Moisture damage is one of the major causes of premature failure of road pavements especially the pavements made using the flexible design concept. This failure occurs as a result of cohesion and adhesion loss between the binder and binder-aggregate interfaces respectively. One of the many ways of mitigating moisture damage effect is the use of anti-stripping agents like liquid polymers, Portland cement, hydrated lime, fly ash, flue dust, etc. Hydrated lime has been found to be one of the most efficient anti-stripping agents among all common additives to asphalt mixtures. Although the majority of research on the use of hydrated lime in asphalt mixtures has been carried out in the USA, the beneficial effects of hydrated lime have also been reported worldwide especially in Europe. In the UK, the use of hydrated lime only started in the early 2000’s and still needs a lot of research in terms of selection of aggregates which can be improved with the use of hydrated lime. Most of the aggregates used in the UK for asphalt mixtures are of good field performance and it is difficult to find aggregates with poor quality. That is the reason why for this research four aggregate types which are commonly used in the UK for flexible road payments are selected. One type of bitumen having penetration grade of 40/60 has been selected for the research. The four aggregate types include granite, limestone, basalt and greywacke. This research focuses on an in-depth investigation of hydrated lime performance against moisture damage in bitumen mastics and asphalts mixtures as a whole. The full project has been broken down into three parts. The first part is a component level study, the second is mixture level study and the third is the study of practical adhesion. In the component level study, the effect of hydrated lime is quantified in terms of adhesion properties between a range of aggregates and binder combinations. For the component level testing, the effect of hydrated lime is quantified by adding it to the bitumen to make a mastic. The test techniques which are used for the component level assessment includes rolling bottle test and surface energy measurement. The second part focuses on the performance of hydrated lime as a whole inside asphalt mixture as filler replacement. The idea behind this methodology is to evaluate the real effect of hydrated lime in the mixture because if hydrated lime is used as additional filler in the mixture it will alter the mixture volumetric rather than simply affecting the mechanical response of the mixture through the properties of the hydrated lime. SATS test has been used to quantify the effect of hydrated lime against moisture damage at mixture level. The third part of the research deals with the measurement of practical adhesion with and without moisture conditioning with the help of pull-off and peel-off test techniques called PATTI and Peel test. The effect of hydrated lime either in the mastic or in the mixture has been found to be aggregate type dependent. Granite aggregates showed a good improvement in the performance against moisture damage resistance with the use of hydrated lime. Limestone aggregate didn’t respond to the addition of hydrated lime in the light of most of the techniques considered in this research and the same applied to the basalt aggregates. Greywacke, on the other hand, responded well and showed an improved moisture damage performance with the use of hydrated lime. Another good thing observed in the results was the consistency between the results among the different test techniques. The results obtained in each technique are in line with each other and give the same conclusion for most of the combinations studied in this research. To conclude, the effect of hydrated lime highly depends on the type of aggregate, its origin and its mineral composition. The aggregates used in this study were either of moderate or good field performance. Although a good improvement in the moisture damage performance of some combinations was clearly observed, it is highly recommended to incorporate the aggregates having bad field performance to see how hydrated lime improves their performance. Keywords: Moisture Damage, Hydrated lime, Surface Energy, Adhesion, Asphalt Mixture, Rolling Bottles Test (RBT), Saturation Ageing Tensile Stiffness (SATS) Test, PATTI test, Peel test.

