Field Evaluation of Asphalt Mixture Skid Resistance and its Relationship to Aggregate Characteristics (original) (raw)
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Predicting Asphalt Mixture Skid Resistance Based on Aggregate Characteristics
2009
The objective of this research project was to develop a method to determine the skid resistance of an asphalt mixture based on aggregate characteristics and gradation. Asphalt mixture slabs with different combinations of aggregate sources and mixture designs were fabricated in the laboratory, and their skid resistance was measured after different polishing intervals. The wheel-polishing device developed by the National Center for Asphalt Technology (NCAT) was used for polishing the slabs. Frictional characteristics of each slab were measured by sand patch method, British Pendulum, Dynamic Friction Tester (DFT), and Circular Texture Meter (CTMeter). Aggregates were characterized using a number of conventional test methods, and aggregate texture was measured using the Aggregate Imaging System (AIMS) after different polishing intervals in the Micro-Deval device. Petrographic analyses were performed using thin sections made with aggregates from each of these sources. Petrographic analyses provided the mineralogical composition of each source. The aggregate gradation was quantified by fitting the cumulative Weibull distribution function to the gradation curve. This function allows describing the gradation by using only two parameters. The results of the analysis confirmed a strong relationship between mix frictional properties and aggregate properties. The main aggregate properties affecting the mix skid resistance were Polish Stone Value, texture change before and after Micro-Deval measured by AIMS, terminal texture after Micro-Deval measured by AIMS, and coarse aggregate acid insolubility value. The analysis has led to the development of a model for the International Friction Index (IFI) of asphalt mixtures as a function of polishing cycles. The parameters of this model were determined as functions of (a) initial and terminal aggregate texture measured using AIMS, (b) rate of change in aggregate texture measured using AIMS after different polishing intervals, and the (c) Weibull distribution parameters describing aggregate gradation. This model allows estimating the frictional characteristics of an asphalt mixture during the mixture design stage.
Wear, 2020
The work presented in this paper aims to find the relationship between the types of coarse aggregates used in asphalt mixes and the long-term skid resistance capacity of the resulting pavements. It builds on previous work which proposed a relationship between the mineralogical composition of aggregates and the skid resistance of asphalt surfacings in the long-term. Here, the focus of the inquiry is shifted from an asphalt surface of one type of aggregate to a mix of several types of aggregates. Polishing tests and friction measurements were performed in the laboratory on different pavement samples, followed by a mineralogical analysis of the coarse aggregates of these samples to define a new parameter termed "Averaged Aggregate Hardness Parameter". The results found that this parameter correlates well with the long-term skid resistance. Finally for practical use, the paper proposes analytical formulas to link the new pavement hardness parameter with the long-term skid resistance of pavements.
Evaluating skid resistance of different asphalt concrete mixes
Building and Environment, 2007
At all stages of pavement life, the highway surface should have some sort of roughness to facilitate friction between car wheels and pavement surface. Skid resistance is a measure of the resistance of pavement surface to sliding or skidding of the vehicle. It is a relationship between the vertical force and the horizontal force developed as a tire slides along the pavement surface. The texture of the pavement surface and its ability to resist the polishing effect of traffic is of prime importance in providing skidding resistance. Polishing of the aggregate is the reduction in microtexture, resulting in the smoothing and rounding of exposed aggregates. This process is caused by particle wear on a microscopic scale. It is a common fact that the lower the skid resistance value, the higher the percentage of the traffic accidents, especially during the wet seasons. Having a low skid resistance value at an asphalt concrete surface might be attributed to one or more of the following reasons: (1) use of higher asphalt content than recommended by the mix design procedure, (2) the Marshall mix design procedure itself, (3) used aggregate gradation, and (4) aggregate quality. To evaluate these factors, a comparative study was performed to find the British Pendulum Skid Resistance Number for a number of mixes. These mixes included, an asphalt concrete mix using local aggregate at the optimum Marshall asphalt content, mixes with 0.5% and 1.0% asphalt contents higher than Marshall optimum asphalt content, a mix designed using Superpave design procedure, a mix with steel slag to replace 30% of limestone aggregate, and a mix with stone matrix aggregate gradation. It was found that the mix with 30% slag has the highest skid number followed by Superpave, SMA, and Marshall mixes, respectively. It was also observed that increasing the asphalt content above the optimal asphalt content value decreases the skid resistance of these mixes.
