bluuebunny/crossref_metadata_2025 huggingface dataset:
Traffic Sign Sight Distance for Low-Volume Roads
Authors: Discetti Paolo , Lamberti Renato
Published: July 2011

Warning signs are a critical signaling element providing information to the monitoring public with respect to potential hazards on the roadway. They should be placed in order to allow the driver enough time to perceive, identify, and decide on and perform any necessary maneuvers. Although stopping-sight distance is adequate for most design situations, some situations require drivers to perform complex maneuvers or make immediate decisions, such as when drivers must respond to an unexpected maneuver, for example, at an intersection or dangerous curve. In these areas, the sight distance of a warning sign is of fundamental importance so as to allow drivers to respond appropriately and to perform the proper maneuver. The placement of the road sign is an integral part of road design; in fact, its correct definition, or rather the choice of the location of the different signs in relation to the geometrical and functional characteristics of the road, represents one of the fundamental tools for improvement of road safety. Such a concept is extremely important for existing roads and, in particular, for those with a low traffic transit. The effectiveness of the sign is subordinate to its perception–response time and therefore to the capacity to influence drivers' speed in order to make it compatible with the road geometry. Therefore, a mathematical model was specifically developed to investigate the relationship between sight distance and sign location according to the Manual on Uniform Traffic Control Devices. To carry out this analysis, a survey was performed on warning curves with inadequate sight distance by using traffic counters capable of recording the 85th percentile speed of vehicles.
Guardrail Optimization for Rural Roads
Authors: Ochoa Carl M. , Ochoa Tania A.
Published: July 2011

Guardrail barriers are optimized to provide a recommended lower-cost barrier solution for rural roadways in the United States, Europe, and developing countries. Physics-based guardrail analysis has determined that barrier behaviors are not random but tend to follow consistent characteristic patterns of response to vehicle impacts. Performance variability in conventional W-beam guardrails is closely associated with components that introduce variability into these patterns. Independent variations in release load of around 360% and 40% combine to result in the three primary guardrail failure modes, known as vehicle pocketing, vaulting, and hard wheel snagging. The solution to this performance variability problem is to optimize the release load in relation to support-post-section properties. This operation is accomplished by introducing a separate deformable release member that consistently provides the needed release load. This procedure enables the simultaneous optimization of cost and performance by reestablishing stable patterns in guardrail response to vehicle impacts; addressing the three primary guardrail failure modes; eliminating complexity associated with unnecessary components such as offset blocks, backup plates, and midspan splices; upgrading the reliability of existing guardrail systems on a retrofitable basis with minimal disruption; enabling a range of standard post types to accommodate local material preferences; and enabling a range of post spacings for diverse terrains and a range of rail heights to accommodate roadway overlays. A versatile W-beam guardrail incorporating these improved capabilities has been successfully crash tested and accepted by FHWA at NCHRP Report 350 test levels and Test Level 3 of the AASHTO Manual for Assessing Safety Hardware.
Speed Table Evaluation and Speed Modeling for Low-Volume Crosstown Roads
Authors: Moreno Ana Tsui , García Alfredo , Romero Mario Alfonso
Published: July 2011

More than 50% of injury accidents in Spain take place on crosstown roads in urban areas. Traffic calming is an initiative to reduce the impact of traffic on local streets by lowering both the number and the severity of crashes. However, the implementation of traffic-calming devices in Spain was not standardized in the past, and no technical criteria were applied. The paper presents the methodology, results, and conclusions of an analysis specifically related to speed tables, which are flat-topped speed humps, as part of the research project MODETRA. For the research, five low-volume crosstown roads with 16 speed tables were selected to analyze drivers' behavior. Speed data were collected from a sample of more than 900 vehicles through the selected crosstown roads using Global Positioning System trackers. For each individual vehicle, a continuous speed profile along the path was obtained. The analysis showed that the minimum speed occurred when the vehicle left the traffic-calming device and the maximum deceleration occurred just before the device. Geometric characteristics of the speed tables were measured by using a digital profilometer. A wide dispersion in the geometry can be concluded. It was found that the speed reduction depended mainly on the separation between traffic-calming devices, whereas the speed over the speed tables depended crucially on the entrance-ramp slope, the speed table length, and the distance from the previous traffic control device. Also, no statistical correlations were found between speed table height and speed reduction or spot speed over the speed table.
Reducing Traffic Injuries Resulting from Excess Speed
Authors: Dell'acqua Gianluca
Published: July 2011

