Yongchun Cheng

Influence of Diatomite and Mineral Powder on Thermal Oxidative Ageing Properties of Asphalt

Ageing of asphalt affects the performances of asphalt pavement significantly. Therefore, effects of diatomite and mineral powder on ageing properties of asphalt were investigated systematically in order to improve the antiageing property of mixture. Thin film oven test (TFOT) was used to conduct the short term ageing in laboratory. Softening points, penetrations, force ductility, low temperature creep properties, and viscosities of asphalt mastics were tested before and after TFOT, respectively. Results indicated that percent retained penetration (PRP) increased with the increasing of fillers. Increment of softening point (), ductility retention rate (DRR), deformation energy ageing index (JAI), and viscosity ageing index (VAI) of asphalt mastics nonlinearly decreased with the increasing of fillers. Ageing of asphalt was reduced by diatomite and mineral powder. And the antiageing effect of diatomite was better than that of mineral powder as a result of its porous structure. It is suggested that the mineral powder could be reasonably replaced by diatomite in order to reduce thermal oxidative ageing of asphalt mixture. The optimal content of diatomite 12.8% is also suggested for engineering.

Damage Identification of Bridge Based on Chebyshev Polynomial Fitting and Fuzzy Logic without Considering Baseline Model Parameters

The paper presents an effective approach for damage identification of bridge based on Chebyshev polynomial fitting and fuzzy logic systems without considering baseline model data. The modal curvature of damaged bridge can be obtained through central difference approximation based on displacement modal shape. Depending on the modal curvature of damaged structure, Chebyshev polynomial fitting is applied to acquire the curvature of undamaged one without considering baseline parameters. Therefore, modal curvature difference can be derived and used for damage localizing. Subsequently, the normalized modal curvature difference is treated as input variable of fuzzy logic systems for damage condition assessment. Numerical simulation on a simply supported bridge was carried out to demonstrate the feasibility of the proposed method.

Reduction of Uncertainties for Damage Identification of Bridge Based on Fuzzy Nearness and Modal Data

To avoid the false results of deterministic identification methods induced by uncertainties, a fuzzy nearness-based method is proposed for the damage identification of bridge. An improved index based on ratios of modal shape components is used as identification measurements. The knowledge base for damage identification is established through corresponding relationship between fuzzified measurements and damage severities. The damage condition of test samples can be assessed based on approaching principle through fuzzy nearness with rules in knowledge base. A numerical analysis on a multigirder bridge considering uncertainty is presented to demonstrate the effectiveness of the proposed method. The results indicate that the fuzzy nearness-based method can achieve an accurate identification with success rate up to 93.75%. Antinoise analysis and the ability for dealing with incomplete information reveal its robustness.

Laboratory Study on Properties of Diatomite and Basalt Fiber Compound Modified Asphalt Mastic

In order to improve the performance of asphalt mastic, some researchers have added diatomite or basalt fiber as a modifier to the asphalt mastic, and the results show that some properties of the asphalt mastic were improved. For the simultaneous addition of diatomite and basalt fiber, two kinds of modifier, compound modified asphalt mastic had not been reported; in this paper, thirteen groups of diatomite and basalt fiber (DBFCMAM) compound modified asphalt mastic with different content were prepared to study the performance. Softening point, cone penetration, viscosity, and DSR tests were conducted, for the high temperature performance evaluation of DBFCMAM, whereas force ductility and BBR tests were used in the low temperature performance study of the DBFCMAM. The results demonstrated that the high temperature performance of DBFCMAM was increased; moreover, the low temperature performance of DBFCMAM improved by diatomite and basalt fiber according to the results of the force ductility test; however, the conclusion of the BBR test data was inconsistent with the force ductility test. In summary, the high temperature and low temperature properties of DBFCMAM had been improved.

Reuse of Boron Waste as an Additive in Road Base Material

The amount of boron waste increases year by year. There is an urgent demand to manage it in order to reduce the environmental impact. In this paper, boron waste was reused as an additive in road base material. Lime and cement were employed to stabilize the waste mixture. Mechanical performances of stabilized mixture were evaluated by experimental methods. A compaction test, an unconfined compressive test, an indirect tensile test, a modulus test, a drying shrinkage test, and a frost resistance test were carried out. Results indicated that mechanical strengths of lime-stabilized boron waste mixture (LSB) satisfy the requirements of road base when lime content is greater than 8%. LSB can only be applied in non-frozen regions as a result of its poor frost resistance. The lime–cement-stabilized mixture can be used in frozen regions when lime and cement contents are 8% and 5%, respectively. Aggregate reduces the drying shrinkage coefficient effectively. Thus, aggregate is suggested for mixture stabilization properly. This work provides a proposal for the management of boron waste.