Quantifying the effect of modified mixture volumetrics and compaction effort on skid resistance of asphalt pavements Quantifying the effect of modified mixture volumetrics and compaction effort on skid resistance of asphalt pavements, 2022
This paper aims to quantify the effect of modified mixture volumetrics and compaction effort on surface characteristics of asphalt pavements. Specimens were prepared using PG 64-10 asphalt binder mixed with crushed limestone aggregate. Three types of asphalt modifiers were added; Crumb Tire Rubber (CTR), Microcrystalline Synthetic Wax (MSW) and Nano Silica (NS). In addition, specimens were adjusted at 4% air void and were compacted at Design Number of Gyrations (Ndes) = 119 and 82 to simulate high and low levels of traffic, respectively. Research findings revealed that Air Voids Volume (V a) and Effective Binder Volume (V be) exert a significant effect on the surface frictional properties. Additionally, the ratio of V a to V be , expressed as P v , was also investigated to study the combined effect of V a and V be on surface friction results. It was concluded that P v has a considerable role in the evaluation process. It was also shown that increasing the level of compaction would result in a positive effect on British Pendulum Number (BPN) measurements and the opposite is true in terms of macrotexture measurements. Furthermore, CTR-modified mixtures exhibited the highest values of friction and macrotexture followed by NS-modified mixtures. MSW-modified and unmodified mixtures exhibited the least fractional characteristics. ARTICLE HISTORY
rodoviasverdes.ufsc.br
The greatest emphasis in pavement performance has been done in structural design components. However, the pavement friction is also important and is one of the factors that determining pavement safety. The wet skidding crashes are largely reduced when friction between a vehicle tire and pavement is high. Skid resistance and texture are important safety characteristics which need to be considered when pavement mixes are tested in laboratory. The objective of this study was to evaluate the skidding based on macrotexture and microtexture used in the International Friction Index (IFI). This study was conducted in asphalt mixtures compacted slab produced in laboratory. Two different mixtures grading (dense and gap) were produced using conventional asphalt and asphalt rubber. The characterization of the macrotexture and microtexture of asphalt pavements surfaces was obtained by the following tests: (i) British pendulum; (ii) Volumetric Method. IFI values were calculated by the pair of the parameters Sp and F60. The results showed that the mixture with gap grading had higher texture in comparison of mixtures with a dense grade gradation. The asphalt rubber mixtures improved the skid resistance compared to conventional mixtures.
Experimental-based model for predicting the skid resistance of asphalt pavements
International Journal of Pavement Engineering, 2013
The skid resistance of asphalt pavement is a major characteristic of road safety. This study aimed at the development of a model that expresses skid resistance as a function of mixture gradation, aggregate texture and traffic level. The model was developed based on comprehensive measurements and analysis of asphalt mixture surface characteristics (friction, texture and skid resistance) in the laboratory and the field. In addition, aggregates were characterised using the aggregate imaging system after different polishing intervals in the Micro-Deval. The aggregate gradation was described using the twoparameter cumulative Weibull distribution function. The developed model provides an estimate of the skid number in the field. Consequently, this model can be used by engineers to select different combinations of aggregate types and mixture designs such that the desired level of skid resistance at a given traffic level is achieved.
Field investigation of factors affecting skid resistance variations in asphalt pavements
The Baltic Journal of Road and Bridge Engineering, 2014
Pavement management activities consist mainly of three sequential yet interconnected processes: condition assessment, performance prediction and needs analysis. On this basis, knowledge of the evolution of skid resistance over time is important for pavement maintenance/rehabilitation planning. Seasonal and long term variations have a significant effect on skid resistance evolution. In the present study this effect is thoroughly investigated by modelling field data to provide a structure for the evolution of skid resistance in asphalt pavements. The considered field data includes the results of skid resistance measurements that were performed along 29 highways pavement sections of similar asphalt mix properties, with a fixed slip system (Grip Tester), over a period of four years and during different seasons. The developed model addresses that skid resistance is strongly related to the past level of surface friction, traffic, temperature and precipitation. The model was verified with a high degree of statistical certainty ensuring that mistakes have not been made in implementing the model. Furthermore, it was validated as its predictions have matched additional experimental data, with high precision (95% confidence level). This result produces evidence in support of the statement that the developed model provides accurate information about the variations of skid resistance in asphalt pavements.