This study investigates drivers' speed behavior on low-volume roads crossing small urban communities both without a gateway or traffic-calming device and with different forms of gateway and traffic calming along the urban environment. Speeds upon entering small urban areas in Italy were collected along several rural road sections. The site with the greater operating speeds was selected as the design site. Two gateways and integrated traffic-calming devices along the road were set up within the urban area. The gateways aimed to slow the vehicles entering the built-up area, and the traffic-calming devices aimed to complement the gateway effect. The proposed gateway design is a combination of low-cost and fast implementation measures. The traffic-calming treatments presented in the study could easily be implemented in other rural communities.
Evaluation of Safety Identification Methods for Low-Volume Roads Using Monte Carlo Simulation
Authors: Cafiso Salvatore , Di Silvestro Giacomo
Published: July 2011

Two-lane rural roads characterized by low traffic volume (fewer than 3,000 vehicles per day) represent a specific road typology of interest in safety analysis. Correct identification of black spots (sites in which the expected number of crashes is abnormally high) is crucial for the road administration when the location and ranking of improvements are chosen. Simply observing unusually high crash counts does not necessarily indicate a true safety problem. In black spot identification on two-lane rural roads with low traffic volume, the reduced number of observed crashes is a critical issue that can emphasize weak results carried out with different safety indicators and control checks. Generally it is assumed that the empirical Bayesian estimate represents the best approach for black spot identification, but the precision of the estimation among different procedures is difficult to define quantitatively. The simulation approach is able to identify crash data similar to empirical data with the unique possibility to define a priori hazardous sites and therefore assess whether a method can correctly identify them. The Monte Carlo simulation presented here was able to define the accuracy and efficiency of the procedures on the basis of observed frequency of crashes, crash rate, empirical Bayes estimation, and potential for safety improvement. The results show that an appropriate selection of exposure values can mitigate the lower performance of some indicators, but the best practice is to use the empirical Bayes approach to identify true positives.
Field Traffic Sign Handbook for Local Highway Agencies
Authors: Orr David P.
Published: July 2011

Using the Manual on Uniform Traffic Control Devices in the field is difficult in New York State because of the need to follow two voluminous documents. There is a need for a field handbook that provides information on the most commonly used signs. The Traffic Sign Handbook has been produced in New York State since the mid-1980s. This handbook has been updated to meet changing standards. Several figures, graphics, tables, and other components make the handbook especially valuable.
Impacts of Reduced Tire Pressure on Strain Response of Thaw-Weakened, Low-Volume Roads in Manitoba, Canada
Authors: Liu Qingfan , Kavanagh Leonnie , Shalaby Ahmed
Published: July 2011

The spring thaw period significantly reduces the bearing capacity of low-volume asphalt roads. To compensate for the reduced bearing capacity, highway agencies apply spring load restrictions (SLR) to limit the damage caused by heavy loads during the period when the road is weakened by thaw. Although the imposition of SLR may reduce road damage, it has a major impact on truck productivity. An alternative to reducing truck loads during the spring is the reduction of truck tire pressure. The reduced tire pressure lowers the tire–pavement contact pressure and the associated damage during the spring period. In 2008, asphalt strain gauges were installed in a section of a low-volume haul road in Manitoba, Canada. Field testing was conducted in the spring and fall of 2009 with a double semitrailer or B-Train equipped with a semiautomated tire pressure control system. The tests were conducted at various loads and speeds and at normal and reduced tire pressures. The results of the field testing showed that when the tire pressure was reduced by 50%, the measured maximum tensile strain at the bottom of the asphalt layer decreased by an average of 15% to 20%. The effects of gauge orientation, truck speed, and tire offset from the strain gauge were analyzed and are presented.
Road Performance Evaluation Using Geometric Consistency and Pavement Distress Data
Authors: Dell'acqua Gianluca , Russo Francesca
Published: July 2011

Many studies on driver speed behavior are found in the scientific literature today, and various researchers have addressed roadway alignment consistency for travel safety in the context of current operating speeds. An experimental analysis of low-volume roads without spiral transition curves between geometric tangent and circular elements on the horizontal alignment was conducted in southern Italy. All selected roadways are located in areas with level terrain and vertical grades of less than 6%. This study is a continuation of a 2009 research project that developed procedures to predict speed factors for horizontal curves and tangents on low-volume roads. The present research focuses on the design of continuous operating speed profiles that reproduce real driver speed behavior at each section of the horizontal alignment with variables that now include the pavement deterioration condition. Four new regression equations were developed to predict the operating speed on tangent and circular curve elements by using speed factors and geometric variables. These models were developed by a traditional ordinary least-squares method involving speed values not surveyed in transition zones. The aim of this refined study is to illustrate the roadway factors influencing optimal and safe driving performance.
Delivery of Low-Volume Road in Pilbara Region of Western Australia by Alliance Contracting
Authors: Cocks Geoffrey , Scott Jacqueline , Pearce Terry , Hazebroek Mark , Fisher Paul , Wilson Robert
Published: July 2011

