Hesham Ali

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.

On the Road to Sustainability: Properties of Hot In-Place Recycled Superpave Mix

Most state departments of transportation (DOTs) adopted the Superpave® mix design method in the late 1990s. The Superpave mix design method replaced the Marshall method and became mainstream. Superpave came with aggregate, binder, and mix requirements to control rutting and cracking. With a life expectancy of about 15 years, many Superpave roads are now becoming candidates for resurfacing or recycling. Can Superpave mixes undergo hot in-place recycling with success? In fact, Superpave mixes contain expensive and high-quality aggregates, which meet the consensus properties, and high-quality binder, which meets the performance grade (PG) requirements. If these mixes can be recycled in place and meet the original Superpave properties, then substantial savings can be realized. The potential savings are in the 30% to 50% range of the cost to mill and resurface. In addition, emissions could be reduced by 70%, while 100% of the existing material could be reused. This paper reports on an experiment conducted in Gainesville, Florida, in 2010 at the Florida DOT State Materials Office, in which a Superpave mix underwent the hot in-place recycling process. The properties of the aggregate, binder, and mix were compared to answer certain questions about aggregate degradation, binder rejuvenation, and mix properties. The answers to these questions shed light on the possibility of the 100% recycle of Superpave mixes. The results showed that minimal aggregate degradation took place. The recycled mixes met Superpave gradation requirements for the most part. The rejuvenated binder met or exceeded the PG requirement. The mix could be engineered to meet the air voids requirement of Superpave.

Life Cycle of Hot In-Place Pavement Recycling: Case Study

It is no secret that all levels of government face unprecedented levels of deficits. While revenues drop, the costs to maintain infrastructure grow with its age. The question of sustainability takes center stage. Can the United States afford to keep its highway assets, all 3 million miles of its paved roads? The study reported in this paper examined hot in-place pavement recycling (HIPR) as a way to reduce the cost of pavement rehabilitation. The Florida Department of Transportation built a test section in 2002 and a control section in 2003 to compare the cost and performance of HIPR with conventional milling and resurfacing. After 8 years, in-service data were used to draw some conclusions. The test and control road sections performed well. The HIPR section was built at less than half the cost of the conventional section. Projections showed that HIPR was cost-effective and would save 40% more than the conventional method of pavement rehabilitation. These cost savings, taken together with derived environmental benefits, make pavement in-place recycling an option that should not be ignored.

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.

Pavement Manager at Risk in Construction of Hot Mix Asphalt

Pavement management is part science, part management, and part experience. After several decades of promoting pavement management, many road owners are still reluctant to use it as they lack the knowledge, the experience, or the confidence. The problem is further complicated by the emergence of a large list of new products and techniques that are self-proclaimed to achieve miracles but fall short. The outcome of this arrangement is that thousands of miles of roads still cost more to maintain than if effective pavement preservation techniques were used. This paper attempts to resolve this dilemma by introducing the role of Pavement Manager at Risk (PMAR), allowing a Pavement Manager to offer a long-term pavement preservation service to a client in return for a fixed per-mile premium. This allows the knowledgeable Pavement Manager, who would typically be a Pavement Engineer or a practitioner with extensive knowledge and experience, to implement effective pavement preservation techniques and share the economic benefit with the owner. In this study, the responsibilities of the Pavement Manager at Risk (PMAR) will be introduced. The type of analysis it needs to run will be demonstrated in a case study. In this paper, a sample analysis is presented to present the financial aspects of managing a network of local roads. Pavement treatment cost, pavement condition, and treatment life extension in addition to the admin, mobilization, striping, and occasional patches expenses are presented. The benefits and risks of this approach are described.