The current manner of constructing roads with virgin aggregates is unsustainable for many urban centers as natural sources for quality aggregates are being or have been depleted. As well, there is little understanding or scientific data published as to the impacts on roadway design and life cycle performance with poorer quality aggregate material. To improve future sustainability of roadway utility, there is a need for better understanding of the mechanistic behavior of road aggregates and their respective role in road structural performance in the field. As well, there is a need to find more sustainable sources of quality aggregates to construct roadways. The goal of this research is to improve road utility sustainability through a better understanding of life cycle performance and incorporating field state mechanistic principles in the initial design of the roadway structure. The primary objective of this research was to investigate the application of recycle rubble materials using a mechanistic materials characterization and structural design process for urban roadways within typical City of Saskatoon roads and field state conditions. Specific technical objectives of this research were to characterize various recycled aggregate materials with regards to their road structural behavior as a high quality base coarse, quantify the cost comparison between various design cross sections, and evaluate the structural behavior of these alternate aggregate sources in typical structural designs and Saskatoon field state conditions. To validate the field behavior of recycled aggregates, various test sections were constructed with different recycled and virgin aggregate structural systems. These test sections were evaluated using non-destructive structural assessment to determine their structural quality in the field. This research studied the use of recycled portland cement concrete aggregates and recycled asphalt cement aggregates as structural granular layers of typical City of Saskatoon roadways. These materials were characterized using conventional and mechanistic lab characterization protocols. Field test sections were constructed to validate that recycled materials could be employed as quality replacements for virgin aggregates. Research was also conducted on how to incorporate mechanistic based materials testing and structural design into City of Saskatoon Design and Materials Selection Specifications and Processes. The resilient modulus of the various road materials was also compared to relate to other mechanistic-empirical design methodologies. The laboratory testing conducted in this research indicated that although conventional empirical testing shows recycled asphalt materials to be of lesser quality, when evaluated using mechanistic characterization protocols, recycled asphalt concrete material yielded superior structural behavior. To illustrate, the dynamic modulus of recycled asphalt concrete was 697 MPa under a fully reversed stress state and a frequency of 0.5 Hz compared to 264 MPa for a high quality conventional high fracture granular base under the same stress state and frequency. As well, the recycled asphalt material showed less moisture susceptibility than conventional granular aggregate. This research showed recycled portland cement concrete aggregate materials showed good drainage and capillary break qualities when tested against the standard granular base materials. Although the well graded recycled asphalt cement and well graded recycled portland cement concrete were shown to have slightly higher moisture intake values, the increased moisture did not increase the swell and therefore indicates adequate frost resistance due to moisture. This research showed conventional roadway design utilized by the City of Saskatoon does not have the means to evaluate recycled asphalt and portland cement aggregates from a materials selection and structural design perspective. Roadway designs using a mechanistic approach were able to accurately represent the field structural primary responses of test roadway structures considered in this study and were able to incorporated recycled aggregate in the design process. Designing roads using a mechanistic design process showed a significant improvement in roadway structural responses in designs using recycled aggregate material. From an economic perspective, this research showed road cross sections utilizing recycle aggregate materials proved to be the least expensive option when evaluated by the initial capital cost and the projected life cycle costing. When comparing primary structural responses to construction cost, up to 20 percent of costs to construct a road can be saved, and a properly designed road structure using recycled aggregates will reduce the strains in the structures by up to 90 percent. As well, using recycled aggregates to construct roadways will reduce the fuel consumption during construction by up to 20 percent due to a reduction in aggregate hauling distances. In summary, when evaluated with a mechanistic road structural design method that accounts for the material characteristics of various aggregates, recycled asphalt rubble processed as a black base and recycled portland cement concrete as a stress dissipating drainage layer within the construction of new roadways is a more sustainable approach to designing and constructing structurally sound roads than the conventional methods. Based on the findings of this research, proper stockpiling and recycling of asphalt and concrete rubble materials is recommended in the City of Saskatoon. In order to optimize and incorporate various recycled aggregate materials into road design it is recommended the City of Saskatoon employ mechanistic based road material characterization and structural design.

Gravel aggregates had been used extensively in the Houston District of Texas Department of Transportation (TxDOT) for continuously reinforced concrete pavements construction for many years. However, some of these pavements have been subject to early age delamination and eventual spalling damage. Therefore, a series of studies funded by TxDOT since the early 1990's has been conducted to gain a better understanding of mechanisms, material properties, and construction practices, and to provide guidelines and recommendations for minimizing early-age delamination in concrete pavements made with gravel aggregates. In this study, a test protocol to measure the bond strength between aggregates and cement mortar was established, and the effects of different material and construction parameters on the bond strength of concrete at early ages using a fractional factorial design were investigated. The significances of each factor to achieve better bonding performance were determined, and the optimum design combination was subsequently chosen and validated. Geometric parameters were proposed to characterize aggregate shape properties relative to bonding performance with the facilitation of the Aggregate Imaging System. A rating system based on utility theory was developed to evaluate the overall contribution of aggregate properties (i.e. physical, geometric, and chemical) to the concrete bonding capability and the feasibility of certain mixture design combinations. As for theoretical representation of the bond strength across the interfacial transition zone, a model of interfacial fracture energy between aggregate and mortar that represents the energy necessary to create a crack along the interface was formulated. This model built the connection between concrete properties at the meso-level (represented by the interfacial fracture energy between aggregate and mortar) and the macro-level (represented by fracture toughness of concrete and significant influencing materials and construction factors). In addition, the moisture effects on stress development of concrete pavements at early ages using field data as inputs were numerically simulated, and a fracture mechanics-based approach was used to predict the occurrence of delamination. A delamination detection protocol for the field was developed to explore the feasibility and potential of utilizing Ground Penetration Radar technology in delamination detection. Research findings from laboratory investigation, field testing, theoretical modeling, and numerical analysis were further validated through field test sections, and the associated framework for delamination guidelines was established.

