The assurance of asphalt pavement layer compaction, expressed by ratio between field and laboratory bulk density and air voids content, is one of the main criteria of the durability of asphalt road pavement. Destructive measures should be applied and cores should be taken from the asphalt pavement seeking to determine the representative compaction level of the constructed asphalt layers. New methods are constantly being sought for fast, non-destructive and accurate asphalt layer density and air void determination on road. Ground Penetrating Radar (GPR) can allow determining the qualitative characteristics of asphalt pavement across the entire length of the road without causing damage to the road structure. Relative dielectric permittivity, usually called dielectric value or constant, is the leading property used in GPR applications on road pavement surveys. This article presents GPR measurement results from asphalt base and binder layers of four test sections. GPR measurements were conducted immediately after the end of asphalt layer compaction process. Test points on each layer were selected and density, air void content were determined by drilling cores and testing them in the laboratory. To estimate asphalt layer density and air void content, GPR data were analysed using different existing mathematical models. To justify the reliability of the data measured by GPR, results were checked by comparing them with the results measured directly on cores taken from the asphalt pavement layers.
The optimum density and air-voids content of asphalt pavement layers are among the main indicators of the durability of asphalt road pavement. The asphalt pavement with insufficient density is less resistant to traffic loading and the damaging effects caused by water. Air-voids ensure the durability of asphalt pavement and the accumulation of free bitumen during a period of hot weather. At present, the main ways to control the quality of compaction and the content of air-voids is to drill core specimens and test them in the laboratory. This method is expensive, it damages the road surface, and the quality of asphalt pavement is verified only at several points. With the rapid development of new technologies, it is necessary to evaluate and to apply innovative non-destructive methods, allowing us to determine the qualitative characteristics of asphalt pavement across the entire length of the road without causing the damage to the road surface and at lower costs. This article describes the use of Ground Penetrating Radar to determine asphalt pavement density and air-voids content provides an overview of global practices and feasibility analysis on the application of Ground Penetrating Radar on the roads of Lithuanian. Santrauka Asfalto dangos sluoksnių optimalus tankis ir oro tuštymių kiekis yra vieni iš pagrindinių dangos ilgaamžiškumo rodiklių. Nepakankamo tankio danga yra mažiau atspari automobilių eismo apkrovoms ir žalingam vandens poveikiui. Oro tuštymės užtikrina dangos ilgaamžiškumą ir laisvojo bitumo akumuliavimą karštuoju metų laikotarpiu. Šiuo metu pagrindinis būdas kontroliuoti sutankinimą ir oro tuštymių kiekį yra gręžti kernus ir juos bandyti laboratorijoje. Šis metodas yra brangus, gadinama kelio danga ir asfalto dangos kokybė patikrinama tik keliuose taškuose. Sparčiai vystantis technologijoms būtina įvertinti ir taikyti inovatyvius neardančiuosius metodus, leidžiančius kokybinius asfalto dangos rodiklius nustatyti neardant dangos, išilgai viso kelio ir mažesnėmis sąnaudomis. Šiame straipsnyje pateikta georadaro (angl. Ground Penetrating Radar) taikymo asfalto dangai sutankinti ir oro tuštymių kiekiui nustatyti pasaulinės praktikos apžvalga ir panaudojimo Lietuvos automobilių keliuose galimybių analizė.
Properly designed and maintained asphalt pavements operate for ten to twenty-five years and have to be rehabilitated after that period. Cold in-place recycling has priority over all other rehabilitation methods since it is done without preheating and transportation of reclaimed asphalt pavement. Multiple researches on the performance of cold recycled mixtures have been done; however, it is unclear how the entire pavement structure (cold recycled asphalt pavement overlaid with asphalt mixture) performs depending on binding agents. The main objective of this research was to evaluate the performance of cold in-place recycled asphalt pavements considering binding agents (foamed bitumen in combination with cement or only cement) and figure out which binder leads to the best pavement performance. Three road sections rehabilitated in 2000, 2003, and 2005 were analysed. The performance of the entire pavement structure was evaluated in terms of the International Roughness Index, rut depth, and pavement surface distress in 2013 and 2017.
Assurance of asphalt pavement layer compaction, expressed by air voids ratio between field and laboratory bulk density, is one of the main criteria of the asphalt pavement durability. Thus, destructive measures should be applied, and many asphalt samples should be taken on site in order to determine the representative compaction level of constructed pavement. With the fast development of technologies, new methods should be considered for fast, non-destructive and accurate determination of asphalt bulk density on site. As there are quite few non-destructive methods related to asphalt pavement density measurement, there is a need to make comparison of such methods. Currently, when GPR methods are used to determine the density, calibration cores are used in all cases to estimate the unknown or unmeasured variables or conditions that may affect the results of dielectric value measurements. The aim of this study is to develop a regression model that can predict the bulk density of the compacted asphalt layer without coring, using the design values of the bulk density determined in the type tests of asphalt mixtures or other currently used non-destructive testing technologies (in this case PQI and NDG) and GPR measured dielectric constant values.
In 2012, the Lithuanian Road Administration initiated a three-year research project ‘The study of effective winter road maintenance of national significance roads in Lithuania’. The main purpose of this research was to optimize road maintenance in winter and to determine the most effective means of combating slippery conditions. The research project was carried out by two institutions: the Road Research Institute of the Faculty of Environmental Engineering of Vilnius Gediminas Technical University and JSC ‘Problematika’. JSC ‘Problematika’ conducted exploratory experiments, which were divided into two phases. In the first phase of the experiment, five different snow melting materials (Slipperiness Reducing Materials – SRMs) were investigated in the laboratory. Different test methods were used in this investigation. In the second phase of the experiment, three SRMs with different properties were selected, and experimental road sections were set up to determine the road slipperiness and the change in coating layer thickness over time concerning different environmental conditions, as well as different snow and ice layer thicknesses. An optical remote sensor of Road Condition Monitor (RCM 411) was used for friction measurements on the roads. This report covers the laboratory test results of five different SRMs, road slipperiness measurement results using three selected SRMs and their analysis, comparison of the performance efficiency of the most widely used SRMs in Lithuania and the tested SRMs under different environmental conditions.
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