M.Ing. (Electrical & Electronic Engineering) / Please refer to full text to view abstract

Road structures are important to the survival of nations. As the cost for the rehabilitation and maintenance of highways soars, civil engineers and administrators face the ever present difficulty of meeting current resurfacing and rehabilitation needs. The deterioration of road structures under growing traffic weight and volume is occurring faster than agencies envisaged coupled with increasingly scarce and expensive new materials required. It is now apparent that for planning, design and construction for road structures, the most efficient and cost effective processes, materials and practices available must be appropriately considered. The use of recycled materials as a sustainable alternative is gaining significant worldwide attention. The overall purpose of this research was to conduct an in-depth investigation and analysis into the design and optimisation of Cold Asphalt Emulsion Mixtures (CAEMs) incorporating high contents of Reclaimed Asphalt Pavements (RAP). To achieve the objectives of the research, four proportions of RAP aggregate materials in addition to Virgin Aggregates (VA) were used as categorised below: - Category 1: 0% RAP (no RAP, 100% VA) - Category 2: 50% RAP (50% RAP, 50% VA) - Category 3: 85% RAP (85% RAP, 15% VA) - Category 4: 95% RAP (95% RAP, 5% VA) The effect of mixing and compaction temperatures at 5°C, 20°C and 32°C and how cement at 0%, 1% and 3% OPC influenced the CAEMs was also investigated. This study presents a practical mix design procedure to act as a guideline for CAEMs incorporating high RAP contents by identifying critical parameters for the various categories of CAEMs which stemmed from the fact that currently there is no universally accepted mix design. The proposed mix design guideline is presented in this thesis. The effect of accelerated curing was investigated to study the effects of temperature, curing duration, conditioning and the influence of cement on the CAEMs. The research showed that an increase in curing temperature results in an increase in the stiffness and strength of the CAEMs. The thesis presents results on the mechanical and performance properties which provided vital information on expected performance of CAEMs incorporating high contents of RAP for use as a road base material. The research was able to highlight the purported effects of residual binder in RAP which could contribute positively to the mechanical and performance properties of the CAEMs. This points to the fact that treating RAP as “black rock” is not the right approach. The RAP needs to be evaluated for its inherent properties and suitability for purpose. The stiffness and strength were investigated using the Indirect Tensile Stiffness Modulus (ITSM) and Indirect Tensile Strength (ITS) tests which proved useful in ranking them. The addition of 1% OPC improved the stiffness of Categories 1-3 mixtures by 32% with Category 4 having the highest increase at 89%. The inclusion of 3% OPC, more than doubled the stiffness values. The Indirect Tensile Fatigue Test (ITFT) was used to investigate the fatigue characteristics. Results showed that if the CAEMs with cement at 1% and 3% experienced strains in the region of 200µε, they tend to fail suddenly soon after crack initiation due to reduced flexibility of the CAEMs. This was more pronounced for the CAEMs at 3% OPC. Resistance to permanent deformation was investigated using the Vacuum Repeated Load Axial Test (VRLAT) which showed that the mixing and compaction temperature influenced the permanent deformation characteristics of the CAEMs. Increasing OPC content to 1% for Categories 2 and 3 resulted in a decrease in permanent strains of 47% and at 3% OPC, the decrease in permanent strains was 54%. Wheel Tracking Test (WTT) was conducted to ascertain the susceptibility of the CAEMs to deform under loading, investigate crack propagation and number of cycles to failure. The test showed that the performance of the specimens was affected by the test temperature. Increased test temperatures resulted in an increased rate of rutting and eventual failure of the specimens. The test further highlighted the positive benefits of adding cement to the mixtures which resulted in reduced strains and an increased number of cycles to failure for the CAEMs. Structural design and modelling was conducted using KENLAYER which was able to account for the non-linearity of the CAEMs. This was crucial in having a total overview of these mixture types. Although, the structural design was based on practical hypothetical layer thicknesses, the results provided useful insight into the structural capabilities of the CAEMs. The RAP CAEMs generally had lower horizontal tensile strain values in comparison to the VA CAEMs. The design charts showed that an increase in the thickness of the base course and surfacing layer resulted in an increase in the overall fatigue life of the pavement structure. Overall, evaluating the complete findings of this research, CAEMs produced with high RAP contents especially at 50% and 85% RAP had considerably enhanced mechanical and performance properties and are suitable for inclusion as a base material for reconstruction and rehabilitation.