Service life of asphalt roads could be extended by enhancing the natural self-healing ability of asphalt mixtures with encapsulated rejuvenators. When crack damage appears, the capsules release healing agents, which dissolve bitumen to flow into cracks. In this research, a new type of capsules was developed. These capsules contain sunflower oil as a rejuvenating agent. The size, morphology, mechanical strength and thermal stability of these capsules were investigated. The composition of the capsules, which nominally divides these capsules into different types based on their oil content, epoxy-cement shell and polymer amount, and its effect on capsule characteristics were also studied. In addition, the effect of the capsules on the chemical composition of bitumen with time of exposure to broken capsules was evaluated by the FTIR test. Results show that the characteristics of the capsules and their effect on chemical composition allow them to be incorporated in asphalt mixtures for further investigations for their effect on asphalt mechanical performance and self-healing. The mechanical performance of aged asphalt mixtures is investigated by using three nominally different types of capsules. Two of these were protected with a hard shell made of epoxy-cement composite; two coats with 1.0 o/w (oil-to-water), three coats with 1.0 o/w and without the hard shell with 0.5 o/w. The optimum amount of capsules used in all mixtures was 0.5% of total mass of asphalt mixture. Tests started by investigating the effect of mixing and compaction processes on these capsules. Results show that the hard shell (epoxy-cement) was not necessary for the capsules to survive mixing and compaction processes. Capsules deformed and broke with cyclic loading, releasing oil that diffused in the bitumen in less than 24h. Healing of cracks in aged asphalt mixtures led to an increase of stiffness under cyclic loading. However, asphalt specimens with capsules had lower deformation resistance. Computer tomography scanning of specimens showed large reductions in cracks around the capsules, after resting 4 days (96h) at 20oC. The mechanical properties of asphalt mixture containing capsules have been evaluated. Including water sensitivity, particle loss, stiffness and permanent deformation. One type of capsule (0.1 o/w) with three different capsule contents by mass of asphalt mixture were used, 0.1%, 0.25% and 0.5% with oil-to-bitumen ratio 1.1, 2.8 and 5.5, respectively. Capsules were strongly bonded to the asphalt mixture and results showed improved or at least similar mechanical properties to that of asphalt mixtures without capsules. This shows that capsules for asphalt self-healing can be safely used in the road, without affecting its quality. Asphalt containing capsules had slightly lower stiffness (no rest period), which can be easily solved by reducing the size of the capsules in the future. Furthermore, a new method for testing asphalt self-healing by the action of capsules was designed and tested. This method was based on a 3-point bending test (3PB) to beak samples and measure their flexural strength. The test was implemented by comparing the strength recovery of the broken beams after healing to their original flexural strength. The test was first applied to asphalt mastic beams, which are asphalt mixtures with higher bitumen content and fine aggregate and filler. Five different types of capsules used, based on their o/w ratios. These were 0.05, 0.1, 0.2, 0.5 and 1.0 o/w ratios with different amounts depending on their oil content so that they can provide a 7.2% of rejuvenator (sunflower oil) to the asphalt mastic beams. The effect of capsule content on self-healing was investigated by the 3PB on samples containing all those five capsule types (different contents) at one healing temperature, namely 20oC and different healing times. Effect of temperature on healing was investigated as well by 3PB test applied to mastic beams containing one type of capsules with 0.5 o/w ratio at four different temperatures, namely 5oC, 10oC, 15oC and 20oC. The main results showed that the capsules can break inside the asphalt mastic releasing the encapsulated oil to bitumen. Healing levels in the asphalt mastic samples with capsules were greater than samples without capsules, and the healing level of asphalt samples with, and without, capsules increased with the healing time. Additionally, the healing level given by the capsules inside the cracked asphalt mastic depended on the oil/water content of the capsule and on the temperature at which the healing process occurs. Finally, a correlation factor was developed between the healing level of asphalt mastic with and without capsules, independent of the temperature and time evaluated. Self-healing of real asphalt mixture was also investigated by same method of 3PB at different healing times and different temperatures. One type of capsules, namely 0.1 o/w with three different capsule contents, 0.10%, 0.25% and 0.50% by total weight of the mixture, were mixed with the asphalt. Eight different healing temperatures were used in this test, namely -5oC, 5oC, 10oC, 15oC, 20oC, 30oC, 40oC and 50oC. It was proven that the capsules can resist the mixing and compaction processes and break inside the asphalt mixture as a result of applying external mechanical loads, releasing the encapsulated oil. The capsules content in asphalt mixture has a significant influence on the healing level, where a higher capsule content led to higher healing levels. It was found that cracked asphalt mixture with capsules recovered 52.9% of initial strength at 20oC versus 14.0% of asphalt mixture without capsules. Likewise, asphalt with, and without, capsules presents an increase of the healing level when the temperature increases. Finally, it was proved that healing temperature over 40oC has significant influence on the healing levels of the asphalt beams.

