Fen Ye

State-of-Practice Review of Deep Soil Mixing Techniques in China

Deep soil mixing techniques have been widely adopted in China since the late 1970s and mainly used for ground improvement for structural support and earth-retaining structures for excavations. A comprehensive state-of-practice review on development, applications, soil-cement properties, mechanistic studies, design methods, and quality control of deep soil mixing techniques in China is presented. These research results will serve as a reference for advancing deep soil mixing techniques in the United States and other countries.

Utilization of Construction and Demolition Wastes in Low-Volume Roads for Rural Areas in China

This paper presents a study in which the engineering properties of recycled construction and demolition wastes were evaluated for application to the construction of low-volume roads in rural areas of China. Crushed clay brick and waste concrete, two types of commonly available construction and demolition wastes, were selected. Scanning electron microscopy was used to characterize the influence of the hydration process on microstructure. Properties, including moisture–density relationships and unconfined compression strength, were evaluated. A field application of the use of construction and demolition wastes in low-volume roads was also presented. The study results indicate that construction and demolition wastes may be successfully used as a cement-stabilized base in constructing rural low-volume roads. The results of laboratory and field investigations from the study also provided reference for future mix design and pavement structural design, as well as construction quality control and quality assurance for similar applications in the future.

Strain response of a semi-rigid base asphalt pavement based on heavy-load full-scale accelerated pavement testing with fibre Bragg grating sensors

Full-scale accelerated pavement testing with a mobile load simulator 66 (MLS66) was conducted on a semi-rigid base asphalt pavement on a highway in Chongming Island, Shanghai, China. The goal was to investigate performance behaviour of an asphalt pavement with fine-sand subgrade in the river bed. Chongming is the terminal of G40 highway where fine sand is abundant. Although commonly found, there are little published data on its performance in a pavement structure. If found reliable in the accelerated test, the design would be used for the construction of G40 highway, which can lower the construction costs greatly and provide an engineering practice for follow-up research. Performance of the pavement structure was evaluated under high-frequency heavy trafficking while being subject to high-temperature and ambient environmental impact. This included monitoring of strains, temperature, modulus, rutting deformation, pavement depth and water level. This paper discusses the cumulative and instantaneous three-dimensional strain at the bottom of each layer in the semi-rigid base asphalt pavement. Generally good agreement was reached between the measured and calculated strains with back-calculation resilient modulus considering modulus reduction of asphalt layers because of temperature. A fatigue equation of the asphalt layer was established between loading applications, strain and seismic modulus, a small-strain value of Youngs modulus. Conclusions regarding the spatial distribution, time-history change of three-dimensional dynamic strain response and the relationships between influencing factors and strains are presented.

Laboratory Study on Recycled Building Waste Materials for Road Construction

Saving of resources is a significant indicator to evaluate social and economic benefits of a highway project. The purposes of this study are to investigate the feasibility of using recycled building materials as base, subbase, and subgrade and provide guidelines for selection and performance evaluation of recycled materials in future projects. This study first considered the requirements for building waste materials which could be recycled. Laboratory tests were conducted to evaluate whether the waste materials fulfilled these requirements. Cement and High strength water stable Earth Consolidator (HEC) were employed as stabilizing/recycling agents. Orthogonal analysis was adopted to evaluate the effect of gradation, type, and quantity of stabilizing/recycling agents on unconfined compressive strength (UCS) and resilient modulus of recycled materials. The laboratory study shows that the use of the recycled waste materials as highway base, subbase, and subgrade is feasible and would fulfill its requirements.

Modulus evolution of asphalt pavement based on full-scale accelerated pavement testing with Mobile Load Simulator 66

A full-scale accelerated pavement testing was conducted with Mobile Load Simulator 66 in Chongming Island, Shanghai, to study the performance response of a semi-rigid base asphalt pavement with fine-sand subgrade designed for the G40 construction. As an index sensitive to temperature and load, three different moduli including the seismic modulus, field falling weight deflectometer back-calculation modulus and interior material testing system resilient modulus were all measured during and after the test. The modulus evolution of asphalt pavement with the loading applications, rutting, strain and temperature, and the comparison of three methods for measuring modulus were analysed. There exists a modulus gradient from top to bottom, which can be considered in the pavement design or fatigue life prediction. Because of the strain level differences, the seismic modulus was the largest, followed by back-calculation and resilient modulus; the development of seismic and back-calculation modulus better reflected the anti-deformation changes.

