Dissertations / Theses on the topic 'Road pavements'

The efficiency of the road management system is increasingly challenged due to the frequent occurrences of extreme weather events, such as intense heavy rainfall, cyclones and flooding. The unpredictable events such as Hurricanes Katrina and Rita in the USA (2005), extreme flooding in January 2011 in South-East Queensland, Cyclones Oswald (2013) and Marcia (2015) in Queensland had severe impacts upon the road infrastructure. These roads are now subject to a wider range of climatic conditions over their service life than was originally anticipated during their design. To date, no deterioration model can accurately predict the impact of floods on pavements. To understand the impact of January 2011 flood on the structural performance of flood affected pavements, Falling Weight Deflectometer (FWD) deflection data and surface condition data (rutting and roughness), on flood-affected roads managed by Brisbane City Council, Department of Transport and Main Roads (TMR), Queensland and Roads and Maritime Services, New South Wales (RMS, NSW), Australia, were collected and examined.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text

Le réseau routier est l'un des atouts majeurs d'un pays. L'évaluation de l’état structurelle des infrastructures de transport routier et de leur évolution dans le temps est essentielle pour l'établissement de plans d'entretien rentables. À cet égard, l'instrumentation des chaussées permet une surveillance continue et à distance sans interruption de la circulation. Cependant, l'instrumentation reste un défi scientifique et technologique majeur en termes de résilience des dispositifs ainsi que de stratégies d'interprétation des données des capteurs. L'objectif global de cette thèse est de prouver la faisabilité du monitoring des routes par technologies de détection embarquées en démontrant l'exploitabilité des données de capteurs pour évaluer le vieillissement de la route et en fournissant une technologie à haute performance et faible intrusion. Nous proposons, via un essai accéléré à l'échelle 1, une validation des jauges de déformation pour la prédiction de l'endommagement par fatigue d'un revêtement routier. Ainsi, nous avons exploré l'utilisation de capteurs embarqués pour le calcul inverse des conditions mécaniques de la chaussée via l'instrumentation d'une route existante avec un réseau de jauges de déformation. La même section d'essai a servi d'environnement pour une première validation d'une nouvelle technologie de détection basée sur l'utilisation de capteurs de déformation flexibles à base de nanocarbone, testés plus tard dans la chaussée dans le cadre d'un essai accéléré. Nous avons ainsi démontré comment la nanotechnologie proposée pouvait répondre aux enjeux de l’instrumentation des chaussées en termes de géométrie, de compatibilité avec l'environnement routier, et de sensibilité
The road network is one of the major assets in our countries. The assessment of pavement conditions and their evolution with time is essential for the establishment of cost-effective maintenance plans. In this respect, pavement instrumentation allows remote and continuous monitoring with no traffic disruption. However it remains a major scientific and technological challenge in terms of devices resilience to the harsh road environment as well as of strategies for sensor data interpretation. The overall goal of this thesis is to prove the feasibility of embedded pavement monitoring by demonstrating the exploitability of embedded sensor data to assess road ageing, and by providing a high performance, low intrusiveness technology. We propose, via an accelerated pavement test, a validation of asphalt strain gauges as monitoring method for fatigue prediction in a road pavement. Thus, we further explored the use of embedded sensors for inverse calculation of pavement mechanical conditions via the instrumentation of an existing road with a network of asphalt strain gauges. The same trial section was the environment for a first validation of a novel sensing technology based on the use of nanocarbon-based flexible strain sensors, later tested under an accelerated pavement test. Thereby we demonstrated how the proposed nanotechnology can overcome some of the drawbacks of existing sensing devices in terms of geometry, compatibility with the road environment, and sensitivity

Research has been conducted into the fundamental mechanical properties of a granular material. This has involved the use of both a repeated load triaxial apparatus and a new hollow cylinder apparatus, which has required development and modification. Building on the foundation of earlier research at Nottingham, models have been developed which predict the stress-strain behaviour of a dry granular material under any combination of applied stresses. This includes repeatable elastic behaviour and the development of irrecoverable plastic strain. The accuracy of these models has been tested as far as possible using available test equipment. The effects of varying particle gradation, degree of compaction, maximum particle size and mineral type have been explored using a repeated load triaxial apparatus. The effect of moisture has also been investigated with respect to both full and partial saturation. A computer program (GRANMAT) has been written, which makes use of the stress-strain equations developed, to analyse a road pavement structure consisting of thin bituminous surfacing, granular base and subgrade. The reliability of the program has been assessed and areas of necessary improvement indicated. In-situ testing at a number of road sites is described and analysed with respect to both the effect of compaction on a granular road foundation and the use of a number of in-situ test devices. Finally, the information gained, in the laboratory and on site, is brought together in a series of design suggestions for granular road foundations, with particular reference to results from the GRANMAT computer program.

Thesis (MEng)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Long term performance of a road pavement structure is significantly influenced by its potential to distribute traffic loading from the surface to the natural subgrade. The interlayer adhesion conditions play a substantial role in the induced stress-strain distribution across all layers of the entire structure. For layers constructed in stages like a granular base (GB) and a cement treated subbase (CTSB), the state of adhesion is questionable. Therefore a detailed investigation on the achievable adhesion and its influence on pavement performance is essential. In this study, the direct shear test was used to assess the interlayer adhesion strength in terms of resistance of the GB layer to slide on top of the CTSB. To evaluate the level of achieved shear strength, the interlayer shear results were compared to the inlayer strength for a granular base and cemented subbase. The shear test results were presented in terms of relationships between shear stress and displacement, shear stress and normal pressure and vertical and horizontal displacements. Based on frictional and dilatant approaches, shear test results demonstrated that the interlayer adhesion strength between the GB and CTSB is significantly influenced by the roughness conditions of the CTSB before placing the GB. Compacting materials of the base layer on top of the scarified CTSB produces a unified compound structure due to intimate interaction between the two layers. Moreover, the achievable adhesion depends on the maximum grain size available in the CTSB layer, confining pressure and moisture condition. The increase in maximum aggregate size deepens the interaction zone between the GB and scarified CTSB which results in high shear resistance. Ingress of water induces lubricant behaviour and weakens the shear resistance. In the design example, it was shown that the assumption of full adhesion between pavement layers, currently used in many design methods, over-estimates the pavement life. The routine construction process of placing the GB on top of quasi-smooth CTSB induces poor adhesion between the layers which therefore affects stress-strain distribution behaviour across all layers of the pavement structure and then reduces the life of every single layer. According to the design example, the granular base layer is the most susceptible to early failure due to its stress-dependent behaviour. The significant difference between pavement life when full adhesion is considered and when partial adhesion is allowed indicates that the achievable adhesion should be considered during the design of the structure rather than assuming full adhesion. Furthermore, the development of practical specifications and technical guidelines for improving the anticipated conditions in the field is recommended.
AFRIKAANSE OPSOMMING: Die langtermyngedrag van 'n plaveiselstruktuur word tot 'n groot mate beïnvloed deur die vemoë daarvan om om verkeerslaste vanaf af die oppervlakte na die natuurlike grondlaag te verprei. Die adhesie tussen die plaveisellae speel 'n belangrike rol in die verspreiding van spannings en vervormings deur al die lae van die struktuur. In lae wat in fases gebou word, soos 'n grofkorrelrige kroonlaag (GB) en 'n sementgestabiliseerde stutlaag (CTSB), is die adhesie onder verdenking. 'n Detailondersoek van die adhesie wat behaal kan word, en die invloed daarvan op plaveiselgedrag, is daarom noodsaaklik. In hierdie ondersoek is die direkte skuiftoets gebruik om die tussenlaag-adhesie vas te stel in terme van die weerstand van die GB-laag om oor die CTSB-laag te skuif. Om die vlak van skuifsterkte wat behaal kan word, te bepaal, is die tussenvlakskuifsterkte vergelyk met die interne skuifweerstand van die grofkorrelrige laag en van die gestabiliseerde laag. Die skuiftoetsresultate is uitgedruk in terme van die verbande tussen skuifspanning en skuifverplasing, tussen skuifspanning en normaalspanning en ook tussen vertikale en horisontale verplasings. Gebaseer op skuifweerstand en dilatansie het skuitoetsresultate gedemonstreer dat adhesie tussen die GB- en CTSB-lae baie beïnvloed word deur die ruheid van die CTSB voordat die GB gebou word. Indien die GB-laag bo-op 'n grofgemaakte CTSB-laag geplaas word, word 'n baie goeie verband en interaksie tussen die twee lae verkry. Die beskikbare adhesie hang ook af van die maksimum korrelgrootte in die CTSB-laag, die inperkspanning en die waterinhoud. Die toename in maksimum aggregaatgrootte maak die interaksiesone tussen die GB en die grofgemaakte CTSB dieper en dit lei tot hoër skuifweerstand. Infiltrasie van water dien as smeermiddel wat die weerstand verlaag. In die ontwerp-voorbeeld is gedemonstreer dat die aanname van volle adhesie tussen plaveisellae, soos wat tans in baie ontwerpmetodes gedoen word, tot oorskatting van die leeftyd van die plaveisel lei. Die normale konstruksiemetode waarin die GB-laag bo-op 'n semi-gladde CTSB-laag geplaas word, lei tot swak adhesie tussen die lae wat verspreiding van spannings en vervormings deur die plaveisel minder gunstig maak en die leeftyd van alle lae in die plaveisel verlaag. Volgens die ontwerp-voorbeeld is die grofkorrelrige kroonlaag die vatbaarste vir voortydige faling as gevolg van die sy spannings-vervormingsgedrag. Die beduidende verskil tussen plaveiselleeftyd wanneer volle adhesie aanvaar of slegs gedeeltelike adhesie toegelaat word, illustreer dat die werklike haalbare adhesie gebruik moet word eerder as om volle adhesie te aanvaar. Verder word die onwikkeling van praktiese spesifikasies en tegniese riglyne om die verwagte toestande in die plaveisel beter in ag te neem, voorgestel.