Alliance contracting differs from other forms of contracting for delivery of road projects: the emphasis is on risk sharing rather than risk transfer. The owner, contractor, and designer form a single organization that contracts with the owner to deliver the project at an agreed target price that is subject to independent audit. Depending on how the project delivers against the target price, the nonowner participants gain various levels of reward. Delivery at a cost higher than the target price results in an escalating forfeit of the overhead and profit portion. Delivery at a cost lower than the target price ensures nonowner participants a share of the savings. An alliance contract is thus an incentivized cost-reimbursement contract with a strong focus on risk sharing and cooperation. In 2005, Main Roads Western Australia elected to deliver Stage 2 of the Karratha Road to Tom Price Road by alliance contracting. The project involved the design, construction, and maintenance of 90 km of a new two-lane highway with a sprayed seal surface in the hot arid Pilbara Region in the northwest of Western Australia. This paper describes the participant selection process, the use of whole-of-life analysis, and quantitative risk assessment in identifying designs for low-volume roads that were of the best value, fostering of an innovative culture, building of a cooperative approach, team building for a virtual organization, and the technical acceptance criteria.
Analysis of Factors Causing Corrugation of Gravel Roads
Authors: Mahgoub Hesham , Bennett Christina , Selim Ali
Published: July 2011

Gravel and unpaved roads are viable and important components of the road transportation network throughout the world. In the United States, gravel and unpaved roads still make up close to 50% of road miles. Motorists traveling on a gravel road will encounter the problem of corrugation. Corrugation, or washboarding, is a problem with many causes and no long-term solutions, requiring continual maintenance to control its appearance. Several factors have been researched and found to contribute to corrugation, such as traffic volumes, vehicle speeds, subgrade characteristics, harmonic vibration of the vehicle's suspension system, and gravel properties. This study examines the causes of corrugation by using variables previously considered by other researchers as well as new variables added by the study's research team. The objective of this study is to develop a comprehensive prediction model that can identify the potential occurrence of corrugation at a specific location. The model calculates corrugation height and wavelength. One significant and considered new conclusion is that corrugation is affected by the amount of natural soil placed between the gravel layer and the natural subgrade material. This natural soil is placed on the road surface during the original construction of the road and comes from formation of the side ditches. Another conclusion is that the moisture content of the subgrade, the ratio of the thickness of the surface gravel to the depth to the subgrade, and traffic speeds are the most significant influencing factors in the formation of corrugation.
Stress Analysis on Triangular-Aperture Geogrid-Reinforced Bases over Weak Subgrade under Cyclic Loading
Authors: Qian Yu , Han Jie , Pokharel Sanat Kumar , Parsons Robert L.
Published: July 2011

Geogrids have been successfully used to improve soft subgrade and reinforce weak base courses for low-volume roads by providing lateral confinement. However, uniaxial and biaxial geogrids with rectangular or square apertures cannot provide uniform resistance in all directions. A new geogrid product with triangular apertures was developed and introduced into the market to overcome this problem. The triangular-aperture geogrid has a more stable grid structure and can provide uniform resistance in all directions compared with uniaxial and biaxial geogrids. However, the performance of triangular-aperture geogrid-reinforced bases has not been well evaluated. In this study, unreinforced and triangular-aperture geogrid-reinforced bases over a weak subgrade were constructed in a large geotechnical testing box (2 × 2.2 × 2 m) at the University of Kansas and tested under cyclic loading. During the tests, surface deformations and vertical stresses at the interface between the base and the subgrade were monitored. The test results showed that triangular-aperture geogrids reduced permanent surface deformations and vertical stresses at the interface compared with an unreinforced base. The benefit became more pronounced when a heavier-duty geogrid was used. The backcalculations from the measured vertical stresses at the interface between base and subgrade showed that the stress distribution angle and the modulus ratio of base course to subgrade decreased with an increase in the number of cycles. The rates of reduction in the stress distribution angle and the modulus ratio for the unreinforced base were faster than those for the reinforced bases. This paper focuses on the stress analysis of the test sections under cyclic loading.
Matting Solutions for Low-Volume Roads
Authors: Rushing Timothy W. , Howard Isaac L.
Published: July 2011

An evaluation of 11 commercial roadway matting systems was conducted to determine their effectiveness in carrying heavy vehicle traffic over loose-sand subgrades. Three of the 11 matting systems were also evaluated under the same loading conditions over soft, fine-grained subgrades. Matting product types included high-density polyethylene, aluminum, fiberglass, and polyester. System installation methods included continuous rolls of material, segmented rolls, and connection of individual panels. The matting products were assembled in test sections of various sizes, which depended on individual panel dimensions and product availability. The mats were trafficked with a 7-ton, six-wheeled U.S. Marine Corps transport truck loaded with a 7-ton payload until 20% of the mat section was no longer reusable or 2,000 truck passes were achieved. Earth pressure cells were installed under nine of the sand test sections to monitor load distributions provided by the matting systems. On the basis of the test results, recommendations are given for selecting the best roadway matting system types for use on low-volume roads with sand or soft, fine-grained subgrades.
Comprehensive Life-Cycle Cost Analysis for Selection of Stabilization Alternatives for Better Performance of Low-Volume Roads
Authors: Praticò Filippo , Saride Sireesh , Puppala Anand J.
Published: July 2011

