Aggregates mineralogical composition dataset to estimate the Averaged Aggregate Hardness Parameter to predict the Long-Term Skid Resistance of pavements

The raw data here are used to calculate the AHPM (“Averaged Aggregate Hardness Parameter”) parameters of pavement surfaces and to determine their capacity of skid resistance in the long term. They are composed by: • the type of aggregates and their proportions by volume in each pavement, • the calculation of the Aggregate Hardness Parameter (AHP) and • the determined AHP of each of the pavements. After the calculation of this parameter and with the help of analytical functions that we recall below, the skid Resistance capacity of that asphalt surfacing in the long term will be deduced. This long-term skid resistance value corresponds to that determined in the test with the Wehner Shulz machine. The reader is invited to read the paper entitled Long-Term Skid Resistance of Asphalt Surfacings and Aggregates’ Mineralogical Composition: Generalisation to Pavements made of Different Aggregate Types referenced WEA203339 [1]

Comparison of homogenization and direct techniques for the treatment of roughness in incompressible lubrication,”

ABSTRACT Homogenization is a formal mathematical two-scale averaging process that can be applied to roughness problems and can replace previous heuristic averaging procedures which have sometimes led to ambiguous results. This procedure was previously mathematically developed and applied to compressible flow problems. The purpose of this paper is the development of a special form of Reynolds equation for such homogenized conditions applied to the incompressible Newtonian case. The equation allows the calculation of the operating characteristics of a contact by taking into account the local geometry of surfaces, while making a substantial improvement in computing time. The method allows for the study of rough surfaces, but requires considerably fewer calculated points than for traditional deterministic discretization methods. INTRODUCTION An understanding of the influence of roughness on the surface of machine elements during lubrication can contribute to an improvement of the performance of the device and an increase in the lifespan of the mechanism. In turn, proper prediction of the performance of a lubricated contact depends on a rigorous characterization of the involved surfaces and on a sufficiently accurate representation of the lubricant flow behavior. When the operating conditions are severe, i.e., the fluid films are very thin, the effect of roughness is all the more significant. As is well-known, the development of the theory of lubrication for thin films first appeared in 1886 with the mathematical model established by Reynolds. The governing equation, which can be written in various forms, is a second order elliptic partial differential equation for the pressure, wit

Use of Wehner Schulze to predict skid resistance of Irish surfacing materials

This paper details the first assessment of asphalt mixes used in Ireland using the Wehner Schulze test equipment. The mixes assessed were 10mm SMA, 14mm SMA and hot rolled asphalt (HRA) made with PSV 62 greywacke aggregate. The Wehner Schulze was developed about 30 years ago in Germany and is currently being considered as a European Standard test method. The equipment used was located at IFSTTAR in Nantes, France. Asphalt test specimens (305mm x 305mm x 50mm) were prepared using a Cooper roller compactor. 225mm diameter cores were then extracted from the slabs for testing on the WS machine. The results found the 10mm and 14mm to have higher friction coefficient values compared to the hot rolled asphalt. Analysis of the data suggests that this is probably due to differing types of contact between the asphalt surface and the Wehner Schulze polishing rollers and rubber pads used for friction measurement. The investigation suggests that the tire / asphalt surface interface needs further research to help explain both the laboratory and on-site measurement of friction

Long-Term Skid Resistance of Asphalt Surfacing and Aggregates' Mineralogical Composition: Generalisation to Pavements Made of Different Aggregate Types

The work presented in this paper aims to find the relationship between the types of coarse aggregates used in asphaltmixes and the long-term skid resistance capacity of the resulting pavements. In builds on previous work whichproposed a relationship between the mineralogical composition of aggregates and the skid resistance of asphaltsurfacings in the long-term. Here, the focus of the inquiry is shifted from an asphalt surface of one type of aggregate toa mix of several types of aggregates. Polishing test and friction measurements were performed in the laboratory ondifferent pavement samples, followed by a mineralogical analysis of the coarse aggregates of these samples to definea new parameter termed “Averaged Aggregate Hardness Parameter”. The results found that this parameter correlateswell with the long-term skid resistance. Finally for practical use, the paper proposes analytical formulas to link the newpavement hardness parameter with the long-term skid resistance of pavements

Skid Resistance: Understanding the Role of Road Texture Scales using a Signal Decomposition Technique and a Friction Model

Skid resistance markedly depends upon road surface texture. That texture is composed of a range of scales each of which contributes differently to the generation of friction at the tire-road interface. This work aims to contribute to understanding the role of these different scales. The method adopted deploys a signal processing technique, termed Empirical Mode Decomposition, to decompose the texture into a set of component profiles of different wavelengths. The Dynamic Friction Model, a computational friction model already validated on real road surfaces, is then used to determine the relative effect of partially recomposed profiles with their components on skid resistance. The results demonstrate the importance of not only ‘small-scale' and ‘large-scale' textures but also their spatial arrangement and shape. Indeed, on wet road surfaces, ‘small-scale-texture' was found to be key to achieving good skid resistance at low speeds, whilst ‘large-scale-texture' was found to be crucial to maintaining it with increasing speed. But furthermore, the distribution of the summits of the large-scale-textures was established as being able to compensate for a lack of small-scale-texture. Conversely, the reverse was established as also being true, with the small sharp local summits of small-scale-texture being found to compensate for a lack of large-scale-texture