Numa primeira fase deste trabalho inclui-se o levantamento das principais patologias que aparecem nos pavimentos rodoviários, assim como, da reabilitação e conservação dos mesmos através da aplicação de técnicas de reciclagem. Seguidamente é analisado um caso de estudo, tendo, para o efeito, sido elaborado um inquérito, o qual foi enviado a várias empresas, com o objetivo de facultarem opiniões, opções e informações sobre, entre outros aspetos, a viabilidade económica da aplicação das técnicas de reciclagem nos pavimentos degradados, em substituição das técnicas tradicionais PAVEMENT RECYCLING ROAD ENGINEERING ABSTRACT: Initially this work includes a survey of the main pathologies that appear on road surfaces, as well as the rehabilitation and conservation of the same by applying recycling techniques. The second part will treat the recycling on site with a cold binder such as cement. Then be analyzed a case study and a survey of the industry, with the objective to verify the practical experience and the economic viability of applying the recycling techniques on degraded pavement.

Society has gripped the concept of road transport and has utilised it for social, personal and economic gain. Amidst the apparent benefits, a number of concerns exist around the dangers, congestion, and monetary loss associated with vehicular transport. To counteract this, the introduction of driverless vehicles is being discussed by manufacturers and the Government. Whilst there are a number of apparent benefits, there is an overwhelming need to consider public perception and acceptance of autonomous vehicles. This research study therefore investigates the aforementioned, analysing and presenting the major issues and concerns related to their uptake. An interview and focus group based approach was adopted for this research, using the Charmaz (2006) constructivist grounded theory methodology. Interviews were conducted with a range of stakeholders and the results of the study detailed that the environment the vehicle and user operate in presents associated issues influencing perceptions, and that technology acceptance is strongly influenced by levels of Motivation in Intention, Acceptance/Usage and Control. Furthermore, acceptance is perceived differently by various stakeholder groups, each with their individual concerns and speculations. The discussion of the study considers the gathered perception to ascertain how best to introduce autonomous vehicles to the public market, highlighting and satisfying the current implications of doing so. This study highlights the need for further research in this discipline, based on the identification of many knowledge gaps. Further work is discussed and recommended in order to combat the limitations and opportunities identified within this thesis.

Pavements represent an important infrastructure to all countries. In Saudi Arabia, huge investments have been made in constructing a large network. This network requires great care through conducting periodic evaluation and timely maintenance to keep the network operating under acceptable level of service. Pavement distress prediction and pavement condition prediction models can greatly enhance the capabilities of a pavement management system. These models allow pavement authorities to predict the deterioration of the pavements and consequently determine the maintenance needs and activities, predicting the timing of maintenance or rehabilitation, and estimating the long range funding requirements for preserving the performance of the network. In this study, historical data of pavement distress and pavement condition on the main and secondary road network of Riyadh, Saudi Arabia were collected. These data were categorized, processed, and analyzed. These data have been employed to generate prediction of pavement distress and condition models for the Saudi Arabia Urban Road Network (SAURN). Throughout the study, the most common types of pavement distress on SAURN have been identified. The behavior of these distress types has been investigated. A sigmoid function was found to be an excellent representation of the data. Seven for urban main pavement distress models (UMPDM) have been developed. In addition, six urban secondary pavement distress models (USPDM) have been developed. Moreover, two pavement condition models have also been developed, one for urban main pavement condition (UMPCM), and the other for urban secondary pavement condition (USPCM). The developed models provide a reasonable prediction of pavement condition. The models were assessed by standard error and residual analysis. A suitable procedure for the implementation of the models has also been proposed.

Alternative materials represent an important potential source of aggregates for road construction. At present, their use remains limited owing to the abundance and low cost of high quality natural aggregates, low costs of landfill disposal and generally restrictive specifications for pavement materials. Nevertheless, their influence in relation to the primary aggregates is likely to increase in the future with the enforcement of more strict environmental regulations at national and European levels. The objective of this research project was to investigate a wide range of alternative materials and provide a practical framework for their assessment enabling pavement engineers to deal with most applications in road construction. Initially secondary materials were assessed according to the present UK specifications and were found to fail the requirements in most cases. However, the current approach does not assess fundamental properties such as stiffness, resistance to permanent deformation, tensile strength, resistance to fatigue and the development of these with time, leading to an inadequate assessment of these materials. To advance towards the development of performance-based specifications repeated load triaxial and indirect tensile tests were used. For their performance the Nottingham 150x300 mm triaxial apparatus was used and an indirect tensile apparatus developed which evolved from the Nottingham Asphalt Tester used for bituminous materials. In triaxial testing, models used to study the resilient behaviour of granular materials were found to give good results for unbound but not for lightly-treated secondary materials. For these, a new resilient model was developed. Testing and specimen preparation techniques together with performance classification systems were developed for both tests and recommendations for an overall methodology for the evaluation of secondary materials are presented. An application of this methodology was made to the study of thirteen mixtures to be considered for full-scale trials. The application of secondary materials in pavements was evaluated using analytical methods of pavement design which demonstrated the potential of these at levels in the pavement as high as the roadbase and the overall thickness reduction that may result.

