This session covers all topics related to pavement surface characteristics including pavement friction, smoothness, texture, and environmental and safety issues.
Using Corundum to Improve Skid Resistance of Pavement Made of Engineered Cementitious Composite
Nen NguyenDinh, tum create limitedShow Abstract
Ali Bawono, tum create limited
En-Hua Yang, Nanyang Technological University
Bernhard Lechner, Technische Universität, München
Engineered Cementitious Composite (ECC) is a unique type of high performance fiber-reinforced cementitious composite. ECC has very high tensile ductility, thus, a high flexural strength of more than 10 MPa, which makes ECC a great material for pavement application. However, as a cementitious material, ECC surface is slippery. Common practices to improve the skid resistance in concrete pavement like broom drag or grinding, etc. cannot be applied for ECC due to the presence of fiber and the lack of coarse aggregate. Therefore, in this research, corundum, a hard and durable material is introduced into ECC mixture in order to improve ECC’s skid resistance. A certain percentage of fine sand in typical ECC mixture was replaced by corundum. Samples were prepared for testing flexural strength and skid resistance. The results showed that the modified ECC with corundum has very high flexural strength of more than 10 MPa. The ECC with corundum, which was exposed aggregate within one day after casting, provides high skid resistance that fulfils the highest requirement for new roads for example in Singapore. The mean texture depth (MTD) of the exposed ECC with corundum is also higher than typical ECC. Further, MTD can also increase with the introduction of grooves. And even after 100,000 load cycles under traffic simulation, the skid resistance of the exposed ECC with corundum remains very high. The extrapolation results indicated that ECC with corundum can fulfil the skid resistance requirement until the end of the pavement life time without any further intervention.
Study of the Influence of Snow and Ice on Roads on the Running Resistance and Fuel Efficiency of Large Vehicles
Kimio Maruyama, Civil Engineering Research Institute for Cold RegionShow Abstract
Takashi Kimura, Civil Engineering Research Institute for Cold Region
This study aims to clarify how snow and ice on the road influence the running resistance and fuel efficiency, and to derive a method for quantitatively determining the influence of snow and ice on the running resistance and fuel efficiency of large vehicles.
A series of coast down tests and fuel consumption testing were conducted on test track covered with several types of snow and ice. Running resistance and fuel efficiency were repeatedly measured. The acquired data were then analyzed. It was found that running resistance and fuel efficiency was influenced by the presence of snow and ice on road surface. Running resistance on snow-covered roads was greater than that on dry surface. Fuel efficiency on snow-covered roads was lower than that on dry surface. Fuel efficiency and running resistance can be expressed as a function of values based on driving speed, International Roughness Index (IRI) and snow density. Regression expressions for quantitatively determining the degree of influence of snow and ice on the road on fuel efficiency and running resistance were proposed.
Probabilistic Evaluation of Pavement-Induced Excess Fuel Consumption Given Data Unavailability and Future Uncertainty
Mehdi Akbarian, Massachusetts Institute of Technology (MIT)Show Abstract
Jeremy Gregory, Massachusetts Institute of Technology (MIT)
Randolph Kirchain, Massachusetts Institute of Technology (MIT)
Franz Josef Ulm
Pavement surface condition and structural properties affect vehicle fuel consumption and result in major contributions to the use phase impact of high-volume roads. This excess fuel consumption is described through Pavement-Vehicle Interaction (PVI) as the effect of pavement texture, roughness, and deflection on the rolling resistance of a moving vehicle. The use of PVI models in pavement design and management decisions are hindered by data unavailability and uncertainties associated with the pavement life time, typically decades long. This study addresses data limitations through a probabilistic approach to evaluating PVI impacts in presence of lifecycle uncertainties. The probabilistic deflection and roughness induced excess fuel consumptions are evaluated for nine data-availability scenarios. Surrogate data is used in absence of structural and material inputs along with distributions of vehicle load, speed, temperature, and roughness over the analysis period. Finally, the probabilistic excess fuel consumption is evaluated for equivalent asphalt and concrete pavement designs and the data-availability scenarios. The probabilistic EFC results indicate that the proposed methodology for characterization and evaluation of uncertainty in PVI can statistically distinguish the excess fuel consumptions in a comparative analysis.