Roads form a key element for the expansion of economy and development of a country. As with most countries, Brunei Darussalam has been facing a rapid development to meet the economic growth that requires an efficient road network. Therefore, the scarcity of conventional road aggregates in Brunei Darussalam means that the country has a strong dependence on imported aggregates from overseas to construct quality roads. Further restrictions on local road specifications make it almost impossible to include low quality granular materials. The study reported in this thesis was undertaken on the basis that the dependence on overseas resources is not a viable long- term solution. The research task has been, therefore, to ascertain the quality of local sandstones for road construction and then to propose means to upgrade their performance quality for optimum utilisation in cost effective applications. This study focused on the road base layer since that is where most aggregate is used. The approach used for this study was to identify the common rock in Brunei Darussalam and review the candidate treatment methods. A weighted matrix for these candidate treatment methods was constructed to determine the overall ranking with selected key criteria on the basis of the local climatic condition, construction preferences and traditions. From the reviews, Foamed bitumen was selected as a feasible treatment method that can improve the sandstone characteristics under local conditions. Three curing conditions were adopted in this study, simulating extreme field conditions in Brunei Darussalam, to characterise the mechanical properties of foamed bitumen stabilised sandstone mixtures, termed 'foam mix'. The following tests were conducted: • The response of stiffness modulus behaviour in the foam mix produced at different levels of mixing moisture content and cement content under dry and wet conditions was measured to study the mixing moisture content (MMC) in foam mix design. • A humid curing study was performed to indicate the short term stiffness of foam mixes in order to aid in the prediction of the delay necessary before a road comprising these foam mixes could be opened to traffic, and to determine how curing time and moisture content affect the development of stiffness modulus with and without cement. • A preliminary investigation was carried out into the potential of coir fibres as a reinforcement agent in the foam mix, measuring its effect on stiffness modulus, tensile strength and permanent deformation. • Being sensitive to moisture, the climatic durability of foam mix was further assessed by studying the effect of dry/wet cycles on the stiffness modulus incorporating other additives such as hydrated lime and pre-blended bitumen with wet fix. • Microscopic analysis has been undertaken as a guide to characterise the microstructure of the foam mix incorporating additives such as cement and coir fibres in order to support the laboratory findings. The laboratory results confirmed that the stiffness behaviour of the foam mix could be influenced by the amount of MMC, cement content and humidity of the environment. It was found that the foam mix with 1% cement (by mass of dried aggregates) at MMC, 70% of OMC, produced a durable mixture with a high stiffness modulus value in both dry and wet conditions as well as when subjected to the effect of alternate dry and wet cycles. The investigation on the potential of coir fibre to reinforce the foam mix indicated that the fibre did help to prevent large cracks in the foam mixes but unfortunately the reinforced foam mixes were easily damaged under a wet environment.

