Asphalt Road Pavement Research Articles

Greenhouse gas emissions from road construction in China: A province-level analysis

Road construction is a major contributor of greenhouse gas emissions in the transport sector. In this study, by using the life cycle assessment method, the greenhouse gas emissions from road construction in China are calculated on both the national and provincial levels. The results show that the equivalent cumulative carbon emissions from road construction in China were 1104 Mt CO2e by 2013. Cement production accounts for the major emission, responsible for 87% of all emissions. The per-kilometer greenhouse gas emissions of cement-paved roads were over 60% higher than asphalt-paved roads. On the provincial level, the per square kilometer greenhouse gas emissions ranged from 10.6 t CO2e/km2 in Tibet to 823.0 t CO2e/km2 in Shanghai. The emissions level in coastal provinces was significantly higher than those in central and western provinces. This implies a huge growth potential of greenhouse gas emissions in the underdeveloped regions. Based on the analyses, it is suggested that greenhouse gas emissions associated with road construction should be paid more attention. A holistic approach should be employed to realize environmental-friendly road construction. Especially, the planning of road network expansion and the choice of road pavement materials should be determined with a strong consideration on their greenhouse gas emissions impacts.

Using traffic speed deflectometer to measure deflections and evaluate bearing capacity of asphalt road pavements at network level

The paper deals with diagnostics of bearing capacity of asphalt pavements by a Traffic Speed Deflectometer (TSD device), which allows to measure pavement deflections continually at the traffic speed on the basis of dynamic loading induced by moving wheel of a reference axle at the speed of up to 80 km/h. The paper aims to inform of a new method to measure road pavement deflections, describes the principles of measuring pavement deflections by TSD device, and presents results of comparative measurements between FWD (Falling Weight Deflectometer) and TSD devices organized by CDV in Italy and Slovakia. Particular attention was paid to the difference between deflections measured by FWD and TSD devices.

Pothole detection on asphalt pavements from 2D-colour pothole images using fuzzy c -means clustering and morphological reconstruction

Abstract In general, potholes on asphalt pavements can be detected and represented in 2D and 3D. However, pothole detections through 3D imaging and image reconstructions have proven to be expensive in terms of acquisition equipment and the computational and processing requirements and time. For potholes at incipient formations, their detection, representation and quantification in terms of the surface-area are important for timely maintenance and repairs. By casting pavement image segmentation for pothole detection as a problem of clustering multivariate features within mixed pixels (mixels), this study presents a low-cost 2D vision image-based approach for the detection of potholes on asphalt road pavements in urban areas. The approach in this study is based on the a priori integration of multiscale texture-based image filtering for textons representation using wavelet transform, into the superpixel clustering of the pavement defects and non-defects using fuzzy c-means (FCM) algorithm. For the extraction of the defects extrema (minima and maxima) in the hybrid wavelet-FCM clustering results, fine segmentation based on morphological reconstruction is adopted to further smoothen and recognize the contour of the detected potholes. The methodology is implemented in a MATLAB prototype, tested and validated using 75 experimental image datasets. With a mean CPU run-time of 95 seconds, the average detection accuracies by comparing the study results and the manually segmented ground-truth data were determined using the Dice coefficient of similarity, Jaccard Index and sensitivity metric as 87.5%, 77.7% and 97.6% respectively. The average magnitudes of the mean and standard deviation of the percentage errors in pothole size extractions were detected as 8.5% and 4.9% respectively. The results of the study show that with well-planned road condition surveys, the proposed algorithm is suitable for the detection and extraction of incipient potholes from 2D vision images acquired using low-cost consumer-grade imaging sensors.