A Comparison of Locked Wheel and Continuous Friction Measurement Equipment
Ross McCarthyShow Abstract
Edgar de León Izeppi, Virginia Polytechnic Institute and State University
Gerardo Flintsch, Virginia Polytechnic Institute and State University
Kevin McGhee, Virginia Department of Transportation
In the United States, the locked wheel skid tester (LWST) fitted with a ribbed tire is the predominant method for testing pavement surfaces ( 1, 2). Many characteristics of a roadway and the pavement surface influence friction. LWSTs using ribbed tires can detect microtexture issues easier. However, macrotexture and travel speed are both critical factors that affect available surface friction, factors that cannot be measured with a ribbed tire friction test.
Although the LWST is the common device used to measure friction in the United states, globally, there are many methods and equipment used to test friction. All devices used for testing friction will have different sensitivities to these macrotexture and travel speed. The differences in sensitivity arise from different design and configuration features regarding the tire, the body, and the applied testing methodology. Since these different sensitivities to road characteristics result in different values of friction measured with different devices at identical travel speed, there have been many past efforts to compare the different devices.
The purpose of this paper is to compare measurements from three different devices using orthogonal regression with equal variances: an LWST equipped with both a ribbed and smooth tire, a Grip Tester, and a Sideway Force Coefficient Routine Investigation Machine (SCRIM). After comparison, the Grip Tester and SCRIM are highly correlated when the International Friction Index (IFI) is used to correct for slip speed. Lastly, the SCRIM is highly correlated with the LWST ribbed tire, whereas the Grip Tester is highly correlated with the LWST smooth tire.
Negative Texture, Positive for the Environment: Results of Horizontal Grinding of Asphalt Pavements
Tiago Vieira, Swedish National Road and Transport Research InstituteShow Abstract
Ulf Sandberg, Swedish National Road and Transport Research Institute
A pavement surface having its texture deflections mostly directed downwards is said to have a “negative texture” and is expected to result in positive tire/road noise and rolling resistance properties. Negative textures are typical of porous asphalt pavements, but another way to achieve this is to grind-off the top of the asperities of a rough-textured surface. This paper explores the application of grinding pavement texture in the horizontal plane (not to be confused with common “diamond grinding” which is made in the vertical plane) on a number of asphalt pavements in Sweden, including porous asphalt and stone matrix asphalt. Noise measurements with the Close Proximity method were carried out to evaluate the different acoustical performance of the ground and the original surfaces. In most cases, also tire/road rolling resistance was measured. Texture and wet friction measurements were carried out to characterize how the grinding operation changed the surface texture. It was demonstrated that the grinding treatment led to a more negatively skewed surface texture, resulting in an A-weighted noise reduction up to 3 dB, while rolling resistance coefficients were reduced by up to 15 %. It is concluded that horizontal grinding indeed creates more “negative textures”, which results in improved noise and rolling resistance properties without sacrificing friction, though with limited longevity.
Use of Close-Range Photogrammetry to Characterize Texture in a Pavement Surfacing Material
Kieran Feighan, PMS Pavement Management Services, Ltd.Show Abstract
Ray McGowan, PMS Pavement Management Services, Ltd.
Brian Mulry, PMS Pavement Management Services, Ltd.
Tom Casey, Transport Infrastructure Ireland
Phillip Millar, Ulster University
David Woodward, Ulster University
Currently Hot Rolled Asphalt (HRA) surfacings make up over 50% of the pavement surface on the Irish national road network. HRA is a dense, gap graded bituminous mixture with a layer of cold coated chippings applied to the surface mat and then rolled.
Detailed visual inspections of relatively new HRA schemes constructed in Ireland indicated that the chippings were in many cases clustered together forming voids below surface level. This type of surface is characterised as having ‘non positive’ texture. When the HRA surface was tested using the specified volumetric patch method, it was possible to achieve the specified texture depth even though the pavement surface material had non-positive texture.
The research analyses 3D models of a variety of HRA pavement surfaces in order to objectively quantify the differentiators between positive and non-positive pavement macrotexture.
Once the 3D surface model is created from multiple camera images, a virtual horizontal slice is taken through the surface at a user defined threshold. The islands are the portions of the model which project above this slice. The number of islands identified at each location, together with the horizontal surface area of each island, was calculated and reported. A parameter, Count50, was introduced based on a combination of the number of islands and the individual island areas. Count50 is a clear and practical discriminator between positive and non-positive textured surfaces, and will be introduced into TII’s latest specifications. This type of 3D surface analysis can be extended to other pavement surfacing problems.
