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Master of Science / Department of Civil Engineering / Mustaque A. Hossain / Over the lifetime of an asphalt concrete (AC) pavement, the roadway requires periodic resurfacing and rehabilitation to provide acceptable performance. The most popular resurfacing method is an asphalt overlay over the existing roadway. In the design of asphalt overlays, the thickness is related to the structural capacity of the existing pavement. As the layers are overlaid, their structural characteristics change due to aging of asphalt. However, currently there is no method to determine the effect of aging on the structural capacity of an existing pavement. This study examined structural characteristics of six test roadways in Kansas using three different test methods: Falling Weight Deflectometer (FWD), Portable Seismic Property Analyzer (PSPA), and Indirect Tensile (IDT) test. The results were analyzed to determine how the modulus of an AC pavement layer changes over time. The results indicate that as the AC pavement ages, its modulus decreases due to pavement deterioration, especially stripping. Two test roadways that showed little signs of stripping had a minimal reduction or even an increase in AC moduli. Thus, the stripping issue needs to be addressed to ensure longevity of AC pavements. While the correlation between test methods studied was mostly consistent for each roadway, no universal correlation was found. The structural coefficient of each AC layer was determined based on the resilient modulus of the layer. It was found the structural layer coefficients do not typically decrease with age at the same rate, and the rate of decrease is a function of the distresses observed.

Doctor of Philosophy / Department of Civil Engineering / Mustaque A. Hossain / Tack coat is a thin layer of asphaltic material used to bind a newly-placed lift of hot-mix asphalt (HMA) pavement to a previously-placed lift or a new HMA overlay/inlay and existing pavement. The purpose of a tack coat is to ensure that a proper bond occurs so that traffic loads are carried by the entire HMA structure. Proper bonding exists when HMA layers act as a monolithic structure, transferring loads from one layer to the next. This depends on appropriate selection of tack coat material type and application rate, and is essential to prevent slippage failure and premature cracking in the wearing surface. This study focuses on development of a three-dimensional finite element (FE) model of HMA pavement structure in order to assess HMA interface bonding. The FE model was constructed using commercially available ABAQUS software to simulate an Accelerated Pavement Testing (APT) experiment conducted at the Civil Infrastructure Systems Laboratory (CISL) at Kansas State University. Mechanistic responses measured in the CISL experiment, such as localized longitudinal strain at the interface, were used to calibrate the FE model. Once calibrated, the model was used to predict mechanistic responses of the pavement structure by varying the tack coat property to reflect material characteristics of each application. The FE models successfully predicted longitudinal strains that corresponded to APT results.

Master of Science / Department of Electrical and Computer Engineering / Dwight D. Day / Balasubramaniam Natarajan / This thesis presents an automated pavement crack detection and classification system via image processing and pattern recognition algorithms. Pavement crack detection is important to the Departments of Transportation around the country as it is directly related to maintenance of pavement quality. Manual inspection and analysis of pavement distress is the prevalent method for monitoring pavement quality. However, inspecting miles of highway sections and analyzing each is a cumbersome and time consuming process. Hence, there has been research into automating the system of crack detection. In this thesis, an automated crack detection and classification algorithm is presented. The algorithm is built around the statistical tool of Principal Component Analysis (PCA). The application of PCA on images yields the primary features of cracks based on which, cracked images are distinguished from non-cracked ones. The algorithm