Low-volume roads (LVRs), such as rural, farm-to-market, and less-used local and city roads, are an important part of the world's transportation infrastructure. LVRs have been credited as a direct cause of the socioeconomic development of rural communities. It has been estimated that 60% of the road network in the United States is made up of low-volume roads. The construction, maintenance, and rehabilitation of these roads are major tasks that result in about 54% of the total annual expenditure of transportation agencies in the United States. Better design and construction methods will lead to lower maintenance and rehabilitation costs of LVRs. Stabilization of weak subgrade soils to support LVRs is a widely accepted method of improving their performance. However, the selection of a stabilization alternative on the basis of cost–benefit analysis is a crucial task for a transportation agency and one that has not been addressed in a systematic manner. In this paper, a new conceptual engineering economics tool–based life-cycle cost analysis (LCCA) is developed to optimize and to select the best stabilizer and the stabilization technique for a given subgrade soil and given traffic conditions. In this analysis, agency, user, and externality costs are addressed. Two case studies are analyzed for European and U.S. road conditions to validate the LCCA model. Results demonstrate that, under specific boundary conditions, soil stabilization can play an important role, merging the environmental and mechanical effectiveness of low-volume roads.
Evaluation of Chemical Stabilization of a Highly Expansive Clayey Soil
Authors: Mutaz E. , Shamrani Mosleh A. , Puppala Anand J. , Dafalla Muawia A.
Published: July 2011

Lime and cement are widely used in stabilization and improvement of the expansive subsoils that support pavement infrastructure. In this research, an attempt is made to stabilize a highly expansive soil rich with smectite minerals with an aim to understand the mechanisms that result in soil property improvements. Influences of both the type of stabilizer and their dosages were studied for modifying expansive clay from the north-central region of Saudi Arabia. Al-Qatif soil is known for its highly expansive nature, and it is known to induce major damage to low-volume roads built on untreated to unbound sandy bases. This research was performed by first characterizing and classifying Al-Qatif clayey soil by means of routine index properties, X-ray diffraction studies, and swell and shrinkage tests. Next, lime and cement were used to stabilize control clayey soils, and the treated soils were then subjected to the same soil tests. Effects of lime and cement treatments on Atterberg limits, swell, and linear shrinkage strain properties are addressed. Major conclusions and findings from experimental investigations are presented.
Soil Stabilization in Low-Volume Roads
Authors: Campbell Alex E. , Jones David
Published: July 2011

Overwhelming evidence supports the importance of gravel roads. However, road agencies are increasingly faced with the necessity of relying on marginal materials in construction of low-volume roads. Use of these materials necessitates that stabilization be used to alter the engineering parameters to ensure that corrugation, erosion, rutting, poor pass-ability, dust, and low-bearing capacity are avoided. Soil stabilization is increasingly being used as an unsealed-road asset management tool in an attempt to reduce the impacts of these issues, and nontraditional soil stabilizers have been a primary area of focus. Yet few such products have gained widespread acceptance. This paper looks at the lack of usage of alternative stabilizers in the marketplace today from the viewpoint of the product supplier. It aims to identify the issues facing the supplier in introducing a competent nontraditional soil stabilizer product to road agencies and to identify the measures such suppliers can take to advance those products that show good potential. Measures that could be introduced to better manage the field of soil stabilization for unsealed and low-volume sealed roads have been suggested. These measures include the following: established guidelines, specifications, test methods, and management principles, all prepared in a format that is readily acceptable and adopt-able by industry engineers; an industry association; and the adoption of a dedicated research protocol establishing minimum requirements for research on such additives.
Evaluation of Sustainability of Low-Volume Roads Treated with Nontraditional Stabilizers
Authors: van der Merwe Steyn Wynand Jacobus , Visser Alex T.
Published: July 2011

