Mojtaba Mohammadafzali

Asphalt Mixture Segregation Detection: Digital Image Processing Approach

Segregation determination in the asphalt pavement is an issue causing many disputes between agencies and contractors. The visual inspection method has commonly been used to determine pavement texture and in-place core density test used for verification. Furthermore, laser-based devices, such as the Florida Texture Meter (FTM) and the Circular Track Meter (CTM), have recently been developed to evaluate the asphalt mixture texture. In this study, an innovative digital image processing approach is used to determine pavement segregation. In this procedure, the standard deviation of the grayscale image frequency histogram is used to determine segregated regions. Linear Discriminate Analysis (LDA) is then implemented on the obtained standard deviations from image processing to classify pavements into the segregated and nonsegregated areas. The visual inspection method is utilized to verify this method. The results have demonstrated that this new method is a robust tool to determine segregated areas in newly paved FC9.5 pavement types.

The Effect of Aging on the Cracking Resistance of Recycled Asphalt

Fatigue cracking is an important concern when a high percentage of Reclaimed Asphalt Pavement (RAP) is used in an asphalt mixture. The aging of the asphalt binder reduces its ductility and makes the pavement more susceptible to cracking. Rejuvenators are often added to high-RAP mixtures to enhance their performance. The aging of a rejuvenated binder is different from virgin asphalt. Therefore, the effect of aging on a recycled asphalt mixture can be different from its effect on a new one. This study evaluated the cracking resistance of 100% recycled asphalt binders and mixtures and investigated the effect of aging on this performance parameter. The cracking resistance of the binder samples was tested by a Bending Beam Rheometer. An accelerated pavement weathering system was used to age the asphalt mixtures and their cracking resistance was evaluated by the Texas Overlay Test. The results from binder and mixture tests mutually indicated that rejuvenated asphalt has a significantly better cracking resistance than virgin asphalt. Rejuvenated mixtures generally aged more rapidly, and the rate of aging was different for different rejuvenators.

Aging of Rejuvenated Asphalt Binders

An important concern that limits the RAP content in asphalt mixtures is the fact that the aged binder that is present in the RAP can cause premature cracking. Rejuvenators are frequently added to high RAP mixtures to enhance the properties of the binder. There is no existing method to predict the longevity of a rejuvenated asphalt. This study investigated the aging of rejuvenated binders and compared their durability with that of virgin asphalt. Various samples with different types and proportions of RAP, virgin binder, and rejuvenator were aged by RTFO and three cycles of PAV. DSR and BBR tests were conducted to examine the high-temperature and low-temperature rheological properties of binders. Results indicated that the type and dosage of the rejuvenator have a great influence on the aging rate and durability of the binder. Some rejuvenators make the binder age slower, while others accelerate aging. These observations confirm the importance of evaluating the long-term aging of recycled binders. For this purpose, critical PAV time was proposed as a measure of binder’s longevity.

Evaluation of cracking resistance and durability of 100% reclaimed asphalt pavement mixtures

E Arc Furnace (EAF) usage in producing steel is gaining importance day by day due to its special advantages. During smelting and refining of steel, the gases leaving the furnace carries a substantial amount of fine dust particles. The amount of dust generated is usually in the range of 9-18 kg per ton of scrap melted. The dust is important resource for the recovery of zinc and always better than its disposal as landfill. In order to recover zinc, the hydrometallurgical processes have been considered which are more eco-friendly and produces residues suitable for safe disposal as zinc could be selectively dissolved in suitable lixivants viz. sulphuric acid, hydrochloric acid, ammoniacal solution, sodium hydroxide have been used on bench scale. Sodium hydroxide however is selective for zinc dissolution but it needs further development for the metal recovery from the sodium zincate solution by electrolysis. Processes based on hydrochloric acid have not yet found any commercial application due to non-selective leaching and costly material of construction. Sulphuric acid have been found to be effective reagents for treatment of EAFD. The present paper examines and optimizes various parameters to recover zinc from EAF dust.