Paving Operations Research Articles

Operator guidance systems in road construction: a technological mediation perspective

PurposeUsing real-time support systems may help operators in road construction to improve paving and compaction operations. Nowadays, these systems transform from descriptive to prescriptive systems. Prescriptive or operator guidance systems propose operators actionable compaction strategies and guidance, based on the data collected. It is investigated how these systems mediate the perceptions and actions of operators in road pavement practice.Design/methodology/approachA case study is conducted on the specific application of an operator guidance system in a road pavement project. In this case study, comprehensive information is presented regarding the process of converting input in the form of data from cameras and sensors into useful output. The ways in which the operator guidance systems translate data into actionable guidance for operators are analyzed from the technological mediation perspective.FindingsOperator guidance systems mediate actions of operators physically, cognitively and contextually. These different types of action mediation are related to preconditions for successful implementation and use of these systems. Coercive interventions only succeed if there is widespread agreement among the operators. Persuasive interventions are most effective when collective and individual interests align. Contextual influence relates to designs of the operator guidance systems that determine human-technology interactions when using them.Originality/valueThis is the first study that analyzes the functioning of an operator guidance system using the technological mediation approach. It adds a new perspective on the interaction between this system and its users in road pavement practice.

Geosynthetic materials properties analysis suitable for controlling reflective cracks in asphalt concrete

Reflective cracks appearing in the new asphalt concrete layer laid during reconstruction over the existing concrete or asphalt concrete pavement is the main cause of premature highways failure. Cracks of this type appear over defects in the old pavement and grow through the new pavement under the influence of vehicle loads and fluctuations in the temperature field. One of the common ways to combat reflective cracks is the use of an intermediate reinforcing layer made of special geosynthetic material, redistributing part of the loads. The paper proposes a multilayer pavement structural model and a temperature field change model based on the design documentation of the M-11 «Neva» highway and data from the temperature monitoring station. Temperature stresses сalculation arising in reinforced asphalt concrete layers in the existing crack vicinity of the old pavement is performed by the finite element method using the approximate method of Hills and Brien, reducing the calculation to the sequence of solving problems of linear elasticity theory. The dependencies of asphalt concrete rigidity modulus on temperature and time of load action are calculated on the basis of penetrative index and the binder softening temperature, taking into account the inevitable aging of the binder during paving and pavement operation. It is shown that significant reduction of dangerous tensile stresses in asphalt concrete is possible at reinforcement with geogrids with maximum tensile strength not lower than 100 kN/m, made on the basis of high-modulus glass or carbon fibers, under condition of joint work of asphalt concrete and reinforcing layers in the absence of mutual slippage.

A review of environmental emissions from asphalt plants and paving

Asphalt is a black, thermoplastic, hydrocarbon material extracted from crude oil and widely used in road construction all over the world. In order to meet the requirements of construction technology, asphalt always needs to be heated to flow state in the process of mixing and paving, during which a large amount of asphalt fume is released. Asphalt fume is a complex mixture of inorganic compound gases, volatile organic compounds and particulate matter, which poses a serious threat to the natural environment and the health of practitioners. This review presents HMA and WMA constituents and the potential health effects of criteria and Hazardous pollutants generated from asphalt pavement construction. Hot mix asphalt (HMA) and warm mix asphalt (WMA)are a major construction materials used for highway roads, building roads, airport runways, parking, and other pavement repairs in the worldwide. During HMA construction, a considerable number of volatile organic compounds (VOCs) are generated during asphalt pavement construction, and present negative effects on workers health. Accurate identification, quantification and measurement of emissions during HMA and WMA paving operations were used to identify and quantify VOCs, SVOCs, hazardous air pollutants (HAPs) and polycyclic aromatic hydrocarbons (PAHs) in asphalt fumes during production and paving activities.