The use of nontraditional stabilizers to treat unpaved (mostly low-volume) roads has received attention over the past several years as various types of stabilizers have been developed and become available. Evaluation of the sustainability of various infrastructure actions, including the provision and maintenance of roads, is becoming more relevant as the effects of actions taken in the natural environment on itself and on the human environment are evaluated and understood in more detail. The Greenroads rating system offers a method for evaluation of the sustainability of the design, construction, and maintenance of roads. The system was developed with a focus on surfaced higher-volume roads. In this paper, the potential applicability of the Greenroads system for the evaluation of the sustainability of unsurfaced low-volume roads is investigated through two case studies of experiments in which unpaved low-volume test sections were treated with various types of traditional and nontraditional material stabilizers. Appropriate parameters were selected from the general Greenroads metric to ensure that those affecting unpaved low-volume roads would be evaluated (e.g., runoff quality and use of regional materials) while parameters such as paving emission reduction were excluded from the analysis. The assumption was made that all compulsory project requirements would be met by each of the options evaluated. It was concluded that the Greenroads metric can be used to evaluate the potential sustainability of unpaved low-volume roads treated with nontraditional stabilizers and that the metric can provide insight into the potential effect of various parameters on the sustainability of the various stabilization options.
Improvements to Linn Run Road
Authors: Shearer David R. , Scheetz Barry E.
Published: July 2011

Because of the ever-increasing cost associated with asphalt repaving, interest has been growing in turning back deteriorating asphalt roadways into maintainable aggregate driving surfaces. For more than 10 years, Pennsylvania's Dirt and Gravel Road Maintenance Program has funded projects that use environmentally sensitive maintenance techniques to reduce sediment pollution on unpaved roads while providing low-cost, long-range road maintenance solutions. The Center for Dirt and Gravel Road Studies at Pennsylvania State University has worked with various state and local entities on projects designed to convert these deteriorated asphalt roadways into durable, maintainable gravel surfaces, with a focus on reducing the environmental concerns related to road runoff. The purpose of this paper is to provide a detailed accounting of one such project. Several accepted options are available to accomplish this task. For this project, the full-depth reclamation process that uses chemical stabilization techniques was selected as the methodology to be demonstrated. As the project progressed, several site-specific challenges were encountered and ultimately resulted in a change in the tactics employed to effect the conversion from asphalt to gravel successfully. The results of the study emphasize the importance of properly evaluating preconstruction site conditions to determine the best methodology to be employed and of providing for flexibility in the design criteria and specifications.
Load and Resistance Factor Design Calibration for Bridge Pile Foundations
Authors: Roling Matthew J. , Abdelsalam Sherif , Sritharan Sri , Suleiman Muhannad T.
Published: July 2011

In response to the documented advantage of the load and resistance factor design (LRFD) approach over the working stress design approach, FHWA issued a policy memorandum on June 28, 2000, requiring all new bridges initiated after October 1, 2007, to be designed according to the LRFD approach. This paper presents current design and construction practices for bridge pile foundations that were established through a survey of Iowa county engineers as well as consulting firms that design piles for the county offices. Conducted during the second and third quarters of 2008 as part of an ongoing research study centered on the LRFD approach for pile foundations in Iowa, this study highlights the benefits associated with a thorough description of regional deep foundation design and construction practices on successive LRFD resistance factor calibrations. The specific topics targeted in the study were current foundation practice; the extent of timber pile usage; pile analysis and design; and pile drivability, pile design verification, and quality control. Since this is the first study to have been conducted at the county jurisdictional level on the topic of pile foundation design after the FHWA mandate, the current status of the implementation of the LRFD approach for bridge foundation design was examined. The responses obtained from 44 Iowa county engineers and eight consulting firms revealed that (a) regional variation in pile foundation practice cannot be captured via a state-level investigation, inhibiting the performance of effective regional LRFD calibrations, and (b) the degree of implementation of the LRFD approach at the county level is about 84%.
Monitoring Report of Frost Heave on Warm Lake Road
Authors: Evans Gary L. , Truebe Mark A. , Hanek Gordon L.
Published: July 2011

The purpose of this study was to evaluate the effectiveness of different measures to reduce or eliminate frost heave. The evaluation was done by specifying three types of fixes, all of which included subexcavation and the use of different drainage fabrics and drainage structures. The sites were monitored by baseline surveying, frost heave surveying, and frost depth monitoring before and after construction to measure the effect of frost heave mitigation measures. In addition, costs were evaluated to determine the economics of the different methods. The most effective methods of eliminating frost heave were the use of substantial depths of subexcavation and backfill with nonfrost-susceptible material and positive methods of ensuring drainage from the subgrade. When both costs and effectiveness were considered, the traditional method of eliminating frost heave by excavation and replacement with a nonfrost-susceptible material was the most expensive method for the amount of frost heave reduced. Using capillary break geocomposite materials to thoroughly remove water was by far the most practical and cost-effective method of reducing frost heave.
Experience with Thin Superpave Mixture Overlay of Small Aggregate Top Size in Kansas
Authors: Rahman Farhana , Hossain Mustaque , Romanoschi Stefan A. , Hobson Cliff
Published: July 2011

