Papers by Author: Ji Qing Zhu

Abstract: The effect of substitution of recycled aggregate by natural aggregate on related properties of blended aggregate (without asphalt and mineral filler) and asphalt mixture was investigated in this paper. Demolition waste obtained from Wenchuan earthquake-damaged buildings was used as recycled aggregate in AC-25 asphalt mixture. The absorption, specific gravity and strength of both blended aggregate and asphalt mixture were tested. Results indicate that fine recycled aggregate is not suitable to be used in asphalt mixture because of its high absorption. The substitution of recycled aggregate by natural limestone aggregate can decrease the asphalt absorption and increase the effective specific gravity and indirect tensile strength of asphalt mixture. The quantitative relationship between related properties of blended aggregate and asphalt mixture was obtained. It was concluded that the substitution of recycled aggregate by natural aggregate is a feasible way to use recycled aggregate in asphalt mixture.

Abstract: Two classification methods for fine recycled aggregate used in asphalt concrete were investigated in this paper, respectively classifying by fine recycled aggregate properties and asphalt concrete properties. When classifying by fine recycled aggregate properties, all test results of fine recycled aggregate properties can meet the technical requirements of China with obvious differences in quality. When classifying by asphalt concrete properties, fine recycled and natural aggregate was respectively used to prepare asphalt concrete with the same gradation, the same asphalt, the same limestone mineral filler and the same coarse natural aggregate. Some related properties of asphalt concrete were discussed to classify fine recycled aggregate. It is proposed in this paper that fine recycled aggregate should be classified into three types by asphalt concrete properties and the proposed classification criterion is given.

Abstract: The static shear creep behavior of asphalt mastic containing recycled red brick powder (RBP) is investigated in this paper. The used mastic consists of asphalt and filler at a mass ratio of 1:1. Dynamic Shear Rheometer (DSR) performed the static shear creep tests at 0°C. The static shear creep behavior of RBP asphalt mastic was analyzed and modeled based on Burgers model. It is concluded that the introduction of RBP results in smaller deformation, higher static shear creep stiffness modulus of asphalt mastic at 0°C. It was also indicated that Burgers model can well explain the static shear creep behavior of RBP asphalt mastic.

Abstract: Some properties of asphalt mastic containing recycled cement mortar powder (CMP) were investigated in this paper. CMP was used as filler in asphalt mastic. The investigated mastic consisted of asphalt and filler at a mass ratio of 1:1. Penetration, softening point and high-temperature viscosity were tested. Dynamic Shear Rheometer (DSR) was used to conduct frequency sweep test of asphalt mastic. The introduction of CMP resulted in reduced penetration, increased softening point, apparent activation energy, complex shear modulus in the low frequency area and high-temperature viscosity. Results indicate that CMP may have some positive effect on high-temperature properties but some negative effect on low-temperature properties of asphalt mastic. It is also believed that the average mixing and compacting temperature of asphalt mixture containing CMP is higher than that containing limestone mineral filler (LMF).

Abstract: Two classification methods for coarse recycled aggregate used in asphalt concrete were investigated in this paper, respectively classifying by coarse recycled aggregate properties and asphalt concrete properties. When classifying by coarse recycled aggregate properties, coarse recycled aggregate was classified into three types by the apparent specific gravity, water absorption, crushed value, Los Angeles abrasion value and brick content of coarse recycled aggregate. When classifying by asphalt concrete properties, coarse recycled aggregate was used to prepare asphalt concrete; and coarse recycled aggregate was classified into three types by the optimum asphalt content ratio (R_OAC), theoretical maximum specific gravity ratio (R_TMSG) and indirect tensile strength ratio (R_ITS) of asphalt concrete containing coarse recycled aggregate. The proposed classification criterions of the two classification methods were respectively given.

Abstract: In order to improve the performance of granite asphalt mixtures, as well as make full use of waste concrete, the AC-25 asphalt mixtures were prepared using fine recycled concrete aggregate and coarse granite aggregate. The moisture stability, high-temperature property, low-temperature property and fatigue property of asphalt mixtures were investigated. Results indicate that fine recycled concrete aggregate (RCA) improves the moisture stability and low-temperature property of granite asphalt mixtures which can meet the requirements of China’s Technical Specification for Construction of Highway Asphalt Pavements (JTG F40-2004) and even are better than those of traditional limestone asphalt mixtures. Meanwhile, fine RCA makes the advantage of granite asphalt mixtures in high-temperature property more distinct with good fatigue property.

Abstract: The construction and maintenance of roads in China require large amounts of aggregates and mineral filler. The use of recycled materials helps conserving natural resources. However, the inferior road performance and additional costs have hindered the widespread use of construction and demolition wastes (C&D wastes) in applications such as surface layers of asphalt pavement that may represent a value application for C&D wastes. Waste concrete, waste bricks and waste glass are selected for this study; and the surface layers of asphalt pavement is considered here as value application. Although there is a large potential for supplying C&D wastes now, a few barriers have effectively depressed the recycling activities. Such barriers are described here and a brief discussion suggests ways of their removal.