Flexible road pavements often fail due to excessive rutting. as a result of cumulative vertical permanent deformation under repeated traffic loads. The currently used analytical approach to flexible pavement design evaluates the pavement life in terms of critical elastic strain at the top of the subgrade. Hence, the plastic pavement behaviour is not properly considered. Shakedown analysis can take into account the material plasticity and guarantee structure stability under repeated loads. It provides a more rational design criterion for flexible road pavements. Finite element analyses using the Tresca and Mohr-Coulomb yield criteria are performed to examine the responses of soil half-space when subjected to different loading levels. Both shakedown and surface ratchetting phenomena are observed and the residual stresses are found to be fully-developed after a limited number of load passes. The finite element results are then used to validate the solutions from shakedown analysis. The main focus of current research is concerned with new solutions for static (i.e. lower-bound) shakedown load limits of road pavements under both two-dimensional and three-dimensional moving surface loads. Solutions are derived by limiting the total stresses at any point (i.e. residual stresses plus loading induced elastic stresses) to satisfy the Mohr-Coulomb yield criterion. Previous analytical shakedown solution has been derived based on a residual stress field that may not satisfy equilibrium for certain cases. In this study, a rigorous lower-bound shakedown solution has been derived by imposing the equilibrium condition of residual stresses. The newly developed shakedown solutions have been applied to one-layered and multi-layered pavements. It was found that the rigorous lower-bound solution based on the self-equilibrated residual stress field is lower than the analytical shakedown solution for cases when the critical point lies on the surface or at the base of the first pavement layer. The results showed that the theoretical predictions of pavement shakedown load limit generally agree with the finite element and experimental observations for pavement behaviours. The shakedown solution has been further extended to study the influence of the shape of contact load area for pavements under three-dimensional Hertz loads. It was found that the shakedown load limit can be increased by changing the load contact shape from a circle area to an elliptical one. A new pavement design approach against excessive rutting has been proposed. The pavement design is suggested by plotting thickness design charts using the direct shakedown solutions and choosing the thickness combination based on the design traffic load.

Road pavement design in Kurdistan is based on ASSHTO 1993. However, it seems not to be entirely satisfactory since it is unable to take full account of properties of local soils or those which have been stabilised. To address this, a design procedure applicable to different material and environmental conditions was developed. The associated research consisted of a suite of laboratory experiment allied to the development of a finite element model. The laboratory work was undertaken on three types of subgrade soils found in Kurdistan to determine their permanent deformation behaviour, UCS and resilient modulus for a range of moisture contents. The experimental investigation considered soils stabilised with 2%, 4% cement content and a combination of cement and lime with 2% cement plus 1.5% lime and 4% cement and 1.5% lime. The results were used to develop empirical equations to: (i) predict resilient modulus values of deteriorated modified soils as a function of different stabiliser contents and types; (ii) correlate resilient modulus values of soils with their UCS and stress state; (iii) determine the accumulation of permanent deformation in modified subgrade soils subject to weathering. These relationships, together with the developed finite element model were used to establish the design procedure.

The performance of roads is known to progressively reduce as a result of separate and interactive effects of climate and traffic. Existing decision support tools such as HDM-4, which are widely used to investigate long-term road maintenance strategies, utilise past climate data instead of future climate predictions. Uncertainties inherent in future climate predictions however imply that application of such tools could lead to outputs that are not robust in light of climate change. The objectives of the study were threefold: firstly, to develop a rut depth prediction model that considered potential effects of future climate; secondly, to formulate a framework for quantification of uncertainties; and finally, to demonstrate the application of the tools developed using a case study. The model was developed using data provided by the UK Highways Agency and UK Climate Impacts Programme. The methodology used was based on Bayesian regression. The developed model was found to perform better than the current asphalt surfacing rut depth model implemented in HDM-4 when future climate data was used. It was concluded that probabilistic outputs from the tools developed including deterioration rates, pavement condition and discounted maintenance costs for each maintenance strategy, and future climate and socio-economic scenarios provide a useful decision making framework for considering alternative strategies for road maintenance on the basis of the level of climate change risks that can be tolerated.

Thesis (MScEng)--University of Stellenbosch, 2005.
ENGLISH ABSTRACT: The study reported in this thesis focuses on the development of algorithms that can be used to schedule routine maintenance work in maintenance wards of a gravel road network, This was undertaken as part of the development of the Blading Optimisation Module of the Gravel Management System of the Provincial Government: Western Cape. Two scheduling algorithms were developed and mapped to a pilot object model on the computer. The algorithms and application interface takes account of the constraints and variables of routine maintenance that were identified through interviews with personnel of the five District Municipalities contained in the Western Cape. The algorithms are tested and evaluated using the pilot application. Based on the evaluation of the algorithms conclusions are drawn and recommendations are made.
AFRIKAANSE OPSOMMING: Die studie beskryf in hierdie tesis fokus op die ontwikkeling van algoritmes vir die skedulering van roetine instandhoudingswerk in instandhoudingswyke van 'n gruispadnetwerk. Dit is ondemeem tydens die ontwikkeling van die "Blading Optimisation Module" van die "Gravel Management System" van die Provinsiale Regering: Wes Kaap. Twee algoritmes is ontwikkel en afgebeeld op 'n loods-objekmodel op die rekenaar. Die algoritmes en toepassingskoppelvlak maak voorsiening vir die beperkings en veranderlikes wat geidentifiseer is tydens onderhoude met personeel van die distrikmunisipaliteite in die Wes Kaap. Die algoritmes is getoets en geevalueer met behulp van die loodstoepassing. Gevolgtrekkings en aanbevelings word gemaak op grond van die resultate van die evaluasie van die algoritmes.

Thesis (M.S.)--West Virginia University, 2005.
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This study focused on the correlation between the primary and the secondary impacts of a road development. Its methodology is aimed at coupling the conventional cost benefit analysis with an economic impact analysis. The secondary impacts of road development concentrated on the changes in land values. These changes were modelled using a new model; which related the percentage change in land values with four variables: the distance from the road; the land use; the land area; and the time that has elapsed since the completion of the roadworks. For a period of 30 years, a comparison was carried out to examine the similarities in the trends of the road users' benefits and the CLVs. Three main periods were found through this comparison. The first period is from year 0 to year 3; the second period is from year 4 after the road's opening to year 19; the last period starts from year 20 and finishes at the end of the analysis. The primary and secondary impacts in the first and the third periods of analysis behaved inversely; while the rest of the analysis period showed similar behaviour for the CLV and the RUCS. It was found that the factors affecting the degree of their similarity were traffic volume and the response of the network users to the new road. In addition, the limitation of the developed model of CLVs in terms of the variables used and particularly in their maximum and minimum values also affects the degree of similarity.

Sustainability is increasingly becoming a significant part of strategic asset management worldwide. Road agencies are providing guidelines to assess the relative sustainability of road projects. Unfortunately, environmental features of a road project are still considered as stand-alone evaluations, an added value. Very little has been done to integrate environmental impacts as a part of pavement management systems and other decision support tools to choose between different strategies. In this way, being awarded with a "green" certificate for a specific road project could result in the belief that recognition would correspond to the optimal strategy. Furthermore, a road project awarded with a "green" rating during the construction phase does not mean that the project results "green" if a life cycle approach is considered. Indeed, the most environmental friendly strategies may not be the ones with the highest performance. Using "greener" materials or performing recycle-related practices may lead to a lower performance over the life cycle and therefore produce an increase in maintenance needed, which could in turn result into more congestion due to work zones and higher total emissions. Therefore, construction and maintenance strategies should be analyzed according to three main parameters: cost, performance or effectiveness, and environmental impacts. The cost analysis part takes into account outflows over the service life of the pavement according to the well-known Life Cycle Cost Analysis methodology. The cheapest maintenance technique over the analysis period was expounded and sensitivity analyses to involved factors were conducted. Performance assessment was developed according to experimental on site data gathered and analyzed over several years to develop deterioration pavement models. Effectiveness of maintenance treatments is further provided and compared to the volume of traffic. In addition, environmental impacts related to maintenance and rehabilitation strategies were analyzed. Emissions were computed over the life cycle of the pavement from the manufacture of raw materials for the initial construction, placement, and maintenance phase. Finally, an optimization procedure was developed for including environmental impacts into a Pavement Management System. A methodology to set a multi-attribute approach system, computing costs, performance, and eco-efficiency over the life cycle of the pavement, is therefore proposed.
Ph. D.