Superpave® asphalt mixture with small (4.75-mm) nominal maximum aggregate size (NMAS) is a promising, low-cost pavement preservation treatment for rural roads. This mixture has the potential to provide a smooth riding surface, be applied in thin lifts, correct surface defects, decrease construction time, and provide an economical surface mixture for low- to medium-volume facilities. Because of budget constraints in highway construction and preservation programs and the economic advantages of such a mixture, many highway agencies are considering implementing it for rural roads. Two rural highway pavements in Kansas were overlaid with a 15- to 19-mm-thick 4.75-mm NMAS Superpave mixture in 2007. Overall, the experience in Kansas with the 4.75-mm NMAS mixture was varied. Both projects had construction issues. Experience on one project showed that extended aggregate drying and drum cleaning would be necessary when producing these mixtures. Performance history on both projects after overlay construction showed that roughness of the road surface was significantly improved and was consistent for the 3 years after the overlay. Transverse cracks seem to be the major concern, although the rutting performance of this small-sized aggregate mixture is satisfactory. Crushed gravel aggregates seemed to perform better in the mixture than crushed limestone aggregates. A binder with a higher grade may be needed to address transverse cracking issues.
Effect of Fine Aggregate Physical Properties on the Engineering Properties of Conventional and Polymer-Modified Bituminous Mixtures
Authors: Suliman Yasreen Gasmalkhalig , Napiah Madzlan B. , Kamaruddin Ibrahim
Published: July 2011

Most studies on hot-mix asphalt have used crushed fine aggregate and gravel; research regarding the use of mining sand or marine sand as fine aggregate is limited. This work investigates the effects of fine aggregate physical properties on the engineering properties of hot-mix asphalt. Four types of sand (quarry, river, mining, and marine sand) with two conventional binders (PEN 50/60 and PEN 80/100) and four types of polymer-modified bitumen (PMB) (PM1_82, PM1_76, PM2_82, and PM2_76) were used. Electron microscopy scanning was performed along with sieve analysis and tests for specific gravity and angularity of the fine aggregate on the different types of sand to determine their properties and thereby examine the effects of these properties when the sands were incorporated into a bituminous mixture. Marshall test results showed that fine aggregate physical properties influenced the optimum bitumen contents and engineering properties. The study also revealed that angular and rougher particles of fine aggregate produced lower voids in mineral aggregate, lower optimum bitumen content, higher shear strength, and higher density, which consequently increased the stability of the resulting mixtures. Moreover, a polymer-modified bituminous mixture enhanced stability and stiffness, reduced density, and slightly increased the voids in mineral aggregate.
Evaluation of Effects of Recycled Concrete Aggregate on Volumetrics of Hot-Mix Asphalt
Authors: Bhusal Sushanta , Li Xiaojun , Wen Haifang
Published: July 2011

Each year around 200 million tons of demolition wastes are produced from aging U.S. infrastructures. Of that amount, 100 million tons are portland cement concrete debris. Disposal of these wastes in landfills has been a traditional solution, but environmental regulations, costs, and a lack of landfill areas have hindered safe disposal. These problems have led to a search for alternate ways of reusing demolition wastes by recycling. Recycling the concrete waste not only reduces the waste disposal problem but also reduces the quarrying of virgin aggregate. The incorporation of recycled concrete as a hot-mix asphalt (HMA) aggregate can be a viable option in terms of costs and environmental considerations. This use of recycled concrete aggregate (RCA) as an HMA aggregate can be beneficial for constructing low-volume roads. RCA differs from virgin aggregates in that there is cement paste on the surface of the recycled concrete. In this study, 5% RCA was evaluated as an HMA aggregate. Mix designs were conducted, and the effect of RCA on the volumetrics of HMA was evaluated. The mix design results indicated that RCA is absorptive, and that as the percentage of recycled concrete increased in the mix, the optimum asphalt content increased linearly. The statistical regression model showed that RCA had significant effects on the volumetrics of the mix.
Decreasing Moisture Susceptibility of Gravel Road Surface Aggregate by Hydrophobic Treatment Agent
Authors: Pylkkänen Kari , Sjöberg Maria
Published: July 2011

The use of a special hydrophobic treatment agent to reduce the moisture susceptibility of gravel road surface aggregate was studied. A treatment agent and dosage were chosen on the basis of positive results from earlier studies concerning different base course aggregates of paved roads. Laboratory pretesting samples from a chosen test site confirmed that, for example, in tube suction tests the dielectric value of the aggregate treated with the chosen agent and dosage was lowered remarkably as compared with untreated aggregate. This result indicated improved water resistance. The treated aggregate also showed increased abrasion resistance and was less density-susceptible as compared with the untreated aggregate. As a result of the encouraging results from the preliminary tests, a 500-m unpaved test section was constructed in 2009. Ordinary bitumen stabilization machinery was used for simultaneous spreading and mixing of 1% resin-based treatment agent emulsion to the gravel surface aggregate. Although the water content was lower than expected, the construction of the test section succeeded; it will be monitored regularly by falling weight deflectometer measurements and visual inspections.
Mechanistic Design and Nondestructive Structural Validation of a “Green Street” Test Section Using Recycled Rubble Materials
Authors: Berthelot Curtis , Haichert Rielle , Podborochynski Diana , Wandzura Colin , Taylor Brian , Guenther Duane
Published: July 2011