The generic term Warm Mix Asphalt (WMA) refers to a variety of bituminous mixtures, which are produced through specific technologies, at temperatures approximately 15°C to 70°C lower than the typical production temperature range of conventional Hot Mix Asphalt (HMA) (i.e. 135°C to 160°C). The lower production temperatures of WMA offer a sustainable and environmental-friendly alternative to HMA via reducing the fuel consumption and greenhouse gas emission. Application of asphalt involves mixing, hauling, placement and compaction. As a general rule for HMA, if, during delivery and compaction, the mixture’s temperature drops below the minimum allowable production temperature at which adequate compaction can be achieved, then significant reductions in the performance of the resultant mixture is expected. In the case of WMA, it is expected that the effects of cool compaction on the properties and performance of the mixture will be less easily described than in HMA. This is due to the complicating presence of additives, which may modify the chemical, rheological and mechanical properties of the bitumen, as well as modifying the surface energy of both bitumen and aggregate, all of which can, consequently, affect the properties and performance of the resultant WMA mixture in a complex way not directly comparable to HMA mixtures. The overall goal of this research has been to investigate the effects and implications of temperature decline on the mechanical performance of WMA mixtures, produced in two different ways, included a ‘wax/organic additive’ technology (using a Fischer-Tropsch paraffin wax) and a ‘chemical additive’ technology (using a cationic surfactant liquid), along with determining the fundamental reasons for such effects. For this purpose, a devised comprehensive matrix of laboratory tests was performed on the produced wax-modified and chemical-additive-modified binders in order to provide the mechanical and rheological characterisation of the binders as well as their surface energy properties. The associated wax-WMA and chemical-additive-WMA, also different reference HMA mixtures were fabricated via mixing at recommended and adequate temperatures (according to the standard or the additive supplier’s advice) and compacting at a declining series of temperatures using two different compaction methods (i.e. gyratory compaction and roller compaction). A devised comprehensive set of laboratory tests was then carried out to fully characterise the manufactured WMA mixtures and their counterpart reference HMA mixtures via studying and understanding the influence of reduced production temperatures on their mechanical performance characteristics, including volumetric properties, stiffness modulus, fatigue resistance, rutting potential and viscoelastic behaviour representatives (complex stiffness modulus). The binder-aggregate dry bond strength of the various binder and aggregate combinations used in the asphalt mixtures was evaluated using the surface energy calculations combining the surface energy properties of the different binders and aggregates (pure and modified). Moreover, a mechanical assessment test was performed on different coating samples of the various binder and aggregate combinations to evaluate the binder-aggregate adhesive or binder cohesive tensile strength in different mixtures. The results show that compaction at lower temperatures does not have a considerable effect on the performance of asphalt mixtures, whether they contain additives or not, unless it occurs below 100°C (i.e. 80 and 85°C), in which case, in spite of some limited negative influences on asphalt performance, overall behaviour still remains in acceptable ranges. Moreover, it seems that overall, additives increase the sensitivity of asphalt mixtures’ properties to production temperatures variations. It was also found that gyratory compactors compact asphalt mixtures to a certain density regardless of the temperature (and probably material) because they are, in effect, strain-controlled. Thus, the compaction process in a gyratory compactor is widely insensitive to temperature. Therefore gyratory compaction is not a suitable method for investigating the performance of compaction site that imposes a fixed or set vibratory stress.

Moisture damage of the asphalt mixture is defined as the loss of strength, stiffness and durability due to the presence of moisture (in a liquid or vapour state) leading to adhesive failure at the aggregate-bitumen interface and/or the cohesive failure within the bitumen or bitumen-filler mastic. The presence of moisture can accelerate the distress of asphalt pavement in several different modes, such as rutting, fatigue cracking, thermal cracking and the formation of potholes. In the field, the moisture damage normally happens first at the interface of two pavement layers or at the bottom of pavement layers and develops gradually upward. Once moisture has come into contact and interacted with the asphalt mixture, moisture damage could be developed by the following mechanisms: detachment, displacement, spontaneous emulsification, pore pressure, and hydraulic scour. It should be mentioned that moisture damage is not limited to only one mechanism but is the result of a combination of several mechanisms. As mentioned previously, the common modes of moisture damage of asphalt mixtures are a loss of adhesion between the aggregate and bitumen and/or a loss of cohesion in the mixture. Among these two failures, the adhesive failure is recognised as the main mode of moisture damage. Hence, the physico-chemical interactions between aggregates and bitumen in the presence of moisture are believed to partially govern the moisture sensitivity of asphalt mixtures, which can also affect the serviceability, performance and durability of the asphalt pavement. This thesis describes the work that was carried out with regard to the moisture damage evaluation of aggregate-bitumen bonds through different procedures. The fundamental properties of the individual material such as the chemical composition and rheological properties of bitumen, moisture absorption, surface morphology and mineralogical composition of aggregates were first characterised. Two types of equipment, namely the dynamic contact angle (DCA) analyser and dynamic vapour sorption (DVS) system were used for determining the surface energy of the bitumen and aggregates, respectively. The obtained surface energy results were then combined thermodynamically to determine the work of adhesion between aggregate and bitumen, and the reduction in the adhesive properties if water is introduced into the system. Three established mechanical tests consisting of the standard peel test, Pneumatic Adhesion Tensile Testing Instrument (PATTI) test and a pull off test were developed and redesigned to make sure that these tests are practical, reliable and feasible to measure the bonding strength of aggregate-bitumen combined specimens. The composite substrate peel test (CSPT) was developed to prepare composite substrates using crushed coarse aggregates as a more practical replacement for the aggregate substrates prepared from aggregate boulders. Finally, the moisture damage results from mechanical tests and thermodynamic results were compared and correlated with the basic physico-chemical properties of the original materials. The results showed that in the dry condition, all techniques used in this research, including the mechanical tests and the surface energy tests led to similar results, with bitumen rather than aggregates dominating the bonding properties of aggregate-bitumen systems. After moisture conditioning, the four mechanical tests, including standard peel test, CSPT, PATTI test and pull-off test showed similar moisture sensitivity ranking and failure surface results demonstrating the good correlation between these four tests. In addition, based on the comparison conducted, the four mechanical tests are all considered to be reliable to evaluate the moisture sensitivity of different aggregate-bitumen systems. However, based on the aggregates considered in this research, the moisture sensitivity parameters obtained from the surface energy tests are suggested unreliable to evaluate the moisture sensitivity of aggregate-bitumen systems.