Falling weight deflectometer (FWD) is currently used by most highway agencies to determine the structural condition of the highway network. Utilizing the deflections measured by the FWD, the resilient moduli of layers in the flexible pavement is determined using backcalculation software packages. The moduli can be input into semi-empirical mechanistic equations to estimate the remaining life of the pavement system and aid in informing pavement engineers about timing of maintenance and rehabilitation needs. There have been concerns among practitioners and the research community about the adequacy of the resilient moduli determined by the backcalculation software. Some of the backcalculation models have been simplified and field verification may be needed. Field-measured stresses and strains may be used to quantify the reliability of the backcalculated moduli. The Virginia Smart Road, which has 12 different flexible pavement designs and was built and instrumented with pressure cells, strain gages, thermocouples, frost probes and moisture sensors. To validate the backcalculated moduli theoretically and through instrument response, this research was conducted with following objectives: 1) to determine the resilient moduli of the unbound granular materials on the Virginia Smart Road using small and large plates of the FWD; 2) to investigate the extent of spatial and temporal variability of the FWD deflections among pavement sections; 3) to develop a temperature correction model for the backcalculated HMA resilient moduli; 4) to define an appropriate backcalculation approach and compare the four widely used software approaches; and 5) to correlate backcalculated and laboratory measured moduli. In addition, the FWD measurements were used to establish a comparison between in-situ measured and computed stresses and strains in the pavement. The analytical approaches used are linear elastic, viscoelastic, and viscoelastic combined with nonlinearity. Results show that estimation of unbound granular materials moduli using surface deflections is more reliable when 457-mm-diameter loading plate is used. Analysis of deflections from different sensors showed evidence of spatial and temporal variability. The lowest coefficient of variation of deflections (7%) within sections occurred at low temperatures (2 to 6 °C), while the highest coefficient of variation (42%) occurred at temperatures between 35 to 40 °C. This resulted in the development of a deflection temperature correction model. The model was validated at different temperature ranges. A backcalculation procedure was defined to achieve good root mean square error using four selected software packages. This resulted in the selection of the most reliable software to perform moduli backcalculation. A correlation was established between the nonlinear models produced by backcalculation and laboratory testing of the granular 21-B material. However, for the HMA materials, difference in loading period between laboratory testing and FWD loading pulse could affect the results. The study found that when utilizing the backcalculated moduli, computed strains using viscoelastic modeling were comparable to in-situ measured values. Similarly, calculated stresses compared well with the field-measured stresses; especially at high temperatures. Mix properties, temperature of testing and loading were found to have an effect on the agreement between the measured and computed strains in the wearing surface. The study also recommended further validation of FWD measurements using embedded instruments to calibrate analytical models and further analysis of deflection data so that optimum number of testing points can be determined to limit amount of testing performed for determination of deflection variability.
Ph. D.

Western Australia (WA) has a road network of approximately 177,700 km, including a 17,800 km stage highway system (Main Roads Western Australia 2009). This infrastructure supports a population of only about two million, and road funds always have to be carefully considered when allocated to highway authorities or other organisations. Pavement design is a process intended to find the most economical combination of suitable materials and layer thicknesses for construction. The pavement must have a carefully-specified unbound granular base to further reduce construction costs, and must be surfaced with an approximately 30 mm asphalt surface in WA. High quality aggregates are therefore required for the base course layer of a pavement because of its proximity to the road surface. Traffic loads on the road surface result in high stress levels on the base course layer. Consequently, Hydrated Cement Treated Crushed Rock Base (HCTCRB) was developed.Current pavement analysis and design in WA is thought to be sub-standard. A number of highways and roads in WA are exhibiting extensive surface damage as a result of the increasing numbers of vehicles in use. Since pavement analysis and design in WA relies predominantly on empirical design, experience and basic experimentation, explanations for the damage occurring under present conditions are difficult to determine and assess.In most areas of the USA and Europe, pavement design and analysis has entered a new era with mechanistic design replacing empirical design. Unlike the empirical approach, a mechanistic approach seeks to explain pavement characteristics under real operational pavement conditions (loads, material properties of the pavement structure, and environments), and is based on design parameters derived from sophisticated tests which can simulate real pavement conditions in the test protocol (WSDOT 2008). The mechanistic approach to pavement design produces more relevant and useful results and these procedures, along with linear elastic analysis, were introduced into Australia by the 1987 NAASRA Guide (NAASRA 1987), of which the revised version became the AUSTROADS Guide (Austroads 2004) to the Structural Design of Road Pavements. AUSTROADS published a National Pavement Research Strategy which has been the keystone for the national co-ordination of pavement research, both within government and industry.Adaptation of the Cement Modified Crushed Rock Base concept has brought about an excellent road base material for Western Australia (WA) by the addition of a small amount of cement (1-2% by mass) to a fresh crushed rock material. The mix is stockpiled for a hydration period, and after that retreated before construction, unlike the traditional concept for cement modified/stabilised materials. This material is usually called Hydrated Cement Treated Crushed Rock Base (HCTCRB), a name established by Western Australia Mainroads (MRWA). More than 250,000 tonnes of HCTCRB has been used at a cost in excess of $10 million over the last eight years.Recently, as a result of early damage on new highways and roads in WA, MRWA and its contractors and organisations have attempted to identify the cause of this damage. HCTCRB, which is currently the best option for base course materials in WA, and Crushed Road Base (CRB), the original road base material, need to be re-examined to overcome the shortcomings in terms of analysis, design, and application. All of the factors involved in HCTCRB and CRB for today’s pavement conditions have been extrapolated far beyond the bounds of the original data, and current experience shows these require detailed re-investigation.This research aimed to study on the characteristics of CRB and HCTCRB and to determine reliable mathematical material models for the improvement in the current pavement design criteria. This study also investigated both elastic and plastic behaviour of CRB and HCTCRB. In this study, there were two relevant factors of both pavement materials which are considered in order to fulfil a lack of understanding in realistic conditions in pavements of the current pavement design. 1) The material strength which indicates the limitation and stability of pavement materials under traffic loads. This study employed the Mohr-Coulomb failure envelope to define the limitation of material implementation and also brought in the resilient modulus of materials to be the significant input parameter for multilayer finite element analysis to characterise the stress distribution in pavements. 2) The pavement failure of long term road performance relating to the design life of pavements. The permanent deformation behaviour and the shakedown concept under various stress conditions, simulated from repeated load triaxial (RLT) tests, therefore, were taken into account to investigate such long-term performance of HCTCRB and CRB and then the implementation of the findings was made to the current pavement analysis and design. Furthermore, more reliable mathematic models of base course materials for short and long term performance during their service life were established based on the laboratory test results of this study.