Interlayer bonding properties of warm recycled asphalt pavements

The need for sustainable road infrastructures has led to great interest in Warm Mix Asphalt (WMA) technologies, which allow the production, lay-down and compaction of asphalt mixtures at reduced temperatures, about 40°C lower than traditional Hot Mix Asphalt (HMA). The use of WMA ensures lower emissions and is also beneficial in the recycling of Reclaimed Asphalt (RA) deriving from the milling of end-of-life pavements. One of the main concerns regarding WMA is the possible poor adhesion between the pavement layers that could be caused by the reduced working temperatures during the paving operations. However, almost no data are currently available in literature on this aspect, which thus could represent a deterrent to the wide application of WMA by road agencies. In this regard, this paper focuses on the investigation of the interlayer bonding properties of warm recycled asphalt pavements constructed along various Italian motorways and national roads using different WMA chemical additives. The Interlayer Shear Strength (ISS) was measured at different pavement interfaces (wearing-binder, binder-base) and time intervals by testing extracted cores with ASTRA and Leutner equipment. The results show that the interlayer bonding properties of WMA pavements are comparable to HMA pavements and are not affected by the WMA additive type. Moreover, ISS depends on the properties of the tack coat applied between the layers and increases over time due to aging effects, especially when the interface is below an open-graded friction course (OGFC). These findings further encourage the use of WMA as environmentally sustainable technologies for the construction and maintenance of asphalt pavements.

Rejuvenating Agents vs. Fluxing Agents: Their Respective Mechanisms of Action on Bitumen Subjected to Multiple Aging Cycles

During the service life of road pavements, the asphalt, more specifically the surface layer, is susceptible to aging due to the oxidation phenomenon and the loss of the volatile compounds of bitumen, which functions as the binder in the asphalt conglomerate. Road pavements that undergo a significant level of oxidation become rigid and susceptible to cracking, and new paving operations will need to be carried out in order to make the road ideal for continued use. However, due to recent eco-friendly initiatives that have been put in place to promote a circular economy and also mitigate the problem of environmental pollution, the asphalt industry is currently devising means of safeguarding the environment while also minimizing the cost of the production of road pavements without compromising their quality. As a general solution to this issue, old asphalt pavements are removed and recycled as reclaimed asphalt (RA), with the aim of restoring the original properties of the binder in such a way that RA can be re-used in combination with virgin materials to produce new road pavements. In this research study, virgin bitumen is subjected to a cycle of aging, after which two recycling agents are used to modify the aged bitumen samples. These samples containing the different recycling agents were subjected to a second aging cycle, a second recycling agent treatment, and then again subjected to a final aging cycle. The two recycling agents have different compositions, and each one of them could be either a rejuvenating agent or a fluxing agent. This study investigates the effect of these recycling agents on aged bitumen, and how the addition of these recycling agents influences the changes observed between virgin, aged and recycled bitumen. This would enable an understanding of rejuvenation and fluxing mechanisms, which will help in the classification of the asphalt recycling agents as either rejuvenating or fluxing agents. Dynamic shear rheology, atomic force microscopy, and light microscopy to determine asphaltene melting point were the techniques used in this investigation. The results obtained demonstrate that rejuvenating agents are more effective in reversing the effects of oxidative aging on the bitumen binder than fluxing agents.

Effect and Mechanism of Rejuvenation of Field-Aged Bitumen Extracted from Reclaimed Asphalt Pavement

Due to wear and exposure to atmospheric agents, road pavements are subject to an inevitable aging process. Asphalt rejuvenating agents implement the reorganization of the colloidal structure of aged bitumen as well as the restoration of the correct asphaltene/maltene ratio. In recent years, several incentives have been put in place regarding conservation of resources and safeguarding the environment by avoiding waste and promoting a circular economy. Reclaimed Asphalt Pavement (RAP) is one of the ways to promote and implement circular economy practices. Recovery of bitumen from RAP conglomerate is a viable way of recycling aged bitumen for use in new pavements. Aged bitumen binder from RAP however needs to be rejuvenated in order to restore its virgin properties for it to be suitable for new paving operations. This paper evaluates the effectiveness of a rejuvenating agent on reclaimed asphalt pavement through both the analysis of the mechanical modulus and the inner micro- structural of the samples. These were conducted through Dynamic Shear Rheology (DSR), Atomic Force Microscopy (AFM), Differential Scanning Calorimetry (DSC) and light microscopy.