Effect of cross-linkers on the performance of polyethylene-modified asphalt binders

Phase separation or lack of storage stability is one of the challenges of using polymer-modified binders in flexible asphalt road pavements. Meeting this challenge while maintaining the performance of these binders is of great interest to pavement engineers. The research reported in this paper aimed to solve the problem of the susceptibility of binders modified with high-density polyethylene to phase separation by using cross-linking agents. Sulfur and polyphosphoric acid were selected to improve the storage stability of the polyethylene. These materials were added to a 60/70 penetration graded asphalt binder in different amounts, and a cigar-tube test was performed to determine the separation tendency of the polyethylene. In addition, a linear-amplitude sweep test was used to evaluate the fatigue performance of the resulting binders. The results showed that, unlike sulfur, polyphosphoric acid improved the storage stability and performance against fatigue of the polyethylene-modified binders.

Road Crashes in Addis Ababa, Ethiopia: Empirical Findings between the Years 2010 and 2014

Ethiopia has a high road crash rate in the world. Among the crashes, more than 60% occur in the capital city, Addis Ababa. The main aim of this research was to inform policymakers and researchers about the current situations of road crashes in the city to tackle the current unacceptable costs of the road crashes. We analyzed road crash data between the years 2010 and 2014. The results showed 14,263 persons sustained different levels of injuries in which 1,911 were fatal whereas the rest were serious and minor injuries. Majority of the fatal (79%) and serious (76%) injuries were males, and pedestrians (87%). Most of these crashes were due to the drivers’ not yielding right of way to pedestrians. On the other hand, an estimated 19 million US dollars cost of property damage was due to the drivers not yielding right of way to other vehicles. Generally, among other risk factors we assessed including road conditions and asphalt pavement, drivers’ not yielding right of way to pedestrians and not yielding right of way to other vehicles were the leading risk factors for road crashes in the city. Key Words : Road Crash; Fatalities; Serious Injuries; Minor Injuries; Safety

Thermal stabilization and permanent deformation resistance of LWA/PCM-modified asphalt road surfaces

This paper presents the results of attempts at reducing the problem of solar overheating of asphalt road pavement surfaces, resulting in weakening and accelerated destruction of the aforementioned structures.To protect pavement surfaces against periodic overheating, standard asphalt mixture AC 16 W 35/50, used for binder course, has been modified by replacing one of the aggregate fractions from the mineral mixture with lightweight aggregate (LWA) soaked in phase-change material (PCM). This modified asphalt mixture, placed under the thin standard asphalt wearing course without any modification (no LWA and no PCM), serves as a temperature and permanent deformation stabilizer of the asphalt surface layer.To ensure maintaining the highest possible resistance to permanent deformation the newly design asphalt mixture has been verified with the rutting tests. Two different asphalt packet layers have been tested. First the configuration contained only the binder course and the second test configuration-double-layered ones – comprised of binder course covered by thin wearing course.To verify the correctness of conclusions drawn from theoretical thermal considerations, experimental temperature simulation tests were conducted under laboratory conditions on two asphalt specimens with dimensions of 0.30×0.30×0.10m. The first one, standard AC 16 W 35/50, served as reference specimen, while the second one, PCM AC 16 W 35/50 containing LWA with PCM (LWA/PCM), was tested. In both cases a binder course was covered by a wearing course from stone mastics asphalt SMA without LWA/PCM. The simulations have confirmed that 3% wt. addition of PCM, in relation to the weight of the asphalt mixture for binder course, reaches a reduction in surface temperature of about 4°C in moderate laboratory conditions, within the tested temperature range between 30 and 60°C.

Novel Heat Harvesting for Low Energy Draw Solution Regeneration: Simulation Study

