Ultra-Thin Continuously Reinforced Concrete Pavement (UTCRCP) is an innovative pavement type that has the potential to fulfil South Africa’s pavement repair strategy requirements. It consists of a 50 mm thick High Strength Steel Fibre Reinforced Concrete (HS-SFRC) layer that is reinforced with 50 x 50 mm aperture steel bar mesh, placed on a newly constructed or rehabilitated pavement. The current design procedure for UTCRCP was extrapolated from conventional concrete design procedures, incorporating the improved flexural properties of the HS-SFRC to design for fatigue cracking. However, the alternative nature of the thin HS-SFRC layer in comparison to a thick normal strength concrete layer has led to the proposal that the response of UTCRCP to traffic loading should be reconsidered to improve its design approach. A literature study revealed that the wheel load configuration, the relative stiffness of the concrete layer and its foundation and the complex response of foundation materials to stress influence the response of pavements to traffic loading. The effect of these aspects was investigated by making use of scaled physical modelling, as well as Finite Element (FE) modelling that incorporated Linear Elastic (LE) and advanced material models. The effect of load configuration on thin asphalt and thin concrete layers was investigated using LE FE modelling. A three-layer system of bound layer, base and subgrade was modelled. It was found that the response of a thin concrete layer is similar to that of a thin asphalt layer subjected to axle loading in that the maximum deflection is at the load location and that a hogging type deflection is induced in the axle centreline. The stress induced at the top of the concrete layer due to this hogging moment was high, indicating the necessity of including significant steel in both the transverse and longitudinal directions of UTCRCP. The difference in substructure response (in terms of horizontal and vertical displacement), modelled using single wheel or axle loading, showed that the compression of the substructure in the axle centreline can be critical, while it is ignored when load configurations are simplified to single wheel loading. A multivariable analysis of the concrete layer thickness and base material stiffness was conducted using LE FE modelling. A similar three-layer system of bound layer, base and subgrade was used. It was found that the location of the maximum deflection is in the axle centreline for pavements incorporating thick concrete layers, while the maximum deflection is in the wheel centreline for pavements incorporating thin concrete layers. The response of thin concrete pavements was more dependent on the substructure. The physical modelling consisted of 1:10 scale models tested in a geotechnical centrifuge. The models consisted of either thick concrete layer or thin concrete layer on compacted dry sand, as well as a thin concrete layer on a cement stabilized base supported by compacted dry sand. The most notable finding was that a rut forms in the wheel path of thin concrete layers on sand, although it cannot be observed from the surface. It was observed that the concrete layer rebounds when the pavement is unloaded, forming a gap between the concrete layer and substructure. An advanced material model for sand was used to explore the effect of incorporating the stress- dependent, elasto-plastic behaviour of granular materials in UTCRCP. A FE model, similar to the three-layer system of the LE FE modelling, was used and the base layer was modelled using a soil model called Nor-Sand, which is based on the critical state framework. The initial void ratio, lateral earth pressure at-rest and overconsolidation ratio were varied. It was found that the combination of the strain hardening and the stress dependence of the elastic material stiffness resulted in higher induced stresses close to the load location. The gap formation observed during the physical modelling was confirmed by the capability of Nor-Sand to model permanent deformation. Overall, the results of this investigation indicate that the response of UTCRCP to traffic loading differs significantly from that of rigid concrete pavements. The thin HS-SFRC layer is subjected to high tensile stresses and deflects significantly into the substructure at the load location. It is proposed that UTCRCP should be designed to limit rutting, as well as that stress dependent, elasto-plastic material models should be used to optimize its layer arrangement. / Thesis (PhD)--University pf Pretoria, 2020. / Southern African Transport Conference / Newton Fund UK (Grant ES/N013905) / Civil Engineering / PhD (Civil Engineering) / Unrestricted

No description available.

No description available.