Biomaterials and Their Potentialities as Additives in Bitumen Technology: A Review.

The carbon footprint reduction mandate and other eco-friendly policies currently in place are constantly driving the trend of the synthesis and application of sustainable functional materials. The bitumen industry is not an exception to this trend and, every day, new technologies that facilitate safer, cost effective and more sustainable industrial processes and road paving operations are being researched and brought to light. A lot of research is currently ongoing to improve bitumen's properties due to its use as a binder in road paving processes. Over the years, the most common method to improve bitumen's properties has been with the use of additives. The major drawback in the use of these additives is the fact that they are substances of strong chemical nature which are either too acidic, too basic or emit toxic fumes and volatile organic compounds into the environment. In the long run, these chemicals are also toxic to the road pavement personnel that carry out the day to day industrial and paving operations. This led researchers to the initiative of synthesizing and applying biomaterials to be used as additives for bitumen. In this light, several studies have investigated the use of substances such as bio-oils, natural waxes, gum, polysaccharides and natural rubber. This literature review is aimed at classifying the different bio-based materials used to improve bitumen's properties and to provide a deeper knowledge of the application of these biomaterials in bitumen technology. In general, we highlight how the research efforts elaborated herein could potentially foster safer, sustainable, eco-friendly approaches to improving bitumen's properties while also promoting a circular economy.

Reclaimed asphalt recycling agents: Looking into the blueprint of their mechanisms of action

As the global environmental crisis is reaching an irreversible point, within the roadway industry, the demand for eco-friendly products such as recycled asphalt pavement is at an all-time high. As a result, and thanks to the promising advancements made in the past decades, doubts no longer exist about the benefits of asphalt recycling. However, the current issue is how to increase the proportion of reclaimed asphalt in new road paving operations. This research study deals with one of the key factors of a successful asphalt pavement recycling; the recycling agents. Several techniques were applied to investigate the mechanism of action of two recycling agents speculated to be rejuvenators and/or flux oils using two different paving grade bitumens. In order to perform a comprehensive study, the testing scheme involved rheological, microscopic, chemical, and physicochemical analyses. Although the physical changes of the aged bitumen containing the studied recycling agents were similar, the chemical impacts were quite different as suggested by the results obtained from the tests performed in this study. The results demonstrate the rejuvenator having an edge over mere fluxing agents in the reversal of the aging phenomenon in bitumen. In fact, this could be determinant in the durability and quality of recycled asphalt pavement.

Effects of Flashing Blue Lights Mounted on Paving Equipment on Vehicle Speed Behavior in Work Zones

Vehicle speed in work zones is a significant concern to state transportation agencies and their construction partners. Prior research indicates that law enforcement vehicles within a work zone with active flashing lights result in reduced vehicle speeds. Placement of flashing blue lights on construction equipment during nighttime construction work has also been identified as a potential control measure to reduce speeds. The goal of this research study is to determine the impact of flashing blue lights on construction equipment on the speed of passing vehicles in mobile work zones. The research design consisted of a controlled experiment involving flashing blue lights mounted on the rear of a paver during mainline paving operations on three case study projects on high speed roadways at night in Oregon. Vehicle speed data were collected during multiple work shifts for each case study, both with and without the flashing blue lights on. The experimental results reveal that vehicle speed is affected by the presence of flashing blue lights during nighttime work. With the blue lights flashing and at distances upstream of the paver where the driver can see and react to the blue lights, mean vehicle speeds tended to be 4.3–25.7 km/h slower than when the blue lights were off. Closer to, immediately adjacent to, and downstream of the paver, the difference in the mean speed with the blue lights on was typically less or not significant; in some cases and mostly downstream of the paver location, the mean speeds were higher with the blue lights on than with the blue lights off. The speed differential (i.e., the speed prior to the work zone minus the speed in the work zone) was measured as 4.8–11.3 km/h greater with the blue lights turned on than with the blue lights off. The results support construction contractors and state departments of transportation for decision making about the use of flashing blue lights on equipment in work zones. The researchers recommend using flashing blue lights on paving equipment during nighttime operations if allowed by local laws to reduce the speed in the work zone and increase worker and driver safety. This research contributes to the construction industry by providing quantitative evidence of the extent to which flashing blue lights mounted on paving equipment impact vehicle speeds in work zones. Recently, all stakeholders, including the Oregon Department of Transportation, law enforcement, and contractors, have agreed to use the flashing blue lights on paving equipment in Oregon during the 2021 construction season.