consists of three levels of classification: a) pixel-level b) subimage (32 X 32 pixels) level and c) image level. Initially, at the lowermost level, pixels are classified as cracked/non-cracked using adaptive thresholding. Then the classified pixels are grouped into subimages, for reducing processing complexity. Following the grouping process, the classification of subimages is validated based on the decision of a Bayes classifier. Finally, image level classification is performed based on a subimage profile generated for the image. Following this stage, the cracks are further classified as sealed/unsealed depending on the number of sealed and unsealed subimages. This classification is based on the Fourier transform of each subimage. The proposed algorithm detects cracks aligned in longitudinal as well as transverse directions with respect to the wheel path with high accuracy. The algorithm can also be extended to detect block cracks, which comprise of a pattern of cracks in both alignments.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / Thesis presented in fulfilment of the requirements for the degree of Master of Science in Engineering at Stellenbosch University / ENGLISH ABSTRACT: Weigh-in-motion (WIM) scales are installed on various higher order South African roads to provide traffic loading information for pavement design, strategic planning and law enforcement using a scientific approach. The two most respected international guideline documents for WIM systems are the American ASTM E1318 Standard and the COST 323 European Specification, yet neither are fully suited to be applied to local WIM systems. The author developed a post-calibration method for WIM data, called the Truck Tractor (TT) Method, to correct the magnitude of recorded axle loads in retrospect. It incorporates a series of powerful data quality checks. The TT Method is robust, accurate and adequately simple to be used on a routine basis. The TT Method uses the truck tractor loads of articulated 6- and 7-axle trucks with single steering- and double driving axles – these vehicle are called Eligible Trucks. Only Eligible Trucks with average axle loads between 6.5 t and 8.5 t are used in the calibration process – these vehicles are called Selected Trucks. A calibration factor, kTT, is determined using a fully automated iterative procedure, and multiplied with all axle load measurements to produce data for which the average truck tractor load of Selected Trucks, TTT, is equal to 21.8 t. The TT Method can be used for WIMs in various operating environments and is not sensitive to the extent of miss-calibration of a WIM, clipping of sensors owing to poor lane discipline or different extents of loading on different routes. The TT Method includes a series of data quality checks that can be used on a routine basis. They are summarised as follows: - The standard deviation of truck tractor loads for Selected Trucks, STTT, should always be below 2.0 t, but preferably below 1.9 t. - The standard deviation of front axle loads for Selected Trucks, SFTT, should always be below 0.9 t, but preferably below 0.8 t. - The post-calibration factor from the TT Method, kTT, should be between 0.9 and 1.1. The factor for any month should not deviate by more than 3% from the moving average of the previous five months. - The average of front axle loads of Selected Trucks, FTT, should be between 5.6 t and 6.6 t; the exact values are influenced by load transfer between the steering and driving axles. - A procedure was formulated using the Front axle / Truck tractor Ratio, FTR, to identify the percentage of Eligible Trucks that in all probability clipped the sensor. The percentage of these records must be below 10 %, but preferably below 6 %. The TT Method has the potential to significantly improve WIM data collection in South Africa. The calibration module of the TT Method, i.e. the procedure to calculate kTT, has already been accepted by SANRAL. Most of the data quality checking concepts associated with the TT Method were also accepted, although their threshold values are still being refined. / AFRIKAANSE OPSOMMING: Weeg-in-beweging (“weigh-in-motion”, WIM) skale word op talle hoë orde paaie in Suid- Afrika gebruik om op wetenskaplike wyse verkeersinligting te