Several benefits are gained from using cold mix asphalt (CMA) instead of hot mix asphalt (HMA). The benefits include conservation of materials and reducing energy consumption, preservation of the environment and reduction in cost. One of the common types of CMA is cold bitumen emulsion mixture (CBEM) which is the mixture produced by mixing mineral aggregate with bitumen emulsion. Despite the efforts applied in the last few decades in order to improve and develop CBEM utilization, certain deficiencies remain that make it inferior to HMA, resulting in restricting or minimizing of its use. However, the development of CBEM for road construction, rehabilitation and maintenance is steadily gaining interest in both pavement engineering industrial and research sectors. The present study was primarily aimed at evaluating the effect of using different cementitious materials on the performance of CBEM. The idea of the research is to provide a sustainable filler from supplementary cementitious materials (SCMs) to be used as fillers to provide enhanced properties of CBEMs. By achieving this aim it is expected that the utilization of CBEM would increase, allowing them to be used as structural pavement materials with some confidence. Research was first undertaken to optimize the mix design of CBEM using a statistical approach known as response surface methodology (RSM), as an alternative approach to achieve acceptable engineering properties. The optimization of CBEM was investigated, to determine optimum proportions to gain suitable levels of both mechanical and volumetric properties. This optimization focussed on the mix design parameters, namely bitumen emulsion content (BEC), pre-wetting water content (PWC) and curing temperature (CT). This work also aimed to investigate the effect of the interaction between these parameters on the mechanical and volumetric properties of CBEMs. The results indicate that the interaction of BEC, PWC and CT influences the mechanical properties of CBEM. However, PWC tends to influence the volumetric properties more significantly than BEC. The individual effects of BEC and PWC are important, rather than simply the TFC which is used in conventional mix design of CBEM. Furthermore, the experimental results for the optimum mix design corresponded well with model predictions. It was concluded that optimization using RSM is an effective approach for mix design of CBEMs. The study also investigated in-depth the performance characteristics of CBEMs using different filler treatments. The study was extended to understand the performance enhancement through mineralogical and microstructural investigations. The research was designed to use cement, binary and ternary blended fillers (BBF and TBF). Fly ash (FA) and ground granulated blast-furnace slag (GGBS) were used as BBF while silica fume (SF) was added to the BBF to obtain TBF. A significant improvement was achieved in mechanical and durability properties of CBEMs due to incorporation of both cement and blended fillers. Also, the results indicated that TBF was more suitable than BBF for the production of CBEMs. The microstructural assessment indicated that the effect of BBF on the internal microstructure of CBEMs was slightly negative and more noticeable in CBEMs containing FA. Mineralogical and microstructural assessments also suggested that the presence of bitumen emulsion might not affect the hydration of the silicates in treated CBEMs. The formation of additional CSH was observed due to the replacement of conventional limestone filler by cement, BBF and TBF. However, it seems that this can cause a delay in the formation of other hydration products (Ettringite) resulting from the hydration of aluminates in cement. Furthermore, it is proposed that the addition of SF to BBF mixtures can eliminate the delay in formation of hydration products caused by the bitumen emulsion. The present work was also aimed at better understanding the curing mechanism of CBEMs and to bridge the gap between laboratory curing and field evolution of these mixtures. This was achieved by evaluating the effect of the curing process on CBEM performance and developing a prediction model to assess in-situ CBEM performance using maturity relationships. Different contributory factors affecting the curing process were investigated such as curing temperature and relative humidity (RH) in addition to the impact of curing time and the presence of cement/active fillers. The results indicated that high curing temperature is responsible for additional stiffness gain by increasing the binder stiffness due to ageing and by increasing the moisture loss by evaporation during the curing process. However, at high curing temperature the moisture loss by evaporation may hinder the hydration of cement/active fillers. Moreover, the results also indicated that the high RH level influences the stiffness modulus of CBEMs negatively. The laboratory results were then used to develop a tool to assess in-situ curing of CBEMs using the maturity approach, which is widely used to estimate in-situ concrete properties. A strong correlation was found between maturity and the stiffness values obtained from the laboratory tests, which resulted in development of maturity-stiffness relationship. The application of this relationship to assess the in-situ stiffness of CBEMs is presented using three hypothetical pavement sections in the United Kingdom, Italy and Qatar; to simulate different curing regimes. A pavement analysis and design study was conducted to evaluate the incorporation of treated CBEMs into a pavement structure. CBEMs are suggested to be used in two scenarios: the first is as a surface course and the second is as a base course. The scope of the study is limited here to design based on the fatigue criterion only. Although, the structural design was based on practical hypothetical layer thicknesses, the results provided useful insight into the structural capabilities of CBEMs.