Construction of an Electrically Heated Asphalt Road Based on Ribbon Technology

Although asphalt pavements are the most common pavement type worldwide, there is no accepted heating solution for this infrastructure class for melting snow and preventing ice formation at the ride-surface. This study was concerned with utilizing electric ribbon technology as a suitable heating solution. A method was proposed to introduce ribbon heaters into the typical paving process in a practical manner, causing minimal disruption to the normal paving operations, that is potentially expandable to large areas. The advocated idea was to deploy ribbons after an asphalt concrete (AC) lift has been paved and compacted, and before paving and compacting the next AC lift(s). In this context, a special grooving machine was envisioned to make shallow channels in the AC for cradling each ribbon. Thus, the system survivability is guaranteed, with all ribbons protected against the maneuvering of trucks, paving equipment, and heavy rollers. Subsequently, the method was demonstrated through the full-scale construction of a heated road that included installing ribbons in-between AC lifts. For this purpose, the protective ribbon channels were grooved with a customized milling machine. The entire construction process was described in detail, and some initial findings from activating the system were also included. An overall system survivability of 97% was achieved, and the installation concept appears practical and up-scalable.

Eksplicitno definiranje postupka asfaltiranja kolnika - temeljni preduvjet za poboljšanje kvalitete

The objective of the paper is to make explicit the paving operations, the related asphalt temperature and density data, and the logistic process, as a fundamental step to identify improvement opportunities. For that, temperature data, roller compactor trajectories, asphalt density, paver speed, and trucks logistics, were collected. The results, analysis, and feedback received, point to specific opportunities for improvement, including avoiding the paver start-stop cycles, uniform compaction of the entire pavement surface, and definition of roller compaction strategy.

Effect of Nighttime Construction on Quality of Asphalt Paving

AbstractThe need to meet increasing economic vitality has caused continued deterioration of road surfaces owing to the constant use fueled by high traffic volume. Nighttime paving operations are of...

Evaluation of a non-nuclear density gauge as an alternate to destructive coring for airport asphalt acceptance testing

A non-nuclear density gauge (NNDG) was evaluated as part of an asphalt runway resurfacing project. The repeatability of the NNDG was found to be high but asphalt temperature and surface moisture had a significant effect on the reliability of NNDG inferred asphalt density. It was also found that a single NNDG inferred density, located immediately over the core location, provided greater agreement with core density than an averaged NNDG density over and around the location of the core. It was concluded that when used 1 day behind the surface paving operation, when the temperature had stabilised and the surface was dry, the NNDG was a reliable replacement for destructive coring for density measurement. Consequently, the coring frequency was reduced by 75% following NNDG calibration. However, the influence of temperature and moisture rendered the NNDG less suited to quality control during the compaction rolling process. Finally, it is recommended that additional research be undertaken to extend these conclusions to other asphalt mixtures, allowing other airports to reduce the frequency of destructive coring for density testing during asphalt resurfacing, following mixture-specific calibration of the NNDG.