Evaluation of Road Pavement Condition Impact on Intersection Accident Frequencies Using Random Parameters Models
Hamid Awad, University of NottinghamShow Abstract
Tony Parry, University of Nottingham
Andrew Dawson, University of Nottingham
Fixed and random parameter negative binomial models were employed in this paper to analyse the impact of road pavement condition on accidents at intersections. Twelve models were used to model: 1. Accidents in dry and wet conditions, and 2. geographical location of the accidents in three Counties. Six-years (2005 – 2010) of accident data were considered at intersections on the A-road networks of Norfolk, Oxfordshire and Nottinghamshire Counties in the UK. This research has two objectives. The first objective is to examine the performance of the fixed and random parameter negative binomial model approaches. The second objective is to investigate the effects of pavement condition (skid resistance, rut depth and texture depth) combined with traffic characteristics (annual average daily flow, heavy vehicles percentage and speed limit) and geometric characteristics (radius of curvature, gradient and number of lanes), on accident numbers. The results suggest that there was a significant improvement in log-likelihood when using random parameters models compared to fixed parameters models for all accident models. Regarding the effects of the explanatory variables, the results reveal that the annual average daily flow, percentage of heavy vehicles, gradients and rut depth are positively associated with more accidents. Speed limit, radius of curvature, number of lanes, skid resistance and texture depth are found to be significant variables decreasing the numbers of accidents.
Walking Friction Tester for Low-Speed Skid Resistance Testing of Pavement
Sen Han, Chang'an UniversityShow Abstract
Mengmei Liu, Chang'an University
Tien Fwa, Chang'an University
The British Pendulum Number (BPN) measured by the British Pendulum Tester (BPT) is commonly used as a surrogate for pavement microtexture. However, there are known operational limitations with the use of BPT. The Walking Friction Tester (WFT) developed at the Chang’an University offers a practical alternative to measure low-speed pavement friction. This paper first describes an experimental program conducted to compare the BPT and WFT tests in the following three aspects: (i) Correlation relationship between BPN and WFT friction coefficients; (ii) Variability of the measured BPN and WFT friction coefficient respectively; and (iii) Speed comparison of field tests using BPN and WFT. Next, tests were performed to examine the variability of WFT test results with respect to walking speed and water film thickness respectively. The study showed that BPN and WFT friction coefficients were positively correlated with a high correlation coefficient of 0.78. WFT measured data were found to have smaller variability than BPN data. The results also showed that WFT tests were independent of changes in walking speeds of operators and variations of water applied from the spray jet. Since WFT with a test tire offers a more realistic testing mode than BPT using a sliding pad, produces less variability in the measured values, and generates continuous friction data in much shorter time than measuring discrete point data by BPT, it can serve as a useful practical alternative to BPT in measuring the low-speed friction properties of pavement materials in the laboratory or in the field.
Predicting Friction with Improved Texture Characterization
Natalia Zuniga Garcia, University of Texas, AustinShow Abstract
Jorge Prozzi, University of Texas, Austin
Andre Smit, University of Texas, Austin
The principal objective of this study was to analyze pavement surface texture characteristics and to evaluate their influence on friction. A Line Laser Scanner (LLS) was implemented to obtain an improved characterization of the pavement texture which includes the characterization of macro- and micro-texture using different parameters. Field measurements of friction and texture were collected around Texas using different tests methods. Thirty-six pavement sections were evaluated, including different surface types. The influence of texture on friction was assessed using various models including the macro- and micro-texture and the surface type. A series of statistical analyses using hypothesis testing were applied to evaluate these models. Among the main conclusions, it was found that there is not a unique relationship between texture and friction. The relationship between texture and friction is strong, but it is different for each type of surface. Thus, regression analysis pooling all data cannot be utilized to quantify the relationship. Panel data analysis should be applied. Additionally, the prediction of friction is significantly improved when incorporating information of both macro- and micro-texture into the prediction model. Therefore, a measure of micro-texture should be included into friction models based on texture. Finally, among the study of different texture parameters, the mean profile depth (MPD) was the most significant parameter for macro- and for micro-texture to explain the distinct friction measures.
Determining the Appropriate Laser Footprint for Pavement Smoothness Measurements
Joseph Yaede, Florida Department of TransportationShow Abstract
James Greene, Florida Department of Transportation
Bouzid Choubane, Florida Department of Transportation
Florida Department of Transportation (FDOT) adopted the use of high speed profiling at the network level in 1985. Recently, it has started piloting an incentive/disincentive smoothness acceptance specification based on the International Roughness Index (IRI) for asphalt surfaced roadways. FDOT is also working towards an IRI based smoothness specification for concrete pavements, which is currently based on a Profile Index using the profilograph. Ultimately, similar smoothness criteria and measurement devices will be used for both flexible and rigid pavements. Therefore, FDOT initiated the present study to assess the impact the laser footprint could have on smoothness measurements on certain pavement surface textures, such as open graded asphalt mixtures and longitudinally ground concrete finishes. This paper presents a description of the testing program, the data collection effort as well as the subsequent analyses and findings.