The City of Saskatoon, Saskatchewan, Canada, commissioned the “Green Street” Infrastructure Program to investigate the potential of using recycled reclaimed asphalt pavement (RAP) and portland cement concrete (PCC) rubble as structural road layers. This study validated the mechanistic materials characterization and structural design of a field test section constructed using recycled RAP and PCC materials in addition to in situ reclaimed and recycled road materials. This paper presents a summary case study of the Green Street test section on 8th Street in Saskatoon. The rehabilitation of 8th Street consisted of two pavement rehabilitation systems: one incorporated a drainage layer and the other did not. The rehabilitation of the right-turn lane included a drainage system incorporating City of Saskatoon offsite impact-crushed PCC rubble material. The entire right-hand-turn lane and sections of the median lane and the driving lane were rehabilitated by rotomixing hot-mix asphalt concrete (HMAC) and granular base layers and adding offsite impact-crushed RAP to top up the remixed base layer. The top 200 mm of this remixed base layer was stabilized with cement–emulsion. The entire 8th Street test section was surfaced with typical City of Saskatoon HMAC. When subjected to mechanistic triaxial frequency sweep characterization, both the cement–emulsion-stabilized in situ remix material (utilized as a black base course) and the HMAC surfacing materials showed good mechanistic structural material constitutive behavior. The stabilized in situ remix material yielded end-product mechanistic material behavior that exceeded that of the HMAC surfacing.
Application of Cashew Nut Shell Liquid in Bituminous Priming of Low–Volume Roads in Ceará, Brazil
Authors: Barroso Suelly Helena De Araújo , Rabêlo Antonio Nobre , Soares Jorge Barbosa
Published: July 2011

Volatile organic compounds are an environmental concern in the asphalt paving industry. A main pollution source is the so-called cutbacks (asphalts with solvents) frequently applied in the priming of base layers. In Brazil, the cutback MC-30 with kerosene is frequently used. However, the use of cutbacks has been restricted in some countries in which environmental legislation is stricter. This has led to the search for alternative materials to substitute for conventional cutbacks. This paper investigates the potential use of a mixture produced from cashew nut shell liquid (CNSL) and asphalt cement (AC) as the prime coat. The purpose is to obtain a less environmentally aggressive bituminous prime coat product. To verify the performance of the prime in sandy soils, 240 specimens were produced and primed with different products: the cutback MC-30, an emulsion MS-1C, and a mixture produced in the laboratory called AC/CNSL (60% AC 50/70 and 40% CNSL). Experimental results have shown that the prime coat is a complex material affected by factors such as the type and the rate of the applied binder, preparation conditions of the base surface, and moisture content in compaction. Results indicated the potential use of the AC/CNSL in compacted sand samples. The product can satisfactorily be used as a cutback, and it attends the parameter of penetration in the base layer.
Indirect Skid Resistance Measurement for Porous Asphalt Pavement Management
Authors: Dell'acqua Gianluca , De Luca Mario , Lamberti Renato
Published: July 2011

This paper focuses on developing a method for road managers to assess the sideways-force coefficient (SFC) in porous asphalt with low-cost standard tests. SFC can be used as a component in road surface condition surveys and asset management decisions. A standard piece of equipment for determining SFC is the sideways-force coefficient routine investigation machine (SCRIM), which can be truck or trailer mounted. This equipment is often beyond the budget of most small, low-volume road agencies. An empirical model for the indirect estimation of SFC for porous road surfaces was developed as a result of this study. With handheld equipment—the portable skid resistance tester [to derive the British pendulum number (BPN)] and the sand patch method [height in sand (HS) test]—a correlation of these test results can be made, and a reasonable approximation to SFC with the use of the SCRIM method can be attained. BPN, the unit of measurement of the skid tester, is a representation of the microroughness of the wearing surface, and the sand patch method (HS test) results yield the macroroughness of the pavement. The study was conducted over 20-km segments of low-volume roadway in southern Italy. The initial results are promising, with a maximum percentage of error of less than 15.2%. Further study is needed to adapt the model to other road surface conditions.
Keeping Springtime Low-Volume Road Damage to a Minimum
Authors: Kestler Maureen A. , Berg Richard L. , Miller Heather J. , Steinert Bryan C. , Eaton Robert , Larson Gregg , Haddock John
Published: July 2011