The traditional method of repairing damaged roads in Atlantic Canada has been to place a hot mix asphalt overlay over the existing road. Though this method provides a new, smooth wearing surface to drive on, it is merely a short term fix. With time, the cracks in the original pavement will reflect to the surface of the new pavement, resulting in failure of the overlay. An alternative option gaining more prominence is the use of a Full Depth Reclamation (FDR) technique, which involves pulverizing the flexible pavement, along with a portion of the underlying layer. This material is then stabilized and recompacted to produce a new base layer that is free of damage. Though FDR has been used for a number of years, there are still problems with variability in the strength of the materials in some projects. It is hypothesized that some of these problems are due to variability and poor quality in the reclaimed materials. It is believed that current pulverization methods contribute to the variability being observed in these materials. Two FDR projects employing different pulverization control methods were studied to examine how the consistency of the reclaimed materials can be improved through the use of a Ground Penetrating Radar (GPR) survey to map the variability in the depth of the pavement. Controlling the thickness ratio of asphalt concrete to granular base materials being pulverized was shown to improve the consistency of materials, properties, and performance. The second phase of this research project studied how improving the gradation of the reclaimed materials with the addition of a crusher dust might result in improved performance of stabilized base materials, in this case stabilized with expanded asphalt. The effect of construction variability on the improved materials was also studied by varying both the moisture content, and asphalt content from optimum conditions, as might be expected during construction. Results indicated that the quality of the stabilized FDR materials can be significantly improved by bringing the material gradation closer to the theoretical maximum density gradation. The performance of the stabilized materials can be affected by both the mixing moisture content, and the asphalt content used during stabilization. This suggests that effective quality control, and stricter specifications on the constructed product would result in more reliable, effective FDR pavements. / A study on the control of the consistency of pulverized FDR materials, as well as a study examining how to improve the performance of these pulverized materials.

In Mpumalanga, only about 25 per cent of households have car access, which makes Mpumalanga one of the provinces with the highest use of public transport by means of bus or taxi in South Africa. Even though the road network in Mpumalanga is extensive, the maintenance and upgrade of this network is a concern, especially for municipal and provincial roads. Deteriorating roads have a direct (such as vehicle operating costs, VOCs) and indirect impact (such as high bus fares) on the road user. This study focuses on the interaction between one bus from Buscor and the pavement surface of one specific bus route, including the associated VOCs generated. The ride comfortability of the bus route was evaluated by interpreting International Roughness Index (IRI), Power Spectral Density (PSD), and vertical accelerations (awz) data, after which the associated vehicle operating costs (VOCs) for the bus were projected. The judgement of ride comfortability in a vehicle is an area of controversy, and studies on this topic dates back from the 1920sThe threshold values from ISO (1997), Cantisani, and Loprencipe (2010) were used for the purposes of this study. The vertical accelerations generated from the surface of the bus route, for a bi-articulated bus were measured with accelerometers. The accelerometers were placed on the bus where the vertical accelerations were expected to be the highest. The identified bus route included different roads with different responsible authorities and roughness levels. A profiler conducted a survey on the route and five different sections were identified. The collected data were analysed with various programs. From the data collected from the accelerometers the PSD, awz, and the speed that the bus travelled on each section could be determined. The IRI data for each section was categorised in three categories, very good to good, fair to mediocre and poor. Anomalies in each section were identified, and the cause of these anomalies determined. The anomalies were analysed with the data, as these values formed part of the route. The impact of road roughness on fuel consumption, tyre wear and repair and maintenance costs were analysed. The calibrated Highway Development and Management System (HDM 4) model was used to predict the fuel consumption, tyre wear and repair and maintenance cost per km of each section of the bus route under consideration. In this analysis, the impact of the vehicle speed proved to be significant, as it affected the PSD values, the awz values and the VOC. The scenario was analysed to improve the riding quality of the two worst sections of the bus route, and by improving the road surface of these two sections, travel time could be reduced and costs could be saved. The scenario of an increase in road roughness was also analysed, to indicate the percentage of increase in costs, if these roads kept deteriorating. The analysis showed a significant increase in repair and maintenance cost, fuel consumption, and tyre wear. The limitations of this study included some correlation issues with the profiler data and the accelerometer data, unidentified bus stops on gravel shoulders, and the suspension system and interior of the bus that were deemed constants and not variables within the scope of this study. Despite these limitations, there are still a number of possibilities with the data collected. Apart for the analyses conducted for the study, recommendations for further refinement include the impact of bus mass on the data (full bus versus empty bus), the suspension type and condition, the interior of the bus, trip duration and congestion, evaluation of driver fatigue, tyre pressure and dynamic wheel loads, and safety. Furthermore, the construction cost of upgrading the two worst sections of the route versus the increase in VOCs because of the deteriorating state of the route could be investigated. In conclusion, the speed played a determining role in the generation of vertical accelerations, therefore user comfort or discomfort, and VOCs. An increase in IRI indicates deteriorating riding quality that affects the comfortability of a ride and the VOCs negatively. IRI can be used to determine the state of the road and qwz gives an indication of the comfortability of a ride. / Dissertation MEng--University of Pretoria 2014 / ay2014 / Civil Engineering / unrestricted