An assessment of the evolution of the skid resistance of proprietary asphalt surfacings in the UK
2012
This paper presents a laboratory and field study of the evolution of the skid resistance of different asphalt surfacing materials. A trial section was laid in September 2006 on a dual carriageway road located in the UK and subjected to heavy traffic conditions. Three different types of mixtures with 14, 10 and 6 mm maximum aggregate sizes and two different aggregate sources were used in the trial. In-situ measurements of skid resistance were carried out periodically using SCRIM and GripTester. Surface texture was also monitored using a laser sensor. Skid resistance values showed good material performance during the first 4 years since installation. Furthermore, surface texture values showed a decrease in texture for the relatively open 14 mm materials whereas no change in texture was practically observed for the denser 10 mm materials. Laboratory measurements of skid resistance were also carried out using the Wehner-Schulze (WS) device. This device is used to determine the friction of an aggregate or asphalt specimen after a polishing period. It was found that the WS ranked the mixtures in the same way as the in-situ methods whereas the PSV test did not. The WS was also used to predict the evolution of the skid resistance with traffic loading. Comparisons were then made between the predicted and measured skid resistance values. It was found that the WS device is a reliable tool for predicting the deterioration of friction due to traffic. Further work is, however, needed to relate laboratory measurements to in-situ methods.
— Stone Mastic Asphalt (SMA) mixtures rely on stone-to-stone contacts among particles to resist applied forces, and permanent deformation. Aggregates in SMA should resist degradation (fracture and abrasion) under high stresses at the contact points. Current practices for asphalt mix design and acceptance testing rely on volumetric properties. Vital to the calculation of mix volumetric properties are specific gravity measurements of the mixture and the aggregate in the mixture. For the Motorways wearing course,SMA stone grid must fulfil the mineralogical-petrographic condition to be on rock of igneous and/or metamorphic origin but of silicate composition, specific weight and LA method on resistance to fragmentation. During the construction of the Kosovo motorway for wearing course was used the SMA as asphaltlayer for providing longer lifetime to the road construction. The super-pave mix design for SMA wearing course has been composed considering the available stone with high mineralogical and petrographic composition. The stone used for the wearing course on this motorway has resistance to crushing of LA =18 which is below the standard criteria for heavy traffic roads and motorways wearing courses. Thespecific weight of used stone was 3100 kg/m3which is about 15% heavier than standard weight. For this specific stone were prepared special super-pave design mix with binder content 4.5% which was well below than typical SMA composition of 6.0−7.0% binder rather of mixture was 3100 kg/m 3. In this paperwork it is described the design mix of SMA composed with relatively high specific weight and their impacts on asphalt mix design properties used in Kosovo Motorway.
Asphalt pavements surface texture and skid resistance — exploring the reality
Canadian Journal of Civil Engineering, 2012
Wet pavement skidding due to inadequate surface texture or friction contributes to 20% to 35% of all wet weather crashes. Many of the past studies of pavement surface texture and friction have deficiency in selecting the model forms or variables and interpreting the models and (or) the findings or have recommended further investigation. These pose a challenge for the highway agencies in selecting the appropriate surface layer and (or) measuring tools. This study was undertaken to re-examine some of the pavement surface texture and skid resistance related issues and aid the highway agencies in this area. Pavement surface texture and skid resistance aspects were carefully examined using the data collected from nine asphalt concrete (AC) surfaces. Pavement surface texture was measured using the sand patch method and a high speed texture laser. Skid resistance was measured using a British Pendulum and a skid trailer. The analysis has reinstated that aggregate quality is the predominant factor for AC surface skid resistance. Both texture depth and ribbed tire skid resistance was shown to increase with an increase in coarse aggregate (CA) content proving their interdependency. Neither the voids in mineral aggregate (VMA) or air voids (AV) contents showed a meaningful or statistically significant correlation with the surface texture or skid resistance. Fairly good correlations were found among the British Pendulum number (BPN), ribbed tire skid number (SN) and mean texture depth (MTD) rejecting the hypothesis that BPN is a measure of only surface microtexture and ribbed tire skid number is insensitive to surface texture.