Please read the abstract (Dissertation Summary) in the section, 00front, of this document / Dissertation (M Eng (Transportation Engineering))--University of Pretoria, 2008. / Civil Engineering / unrestricted

The United States has the world’s largest road network with over 4.1 million miles of roads supporting more than 260 million of registered automobiles including around 11 million of heavy trucks. Such a large road network challenges the road and traffic management systems such as condition assessment and traffic monitoring. To assess the road conditions and track the traffic, currently, multiple facilities are required simultaneously. For instance, vehicle-based image techniques are available for pavements’ mechanical behavior detection such as cracks, high-speed vehicle-based profilers are used upon request for the road ride quality evaluation, and inductive loops or strain sensors are deployed inside pavements for traffic data collection. Having multiple facilities and systems for the road conditions and traffic information monitoring raises the cost for the assessment and complicates the process. In this study, an integrated system is developed to simultaneously monitor the road condition and traffic using in-pavement strain-based sensors, which will phenomenally simplify the road condition and traffic monitoring. To accomplish such a superior system, this dissertation designs an innovative integrated sensing system, installs the integrated system in Minnesota's Cold Weather Road Research Facility (MnROAD), monitors the early health conditions of the pavements and ride quality evaluation, investigates algorithms by using the developed system for traffic data collection especially weigh-in-motion measurements, and optimizes the system through optimal system design. The developed integrated system is promising to use one system for multiple purposes, which gains a considerable efficiency increase as well as a potential significant cost reduction for intelligent transportation system. / USDOT (U.S. Department of Transportation) / MPC (Mountain-Plains Consortium)

Reusing RAP in the base layer became a common practice in the last decade. However, some crucial issues must be resolved to succeed in using RAP satisfying the standard specifications as a base layer. The most important unknown factor is the mechanistic behavior of RAP. This question may be satisfied by understanding the role of RAP in terms of whether it just behaves as a black rock or has a stabilizing effect with traditional aggregates used for base layer. The first stage of this study is modeling the structural behavior of RAP via prediction MR. This stage then comprises comparing the predicted results to actual measured data under several field conditions. The second stage focuses on the modeling behavior of PD. This stage takes in consideration two sets of data, the first is for the measured PD data calculated from MR test. While another traditional set of measured data for PD from repeated tri-axial loading (RTL) test either single or multi-stage is collected for the same RAP sources used in the first stage. The third stage concerns on MR-PD relationship. It indicates the typical relationship for the MR-PD behavior that can be understood for the RAP in base layer. The fourth and last stage is essential to investigate the Poisson’s ratio of RAP blends and its effectiveness on both parameters MR and PD. This ratio is measured during un-confined compression test. Two main testing conditions: various water and RAP contents are taken in consideration during this measurement for different RAP/Aggregate sources. This study proves that both prediction models used in the MEPDG for prediction of both parameters MR and PD are totally significant for RAP/Aggregate blends used for pavement base layer. The prediction is at the highest accuracy at water content levels close to OMC%, MDD and with 50% to 75% RAP content. In addition, it is proved that Poisson’s ratio is an effective parameter on both MR and PD parameters especially with variation of water content. This conclusion recommends to take in consideration Poisson’s ratio as an effective parameter in MR and PD prediction models used in MEPDG software. / National Science Foundation (NSF)