abstract: Pavement preservation is the practice of selecting and applying maintenance activities in order to extend pavement life, enhance performance, and ensure cost effectiveness. Pavement preservation methods should be applied before pavements display significant amounts of environmental distress. The long-term effectiveness of different pavement preservation techniques can be measured in terms of life extension, relative benefit, and benefit-cost ratio. Optimal timing of pavement preservation means that the given maintenance treatment is applied so that it will extend the life of the roadway for the longest possible period with the minimum cost. This document examines the effectiveness of chip seal treatment in four climatic zones in the United States. The Long-Term Pavement Performance database was used to extract roughness and traffic data, as well as the maintenance and rehabilitation histories of treated and untreated sections. The sections were categorized into smooth, medium, and rough pavements, based upon initial condition as indicated by the International Roughness Index. Pavement performance of treated and untreated sections was collectively modeled using exponential regression analysis. Effectiveness was evaluated in terms of life extension, relative benefit, and benefit-cost ratio. The results of the study verified the assumption that treated sections performed better than untreated sections. The results also showed that the life extension, relative benefit, and benefit cost ratio are highest for sections whose initial condition is smooth at the time of chip seal treatment. These same measures of effectiveness are lowest for pavements whose condition is rough at the time of treatment. Chip seal treatment effectiveness showed no correlation to climatic conditions or to traffic levels. / Dissertation/Thesis / M.S. Civil Engineering 2012

<p dir="ltr">Cold mix asphalt (CMA) is an eco-friendly paving material produced at ambient temperatures, offering energy savings by requiring less energy to decrease asphalt binder viscosity. This technology eliminates the need for heating during the mixing and compaction processes, further magnifying its economic benefits when used as a cold-in-place recycling technique. Unlike hot mix asphalts that gain strength through cooling, CMA achieves its final strength through a curing process involving the evaporation of volatiles and the hardening of the emulsified asphalt binder over time. However, its reliance on a curing process for strength development raises concerns about its short-term performance.</p><p dir="ltr">A typical CMA mixture consists of four main components: air voids, mineral aggregate, water, and asphalt droplets suspended in water. The presence of water can significantly influence the overall performance of the mixture under both traffic and environmental loads. Most existing studies on CMA have predominantly focused on the behavior of the mixtures after they have fully cured. However, in real-world scenarios, pavements are often subjected to various stresses during the curing process, which takes up to several months. As a result, premature distress can compromise the early performance of the pavement. Asphalt undergoes significant chemical and physical changes throughout this phase that can influence its final characteristics and in-situ performance. Overlooking this crucial stage can lead to a poor understanding of the material's capabilities and limitations. Despite the importance of this phase, the micromechanical and rheological behaviors of CMA during curing remain largely uncharted territories. Therefore, this dissertation aims to investigate the micromechanical performance of CMA during the curing phase.</p><p dir="ltr">This research study was performed in two study scales: Mastic and Mixture. The first scale focused on the rheological performance of emulsified-cold asphalt mastic (ECAM), considering varying curing levels, different filler-binder ratios, and filler surface treatments. Comprehensive rheological tests, including frequency sweep, temperature sweep, and strain sweep tests, were conducted on fully and partially cured mastic samples, i.e., 20%, 40%, 60%, and 80%, across a wide range of test temperatures. To analyze the physio-chemical adhesion properties between filler and emulsified asphalt, an analytical tool named the “asphalt-filler interaction” theory was formulated to determine the adhesion bond between filler and binder in the presence of moisture. Microscopic images were also captured to analyze the micro-structure and moisture interaction in the CMA’s matrix. Moreover, the presence of moisture in the CMA brings up another complexity during curing time: The water-to-ice phase transition. Normal Force (Nf) was used as a novel measurement parameter to determine water-ice phase transition effects on the rheological study of emulsified mastic. In the mixture scale, mechanical tests were performed on specimens fabricated with two gradations at fully and uncured CMA samples. The mixture experimental tests included the dynamic modulus test, Illinois flexibility index test, Hamburg wheel loaded test, and disc-shaped compact tension test.</p><p dir="ltr">This dissertation presents a thorough analysis and detailed findings that illuminate the complex relationships and behaviors of CMA, particularly at the mastic scale. A significant observation is the direct influence of the filler-to-binder ratio on the curing time; increasing this ratio prolongs the curing process while using a filler with less surface area accelerates it. Notably, 25% of the filler-to-binder ratio enhances the rheological properties of ECAM, particularly at lower loading frequencies. This study further pinpoints the 60% curing level as a crucial threshold in the CMA curing process. Below this, moisture's effect on rheological performance overshadows that of the primary asphalt material, leading to brittle characteristics in freezing conditions and viscous behavior at intermediate temperatures. In the curing stage, the trapped and blocked waters that emerge during the coalescence phase of the emulsified asphalt breaking contribute to the extended curing time of ECAM.</p><p dir="ltr">Additionally, freezing temperatures yield a water-to-ice phase change in uncured ECAM, resulting in a brittle behavior. Interestingly, a direct correlation emerges between curing percentage and freezing point; higher curing percentages relate to lower freezing points. Another significant discovery is the appearance of micropores in fully-cured ECAM, likely due to water evaporation and emulsifier presence, which potentially compromises its performance compared to ECAM fabricated with residual asphalt binder. Furthermore, adjusting the pH, especially by treating limestone filler with hydrochloric acid (HCl), showed noticeable improvements in CMA’s rheological behavior. At the mixture scale, the CMA mixture contained a higher filler-binder ratio in the mixture scale, presenting a better viscoelastic performance and higher cracking resistance at intermediate and freezing temperatures. Moreover, a minimum amount of water, 2.5% by total mass, added to the CMA mixture is essential to ensure adequate mixability, workability, and compactibility. Viscoelastic analysis showed that the curing process changes the transition point from elastic to viscous behavior of CMA mixtures. This shift towards lower frequencies results in a CMA mixture with poor resistance to higher temperature performance.</p>

