); and (3) both loading and maintenance time significantly affect the strength forming process. Moreover, the cohesion of the material and internal friction increase, and the Marshall samples gain strength more rapidly with both the factors. Loading and maintenance time affect the internal friction and cohesion of the material, respectively. The results of this study provide guidance for design and construction of HWMA.

Experimental Study on the Tension and Compression Performance of Modified Asphalt Bridge Expansion Joints

Under the comprehensive influences of the overall deformation of the whole bridge structure, the repeated moving vehicle and temperature loading, the bridge expansion joint was the weak part of bridge structure. The paper chose a new type of modified asphalt binder to test the elastic recovery performance of the modified asphalt binder under different temperatures. Meanwhile the cycle Marshall stability test and direct tensile test of modified asphalt mixture were conducted. Then, the effects of different temperature conditions on the performance of the modified asphalt binder and the asphalt mixture were analyzed to explain its performance mechanism. The results indicated that: (1) The performance recovery of the special cementing material was affected by temperature. The recovery rate gradually increased with the increasing of temperature. The recovery performance showed some “Time-Temperature” characteristics. (2) Affected by the amount of Oil-stone ratio (33.3%) and the single particle size coarse aggregate, the modified asphalt mixture of the suspended structure type had good recovery performance under all test temperature conditions. (3) The tensile elongation rate of the asphalt mixture was large under the high temperature, and the mixture had a good ability to adapt to the flexible deformation. The research results provided that the modified asphalt binder could be used as the bridge expansion joint material.

Evaluation and optimisation of stone matrix asphalt (SMA-13) mix design using weight-matrix method

The mix design of the stone matrix asphalt (SMA) mixture is critical to its performance and thereby has attracted considerable attention. In this research, abiding by the principals of orthogonal experimental design, a series of laboratory tests are conducted to assess and optimise the SMA-13 mixture mix designs. Different levels of three critical factors, gradation, asphalt-aggregate ratio, and fibre contents, are applied in the factorial experimental designs. Five performance measures, residual stability, dynamic stability, fatigue lifespan, bending strength, and coefficient of friction, are tested. With the laboratory testing results, weight-matrix analysis is employed to identify the impact of different levels of different factors on overall performance. Based on the results, the influences of the three factors are ranked: gradation, asphalt-aggregate ratio, and fibre contents, from the most influential to the least. Furthermore, analyses are conducted to determine the optimum SMA-13 mix design for four representative climate zones in China. Results are verified with the compared mixture groups.