Analysis on Three-Direction Strain of Asphalt Pavement Structure Based on Accelerated Pavement Testing

The internal mechanical response of asphalt pavement structure is difficult to be obtained because of the limitations of theoretical calculation and present testing methods. In order to get practical information of instructure layers, this paper analyzed the cumulative and instantaneous strains of layers’ bottom of semi-rigid base asphalt pavement based on Accelerated Pavement Testing and Fiber Bragg Grating sensors, as well as got the spatial distribution and time-variation law of longitudinal, lateral and vertical strain responses under controlled loading condition. The research result shows that under the moving vehicle loads, there is an obvious alternative property of tension-compression as the strain response of the pavement structure, and different variation shapes of instantaneous stain are in different layers from top to down. Also the measured instantaneous three-direction strain of the bottom of each surface are higher than the calculated values with BISAR, while they anatomizes well in base. This paper can be regarded as useful and tentative research and application on future correlative study.

Behavior Evolution on Performance of UV-Irradiation Aged Asphalt Mixtures Under Reduced-Scale Accelerated Trafficking

In order to investigate the actual behavior evolution of asphalt pavement after the Ultra Violet irradiation (UV-irradiation) aging, reduced-scale accelerated pavement tests were conducted on two separate asphalt mixtures with a stone matrix asphalt (SMA-13) structure, respectively, crumb-rubber modified asphalt mixture and its matrix asphalt mixture, at ambient air temperature. In each group, UV-irradiation aged asphalt mixture after ultraviolet irradiation of 300 h and its corresponding non-aged asphalt mixture were trafficked at the same time by the 1/3 model mobile load simulator (MMLS3) till the cumulative loading applications up to 500,000. The test results show that the performance attenuation degree of the crumb-rubber modified asphalt mixture was lower than that of the matrix asphalt mixture, so the rubber additive helps to reduce the effect of the UV-irradiation aging. Rutting deformation, three-dimensional dynamic strain and seismic modulus were measured during the accelerated loading test. The rutting results (including the rutting depth, rutting area and its development rates), the surface dynamic strains, and the decay rate of the seismic modulus from the UV-irradiation aged asphalt mixture were greater than those of non-aged sample, and the difference narrowed after the cumulative loading applications reached more than 100,000. In addition the analysis of the modification rutting factor from the dynamic shear rheometer (DSR) test, the UV-irradiation aging weakened the high temperature stability and mechanical strength. Therefore, the UV-irradiation aging aggregated the performance decay of asphalt mixture and will inevitably shorten its service life.

An Evaluation System of Anti-Aging of Rubber Asphalt

With an ultraviolet radiation aging simulation system, designed by Ye Fen (2005), this chapter proceeded with the short-term aging on rubber asphalt indoor in the conditions of different aging time and temperatures. Laboratory tests on penetration, softening point, ductility of 5 °C, viscosity, elastic recovery were implemented to qualitatively analyze the relation between macro-indicators and micro ones. It was aimed to screen rational indexes to characterize the aging degree of rubber asphalt. The test results took softening point as a parameter and viscosity as a reference one during the kinetic equations deducing. Furthermore, this experimental study introduced the concepts of asphalt aging degree and anti-aging factor, and established evaluation system of rubber asphalt anti-aging.

Comparison of Asphalt Ultraviolet Radiation Aging with other Aging Types by Infrared Adsorption Spectrum

This study introduces the theory of asphalt aging with infrared adsorption spectrum. Qualitative and quantificational comparisons are carried out between Karamay asphalt ultraviolet radiation aging, after which asphalt turns from sol-type to gel-type and other aging types. The variance ratio of absorbance A at 1700 cm-1 in infrared spectrum chart is consistent with the tendency of asphalt’s three general indexes, including penetration, ductility and softening point. The oxidation speed of ultraviolet radiation aging is 1.80~6.23 times that of thermal aging. In addition,the process of photo-oxidation, the order of carbonyl content in different asphalt samples, the influence of ultraviolet radiation on long term aging of asphalt and other useful information has been gained for better and further researches in this field.

Study on the Performance Influencing Factor of Epoxy Asphalt Waterproof Cohesive Layer in Steel Deck Pavement

In recent years, epoxy asphalt is used widely in the waterproof cohesive layer material of steel deck pavement. This material has obvious advantages in cohesion, deformation capacity and hot stability. This paper analyses the effects of water and temperature on the performances of epoxy asphalt waterproof cohesive layer by indoor shearing and pulling tests. It has important theoretical significance and practical value for the development and application of epoxy asphalt waterproof cohesive layer material.