This study focused on the material characterization of granular materials containing different percentages of “RAP”. A series of laboratory tests results were carried out to determine the physical and mechanical properties of natural aggregates and various aggregate-RAP blends. The results were used to evaluate methods to develop high-performance granular layer for pavement construction through proper compaction and control of RAP usage. The resilient modulus and accumulative deformation characteristics were determined in relation to RAP content, relative density, compaction method, stress level, stress state and the number of load applications. The effects of RAP content and density on the CBR values of aggregate-RAP blends under various conditions were also investigated. In addition, the effect of small strain cyclic loading on shear strength of aggregate-RAP blends was observed in laboratory tests. Results from this investigation demonstrated that: 1) adding RAP to natural aggregates may increase the resilient modulus of natural aggregates, and optimum content can be found to achieve the highest resilient modulus; 2) resilient modulus generally increases with density; higher density of aggregate-RAP blends can be achieved by using methods combining vibration and static loading. 3) deviatoric stress has more pronounced influence on accumulative deformation than confining pressure. 4) proper compaction method can reduce accumulative deformation of samples. 5) addition of RAP into aggregates results in little change in accumulative deformation when the RAP content is less than a threshold. 6) CBR value decreases with increasing RAP content and decreasing compaction effort or compacted dry density. 7) shear strength of an aggregate-RAP blend tends to increase after small strain cyclic loading. / Thesis / Master of Applied Science (MASc)