Skid resistance, the road surface’s contribution to friction, is a crucial property of a road surface course required to maintain a safe and serviceable road network. Measurement of skid resistance is restricted by the need to measure the forces acting on a rubber wheel or slider while it is dragged across the surface. If the skid resistance of the road could be determined without the need for contact then measurement could be cheaper and more thorough. One route to achieving this goal is by measurement of the texture of the road that generates the friction experienced by a sliding tyre. However, the form and scale of the texture required is not well defined. The work presented in this thesis attempts to establish a robust methodology for measurement of texture on the surfaces of aggregate particles (the main constituent of the road surface course) so that it can be compared with friction. The stages of development are described in detail and the methodology is employed to examine the changing texture on two types of aggregate. The mechanisms by which these aggregates polish, methods for characterising their surface texture, and the consequences for the friction they are able to generate are explored.

Thesis (MEng)-- Stellenbosch University, 2013.
ENGLISH ABSTRACT: Two common methods of road pavement, granular material stabilisation used in road construction throughout South Africa today include Cold in Place Recycling (CIPR) and stabilisation with cement or bitumen and an active filler to create Bitumen Stabilised Materials (BSM). As part of the updating of the South African Pavement Design Method (SAPDM) an experimental section, investigating the structural capacity of cement and lime stabilised and BSM pavement layers, was constructed and will be monitored over a two year period. As part of this study Falling Weight Deflectometer (FWD) measurements were taken on the various experimental stabilised pavement layers constructed. The FWD deflection data, measured at various time intervals over a 360 day period, forms the basis of the study presented here. The objective of this thesis was to identify typical back-calculated layer stiffnesses and their variability over time for the various in-situ recycled and stabilised base layers constructed within the experimental section. Stabiliser type, content and layer thicknesses were varied across experimental sub-sections. Trends in back-calculated stiffness of cement stabilised base layers consistently showed significant reductions in layer stiffness subsequent to construction traffic loading. Subsequent to the initial reduction in stiffness little change in stiffness was noted under normal traffic loads. Observations on the trends in back-calculated stabilised layer stiffness per material type over time indicated that seasonal moisture and temperature fluctuations have an effect on the stiffness of the pavement structure as a whole. BSM materials showed significant variability over time in-line with seasonal variability in the supporting subgrade stiffness in the southbound lane. BSM materials with 1% cement added in the northbound lane show initial stiffness reductions due to direct rainfall application however a significant increase in layer stiffness occurs up to 360 days after construction. BSMs with 2% cement in the northbound lane show significant increases in layer stiffness over the 360 day observation period. No significant difference in stiffness trend was observed between BSM emulsion a BSM foam materials. The BSM emulsion with 0.9% residual bitumen and 1% cement was observed to show rapid reduction in stiffness upon opening to traffic and reverting to stiffness values similar to an unbound material of approximately 350 MPa. Cement and lime stabilised materials showed typical post 28 –day average stiffnesses per sub-section ranging between 600 MPa and 1800 MPa. BSM foam with 1% cement added were observed to have average stiffnesses per sub-section in the range of 400MPa to 2200 MPa and BSM emulsion with 1% cement with stiffnesses between 400 MPa to 1700 MPa over the 360 day period. BSMs with 2% cement added showed stiffness ranges between 900 MPa to 4300 MPa for BSM foam and 900 MPa to 3900 MPa for BSM emulsions over the 360 day period. The spatial variability of back-calculated stiffness per sub-section of a particular stabilisation design was significant and was observed, through the Co-efficient of Variation (COV), to increase over time. The effect of the observed variability when incorporated into a pavement design scenario, requiring a design reliability of 90%, showed 50% of the pavement structure would be overdesigned by a factor of 4. With respect to the current philosophies on the development of stiffness over time of cement and lime stabilised and BSM pavement layers some useful observations were made. Cement stabilised materials correlate well with stiffness development theories predicted by previous studies. Theories relating to the stiffness development of BSMs however did not predict the levels of variability in base layer stiffness observed on the experimental section. The continued observation of the experimental section for another year will give greater insight to the stiffness trends of the stabilised materials discussed above.

Several thousand people die as a result of a road accident each year in Great Britain and the trend in the number of fatal accidents is monitored closely to understand increases and reductions in the number of deaths. Results from analysis of these data directly influence Government road safety policy and ensure theintroduction of effective safety interventions across the country. Overall accident numbers are important, but when disaggregating into various characteristics, accident risk (defined as the number of accidents relative to an exposure measure) is a better comparator. The exposure measure used most commonly for accident rate analysis is traffic flow which can be disaggregated into vehicle types, road type, and year. Here we want to assess the accident risk across different car types and car ages, and therefore alternative exposure sources are required. We disaggregate exposure to a further extent than possible with currently available data in order to take the increased variability within these new factors into account. Exposure data sources are mainly based on sample surveys and therefore have some associated uncertainty, however previous accident risk analysis has not, in general, taken this into account. For an explicit way to include this uncertainty we use a Bayesian analysis to combine three sources of exposure using a log-Normal model with model priors representing our uncertainty in each data source. Using further Bayesian models, we propagate this uncertainty through to accident rates and accident severity, determining important factors and inter- relationships between factors to identify key features affecting accident trends,and we make the first exploration of the effect of the recent recession on road accidents.

The primary aim of the research work is to focus on the effects of climate change for maintaining physical infrastructures (i.e. such as buildings, dams, bridges, road pavements and other road infrastructures). As infrastructure requires major investment, it is important to build necessary management system to cope with future changes. This means that recognition of likely climate change impacts and appropriate adaptation measures are critical. However, most infrastructures has been designed, built and maintained on the premise that the future climate will be similar to that experienced in the past. Since the occurrence of the most recent climate disasters in Queensland, Australia, it has become mandatory to put especial policies for design and maintenance purposes of infrastructures . Recognition of the risks associated with climate change is a valuable initial step towards improved planning of new infrastructure investments and mitigating. Road infrastructure especially pavement requires special type of maintenance policy as the material of pavement like bitumen is very much sensitive to these types of effects such as moisture or temperature.
Thesis (Masters)
Master of Philosophy (MPhil)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text

The potential for binder rich bituminous road surfaces to deliver low levels of dry friction was first noted in 1944. Using established test methods exploiting basic principles of physics first tested in criminal court in the 1940s (and still in use today) it has been possible to show statistically that modern negative textured road surfaces (NTS) deliver levels of dry friction significantly below those considered typical by collision investigators for the more traditional positive textured surfaces (PTS). NTS surfaces are shown to perform relatively worse in the absence of ABS (Anti-Blockier System, Anti-lock braking) than PTS equivalents such as Hot Rolled Asphalt (HRA). Skid tests undertaken on DRY NTS surfaces with ABS braking have been shown to manifest momentary low levels of deceleration similar to those experienced during NOABS tests on the same surfaces and to generate dash like skid marks atypical of ABS tests on DRY PTS surfaces. The ratio of peak to sliding friction also appears lower for dry NTS surfaces than for Dry PTS surfaces documented in the literature. Using high-speed video and false colour infrared imaging it has been possible to see the low friction phenomenon termed “bituplaning”. Vehicles equipped with ABS have also been shown to suffer momentary “bituplanes” resulting in less than optimum performance. Tyre deformation during dry skidding on NTS appears reduced in relation to a PTS equivalent.