In hot regions like the Middle East, the road asphalt pavement experience many fluctuations in their temperature profile that provides the large dark surface area with intensive heat absorption capacity, which warms the roads up to 75°C or more in summer. This phenomenon is negatively affecting the performance and urban heating. On the other hand, the most amount of water available (about 97%) is low-quality water or seawater, which needs to be treated in an efficient way to cope with the dramatic increase on demand of clean water due to population growth and agriculture requirements. Several techniques have been used for water desalination and most are thermally based techniques. Therefore, they are consuming high energy per water desalinating volume. The aim of this study is to design a novel heat harvesting system combined with a membrane based unit, to produce clean water from impure water. The heat will be harvested from the roads and buildings, by a low-grade system through Forward Osmosis (FO) unit. The diluted draw solution (SD) will be regenerated at low operating temperature, while the road and building’s roofs surfaces are cooled and maintained at a lower temperature. The proposed technology will save energy and enhance microclimate conditions as well. The innovative DS regeneration system was simulated by HYSYS V8.8 and the results show a 1.17 m3 /hr of treated water can be recovered for each one-m2. The quality of water depends on the amount of heat harvested and, consequently the surface temperature. Potable water is achievable only when the surface temperature is higher than 70°C and, therefore a trim heater is recommended for the winter season otherwise, the water will be used for non-drinking applications. Although the required Capex for this technology is around $13778/m2, but the payback is two years.

Factors affecting raveling of motorway pavements—A field experiment with new additives to the deicing brine

Recently, a novel additive to the de-icing brine has been introduced. It reduces raveling, i.e., the loss of stones of aggregate from asphalt road pavements. To assess the scale of this reduction, a field experiment was conducted. It lasted for two years and consisted of repeated measurements of 540 lane km of motorways in three European countries. Tailored statistical models were used to elucidate the relative importance of different factors influencing raveling—the novel additive, traffic intensity, asphalt age, and initial raveling. The reported results and predictive models are coupled with a detailed accuracy analysis.

Risk provision using field spectroscopy to identify spectral regions for the detection of defects in flexible pavements

Natural and physical hazards accelerate the deterioration of asphalted surfaces. Climatic factors are unavoidable and can affect the properties of asphalt mixtures, making them weaker and less durable. Thus, continuous monitoring of bituminous surfaces is something that can reduce the risks of public health. Remote sensing techniques have become an effective, noninvasive method for early detection of damaged asphalt pavements. This paper outlines a range of different remote sensing methodologies that can be used to monitor asphalt road pavements. This is complemented by the use of field spectroscopy for the examination of asphalt pavements of varying age and conditions. The results of the study found spectral differences regarding asphalt defects, such as physical cracking, patched cracking and polishing. These spectral changes were examined through “in-band” simulation analysis of the Landsat 7 ETM+ sensor, using appropriate relative spectral response filters, concluding that the ratio band 5/band 1 can be used to distinguish asphalt pavements of different date of construction and condition.

Using Crumb Rubber from Waste Tires to Reduce Road Traffic Noise

The results of measurements of sound pressure levels on an experimental road section (road pavement with addition of crumb rubber from waste tires) in Mala Ida village (Kosice region, Slovakia) and on a road with stone mastic asphalt in Haniska village (Presov region, Slovakia) are presented in the paper. The results obtained using statistical pass-by methods were compared and they confirmed that road surface with addition of crumb rubber from waste tires produced quieter pavement than stone mastic asphalt road pavement alone.

Temperature and Moisture Variation in Pavement Structures of the Test Road

Environmental conditions (temperature, moisture, intensity of sun, etc.) influence variation in asphalt pavement strength during the year. Lithuania is situated in a zone of cool average climate characterized by average warm summers and average cold winters. One of the most important climatic factors is the air temperature variation per day. In order to evaluate the dependence of road pavement strength on temperature and the dependence of Eo modulus of separate layers on seasonal factors a comprehensive research was carried out on the unique Test Road section that was constructed in 2007 in Lithuania and is operated almost for 8 years. This road is affected by real climatic conditions and high intensity heavy vehicle traffic. It consists of 27 different flexible pavement structures with the same class of pavement structure but the different type and composition of materials and all necessary electronic sensors (loop profilers, temperature and moisture sensors, stress and strain transducers). Temperature and moisture sensors are installed in 4 different pavement structures. In order to analyse behaviour of asphalt pavement structure under Lithuanian climatic conditions, taking into account temperature and moisture, as one of the most important climatic factors influencing structural strength of road asphalt pavement, the experimental research was carried out and results are presented in the article.