There are approximately 3 million miles of low-volume roads (LVRs) in the United States, and approximately half of them are located in seasonal frost areas. Limiting or prohibiting loads during spring thaw can keep damage to a minimum. However, methods of determining when to place and remove spring load restrictions, particularly on LVRs, are often highly subjective—if restrictions are imposed at all. In partnership with several other agencies, the U.S. Department of Agriculture Forest Service has been compiling a toolkit of practical low-cost diagnostic techniques for determining conditions under which spring load restrictions should be placed and removed. This paper expands on techniques reported in a previous paper from a TRB low-volume roads conference and reports on further developments of additional methods. Techniques discussed include (a) subsurface instrumentation, (b) lightweight deflectometer, (c) thaw index, (d) climatic thaw predictor model, and (e) length of time. Requirements and equipment needed to use each of the techniques are described, strengths and weaknesses of each are outlined, and recommendations on various combinations of methods are provided to enable road managers to optimize placement of spring load restrictions.
Development of Roughness Prediction Models for Low-Volume Road Networks in Northeast Brazil
Authors: Albuquerque Fernando S. , Núñez Washington Peres
Published: July 2011

Roughness evaluation is the most effective way to diagnose pavement condition for design and decision making. The index most commonly used worldwide to indirectly describe the surface condition of asphalt pavements is the international roughness index (IRI). However, few studies have tried to predict the pavement performance of low-volume roads (LVRs) on the basis of the IRI, especially for LVRs in tropical regions. In an attempt to remedy that lack of knowledge, this paper presents IRI-based prediction models developed for asphalt pavement LVR networks in northeast Brazil. The following independent variables were considered to affect the IRI: Thornthwaite's aridity index, which describes local climate; the modified structural number, representing pavement bearing capacity; and the cumulative number of equivalent single-axle loads, representing the traffic applied to the pavements. A multiple regression analysis was carried out, and the results showed that the IRI increases exponentially over time. The analysis of the model parameters confirmed their significance, and the R-square values were 0.87 and 0.94, respectively, for low-volume roads with hot asphalt mixes and bituminous surface treatments. The hot-mix asphalt model was compared with that of the Highway Development and Management Model and with other models developed in research also sponsored by the World Bank. Because of regional differences (especially climate and materials), the models proposed in this paper provide a better estimation of roughness progression in LVRs of the northeast of Brazil.
Operational Service Management System of Forest Roads
Authors: Kivilands J. , Strezs A.
Published: July 2011

The joint-stock company Latvian State Forests is the largest Latvian forest management company; it manages approximately 1.6 million ha of state-owned forests. Key areas of activity are forest management and development. The company maintains a network of forest roads to provide for the removal of timber from the forests to supply cooperative partners. At the beginning of 2010, the company owned a network of roads with a total length of 10,158 km. In 2009, 5 million m3 of timber were transported through this network of forest roads. Options for forest road operation in Latvia depend largely on weather conditions. After extended or intense rain or during spring thaws, the forest road surfacings are too wet, resulting in a significant reduction in their bearing capacity. When the bearing capacity of the pavement layers is low, there is heavy damage to or even destruction of the pavement in the course of timber transportation. Every year hundreds of kilometers of forest roads have to be repaired or even rebuilt because they are operated under inappropriate circumstances. To develop a management system, a research project was organized, which was expected to be fully completed in 5 years. During the first 2 years the principal part of the research took place—development of a basic model of the forest road network management system. The next 3 years of the study are provided for the introduction of this model. The study is to be carried out in seven stages, the first two of which have been completed. This paper describes the progress and conclusions made during the first two stages of the research. Completion of the remaining five stages is expected during the next 3 years.
Direct Measurement of the Impact of Heavy Loads on Thin Membrane Pavements
Authors: Falls Lynne Cowe , Clary Linda , Hamad A'arif , Abdelfattah Ahmed
Published: July 2011

This paper presents the results of a field study of the loads imposed by heavy oilfield cranes (with hydraulic suspensions and super single tires) on thin membrane asphalt pavements in Alberta, Canada. Three 150-m test road sections (thin asphalt wearing course, bituminous surface treatment, and granular surface) were built and instrumented for strain at the bottom of the asphalt layer, surface deflection, and subgrade pressures. Temperature and moisture profiles were also measured. Field testing involved controlled speed experiments of standard axle configurations and heavy-axle (12,000-kg) vehicles with and without hydraulic suspensions. Focusing on the hot-mix asphalt section, this paper presents a description of the test road design, instrumentation, and testing plan, followed by some results and findings from two seasons (spring and fall 2005) of testing. Vertical stress in the subgrade, longitudinal interfacial strain, and surface deflection are compared for three vehicle types used in the test. Results from tests show that subgrade stress and interfacial strain are very similar for the standard axle configuration during spring compared with those of the cranes without the dolly during the fall season. It could be argued that on the basis of the pavement response, the cranes could operate during the winter season without the dolly (and thereby increase road safety by removing a long combination vehicle from the traffic stream) without causing substantial long-term deterioration.