Combined Prediction Method for Thermal Conductivity of Asphalt Concrete Based on Meso-Structure and Renormalization Technology

Pavement temperature field affects pavement service life and the thermal environment the near road surface; thus, is important for sustainable pavement design. This paper developed a combined prediction method for the thermal conductivity of asphalt concrete based on meso-structure and renormalization technology, which is critical for determining the pavement temperature field. The accuracy of the combined prediction method was verified by laboratory experiments. Using the tested and proven model, the effect of coarse aggregate type, shape, content, spatial orientation, air void of asphalt concrete, and steel fiber on the effective thermal conductivity was analyzed. The analysis results show that the orientation angle and aspect ratio of the aggregate have a combined effect on thermal conductivity. In general, when the aggregate orientation is parallel with the heat conduction direction, the effective thermal conductivity of asphalt concrete in that direction tends to be greater. The effective thermal conductivity of asphalt concrete decreases with the decrease of coarse aggregate content or steel fiber content or with the increase of porosity, and it increases with the increase of the effective thermal conductivity of coarse aggregate.

Model development and prediction of anti-icing longevity of asphalt pavement with salt-storage additive

This study established a systematic simulation framework to predict the anti-icing longevity of a thin overlay of asphalt pavement with salt-storage additive (APSSA). The water and chloride transport in the overlay when subjected to varying precipitation, temperature, thermal cracking, and fatigue cracking over time were modeled using a Finite Element Method based software. The simulation included two parts: water transport followed by chloride transport. Water transport that obeys the law of conservation of mass was modeled using the phase transport in porous media (phtr) interface of COMSOL, while chloride transport based on Fick’s second law was modeled with the transport of diluted species (tds) interface. The simulation results show that the anti-icing function of a 16-mm thick overlay was fully effective in 2 years and 5 years for the minimum pavement temperature above -3.4 °C and -2.4 °C, respectively. These two pavement temperatures are equivalent to 97.4-percentile and 96.3-percentile of historical hourly pavement temperature near Pullman, Washington. Graphical abstract

Temperature Correction of Deflections and Backcalculated Elasticity Moduli Determined from Falling Weight Deflectometer Measurements on Asphalt Pavements

The evaluation of the bearing capacity of asphalt pavements is usually performed by analysing the deflections measured by a Falling Weight Deflectometer (FWD). The deflection changes with the pavement temperature. In evaluation is necessary to consider the thermal gradient of pavement and perform the temperature correction. The article contains an analysis of effects of the pavement temperature on FWD results on the long-term monitored sections. The temperature correction was performed on measured deflections or back-calculated elasticity moduli. The moduli recalculated to the temperature of 20 °C according to both procedures were similar. Comparison of moduli determined by recalculation to moduli backcalculated from the deflection bowls measured at the temperature of 20 °C, has proven smaller differences for the moduli determined from the deflection bowl corrected to the temperature of 20 °C.

Bitumen Rheological and Chemical Investigation

This paper is to study the mechanism of aging on the Rheological and Chemical Investigation of the bitumen and make correlations with the actual field behavior of the binder. The effects of ageing on rheological properties of asphalt has been studied by Bending Beam Rheometer(BBR). The objective of conducting these tests is to evaluate the performance of the bitumen in an aged and unaged states in relation to the effects of traffic speed and/or pavement temperature, traffic volume (number of load repetitions), and (thermal/load) cracking behavior.

Emission Characteristics of VOCs during Asphalt Pavement Construction

As the important part of expressway, the construction technology of asphalt pavement will contribute to the production of greenhouse gases and other volatile organic compounds (VOCs), which has a significant impact on the environment. In order to further analyze the composition, distribution and release of VOCs during asphalt pavement construction, the VOCs emission during paving and rolling were measured through field investigation and sampling. The results show that there are approximately 100 kinds of VOCs substances detected due to the complex organic component of asphalt binder, which is a critical factor to influence the VOCs emission during asphalt pavement construction. During the paving process, the largest VOCs release is 1015.05 ug/m3. With the increase of rolling times, the pavement temperature gradually decrease, and the VOCs emission drops to 266.73 ug/m3. The content of the 10 kinds of substances with the highest concentration accounts for more than 50% of the total VOCs content, in which the proportion of aliphatic hydrocarbons (ALH) and oxygenated hydrocarbon (O-HYD) of the paving process are the highest, while the proportion of aromatic hydrocarbons (ARH) is dominated in the rolling process. The results are vulnerable to the external environment, especially at lower emission level. The relevant research results have certain guiding significance for the control and treatment of harmful gas emission in the construction process of asphalt pavement.