Pavement performance evaluation of asphalt mixtures containing oil shale waste

Oil shale ash (OSA) is a waste or by-product material, which may cause hazards for human health and environment. The objective of this paper is to evaluate the potential of OSA as partial replacement of mineral powder in asphalt mixture. For this aim, asphalt mixtures were prepared by two types of OSA wastes as partial filler replacement and compared with the control mixtures prepared with traditional mineral filler in this paper. Marshall tests were performed to investigate the volumetric and mechanical properties of asphalt mixtures. Moreover, the pavement performance including high-temperature dynamic stability, low-temperature cracking resistance and moisture stability were conducted. Results show that all required properties and pavement performance of asphalt mixture containing OSA at the optimum asphalt content (OAC) are satisfied or even improved in comparison with ordinary asphalt mixture in accordance to Chinese standard specification. The performance of asphalt mixture containing OSA was also evaluated based on a test road. In terms of environmental and economic as well as pavement performance points of view, OSA can be used instead of partial mineral filler in asphalt mixtures.

Design Optimization of SBS-Modified Asphalt Mixture Reinforced with Eco-Friendly Basalt Fiber Based on Response Surface Methodology

This paper investigates the effects of basalt fiber content, length and asphalt-aggregate ratio on the volumetric and strength properties of styrene-butadiene-styrene (SBS)-modified asphalt mixture reinforced with eco-friendly basalt fiber. An experimental scheme was designed to optimize three preparation parameters for the Marshall test indices based on response surface methodology (RSM). The results showed that basalt fiber content presents a more significant effect on air voids, voids in mineral aggregates and voids filled with asphalt. Basalt fiber length is more related to Marshall stability, and flow value exhibits a significant variation trend with asphalt-aggregate ratio. The optimization of preparation parameters is determined as follows: basalt fiber content is 0.34%, length is 6 mm, asphalt-aggregate ratio is 6.57%, which possesses favorable and reliable accuracy compared with experimental results. Furthermore, basalt fiber reinforced asphalt binder and mixture were also studied, and it was found that basalt fiber can enhance the performance of asphalt binder and mixture in terms of cone penetration, softening point, force ductility, as well as pavement performance tests.

Analysis of Aggregate Morphological Characteristics for Viscoelastic Properties of Asphalt Mixes Using Simplex Lattice Design

Morphological characteristics of aggregates have direct impacts on performances of asphalt mixes. This paper aims to investigate the effects of the morphological characteristics of fine and coarse aggregates on the high-temperature viscoelastic properties of asphalt mortars and mixtures. For this purpose, an experimental proportion scheme was designed for asphalt mixes prepared with three different types of aggregates (basalt, andesite and pebble/river sand) based on the simplex lattice design (SLD) method. Three morphological parameters were chosen to characterize shape, angularity and texture of aggregates. Afterwards, the uniaxial compression creep test was conducted for asphalt mixes and the high-temperature viscoelastic properties were obtained based on Burgers model. The effects of fine and coarse aggregates on the viscoelastic properties are analyzed through asphalt mortars and mixtures, respectively. The results showed that aggregate morphological characteristics correlate with the high-temperature viscoelastic properties of asphalt mixes, especially for fine aggregates. Aggregates with complex morphological characteristics are conducive to improving the deformation recovery and anti-deformation of asphalt mixes. Furthermore, coarse aggregates can enhance the anti-deformation of asphalt mixture effectively due to its skeleton effect.

Dynamic Response of a Nonuniform Timoshenko Beam with Elastic Supports, Subjected to a Moving Spring-Mass System

This paper is concerned with the dynamic response of a nonuniform Timoshenko beam with elastic supports subjected to a moving spring-mass system. The modal orthogonality of nonuniform Timoshenko beams and the corresponding overall matrix of undetermined coefficients are derived. Then the natural frequencies and mode shapes of nonuniform Timoshenko beams are obtained by the Runge–Kutta method and cubic spline interpolation method. By using the Newmark-β method and the mode summation method, the vibration equation of Timoshenko beams subjected to a moving spring-mass system was established. A comparison of results between the proposed method and finite element method reveals that this method possesses favorable accuracy for dynamic response analysis. In numerical examples, the effects of the support spring and moving spring-mass system on Timoshenko beams have been examined in detail.

Fuzzy Neural Network-Based Damage Assessment of Bridge under Temperature Effect

Vibration-based method has been widely applied for damage identification of bridge. Natural frequency, mode shape, and their derivatives are sensitive parameters to damage. However, these parameters can be affected not only by the health of structure, but also by the changing temperature. It is essential to eliminate the influence of temperature in practice. Therefore, a fuzzy neural network-based damage assessment method is proposed in this paper. Uniform load surface curvature is used as damage indicator. Elasticity modulus of concrete is assumed to be temperature dependent in the numerical simulation of bridge model. Through selecting temperature and uniform load surface curvature as input variables of fuzzy neural network, the algorithm can distinguish the damage from temperature effect. Comparative analysis between fuzzy neural network and BP network illustrates the superiority of the proposed method.