The road system under the care and control of the State of Queensland, Australia has an estimated replacement value of $23 Billion (US$12 billion), excluding structures. Pavement management systems for recording, rating, and predicting a pavement's condition are used to prudently manage this large asset. Tne of the fundamental components of a pavement management system is the method of determining a pavement's rate of deterioration over time. Throughout the world, "pavement roughness" is one of the most widely used methods of measuring the performance of a pavement. Queensland is a large State, having an approximate area of 1.7 million square kilometres, and incorporates many small communities separated by vast distances. The majority of bitumen sealed pavements exist in low traffic volume rural areas, and consist of either a flexible unbound granular pavement or a semi-rigid modified granular pavement. This study has focussed on the roughness progression of these pavement types. Roughness data has been collected at varying frequencies since 1987, across the State's road network. In order to understand roughness progression behaviour, this research has considered 16,000 pavement segments (each lkm) from all parts of the State. This number is significant, as many previous research efforts, which form the basis of the current roughness progression models, have been based on the study of typically between forty and several hundred pavement segments. This extensive database has been used in this study to investigate trends in roughness pogression over time (~R). Traditionally, roughness progression has been represented in many road asset management models as an exponential relationship, providing rapidly increasing roughness values as the pavement approaches the end of its theoretical life. However, this relationship has not been commonly observed in the State's pavement asset. Investigations revealed that a linear relationship, termed the Linear Roughness Progression Rate (LRPR), represented the roughness progression of the pavement segments very well, and thereby assists in the identification of poor performing pavement segments. Pavement maintenance costs can also be used to identify poor performing pavement segments, based on excessive use of pavement maintenance funds to maintain functionality. This information assists in 'unmasking' pavements that may possess an umepresentative LRPR. For this reason, the effects of pavement maintenance costs (~PMC) on roughness progression have also been examined. Independent variables which are typically considered to affect roughness progression, have been examined with LRPR in this study. These variables include traffic volume, traffic loading, pavement type, subgrade soil classification, climate (rainfall, temperature, Thomthwaite Index), pavement age, and width of bitumen surface (seal width). It has been established that the roughness progression of each individual pavement segment is unique. No particular formula or model has been identified, which can accurately predict the roughness progression of any particular pavement segment from a population, based upon known values of the independent variables. In order to develop an understanding of the effects of these variables on pavement performance, a means of rating a pavement's condition using a combination of LRPR and excessive pavement maintenance expenditure has been established. Subsequently, a discrete rating scale from "Good", "Fair" to "Poor" has been used. The effects of the independent variables on pavement rating have been examined across the population of study pavement segments, using summary charts. This has enabled the proportions of pavement rated within each category to be examined with changes in each independent variable, to establish whether that variable has a global influence on pavement rating. For instance, whether the proportion of pavements rated "Poor" varies with Annual Average Daily Traffic. These summary charts provide the basis of a Network Performance Profile, which has yielded a better understanding of the variables globally influencing pavement rating across the State's road network. Further, the Network Performance Profile provides insight into the inbuilt risk of the past and current pavement design and delivery system. The knowledge gained from a whole of network analysis of condition may form a catalyst for the assessment of material quality, design methods, construction technology, and contract delivery, to ensure that pavements have the best chance of performing well. Currently, road network performance is commonly defined only by a measure of the road network's 'Absolute Condition'. The Network Performance Profile developed in this study will add new measures of pavement performance to the current definition. By including a Current Network Profile, and a more robust method for predicting mid term (five year) roughness values, asset managers will have a suite of information on historic, current, and estimated future road network condition, to use in evaluating the impact of previous and current management decisions. Pavement roughness prediction analysis, based on site-specific extrapolation of LRPR, has shown that at least six time-series roughness data points are required if an accurate short term prediction (4 to 6 year) is to be achieved. It is believed that the research of roughness progression has highlighted the unique nature of pavement segment deterioration. It is interesting to note that all categories of pavements suffer from a range of good to poor performance, and this finding is considered to be one of the keys in understanding pavement behaviour. At a network level, the study of performance has been considered very successful and has not only provided a robust methodology for quantifying road network performance, but also provides information for input into the improvement of technical policies and funding distribution decisions.

This thesis aims to apply recent conceptual frameworks for climate change impact assessment to the road freight sector of Great Britain in order to identify potential future safety issues. The freight sector is a key component of Great Britain’s economy, and one which is particularly vulnerable to the effects of adverse weather. An assessment of the current patterns in weather related freight accidents is produced, and existing studies on accident causation are elaborated upon to arrive at relationships between key meteorological parameters and freight accident rates. These relationships are extrapolated onto various climate scenarios under low, medium and high emissions for the 2020s, 2050s and 2080s using UKICP09 climate tools to arrive at projections of possible impacts at a regional scale. This thesis also addresses a key criticism of the previous climate change impact assessment literature; that studies usually neglect the consideration of what the network will look like in the future, how it will be used, and how this will impact upon its vulnerability to meteorology. The way in which the network is designed, the resilience of the vehicles that operate on it and the split of usage between the various modes will all affect the impacts that are likely to be seen, and are all determined by the broader socio-economic pathway of the country. Delphi techniques are used for short term forecasts of growth and to identify emerging issues with the industry. UKCIP data is used to extend these projections to 2050. By combining social and physical techniques, a more holistic picture of future impacts is found. Although the confluence of safer technology and a reduction of winter road icing and summer precipitation events could potentially lead to a safer operating environment, certain scenarios which promote high emissions, a larger freight fleet and low investment in infrastructure could cause problems, especially for winter precipitation events.

Thesis (M.Ing.)--Stellenbosch University, 2000.
ENGLISH ABSTRACT: Laterites are used extensively in the tropics as road building materials in unbound base, sub-base layers and in surface layers. However, most base course specifications usually require the provision of crushed and graded stone or stabilized base and often exclude the general use of as-dug laterites or other naturally occurring gravels. Various field studies in the past have clearly indicated that many lateritic gravel deposits can be used successfully as base course materials in roads carrying low to medium traffic without incurring additional maintenance costs and with considerable cost savings in pavement construction rehabilitation. Further research is needed for the more precise definition of the relationship between laterite characteristics, traffic loading, environment, and pavement performance. In this study, extensive use was made of static and cyclic triaxial testing to investigate the fundamental behaviour of a lateritic gravel material. The tests produce information for characterizing the shear strength, stress-strain properties and behaviour under repeated loading. The gravel was sourced from stockpile at Malans Transport borrow pit at Maaitjies Kuil near Cape Town. Testing was conducted on the material both as granular material and stabilized with cement and foamed bitumen. Testing was done under various conditions of stress, moisture and compaction. The resilient modulus of the lateritic gravel was found to be affected by moisture and compaction apart from the stress condition. Well known models were used to characterize the stressdependent resilient modulus. A model for prediction of permanent deformation was developed which together with the resilient modulus model were applied to the design of a light pavement structure composed of lateritic gravel base.
AFRIKAANSE OPSOMMING: Lateriete word wydverspreid gebruik in die trope as 'n padbou materiaal. Die materiaal word gebruik in ongebonde kroonlae, stutlae en oppervlaklae. Die meeste spesifikasies vir kroonlae vereis dat gegradeerde gebreekte klip of gestabiliseerde materiaal in die kroonlaag gebruik word. Die spesifikasies maak nie voorsiening vir lateriet en gruis wat natuurlik voorkom nie. Verskeie veldstudies in die verlede het duidelik getoon dat lateritiese materiaal met sukses gebruik kan word in die kroonlae van paaie wat ligte tot medium verkeer dra. Lateriete kan gebruik word sonder addidionele onkoste vir instandhouding en daar is merkbare kostebesparings wanneer plaveisels rehabiliteer word. Die verhouding tussen lateriet eienskappe, verkeerslas, omgewingsinvloede en plaveisel werkverrigting moet beter gedefinieer word deur verdere navorsing. In hierdie studie is omvattend gebruik gemaak van eenmalige en herhaalde belasting drie-assige toetse om die fundamentele gedrag van lateritiese materiaal te definieer. Hierdie toetse se resultate lewer inligting oor die skuifsterkte, spanning-vervorming eienskappe en gedrag onder herhaalde belasting. Die gruis wat gebruik is, is verkry vanaf 'n materiaalopslag by die leengroef van Malans Transport te Maaitjies Kuil naby Kaapstad. Die materiaal is getoets as granulêre materiaal en gestabiliseer met sement en skuim-bitumen. Die toetse is gedoen onder verskillende toestande van spanning, voginhoud en verdigting. Daar is bevind dat die veerkragtigheidmodulus van die lateritiese gruis nie net deur die aangewende spanning beïnvloed word nie, maar ook deur die voginhoud en verdigting van die materiaal. Welbekende modelle is gebruik om die spanningsafhanklike gedrag van die materiaal te karakteriseer. 'n Model is ook ontwikkel om die permanente vervorming van die materiaal te voorspel. Die twee modelle vir die veerkragtigheidsmodulus en permanente vervorming is gebruik om 'n ligte plaveiselstruktuur mee te ontwerp wat 'n lateritiese kroonlaag bevat.