Tire/Road Friction Prediction: Introduction a Simplified Numerical Tool based on Contact Modelling

The present paper introduces a tire/road friction prediction tool based on modelling the tire/road contact as dynamic, viscoelastic, rough, and lubricated. The tool takes into account a considerable part of influent parameters related to tire, road, contaminant, and contact operating conditions: For the tire, the tool takes into account its geometry and rubber material behaviour. For the road, the texture is taken into account via the surface topography. At the contact interface, dry or wet conditions are taken into account through the lubricant depth, viscosity, and density. The operating conditions are taken into account through the normal load, speed, and slip ratio of the tire. The real novelty of this tool lies in its ability to reproduce the complete curve of the tire/road friction coefficient as a function of the slip rate. The validation of the tool is initially done through parametric studies by analyzing the trends of the results, then by performing braking tests on a passenger car at various speeds on different wet roads with different textures. The tool correctly ranks the peak friction and the sliding friction on these various road surfaces

eRoads Group (from a pavement point of view)

International audienc

Quantifying long-term rates of texture change on road networks

Texture is required on pavements to provide safe and comfortable ride performance for users. This paper provides the first meaningful analysis of a long-term study of texture data obtained using TRACS (TRAffic Speed Condition Survey) at a site in the UK. TRACS data were collected annually, over a 2 km stretch of motorway from 1995 to 2019. A new data analysis approach utilising time series data with spectral analysis and spatial filtering procedures is presented. The results reveal that the approach enables legacy TRACS laser profile Sensor Measured Texture Depth (SMTD) data to be used to determine long term rates of change in road surface macrotexture. Thus, the technique has unlocked the potential for SMTD data collected annually for 7000 km of the Strategic Road Network in the UK, to inform road maintenance programmes by extrapolation. Additionally, results expose a systematic periodicity occurring each year within the SMTD data studied, corresponding to longitudinal oscillations with wavelengths between 33 and 62 m. The time-invariant periodicity of these oscillations suggests that it is ‘imprinted’ in the early life of the pavement. ‘Imprinting’ may theoretically arise with cyclic tyre loading applied by the suspension systems of heavy vehicles or during road construction

Seasonal Signals Observed in Non-Contact Long-Term Road Texture Measurements

Texture is required on road pavements for safe vehicle braking and manoeuvres. This paper provides a unique analysis of long-term texture obtained using traffic speed condition survey (TRACS) data from 14 sites, located along a north to south transect spanning the longest highway in the UK. A total of 19 years of sensor measured texture depth (SMTD) data have been analyzed using spatial filtering techniques and compared with meteorological and traffic datasets. The results for hot rolled asphalt (HRA) surfaces reveal that changes to SMTD follow a linearly increasing trend with time. The “rate of change” is influenced by the order of magnitude of annual average daily traffic (AADT), when factored for the percentage of heavy goods vehicles. This linear trend is disrupted by environmental parameters, such as rainfall events and seasonal conditioning. In the summer, this signal is evident as a transient peak in the “rate of change” of texture greater than 0.04 mm, and in the winter as a reduction. The transient changes in texture corresponded to above average rainfall occurring in the week prior to SMTD measurement. The signal observed demonstrates an inverse pattern to the classically understood seasonal variation of skid resistance in the UK, where values are low in the summer and high in the winter. The findings demonstrate for the first time that texture measurements experience a seasonal signal, and provide compelling evidence pointing toward surface processes (such as polishing and the wetting and drying of surface contaminants) causing changes to texture that are affecting seasonal variation in skid resistance

Improved non-contact 3D field and processing techniques to achieve macrotexture characterisation of pavements

Macrotexture is required on pavements to provide skid resistance for vehicle safety in wet conditions. Increasingly, correlations between macrotexture measurements captured using non-contact techniques and tyre-pavement contact friction are being investigated in order to enable more robust and widescale measurement and monitoring of skid resistance. There is a notable scarcity of research into the respective accuracy of the non-contact measurement techniques at these scales. This paper compares three techniques: a laser profile scanner, Structure from Motion photogrammetry and Terrestrial Laser Scanning (TLS). We use spectral analysis, areal surface texture parameters and 2D cross-correlation analysis to evaluate the suitability of each approach for characterising and monitoring pavement macrotexture. The results show that SfM can produce successful measures of the areal root mean square height (Sq), which represents pavement texture depth and is positively correlated with skid resistance. Significant noise in the TLS data prevented agreement with the laser profiler but we show that new filtering procedures result in significantly improved values for the peak density (Spd) and the arithmetic peak mean curvature (Spc), which together define the shape and distribution of pavement aggregates forming macrotexture. However, filtering the TLS data results in a trade-off with vertical accuracy, thus altering the reliability of Sq. Finally, we show the functional areal parameters Spd and Spc are sensitive to sample size. This means that pavement specimen size of 150 mm × 150 mm or smaller, when used in laboratory or field observations, are inadequate to capture the true value of areal surface texture parameters. The deployment of wider scale approaches such as SfM and spectrally filtered TLS are required in order to successfully capture the functional areal parameters (Spc and Spd) for road surfaces