Determination of in-field temperature variations in fresh HMA and corresponding compaction temperatures

Hot mix asphalt (HMA) compacted at low temperatures develops many distresses due to high air voids. Asphalt compaction operations in the field are mostly based on the experience of field staff. Hence, independent of the actual temperature of the HMA. In this study, temperature variation in hot mix asphalt (HMA) was investigated during paving operations at eight test locations in field. Two most commonly used HMA layer thicknesses i.e. 5 cm and 8 cm were studied. Temperature of the fresh HMA layer was noted at the centre, surface and at the interface points by four node K-type thermocouple assembly. The average laying temperature of the HMA for eight tests was calculated as 136.92 °C. Whereas, the average compaction start temperature for eight tests was noted as 127.81 °C which shows the critical temperature loss of 9.11 °C before the compaction starts. The average compaction end temperature calculated was 62.89 °C which is below the common cut off temperature of 80 °C. Temperature difference between day and night tests was 10 °C which can be attributed as the effect of sunlight. The results of this study can be helpful to the field staff in decision making during paving operations.

Stone mastic asphalt (SMA) with crumb rubber according to a new dry-hybrid technology: A laboratory and trial field evaluation

Today the use of recycled and second-hand materials can be considered as a suitable solution for the construction or the rehabilitation of road pavements. The increasing interest in this process lead to the study and the evaluation of different waste materials, not directly connected to the construction field, among these Crumb Rubber from end-of-life tires. To date, this recycled material has been added into bituminous mixes for road pavements according to several technologies, for the production of different mixtures. In the present paper, the crumb rubber was used for the production of Stone Mastic Asphalt (SMA) according to a new dry-hybrid technology. A full laboratory investigation and a trial field study are here presented. A complete physical and mechanical characterization was carried out to define a specific mix design. Once defined these properties, a full-scale test section was constructed: specific in situ tests and collection of samples were planned. In both the laboratory and trial field phases, tests results were always compared to those obtained with a traditional SMA mixture. In an environmental prospective, fumes and emissions during laying were also analyzed. The goal of this research project was to analyze and evaluate the different physical, mechanical and functional characteristics induced by the use of Crumb Rubber for the production of SMA mixtures according to the proposed new dry-hybrid technology. As overall result, the presence of Crumb Rubber does not seem to negatively affect the volumetric properties of the mixture. SMA1.20 shows mechanical properties comparable to the reference mixture and higher if compared to SMA0.75. As for the acoustic properties, both the rubberized surfaces reduce the emission of noise if compared to the traditional SMA layer. The monitoring of pollutants during paving operations confirms the effective environmental benefits deriving from the use of the new dry-hybrid technology here proposed.

Temperature segregation and its impact on the quality and performance of asphalt pavements

Temperature segregation is non-uniform temperature distribution across the uncompacted asphalt mat during paving operations and may have detrimental effects on the quality and performance of asphalt pavements. However, many research studies conducted across the US have reported mixed observations regarding its effects on the initial quality and long-term performance of asphalt pavements. The objective of this study was to determine the effects of the temperature segregation on the density and mechanical properties of Louisiana asphalt mixtures. Seven asphalt rehabilitation projects across Louisiana were selected. A multisensor infrared bar (Pave-IR) system and a hand-held portable thermal camera were used to measure the temperature of asphalt mats. Field core samples were collected from various areas with varying severity levels of temperature segregation and tested for the density, fracture resistance (Jc) by semi-circular bending (SCB), rut depth by wheel tracking, and dynamic modulus (|E*|) by indirect tension (IDT) devices. Two distinctive patterns of non-uniform temperature distribution were observed: a cyclic and irregular temperature segregations. Laboratory test results showed that highly temperature segregated asphalt pavements (i.e., temperature differentials ≥41.7°C) can have significantly lower densities and the mechanical properties than the non-segregated area, especially when the temperature differentials are measured at compaction.

Full-Scale Emergency Paving Demonstration of Hot-Mixed and Warm-Compacted Asphalt

AbstractAsphalt can be more effectively used in emergency paving operations than it has been in previous years. This paper is the culmination of a multiyear emergency paving effort which demonstrat...