The research was aimed at the development of an optimal road fund allocation model for road maintenance to three road agencies in Ghana. The objective was to compare a novel model by multicriteria analysis (MCA) with deterministic outcome and a model based on preferential analysis to determine optimality. The deterministic model was efficiency based with quantitative analysis from a decision maker’s perspective whilst the approach by preferential analysis was equity based with qualitative analysis from stakeholder perspective. The input parameters of the deterministic model were based on the value function method (VFM) and the concept of efficiency frontier. It determined a scaler index for the proportionate allocation of road fund by road type. It was based on a set of attributes including road length, traffic, pavement roughness and percentage of work achievement. The concept of efficiency frontier was used to sub divide the proportion of funds allocated by road type into economic efficiency and equity components based on the Net Present Value/Capital, Vehicle Operation Cost (VOC) and income. The values of the selected attributes were generated from the outputs of HDM-4 analysis. The model based on the preferential analysis was set on the Analytical Hierarchy Process (AHP). It involved pairwise comparison of defined criteria and sub criteria by stakeholder priority at national, district and community levels. Priority vectors were estimated for road fund allocation into efficiency and equity proportions by road type. A comparison of the outputs of the two models on the basis of the impact on pavement roughness performance indicated the stated preference based model yielded better impacts than the model with deterministic approach. It was concluded that road fund allocation based on a well logically determined value judgement with mathematical analysis yields better results.

Thesis(PhD (Civil Engineering))-- University of Stellenbosch, 2004.
ENGLISH ABSTRACT: Bitumen based road surfacing seals and asphalt wearing courses have been used by society's Engineers "to counter the damage to the existing unsurfaced roadways by the newly developed automobile with its rubber driving wheels" since the early 1900's. Early experiments were conducted with both tar and bitumen to find a suitable material to alleviate the situation, and ongoing research has been carried out through the past century and into the new millennium, throughout the world, examining improvements, from materials used, to design and construction methods. However, there is still much to be understood, improved and refined, when considering road surfacing seal design. Pavement designers have the choice of utilizing either an asphalt (graded aggregate remanufactured with a bitumen binder and applied as a complete product) or a surfacing seal (including variations of bitumen binder sprayed onto the road surface, with the addition of single size stones, either in one or two layers of binder and aggregate, i.e. single or double seals) as a pavement wearing course. Current road surfacing seal design practice depends on empirical analysis and experience, being primarily a volumetric based assessment of bitumen application. This research project assesses South African seal design philosophy, investigates design areas where review or updating is required to accommodate changing bitumen sources and types, and traffic loading. Seal performance criteria are examined, with the development of a matrix of influences on seal performance. Using this, the need for a seal design method based on mechanistic material properties is proposed, and the prototype example of such a numerical model using finite element method is presented. To contribute further towards a performance related seal design method, the feasibility of modelling of road surfacing seals using mechanistic principles was examined. The potential of developing failure and fatigue criteria or relationships to enable assessment of the expected seal performance, with inclusion of different component material characteristics and variations, varying traffic and environmental conditions, was also examined. From assessment of literature, and understanding of the components of the seal, pavement, and influencing factors, a choice of numerical model of seal performance was made. The Finite Element Method (FEM) Analysis was selected for the purpose of modelling seal performance. The model was developed to enable examination of the interaction of individual seal components (i.e. stone and bitumen), at micro-mechanic scale. The prototype 3-dimensional numerical seal model was undertaken in 2002 and 2003 at Technical University Delft, using the CAPA research program. On the basis of the linear calculations the developed numerical prototype model is able to provide insight into seal behaviour and distinction between mechanical (seal geometry) and chemical (components) seal aspects, and insight into stress and strain development in the different seal types. Simulations of different seal, environmental and traffic scenarios are provided to demonstrate the potential of the model (excluding seal aggregate interlock and embedment effects at prototype stage). In order to provide data for the verification of the prototype numerical model, and to further contribute to the development of a performance related seal design method, performance tests were developed, with a new tool for assessment of comparative seal performance using the Model Mobile Load Simulator Accelerated Pavement Testing apparatus. The performance of each different seal binder type - Penetration grade Mumen, SBS, SBR, EVA and Bitumen Rubber - was undertaken. A methodology for the assessment of in-service seal performance was developed, and the performance of the respective seals reported. The results of this examination showed that each binder type has its unique contribution to seal performance. These new performance tests will be able to assist designers in the added determination of the fundamental binder properties on seal performance, and the seals' ability to contribute to the overall performance of the pavement. An additional comparative performance test method was developed to enable assessment of the effect of ageing and moisture, to complement the MMLS results. In summary, the performance testing has assisted in identifying the critical parameters a seal designer should consider during the design process. From this research, it is evident that the current seal design method requires further development to able designers to predict the effect of: Varying axle loads, tyre pressures and design speed; Varying characteristics of the different binders, (i.e. temperature - viscosity relationships, adhesion and visco-elastic behaviour); on the performance of seals. The major areas for suggested improvement in current seal design methods towards a performance based design method are: inclusion of variable traffic load and environmental characteristics, including temperature and moisture influences, and inclusion of mechanistic material characteristics into the design methodology.
AFRIKAANSE OPSOMMING: Bitumengebaseerde padoppervlakseellae en asfaltslytlae is sedert die 1900's deur ingenieurs gebruik as teenwig teen die skade wat die pas ontwikkelde voertuig met sy rubberwiele aan bestaande ryvlakke sonder oppervlakbehandeling aangerig het. In vroeëre eksperimente wat daarop gemik was om 'n geskikte materiaal te vind om die probleem teen te werk, is 'n kombinasie van teer en bitumen gebruik. Sedertdien word voortgesette navorsing steeds wêreldwyd gedoen om verbeterings te ondersoek, nie net ten opsigte van materiale nie maar ook ontwerp- en konstruksiemetodes. Wat die ontwerp van padoppervlakseëling betref is daar egter heelwat wat reg begryp, verbeter en verfyn moet word. Plaveiselontwerpers het die keuse om of 'n asfalt te gebruik (gegradeerde aggregaat voorafvervaardig met 'n bitumen bindmiddel en aangewend as 'n klaarproduk), of 'n oppervlakseël (een laag of twee lae [m.a.w. enkel- of dubbelseël] bitumen bindmiddel met aggregaat [enkelgrootte klippies] bygevoeg, gespuit op die padoppervlak). In die praktyk berus die ontwerp van padoppervlakseëling tans op empiriese analise en ervaring (wat hoofsaaklik 'n volumetriesgebaseerde assessering van die aanwending van bitumen is). Hierdie navorsingsprojek doen 'n waardebepaling van die Suid-Afrikaanse filosofie van seëlontwerp, en ondersoek ontwerpterreine wat hersiening of bywerking benodig om vir veranderende bitumenbronne en -tipes, asook verkeerslading, voorsiening te maak. Met die ontwikkeling van 'n matriks van die invloede op seëlprestasie is die kriteria vir seëlprestasie ondersoek. Op grond daarvan word aangevoer dat daar 'n behoefte is aan 'n seëlontwerpmetode gebaseer op die meganistiese eienskappe van materiaal, en word 'n voorbeeld van 'n numeriese modelprototipe wat die eindige-element-metode gebruik, voorgelê. Ten einde 'n verdere bydrae te lewer tot die ontwikkeling van 'n prestasiegerigte seëlontwerpmetode, is die uitvoerbaarheid van die modellering van padoppervlakseëllae gebaseer op meganistiese beginsels, ondersoek. Daar is ook ondersoek ingestel na die potensiaal vir die ontwikkeling van kriteria vir die vasstel van mislukking en vermoeidheid of verhoudinge wat die assessering van die verwagte seëlprestasie (ingesluit die verskillende kenmerke en variasies van seëlkomponentmateriaal en wisselende verkeers- en omgewingsomstandighede) moontlik kan maak. Met oorweging van die bestudeerde literatuur en 'n begrip van die komponente van seël, plaveisel en inwerkende faktore, is 'n keuse van 'n numeriese model vir seëlprestasie gemaak. Die eindige-element-metode (Finite Element Method [FEM]) is gekies as die analitiese metode vir die modellering van seëlprestasie. Die model is ontwikkel om die ondersoek van die interaksie tussen individuele seëlkomponente (klip en bitumen) op mikromeganiese skaal moontlik te maak. Die ontwikkeling van die driedimensionele, numeriese, model-seëlprototipe is tussen 2002 en 2003 by die Delft Tegniese Universiteit gedoen, met gebruikmaking van die CAPA-navorsingsprogram. Wat lineêre berekenings betref, kan die ontwikkelde numeriese modelprototipe 'n insig gee in seëlgedrag en in die onderskeid tussen aspekte van seëlgeometrie (meganies) en seëlkomponente (chemies), asook in die spanning- en vervormingsontwikkeling van die verskillende tipes seël. Simulasies van verskillende seël-, omgewings- en verkeerscenario's word voorgestel om die potensiaal van die modelprototipe te demonstreer. Met die oog daarop om data vir die verifikasie van die numeriese modelprototipe te voorsien, en om verder tot die ontwikkeling van 'n prestasiegerigte seëlontwerpmetode by te dra, is prestasietoetse, met 'n nuwe instrument vir die assessering van vergelykende seëlprestasie met behulp van die Model Mobile Load Simulator Accelerated Pavement Testing apparaat, ontwikkel. Die prestasie van elke verskillende tipe seëlbindmiddel- penetrasiegraad bitumen, SBS, SBR, EVA en bitumenrubber - is getoets. 'n Metodologie vir die assessering van die ingebruiksprestasie van seëllae is ontwikkel, en daar is verslag gedoen oor die prestasie van die verskillende seëllae. Die resultate van die ondersoek het getoon dat elke tipe bindmiddel 'n eie unieke bydrae tot die prestasie van die seël lewer. Die nuwe prestasietoets sal ontwerpers help met die bepaling van die grondliggende bindmiddeleienskappe wat by seëlprestasie ter sprake is, asook van die seël se vermoë om tot die algehele prestasie van die plaveisel by te dra. 'n Bykomende prestasievergelykingstoetsmetode vir die assessering van die effek van veroudering en vogtigheid is ontwikkel om die MMLS-resultate aan te vul. Ter opsomming, die prestasietoetsing het bygedra tot die identifisering van die kritiese parameters wat die seëlontwerper tydens die ontwerpproses in gedagte behoort te hou. Die navorsing wat gedoen is, dui daarop dat die huidige seëlontwerpmetode verder ontwikkel moet word om ontwerpers in staat te stel om die effek van die volgende te kan voorspel: Wisselende aslas, banddruk en ontwerpspoed; Verskillende kenmerke van die verskillende bindmiddels (bv. temperatuur viskositeitsverhoudinge, vashegting en viskoëlastiese gedrag). Wat huidige seëlontwerpmetodes betref, is die hoofterreine waarop 'n verbetering voorgestel word, die insluiting van veranderlike verkeerslas- en omgewingskenmerke, ingesluit die invloed van temperatuur en vogtigheid, en insluiting van meganistiese kenmerke van materiaal in die ontwerpmetodologie.