Aubrey Berrangé, a South African roads engineer, invented the impact compactor in 1949 with the intention of achieving improved compaction to greater depths than possible with conventional equipment available at the time. The aim of this dissertation is to present a simple prediction model for the profile of improvement in the ground, using surface settlement as the main input parameter. The model is based on the information reviewed, observation of field data and a static numerical analysis. For simplicity sake, no attempt is made to predict the energy requirement to achieve the input value of settlement. The model is then verified on fifteen impact compaction profiles at six different sites. A 2 ton-meter dropping mass compactor was also used in the verification process with reasonable success. In addition, the model was tested against comprehensive testing performed at a dynamic compaction site with very promising results. The method is also shown to give acceptable results for prediction of density increase during a vibratory compaction trial. It is concluded that the improvement in the ground can be estimated with reasonable success if the surface settlement is monitored, providing strains are taken into account. / Dissertation (MEng (Geotechnical Engineering))--University of Pretoria, 2006. / Civil Engineering / unrestricted

No description available.

The focus of highway work is shifting from new construction further into maintenance, rehabilitation, and reconstruction of existing facilities. Work zones constitute sections of highway where these efforts are actively pursued. Excessive speed is often a contributing factor to work zone accidents. One method of speed control in work zones is the deployment of unmanned, or drone, radar transmitters, to simulate and supplement police presence in work zones. A review of the literature and past research on speed control techniques was conducted, and data was collected in several work zones on Interstate 81 in Virginia. Traffic data were gathered both upstream and in the range of the unmanned radar units. Effectiveness of the unmanned radar was expressed as changes in mean speed, speed variance, percent of traffic exceeding the speed limit, and eighty-fifth percentile speed. Statistical analyses on the resulting speed distributions utilized hypothesis testing to determine the significance of differences in the measures of effectiveness among speed control conditions in work zones. User costs associated with work zones were also examined. At the sites studied, significant reductions in mean speed and in percent of traffic exceeding the speed limit were observed, as were minor reductions in speed variance and eighty-fifth percentile speed. Unmanned radar was found to be particularly effective when police presence was expected by motorists. From this research effort, recommendations were developed to assist traffic engineers in determining the most effective way to use unmanned radar to maximize their safety benefit on the traffic stream. / Master of Science

Performance goals for a highway system are an indication of the desired system condition, and the level of service to be provided to its users. Setting the appropriate performance goals has a significant impact on the way highway agencies conduct business. With growing needs and limited resources, the consequences of setting different levels of performance goals should be examined and compared to optimize the highway infrastructure needs at the network level. Three interacting sets of costs are typically considered for a complete economic appraisal of highway projects: construction, maintenance and road use costs. Due to the shift in focus from design-and-build mode to the repair-and-maintain mode, this study focuses on maintenance related costs and the road user cost aspects only. Maintenance and rehabilitation activities on pavement infrastructure are ongoing processes that are required for the entire road network. This suggests that for long planning horizons and geographically extensive networks, their application usually results in significant financial needs. Typically, highway agencies have based their policy decisions such as the target condition levels for the system on the budget needs for maintenance and rehabilitation actions. Since in most cases, the funding needs exceed the available budget, the required preventive and routine maintenance activities suffer or are overlooked completely. Failure to timely apply these maintenance actions cause the pavements to deteriorate more rapidly into condition states that require for more expensive rehabilitation actions during the life cycle of the pavement. Over time, a vicious cycle is instigated in which the maintenance and rehabilitation needs of the network keep increasing each year. Although most highway administrators acknowledge the fact that pavement preservation is perhaps the most effective way of using the limited budgets available, the costs associated with deferring maintenance actions is oftentimes overlooked when establishing performance goals for the system. Road user costs in the form of costs for vehicle operation have been recognized as another large component of the total transportation related costs. These costs are then arguably the most important to consider for a complete economic appraisal. Ironically, they are also often disregarded while making important policy decisions. Other road user costs such as those related to the impact of traffic congestion and detours caused by construction and maintenance activities are difficult to quantify and were not accounted for in this study. Although it is widely accepted that establishing suitable performance goal is critical for system maintenance and preservation, a framework that considers the inter-relationship between conflicting objectives of minimum maintenance and rehabilitation costs, deferred maintenance costs, and vehicle operating costs to the users does not exist. This thesis proposes a methodological framework that is aimed at assisting highway agencies with the problem of objectively analyzing policy decisions in terms of the performance goals for their highway networks that would minimize the total transport costs to the society. In a case study of the proposed framework, the highway network managed by the Texas Department of Transportation was examined for different performance goals. The results from the case study indicate that setting lower performance goals lead to savings in the M&R needs, but at the same time, they also significantly increase the exogenous costs such as deferred maintenance costs and the vehicle operating costs. / text