verskaf wat gebruik word vir plaveiselontwerp, strategiese beplanning en wetstoepassing met betrekking tot oorlading. Nie een van die twee vooraanstaande internasionale riglyne vir WIM sisteme, die ASTM E1318 Standaard en die COST 323 Europese Spesifikasie, is in geheel geskik vir Suid-Afrikaanse kondisies nie. Die outeur het ‘n unieke kalibrasie metode, genaamd die TT Metode, ontwikkel wat ’n reeks roetine kwaliteitsbeheertoetse vir WIM data insluit. Die TT Metode is eenvoudig, akkuraat en toepaslik vir ’n wye verskeidenheid WIM sisteme in Suid-Afrika. Die massa van trekkers van geartikuleerde 6- en 7-as vragmotors met enkel stuur- en dubbel dryf-aste en ’n gemiddelde asmassa tussen 6.5 en 8.5 ton (ook genoem Geselekteerde Vragmotors) word as verwysingsmassa gebruik. ’n Iteratiewe prosedure word gevolg vir die bepaling van die kalibrasie faktor, kTT. Dieselfde faktor word met alle asmassas in die data vir die analise periode vermenigvuldig, met die einddoel dat die gemiddelde trekker massa van die Geselekteerde Vragmotors, TTT, gedryf word na die teikenwaarde van 21.8 ton. Die TT Metode is ewe toepaslik ongeag die tipiese belading van trokke op ’n roete, hoe goed die WIM sisteem oorspronklik gekalibreer was of hoe goed laandissipline by die WIM sensor is. Die kwaliteitsbeheertoetse kan op ’n roetine basis toegepas word as deel van die uitvoering van WIM kalibrasie prosedure, en word soos volg saamgevat: - Die standaard afwyking van trekker massas van Geselekteerde Vragmotors, STTT, behoort altyd laer as 2.0 ton, maar verkieslik laer as 1.9 ton te wees. - Die standaard afwyking van voor-as massas van Geselekteerde Trokke, SFTT, behoort altyd laer as 0.9 ton, maar vekieslik laer as 0.8 ton te wees. - Die kalibrasiefaktor, kTT, moet verkieslik tussen 0.9 en 1.1 wees, en mag nie met meer as 3 % van die gemiddelde kTT vir die voorafgaande vyf maande verskil nie. - Die gemiddeld van voor-as massas van Geselekteerde Vragmotors, FTT, behoort tussen 5.6 ton en 6.6 ton te wees. Die presiese waarde hang af van die mate waartoe gewig tussen die voor-as en dubbel dryf-as oorgedra word weens dinamiese effekte op die trekker. - Die verhouding tussen die voor-as en dubbel dryf-as, bekend as die FTR, kan gebruik word as ‘n aanduiding of ’n trok weens swak laandissipline slegs gedeeltelik oor die WIM sensor gery het. Die persentasie gedeeltelike metings moet laer as 10%, maar verkieslik laer as 6 % wees. Die TT Metode het die potensiaal om die insameling en kwaliteit van verkeersdata deur middel van WIM sisteme noemenswaarding te verbeter. Die kalibrasie module van die TT Metode, m.a.w. die prosedure om kTT te bereken, is reeds deur SANRAL aanvaar. Die meeste van die kwaliteitsbeheerkonsepte wat met die TT Metode gepaard gaan is ook aanvaar, maar die drempelwaardes hiervoor word nog verfyn.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The increasing awareness of climate change causes a growing interest in pavement rehabilitation. Pavement rehabilitation by in-situ stabilisation with bitumen reduces the extraction of natural aggregate resources while enhancing flexibility and durability properties, which lowers maintenance costs over the design-life of the pavement structure. Incorporating Bitumen Stabilised Materials (BSMs) into a pavement structure can therefore have economic and environmental benefits, but more research is needed to fully understand the behaviour and potential of these materials. Stabilising materials with bitumen provides useful properties to pavement layers. The “TG2 2nd Edition, Bitumen Stabilised Materials” was published by the Academy of South Africa in May 2009, which provides a good understanding of the usage of Bitumen Stabilised Materials (BSMs). However, the shrinkage and flexible behaviour of these materials are still not fully understood and therefore more research on these materials is needed. The aim of this project is thus to determine the shrinkage and flexible behaviour of BSMs to incorporate these behavioural types in the revised design method for flexible pavements in the SAPDM. In addition, the influence of several additives on the shrinkage and flexible behaviour of BSMs have been evaluated to get an improved understanding of these properties. The additives included cement (1% and 2% content) and both bitumen emulsion (0.9% and 2.4% content) and foamed bitumen (only 2.4% content). Two linear shrinkage testing methods have been designed to test the shrinkage potential of BSMs, including a beam testing method and a cylindrical testing method. Based on the usage of the shrinkage measurements the applicable method can be used to determine the shrinkage potential of a BSM. The flexibility is a more complex property and was tested using a simple monotonic beam test. The strain-at-break parameter obtained from this test provided an indication of the material flexibility. Slight differences in the trends were observed between beam and cylindrical shrinkage due to specimen geometry, exposed surface area and shrinkage testing direction. Beam specimens initially show swelling when bitumen is added to the mixture and shrinks thereafter. Cylindrical specimens on the other hand show initial shrinkage followed by a slight length increase, where after shrinkage continues. The additives had the same influence on the shrinkage for both the beam and cylindrical specimens. Although all shrinkage measurements were small, an increase in bitumen reduced shrinkage and an increase in cement increased shrinkage. Stabilisation with foamed bitumen rather than bitumen emulsion proved to show less shrinkage, but only in combination with 2% cement. The strain-at-break, dissipated energy and material stiffness calculated from the monotonic beam tests provided a good indication of the flexibility behaviour of BSMs. Higher bitumen content increased the flexibility potential and an increase in cement decreased the flexibility potential of BSMs. This project has provided good insight on both the shrinkage and flexibility behaviour of BSMs, which can be used in the revised copy of the SAPDM. Increased bitumen contents decreases the shrinkage potential and increases the flexibility of a BSM. Increased cement contents on the other hand, increases shrinkage and decreases flexibility of BSMs. The correct combination of cement and bitumen in a BSM can thus provide a material with the wanted flexibility while keeping the shrinkage to a minimum. / AFRIKAANSE OPSOMMING: Die toenemende bewustheid van klimaatsverandering veroorsaak toenemende belangstelling in die rehabilitasie van plaveisels. Plaveisel rehabilitasie deur in-veld stabilisasie met bitumen verminder die ontginning van natuurlike hulpbronne, terwyl die verbetering van buigsaamheid en duursaamheid eienskappe die onderhoudskoste verlaag oor die ontwerp-lewe van die plaveiselstruktuur. Die inkorporasie van Bitumen Gestabiliseerde Materiale (BGM) in 'n plaveisel struktuur kan dus omgewings en ekonomiese voordele inhou. Meer navorsing word wel benodig om die gedrag van hierdie materiale beter te verstaan. Die stabilisering van materiale met bitumen verskaf nuttige eienskappe aan 'n plaveisellaag. Die "TG2 2de Uitgawe, Bitumen Gestabiliseerde Materiale" is gepubliseer deur die Akademie van Suid-Afrika in Mei 2009 en verskaf 'n goeie begrip van Bitumen Gestabiliseerde Materiale (BGM). Die krimpings en buigsaamheid gedrag van die materiaal word wel nog nie ten volle verstaan nie en daarom word meer navorsing oor hierdie materiaal benodig. Die doel van hierdie projek is dus om die krimpings gedrag sowel as die buigsaamheid gedrag van 'n BGM te bepaal en sodoende die kennis te gebruik in die hersiende ontwerp metode vir buigsame plaveisels in die SAPDM. Die invloed van verskeie bymiddels op die krimpings en buigsaamheid gedrag van 'n BGM is ook geëvalueer om 'n beter begrip van hierdie eienskappe te verkry. Die bymiddels sluit sement in (1% en 2% inhoud) asook beide emulsie bitumen (0,9% en 2,4% inhoud) en skuim bitumen (slegs 2.4% inhoud). Twee lineêre krimpings toets metodes was ontwerp om die krimping potensiaal van BGM's te bepaal, wat 'n balk toets metode en 'n silindriese toets metode insluit. Die metode wat gebruik sal word om die krimping van 'n BGM te bepaal moet baseer word op die toepassing waarvoor die krimpings resultate gebruik gaan word. Die buigsaamheid is 'n meer komplekse eienskap en was getoets met behulp van 'n eenvoudige monotoniese balk toets. Die spanning-by-breekpunt waardes wat verkry was vanuit die balktoetse, het 'n goeie aanduiding van die