Comparative Evaluation of Locked-Wheel and SCRIM Friction Testers
Emmanuel Fernando, Texas A&M Transportation InstituteShow Abstract
Dusty Arrington, A&M Forensics and Engineering, Inc.
Richard Zimmer, Texas A&M Transportation Institute
State departments of transportation (DOTs) are required to implement a pavement friction management program to minimize friction-related vehicle crashes over the state highway network. This implementation requires the collection and analysis of friction, crash, and traffic data to make informed and timely decisions, and provide pavements with adequate and durable frictional properties for the safety of the driving public. For friction measurements, most states use locked-wheel skid trailers to monitor the frictional performance of the highway network. The locked-wheel method, developed in the 1960s, simulates emergency braking without anti-lock brakes. In contrast, fixed slip, side force, and variable slip friction measurement systems more closely replicate the action of modern vehicles in an anti-lock braking situation. In addition, these systems provide continuous friction measurements over the test lane. However, the friction numbers from these measurement systems are not the same as the skid numbers obtained from the more commonly used locked-wheel skid trailers in the U.S. Thus, there is a need to compare the locked-wheel with continuous friction measurement devices. This paper presents results from side-by-side tests to compare measurements from the locked-wheel and the Sideway-force Coefficient Routine Investigation Machine (SCRIM). For state DOTs considering deployment of the SCRIM to support pavement friction management activities, relationships between friction numbers from both systems are evaluated to show how the SCRIM readings may be related back to historical data collected with locked-wheel skid systems.
Impact of Surface Characteristics on Flexible-Pavement Rolling Resistance Utilizing the Circular Road Tester
Matteo Pettinari, Danish Road DirectorateShow Abstract
Lasse Andersen, Vejdirektoratet
Imad Al-Qadi, University of Illinois, Urbana Champaign
Hasan Ozer, University of Illinois, Urbana Champaign
Significant energy consumption in the road-transport sector can be associated with rolling resistance (RR) between tire and pavement. Tire dynamic deformation and relative RR, due to texture characteristics and longitudinal unevenness, are considered the largest contributors to energy use and, hence, greenhouse gases. In addition, pavement structure can also be important for heavy vehicles.
In Denmark, the CO2 emission from road transport alone has been quantified as 4.6 Mt/yr. It is expected that implementing durable, low-RR pavements on the entire 4,000 km of state roads in Denmark would provide a reduction in CO2 emission by 160k to/yr. Since 2012, the Danish Road Directorate has worked on implementing stone-mastic asphalt (SMA) as a wearing surface for possibly reducing RR between vehicles and road pavements. In 2016, a test section was paved in Kalvehave, where two low-RR SMAs were compared to a reference asphalt concrete (AC) mixture. To evaluate the texture durability, the three mixtures were sampled at the construction site and tested with the circular road tester (CRT). The CRT is an accelerated load facility used to study changes in surface properties due to tire passes. The experiment was performed under various climate-condition simulations to evaluate the effect of changes in surface characteristics such as permanent deformation, texture depth, and texture negativity. The collected results have shown that durability of low-RR pavements can be enhanced by using premodified binder which reduces changes in textural properties and increases rutting resistance.
Pavement Surface Texture Characterization at the Network Level
Shuvo Islam, Kansas State UniversityShow Abstract
Mustaque Hossain, Kansas State University
Richard Miller, Kansas Department of Transportation
Humaira Zahir, Kansas State University
Network-level surface texture data was collected on the highway network of the Kansas Department of Transportation using a 3-D laser system (LCMS) in 2014. In this study, variations in texture depth within a given roadway project and across different projects were studied. In order to assess how surface texture varies with pavement surface type, differences in mean texture depth (MTD) were estimated for five surface types (Portland concrete cement (PCC);
Superpave mix SM-9.5A; Chip seal; SR-12.5A; Ultra-thin bonded asphalt surface (UBAS)) considering the random effects of geography of roadway projects, surface age and annual average daily traffic. Variations in surface textures were also investigated at horizontal curves. In addition, the relationship between the texture depth and the skid number obtained by the ASTM skid trailer were investigated at the network level. Results show that there are significant differences in average texture depth within a project and across projects. Highest MTDs were obtained for UBAS and lowest for PCC. At the network level, skid number did not correlate well with the MTDs, irrespective of surface type. However, project-level correlation is quite acceptable.