Thesis (M. Sc.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 64-65).

The system dynamics methodology is used to develop a computer simulation model to determine whether to add lanes to a congested highway or build a new, more direct, facility. Fundamental to this evaluation is the incorporation of non-user measures of effectiveness to go with the traditional highway user measures of effectiveness, such as the Benefit-Cost Ratio. In the system dynamics methodology three alternative forms of the model of a system are used: verbal, visual, and mathematical. The verbal description is diagrammatic and shows cause-and-effect relationships between many variables in a simple, concise manner. The visual model or "causal diagram" is translated into a mathematical model and system equations. The model is comprised of four sectors: 1. population sector 2. economic sector 3. university sector 4. transportation sector The model applies to the area of Blacksburg, Christiansburg and Roanoke (city and county). with special treatment to Virginia Tech through the university model. The simulation results of the non-user benefits along with user benefits is used to evaluate the alternatives in the Blacksburg-Christiansburg-Roanoke corridor. / Ph. D.

Highway alignment development is recognised as a non-linear constrained optimisation problem. It is affected by many economical, social, and environmental factors subject to many design constraints. The highway alignment development process is therefore considered complex but very important. Highway alignment development is about finding an optimum alignment solution between two termini points in a 3D space, subject to several constraints. The development process using the current method is considered complex because of the number of the design elements involved, their interactions, and the formulations required to relate them to a realistic highway alignment. Moreover, it is considered that an alignment, generated using the existing method, results in a sub-optimal solution. This is due to the fact that the two alignments (horizontal and vertical alignments) are found in two independent stages and from only a handful number of alternative evaluations. This research reports on a new approach for improving the process of highway alignment development by utilising modern technologies. It proposes a novel design approach, as an alternative to the existing method, for highway alignment development in a three-dimensional space (considering the horizontal and vertical alignments simultaneously). It describes a method for highway alignment development through station points. Station points, as points along the centre line of alignment which are defined by their X, Y, and Z coordinates, are used to define the alignment configuration. The research also considers the implications of access provision (in term of junctions) and their locations on highway alignment. The environmental factors (noise and air pollution in terms of proximity distance) and accessibility (user and link construction costs in terms of access costs) are embedded in the formulations required to represent junctions in the model. The proposed approach was tested through the development of a genetic algorithms based optimisation model. To achieve this, several algorithms were developed to perform the search. The evaluation of the solutions was handled by a fitness function that includes construction (length), location (land acquisition, environmentally sensitive areas, and soil condition), and earthwork (fill and cut material) dependent costs. Other forms of costs that are quantifiable can also be incorporated within the fitness function. The critical constraints, believed important for realistic alignments (horizontal curvature, vertical curvature, and maximum gradient) are also dealt with within the model formulation. The experimental results show that the problem of highway alignment can be better represented using the concept of station points, by which better alignment solutions (global or near global solutions) were achieved. It was also shown that the alignment development process could be simplified through the use of station points, resulting in the efficient evaluation of more alternatives. Furthermore, the results conclude that a highway alignment cannot be optimum unless it is simultaneously optimised with junctions. Further investigations and development are also recommended for future studies.