buigsaamheid van die materiaal verskaf. Klein verskille in krimpingstendense tussen balk en silindriese proefstukke is opgemerk tydens die projek en is veroorsaak deur die geometrie van die proefstuk, die blotgestelde oppervlakte asook die rigting van kimp toetsing. Balk proefstukke toon aanvanklike swelling wanneer bitumen bygevoeg is, gevolg deur krimping. Silindriese proefstukke aan die ander kant toon aanvanklike krimping gevolg deur 'n effense toename in lengte, waarna krimping weer plaasvind. Die bymiddles het dieselfde invloed op die krimping van beide die balk en silindriese proefstukke. Alhoewel al die krimpingswaardes baie klein was, het 'n toename in bitumen 'n vermindering in krimping voortgebring en 'n toename in sement het 'n toename in krimping voortgebring. Stabilisasie met skuim bitumen in plaas van emulsie bitumen toon verlaagde krimping, maar slegs in kombinasie met 2% sement. Die spanning-by-breekpunt, verkose energie en materiaal styfheid wat bereken is vanaf die monotoniese balk toets resultate, het 'n goeie aanduiding van die buigsaamheid gedrag van BGM's verskaf. 'n Hoër bitumen inhoud verhoog die buigsaamheid potensiaal van BGM‟s terwyl 'n toename in sement die buigsaamheid potensiaal van BGM's verlaag. Hierdie projek bied goeie insigte vir beide die krimpings en buigsaamheid gedrag van BGM's, wat in die hersiende ontwerp metode van die SAPDM gebruik kan word. Verhoogde bitumen inhoud verminder die krimping potensiaal en verhoog die buigsaamheid van 'n BGM. Verhoogde sement inhoud aan die ander kant, verhoog krimping en verminder buigsaamheid van BGM's. Die korrekte kombinasie van sement en bitumen in 'n BGM kan dus 'n materiaal produseer met die gewenste buigsaamheidseienskappe en terselfde tyd die krimping tot 'n minimum beperk.

Permeable friction course (PFC) is a porous asphalt pavement placed on top of a regular impermeable roadway. Under small rainfall intensities, drainage is contained within the PFC layer; but, under higher rainfall intensities drainage occurs both within and on top of the porous pavement. This dissertation develops a computer model—the permeable friction course drainage code (PERFCODE)—to study this two-dimensional unsteady drainage process. Given a hyetograph, geometric information, and hydraulic properties, the model predicts the variation of water depth within and on top of the PFC layer through time. The porous layer is treated as an unconfined aquifer of variable saturated thickness using Darcy’s law and the Dupuit-Forchheimer assumptions. Surface flow is modeled using the diffusion wave approximation to the Saint-Venant equations. A mass balance approach is used to couple the surface and subsurface phases. Straight and curved roadway geometries are accommodated via a curvilinear grid. The model is validated using steady state solutions that were obtained independently. PERFCODE was applied to a field monitoring site near Austin, Texas and hydrographs predicted by the model were consistent with field measurements. For a sample storm studied in detail, PFC reduced the duration of sheet flow conditions by 80%. The model may be used to improve the drainage design of PFC roadways. / text

This research evaluates four options to produce quality axle load data for pavement design: piezoelectric WIM sites (corrected and uncorrected data), static weigh scales, and a piezo-quartz WIM site. The evaluation applies four data quality principles: data validity, spatial coverage, temporal coverage, and data availability. While all principles are considered, the research contributes in the development and application of an integrated and sequential approach to assess data validity of the options by performing analyses to determine the precision and accuracy of axle load measurements. Within the context of Manitoba, the evaluation reveals that data produced by piezo-quartz and static weigh scales have superior validity, with piezo-quartz data offering better temporal coverage, data availability, and future geographic coverage. Ultimately, the selection of the best option for providing quality axle load data depends on the relative importance of data quality principles for producing data supporting sound pavement designs and infrastructure management decisions. / May 2017