Assessing the feasibility of impregnating phase change materials in lightweight aggregate for development of thermal energy storage systems

This paper assesses the feasibility of impregnation/encasement of phase change materials (PCMs) in lightweight aggregates (LWAs). An impregnation process was adopted to carry out the encasement study of two different PCMs in four different LWAs. The leakage of the impregnated/encased PCMs was studied when they were submitted to freeze/thawing and oven drying tests, separately. The results confirmed that, the impregnation/encasement method is effective with respect to the large thermal energy storage density, and can be suitable for applications were PCMs cannot be incorporated directly such as asphalt road pavements.

Using carbon dioxide emissions as a criterion to award road construction projects: a pilot case in Flanders

In the last decade, innovative technologies with regard to improved energy and material efficiency of asphalt pavement construction have been implemented by road industries. Two technologies are currently advocated: warm mix asphalt technologies and the increased use of reclaimed asphalt pavement. Unfortunately, these technologies were evaluated only by their technical and economic benefits and in most cases without an environmental impact study for the overall process. For encouraging the endeavour of the industry to implement newer – greener – technologies with focus to environmental benefit, the procuring authorities made an effort to enforce a sustainable approach for road works by the Project Carbon Free-ways. This pilot project included basic environmental parameters in the award criteria for public tenders on road works in Flanders. For this project two calculation tools, called Carbon Counter and Traffic Tool, were developed by the Flemish Agency for Roads and Traffic in order to estimate the carbon dioxide emissions of respectively the construction process and the traffic disturbance caused by the construction. The subject of this first public tender – with an evaluation of both tools – was the reconstruction of an asphalt road pavement in Kontich (Belgium). In this contribution the preliminary study on the methods of the tools and the main conclusions of the project are reported and discussed. The study illustrated that the current tendering process and the tools used, do have some limitations and drawbacks: the tools do not cover the total environmental impact as e.g. LCA do, the data concerning recycling or specific plant-related processes are outdated or missing and the data collection for back calculation of the total emission required too much manual efforts and shortcomings. Nevertheless, this pilot project proved to be a valued attempt to achieve more innovative and sustainable public procurement – as a first step, giving an unambiguous signal to the industry that this type of selection will be part of future tenders.

The Dynamic Response of Large Longitudinal Slope of Asphalt Road Pavement under Heavy Impulsive Load

In order to conduct a further investigation of the causes of damages in large longitudinal slope of asphalt road pavement under actual heavy load, a three-dimensional finite element model was established by ANSYS finite element software. Through applying impulsive load in this model, the variation of the strains of large longitudinal slope of asphalt road pavement under different conditions was obtained and the influence of gradient on the dynamic response of large longitudinal slope of asphalt road pavement was analyzed. The results show that the strains of large longitudinal slope of asphalt road pavement increased with the increase of load times. Flexure tensile strain and shear strain were similitude with the change tendency of the increase of overloading rate but the data increased significantly. The transversal shear strain increased with the increase of gradient.

The importance of the use phase on the LCA of environmentally friendly solutions for asphalt road pavements

In order to assess sustainability of products and processes, different methodologies have been developed and used in the last years. In the road pavement construction area, most methodologies used for Life Cycle Assessment (LCA) are essentially focused in the construction phase. The present paper analyses the importance of the use phase of a road in the LCA of different paving alternatives, namely by evaluating energy consumption and gaseous emissions throughout the road pavement’s life. Therefore, a new LCA methodology for road pavements was developed, and the results of its application to a case study involving the construction of alternative pavement structures are discussed. The study intends to assess the influence of using more sustainable paving construction alternatives (asphalt recycling vs. conventional asphalt mixtures), and/or different surface course materials (which have a higher influence on the rolling resistance and, therefore, affect the performance during the use phase). The LCA results obtained for this case study showed that the reductions in energy consumption and gaseous emissions obtained during the use phase, for pavement alternatives with a lower rolling resistance surface course, are higher than the total amount of energy consumption and gas emissions produced during construction. It is therefore clear that some improvements in the characteristics of the surface course may have an effect over the road use phase that will rapidly balance the initial costs and gas emissions of those interventions. The LCA results obtained also showed that the sustainability of pavement construction may also be improved using recycled asphalt mixtures.