El estudio de la presente tesis fue validar la hipótesis que plantea el mejoramiento de las propiedades físico-mecánicas de suelos arcillosos de la Av. La Despensa desde Antenor Orrego hasta Dorado la cual presenta un suelo de baja capacidad de soporte, con un grado de plasticidad alto, siendo este el responsable de generar problemas de transitabilidad en épocas de lluvias, asentamientos a nivel de vereda y hundimientos en la vía con ausencia de pavimento. Debido a la problemática anterior, se hizo el estudio incorporando agregados provenientes de los residuos calcáreos de las siguientes combinaciones: 20%RC+80%S, 30%RC+70%S, 40%RC+60%S y 50%RC+50%S, Para ello, se experimentó dichos porcentajes en tres muestras: C-01, C-02 y C-03, clasificándose como: CL (Arcillas de baja plasticidad) respectivamente. Así mismo, en base a los ensayos de laboratorio, se determinó como porcentaje óptimo, el 40%RC+60S%, donde tiene un IP de 19.00%, 20.00% y 19.00% según sea la muestra de suelo, alterándolo en 0.1 a 2.00 veces su valor natural, a su vez, la MDS resultó de 1.98, 1.96 y 1.93 g/cm3 correspondientemente, aumentándola en 0.37 hasta 0.25 veces su valor natural, en tanto, el CBR (95%) obtuvo los valores de 10.12%, 9.52% y 11.10% respectivamente, incrementándose 7 hasta 7.67 veces de su valor inicial. Recategorizándose las tres muestras de subrasantes de pobre a buena. Finalmente, para la ejecución de pavimento flexible cuya subrasante esté mejorada con 40%RC+ 60%S. se necesitará S/844,145.57 soles por cada 500m, no obstante, esta propuesta disminuye al 61.15 % los impactos que tradicionalmente se generarán. / The study of this thesis was to validate the hypothesis that the improvement of the physicalmechanical properties of clayey soils of Av. La Despensa from Antenor Orrego to Doradon presents a soil with low support capacity, with a degree of plasticity. high, this being responsible for generating traffic problems in the rainy season, settlements at sidewalk level and subsidence on the road with no paving. Due to the above problems, the study was carried out incorporating aggregates from calcareous residues of the following combinations: 20%RC+80%S, 30%RC+70%S, 40%RC+60%S and 50%RC+ 50%S, For this, these percentages were experimented in three samples: C-01, C-02 and C-03, being classified as: CL (Low plasticity clays) respectively. Likewise, based on laboratory tests, the optimal percentage was determined to be 40%RC+60S%, where it has an IP of 19.00%, 20.00% and 19.00% depending on the soil sample, altering it by 0.1 to 2.00. times its natural value, in turn, the MDS was 1.98, 1.96 and 1.93 g/cm3 correspondingly, increasing it by 0.37 to 0.25 times its natural value, while the CBR (95%) obtained values of 10.12%, 9.52 % and 11.10% respectively, increasing 7 to 7.67 times from its initial value. Recategorizing the three subgrade samples from poor to good. Finally, for the execution of flexible pavement whose subgrade is improved with 40%RC+ 60%S. S/844,145.57 soles will be needed for every 500m, however, this proposal reduces the impacts that would traditionally be generated to 61.15%.

La baja resistencia y las fallas estructurales tempranas en carreteras asfálticas son problemas comunes en la ingeniería de pavimentos. La causa principal de estos problemas es la deformación constante de las capas que lo componen provocada por el aumento de operación de las cargas del tráfico. La modificación de los ligantes asfálticos es una aplicación empleada desde hace algunos años para mejorar las propiedades del cemento asfaltico y prolongar la vida útil de los pavimentos asfálticos. Los modificadores deben tener características especiales, como en el caso de los elastómeros, que son polímeros con propiedades elásticas y que se pueden manejar a altas temperaturas. En la presente investigación, se analizaron las propiedades básicas del ligante modificado con el elastómero Poliuretano Termoplástico (TPU) en 5, 10 y 15% de adición en peso de asfalto. Asimismo, se empleó el método Marshall para evaluar las propiedades mecánicas y el comportamiento elástico de las mezclas bituminosas modificadas para tránsito liviano, mediano y pesado. Se logró determinar que el punto de inflamación y la recuperación elástica torsional del ligante modificado tuvieron un comportamiento positivo incremental con el aumento de contenido de TPU, mientras que otras propiedades como la solubilidad y la ductilidad no sufrieron variaciones significativas. Por otro lado, la propiedad de penetración disminuía con el contenido del polímero, mejorando su consistencia. Además, se descubrió que las mezclas asfálticas tendrán una mejor capacidad para resistir las deformaciones y un comportamiento mejorado a la fatiga, aunque este último no tan notable. / Low strength and early structural failures in asphalt roads are common problems in pavement engineering. The main cause of these problems is the constant deformation of the layers that compose it caused by the increase in the operation of traffic loads. The modification of asphalt binders is an application that has been used for some years to improve the properties of asphalt cement and extend the useful life of asphalt pavements. Modifiers must have special characteristics, as in the case of elastomers, which are polymers with elastic properties and can be handled at high temperatures. In the present research, the basic properties of the binder modified with the elastomer Thermoplastic Polyurethane (TPU) were analyzed in 5, 10 and 15% addition by weight of asphalt. In addition, the Marshall method was used to evaluate the mechanical properties and elastic behavior of bituminous mixtures modified for light, medium and heavy traffic. It was determined that the flash point and torsional elastic recovery of the modified binder had an incremental positive behavior with the increase in TPU content, while other properties such as solubility and ductility did not undergo significant variations. On the other hand, the penetration property decreased with the content of the polymer, improving its consistency. In addition, it was found that asphalt mixtures will have a better ability to resist deformations and improved fatigue behavior, although the latter is not as noticeable.