Bibliography: pages 136-145. / The aim of this report is to develop a procedure for the environmental evaluation of roads in South Africa, because in the past the environmental evaluation of road projects have been on an ad hoc basis, often using different formats. The procedure is therefore to be replicable from scheme to scheme, procedure, Management and is to be incorporated into the existing road development while drawing on the principles of Integrated Environmental The first part of the report is a study of the environmental evaluation procedures adopted in the United Kingdom, United States of America and Ontario (Canada). The environmental evaluation of roads in these countries are compared under the following headings: contextual features of the environmental evaluation procedures; the planning, location and design stages of the environmental evaluation procedures, and the environmental evaluation documentation. In this comparative study, the common and unique steps and elements are identified in order to generate an 'Ideal'. The second part of the report is a study on the environmental evaluation of roads in South Africa. The administrative structure, legislation, policy and planning procedures for roads in South Africa, and Integrated Environmental Management (IEM) are discussed. Although IEM is currently been developed and road authorities are committed to IEM, the procedure still needs to be incorporated into the existing road development procedure. The third part of the report develops a procedure for the environmental evaluation of roads in South Africa. The procedure developed incorporates common and unique steps and elements generated in the 'Ideal' into the existing road development procedure. The Environmental Conservation Act and Integrated Environmental Management are also taken into account in developing the procedure. Finally, as there is at present no formal documented procedure for the environmental evaluation of roads in South Africa, it is recommended that the procedure be considered by road and environmental authorities with a view to implementing it.

This study concentrated primarily on how the changes in the trunk A transportation network configuration in Nigeria alter both the hierarchy of the network system and the connectivity of the network itself. Using the graph theory, the study looked at the network development in Nigeria in 1949, 1961, 1976, and 1982. The period covered in the study spanned from the colonial to the post-colonial eras. Road maps of each of these years were the primary sources of data. The maps were translated into abstracted networks and subsequently converted into square matrices, and analyzed. The analysis resulted in the establishment of the network connectivity and the accessibility of individual nodes. Gamma and alpha indices were used to determine the complexity (the degree of connectivity) of networks in each of the study periods. The sporadic changes in the number of nodes and linkages resulted in the fluctuation of the network connectivity. This type of fluctuation is a common problem in network development within the developing economies. Political and administrative factors exert stronger influence in shaping the content and the outcome of transportation programs than the Taaffe, Morrill and Gould (1963) and Lachene (1965) models imply. The sporadic fluctuations in the number of nodes, linkages and in the values of the gamma and alpha indices suggest that neither the sequence of network development nor its supposed discrete nature is appropriate to postcolonial development. There is a significant difference between network development during the colonial and post-colonial eras. During the colonial era, there was a strong connection between network development and primary economic activities. The conditions during the colonial era support the link between the network and economic development as illustrated in Kansky (1963) work. The post-colonial era in the other hand, is marked by the need for both social and political integration. Thus, the pattern of network development in Nigeria in the eighties is quite consistent with Friedmann (1975) assertion that social and political factors should be assigned a higher score than economic in the development model for Third world. After nearly ninety years of network development, the trunk A network system in Nigeria is in transition. It is now moving from elementary into an advanced stage of development. One of the things that is likely to at least slow down the rate of such transformation is the political sub-division of the nation into smaller constituent units, coupled with lack of political predictability. From most indications, network development is moving away from concentration in relatively few nodes to a system that imposes a grid on the nation. The imposition of such a grid is likely to induce and enhance the interregional linkages and competition. Such phenomenon is indeed healthy in the light of the existing imbalance in terms of responsibilities between the three levels of government. It is also a good approach towards redressing the existing regional disparities as regional integration is very likely to bring about incentives and opportunities for a fair competition.