Durability of asphalt mixtures: Effect of aggregate type and adhesion promoters

Asphalt road–pavements are sensitive to water ingress, which degrades the bitumen to aggregate adhesion, promoting failure. The effects of water on a range of asphalt systems have been quantified using peel tests. The bitumen binder on an aluminium backing was peeled from the aggregate fixed arm and the fracture energy was determined. In dry conditions, failure was cohesive within the bitumen, but became mainly interfacial between the bitumen and aggregate after immersion in water. The effect of water on the adhesion of bitumen to three aggregates (limestone, marble and granite) was evaluated. Acidic aggregates (granite) showed a greater loss of adhesion than basic aggregates (limestone and marble) under wet conditions. The porosity of the aggregates, although shown to be significant, was less important than their chemical composition. The interfacial adhesion in wet conditions can be improved by mixing a silane, amine or rubbery polymer into the bitumen.

Environmental Impact Assessment of Road Asphalt Pavements

This paper deals with a versatile, synthetic, simple and user-friendly method based on Life Cycle Assessment studies which summarizes multifaceted, often competing, environmental, technical and economic aspects in road construction. In many cases just economic criteria are applied in call for tenders, because the calculation of the environmental impact of road construction is difficult. In fact, it can be referred to many available options and both the economic and the environmental suitabilities have to be considered, in order to achieve globally sustainable results about road infrastructure work. In this research, the weighted sum model of multicriteria analysis is identified as the tool to evaluate global impact of road works, to compare solutions and to choose the best one. The advantages of the proposed approach are that the local contest and the stakeholders’ objective are represented by adopting variable parameters and weights, in order to apply the method to several contexts. A case study explains potential environmental implications of using this new Road Environmental Impact Assessment to calculate effect related to the production of asphalt pavement, considering the production system for aggregates from cradle to gate, the materials transportation to road site and the works to have the road done.

Traffic load impact on the initiation and development of plastic deformations in road asphalt pavements

The up-to-date road pavement structure research methods and application computer programs are based on the theory of elasticity. This theory is most widely used in the model of road pavement structure response where the load under the action of vehicle wheel causes stresses and strains in pavement structure. When determining the bearing capacity of existing pavement structures and the need for their strengthening the most often used are the research data collected and/or engineering experience gained. This article presents the initiation and development of plastic deformations in asphalt pavement layers that were evaluated knowing the real loading conditions of tested structures. Research was accomplished in 12 structures with the different asphalt layers during the road exploitation period for 5 years used at identical conditions: under the same traffic load, weather conditions and hydrothermal regime of pavement structures.

Micro-Mechanism Study and Road Engineering Application of Asphalt Rubber

Based on the results of electron microscope observation, the formation mechanism of asphalt rubber can be explained as followed: both chemical and physical reaction take place when crumbed rubber and base bitumen are mixed together. Physical swelling of the crumbed rubber particles take place during the process, at the same time a layer of gel comes into being on the surface of the crumbed particles, through which the particles connect with each other and form a network structure. Because of the unique formation mechanism of asphalt rubber, the material provide some much better properties than other kinds of bitumen. The main points of choosing raw material and production technology of asphalt rubber is given out based on the results of a series of contrast tests such as different sizes of crumbed, different crumbed rubber content, different reaction time and different reaction temperatures. The good performance of asphalt rubber in the field of road engineering is proven based on the test results of asphalt rubber premix and road pavement.

The Investigation and Analysis of City Road Asphalt Pavement Damage in Hohhot

With the development of local economy, the increase of urban population and the poor infrastructure in old urban area cant meet the development of the modern city. Small and medium-sized city traffic problems have gradually become the negative factors which hinder and restrict the city social economy development. As viewed from Hohhot, this article mainly aims at the urban road asphalt pavement damage condition, analyses the main damage types and puts forward to the renovation and maintenance programs.