Analytical assessment of asphalt odor patterns in hot mix asphalt production

During the various stages of asphalt paving mixtures production and placement, as a result of binder heating, a complex mixtures of hydrocarbons and volatile organic compounds (VOCs) is released into the atmosphere. As far as hot mix asphalt plants is concerned, several standards and directives were drawn up for limiting the emissions of certain specific substances, without setting any specific limit on the odorous perspective. But, odor is increasingly considered an atmospheric pollutant that can have a significant negative impact on both quality of life and economic activity. The odorous flows of HMA emitted in plants or during the paving operations and hot-in-place recycling processes in the worksites can severely limit the usability of the territory. Advances in sensor technology have made possible the development of artificial olfactory systems (AOS), which are devices designed to mimic the human olfactory system capable of characterizing osmogene mixtures. However, their potentialities have not been explored until now at any stages of asphalt and asphalt mixtures production chain. Thus, the main purpose of this study was an analytical-sensory characterization, mainly based on AOS approach, of asphalt emissions generated during the various stages of road pavement construction. The analytical and sensory analyses have firstly demonstrated the effective application of these instruments in the pavement engineering sector: an odor fingerprint of asphalt emissions, specific for each type of binder and temperature class, was determined. Thanks to the photoionization, a technique which allow the detection of organic compounds in gaseous mixtures, a pseudo-hyperbolic relationship between the release of airborne substances in asphalt emissions and the heating temperature was identified; whereas the AOS demonstrated that this increase of VOCs corresponded contextually to a change in their odorous patterns. Moreover, the existence of variations in the odor fingerprints of different asphalt binders heated at the same temperature was assessed. Through a specific statistical approach for the treatment and post-processing of data and the following elaboration of a geometric based procedure for the determination of the numerical inter-class separation, a quantitative value to the purely qualitative response of the AOS was assigned.

Dynamic characteristics modelling of the tamper–asphalt mixture interaction: application to predict asphalt mat density

ABSTRACTRecently, the study of machinery/medium interaction is becoming increasingly important in terramechanics. In order to maximise the performance of existing equipment and obtaining desired compaction density in road construction, reasonable and effective paving operations are essential. However, the operations always depend on empirical approaches. In this paper, a model based on vibration compaction theory was used to describe the deformation property of asphalt mixture, which can lay a foundation for future analysis. And then, a dynamic model of tamper/asphalt mat interaction, based on the principles of resonance, was developed to predict asphalt mat density during paving operation. The model inputs included excitation frequency, tamper stroke, paver forward speed and asphalt mixture properties parameters for different tamper or asphalt mixture. The numerical simulations are provided to demonstrate how the tamper/asphalt mat interaction model can be used to predict asphalt mixture compaction in the field of road construction engineering.

Evaluation of potential gaseous emissions of asphalt rubber bituminous mixtures. Proposal of a new laboratory test procedure

When deviating from standard paving solutions, it is necessary to verify that the use of supplementary components or the adoption of different processing conditions do not lead for construction workers to an increase of the risk associated to fume exposure. In the specific case of bituminous materials containing crumb rubber from end-of-life tyres, such an issue was addressed in an investigation in which a new laboratory test procedure for the evaluation of the composition and of the potential hazardous effects of gaseous emissions released during paving operations was developed and validated. Experimental activities were carried out by considering six different asphalt rubber mixtures, the emissions of which were sampled both in the field and in the laboratory. Subsequent analyses were performed by evaluating concentrations of volatile organic compounds and polycyclic aromatic hydrocarbons and by calculating corresponding toxic and carcinogenic risk parameters by means of adequate models. Effects of material-specific and site-specific factors were clearly distinguished and in most cases it was observed that analyses derived from laboratory-generated emissions led to a conservative estimate of risk. In general terms it was therefore concluded that the proposed procedure may be extremely valuable for the assessment of the true emission potential of bituminous mixtures containing crumb rubber and that in the future it may be employed as an evaluation tool during the mix design and field monitoring phases.