Drivers for sustainability have made it necessary for the construction industry to adapt its traditional processes to become both more efficient and produce less waste. Performance based design and specification in the UK for motorways and trunk roads permits a very flexible approach to pavement design, material selection and performance related testing aimed at utilising materials to their maximum potential. However, it is clear that within the emerging philosophy of using materials that are 'fit for purpose' there are many technical challenges for design and specification. There is a need to develop suitable methods of evaluating materials prior to their being used on site. This project was born out of this requirement, with a particular emphasis on coarse granular materials due to their common role in capping construction and also their unique difficulty for measurement under laboratory conditions due to their large range of particle size. A novel assessment test for coarse capping materials for roads that can be used to indicate their likely short-term in situ performance, under controlled laboratory conditions before construction on site, has been developed during this research programme. Key findings relating to the behaviour of coarse capping materials, the use of stiffness measuring devices and variables that influence the measurement of composite stiffness are discussed in detail. The research highlights the necessity for adequate drainage and protection of foundation materials against increase in water content. When adopting a performance specification the timing of the pavement assessment is critical, both on site and in the laboratory. The performance measured on site should perhaps only be considered as a 'snapshot' relating to the stress state in the material at the time of testing.

Because winter maintenance is so costly, Utah Department of Transportation (UDOT) personnel asked researchers at Brigham Young University to determine whether asphalt or concrete pavements require more winter maintenance. Differing thermal properties suggest that, for the same environmental conditions, asphalt and concrete pavements will have different temperature profiles. Climatological data from 22 environmental sensor stations (ESSs) near asphalt roads and nine ESSs near concrete roads were used to 1) determine which pavement type has higher surface temperatures in winter and 2) compare the subsurface temperatures under asphalt and concrete pavements to determine the pavement type below which more freeze-thaw cycles of the underlying soil occur. Twelve continuous months of climatological data, primarily from the 2009 calendar year, were acquired from the road weather information system operated by UDOT, and erroneous data were removed from the data set. To predict pavement surface temperature, a multiple linear regression was performed with input parameters of pavement type, time period, and air temperature. Similarly, a multiple linear regression was performed to predict the number of subsurface freeze-thaw cycles, based on month, latitude, elevation, and pavement type. A finite-difference model was created to model surface temperatures of asphalt and concrete pavements based on air temperature and incoming radiation. The statistical analysis predicting pavement surface temperatures showed that, for near-freezing conditions, asphalt is better in the afternoon, and concrete is better for other times of the day, but that neither pavement type is better, on average. Asphalt and concrete are equally likely to collect snow or ice on their surfaces, and both pavements are expected to require equal amounts of winter maintenance, on average. Finite-difference analysis results confirmed that, for times of low incident radiation (night), concrete reaches higher temperatures than asphalt, and for times of high incident radiation (day), asphalt reaches higher temperatures than concrete. The regression equation predicting the number of subsurface freeze-thaw cycles provided estimates that did not correlate well with measured values. Consequently, an entirely different analysis must be conducted with different input variables. Data that were not available for this research but are likely necessary in estimating the number of freeze-thaw cycles under the pavement include pavement layer thicknesses, layer types, and layer moisture contents.