Technologies for Asphalt Pavement Surface Testing in Road and Bridge Construction

Asphalt pavement is currently one of the main components in the construction of roads and bridges.However,from a practical point of view,various quality problems are prone to occur in the surface layer of asphalt pavement,which will lead to the poor overall quality of road and bridge projects.Therefore,it should be applied reasonably.Advanced testing technologies are used to test the mixture quality,compaction,segregation,thickness,and other aspects of the asphalt pavement surface layer,so as to improve the quality of the asphalt pavement surface layer,and then improve the overall quality of road and bridge construction.Therefore,this paper mainly analyzes the technologies for asphalt pavement surface layer testing in road and bridge engineering construction.

Study on the temperature characteristic and high temperature risk of asphalt layer of Beijing-Xinjiang ExpresswayWutong Daquan to Yiwu Section

High temperature rutting is a typical highway damage in Xinjiang, China, and its trigger process usually has a close relationship with characteristics of road temperature distribution. A numerical model of earth-atmosphere coupling heat transfer on a typical section of the Beijing-Xinjiang Expressway(G7) from Wutong Daquan to Yiwu was established in this work. Spatiotemporal characteristics of pavement structure layer temperature distribution, frequency and duration times of road surface high temperature from May 1 to September 30 are statistically studied. The effects of wind speed, weather and air temperature on asphalt layer and pavement temperature are analyzed. The results show that:(1) Spatial and temporal temperature distribution characteristics of pavement structural layers are greatly affected by the coupled earth-atmosphere heat transfer process. Surface temperature increases along the airflow direction and daily temperature variation of the pavement structure layer decreases with an increase of depth.(2) G7 expressway will face the challenge of high rutting damage. The proportion of temperature higher than 50 ℃ for pavement surface and asphalt upper layer both exceeds 50%and high temperature of road lasts for more than six hours in numerous days.(3) High temperatures of asphalt pavement are usually associated with low ambient wind speeds, while the wind flow has little cooling effect when the road surface temperature is relative high. Weather conditions have a significant impact on temperature of the road surface. The probability of high temperature in sunny days is obviously higher than other weather conditions.(4) Pavement temperature rises as air temperature rises. When air temperature is higher than 30 °C, the proportion of pavement daily maximum temperature over softening point reaches up to 78%.

An empirical method for estimating surface area of aggregates in hot mix asphalt

Bitumen requirement in hot mix asphalt （HMA） is directly dependent on the surface area of the aggregates in the mix, which in turn has effect on the asphalt film thickness and the flow characteristics. The surface area of aggregate blend in HMA is calculated using the specific surface area factors assigned to percentage passing through some specific standard sieve sizes and the imaging techniques. The first process is less capital intensive, but purely manual and labour intensive and prone to human errors. Imaging techniques though eliminating the human errors, still have limited use due to capital intensiveness and requirement of well-established ]aboratories with qualified technicians. Most of the developing countries like India are shortage of well-equipped laboratories and qualified technicians. To overcome these difficulties, the present mathematical model has been developed to estimate the surface area of aggregate blend of HMA from physical properties of aggregates evaluated using simple laboratory equipment. This model has been validated compared with the existing established methods of calculations and can be used as one of the tools in different developing and under developed countries for proper design of HMA.