A new mineralogical approach is introduced to predict aggregate and concrete coefficient of thermal expansion (CoTE). Basically, a modeling approach is suggested based on the assumption that the CoTE of aggregate and concrete can be predicted from the CoTE of their constituent components. Volume percentage, CoTE and elastic modulus of each constituent mineral phase are considered as input for the aggregate CoTE model, whereas the same properties for coarse aggregate and mortar are considered for the concrete CoTE model. Methods have been formulated to calculate the mineral volume percentage from bulk chemical analysis for different type of rocks commonly used as aggregates in Texas. The dilatometer testing method has been established to measure the CoTE of aggregate, pure minerals, and concrete. Calculated aggregate CoTE, based on the determined CoTE of pure minerals and their respective calculated volume percentages, shows a good resemblance with the measured aggregate CoTE by dilatometer. Similarly, predicted concrete CoTE, based on the calculated CoTE of aggregate and mortar and their respective volume percentages compares well with the measured concrete CoTE by dilatometer. Such a favorable comparison between predicted and measured CoTE provided a basis to establish the composite model to predict aggregate and concrete CoTE. Composite modeling will be useful to serve as a check of aggregate source variability in terms of quality control measures and improved design and quality control measures of concrete.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 315-323). Available also in a digital version from Dissertation Abstracts.

Crack Attenuating Mix (CAM) is relatively a new asphalt mixture type used by the Texas Department of Transportation (TxDOT). These mixtures are fine graded, designed using relatively small stone sized aggregates and screenings with a high asphalt content, specifically for retarding the reflective cracking in thin asphalt overlays without sacrificing rutting resistance. The main goal of this study is to promote the use of local aggregates in CAM design. In order to achieve the goal, the development of a mix design procedure and aggregate quality guidelines for CAM design with local aggregates are essential. Several aggregate sources were identified and characterized in terms of their frictional, strength, and durability properties. A refined mix design procedure is recommended using a Superpave gyratory compactor with the capability to measure shear stress during compaction. The emphasis was on preventing rutting and flushing resulting from overfilling of binder in these mixtures, which was observed during compaction by consistent shear failures. The Hamburg Wheel Tracking Device (HWTD) was used for performance evaluation of rutting, whereas the Overlay Tester (OT) was used for cracking evaluation. It is hypothesized that current performance criteria in terms of HWTD and OT are too severe for being applicable to CAM mixes with local aggregates. A modification in HWTD failure criterion is recommended and is used in developing new aggregate guidelines. A correlation analysis was conducted relating aggregate properties and CAM performance in rutting and cracking. Finally, aggregate quality guidelines were developed for CAM using local aggregates based on the correlation study. The mix design recommendations as well as aggregate guidelines and quality criteria provided in the report are based on laboratory investigations and field validation of these is strongly recommended before implementation. / text

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Mycorrhizae improve plant growth and ecosystem sustainability by forming a symbiotic association with higher plants including the economically important willows (Salix spp.). With the recognition of the importance of mycorrhizae in terrestrial ecosystems, inoculation of plants with mycorrhizae is becoming a common practice in agricultural and land reclamation industries. However, little information is available on important ecological parameters such as soil aggregation, soil organic carbon content (SOC) and mycorrhizal communities associated with willow rhizospheres in response to mycorrhizal inoculation in willow systems. The main objectives of this research were to explore how commercial mycorrhizal inoculation of willows impacts (1) percent water-stable soil aggregates (%WSA); (2) indigenous arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi (EMF) community composition associated with different size soil aggregates; (3) SOC, and (4) willow growth. These objectives were examined under both greenhouse and field conditions. Using molecular approaches, we observed the existence of spatial variability in indigenous AMF communities among different soil aggregate size classes. This spatial variability varied with type of soil and could be reduced by inoculating with a commercial AMF inoculant. The indigenous EMF diversity was low and did not show spatial heterogeneity among soil aggregates, but it did vary with soil type. In addition, other parameters, including %WSA, SOC within the willow rhizosphere, and willow plant growth also varied by soil type and changed in association with commercial mycorrhizal inoculation. In the field experiment, soil extracts from willow nursery soil had comparable plant growth promotion with commercial mycorrhizal inoculation, and altered the AMF community associated with bulk soil and soil aggregates in the willow rhizosphere. These results suggest that historically superior willow growth in the willow nursery soil could be due to pre-existing soil microbiological factors. Overall this research indicates that AMF and EMF inoculation has the potential to influence the composition of the AMF community, but had little influence on the composition of the EMF community in the systems tested. / Natural Sciences and Engineering Research Council of Canada

No description available.

The aim of this work was to use simulation as a tool to better understand areas of orthokinetic (shear-induced) aggregation which are still not well understood. These areas include aggregate structure, aggregate strength, breakup and restructuring and combined perikinetic/orthokinetic aggregation. Previous simulation studies were reviewed and it was concluded that the methodology of Chen and Doi (1989) was an appropriate starting point for this study. The modified simulation was validated by comparison with theoretical and experimental results. Orthokinetic aggregates were found to have a fractal structure with an estimated value of 1.65. Scaling exponents, which were shown to be indicative of fractal dimension, of 2.1-2.7 were also obtained. Flexible bonds allowed restructuring to occur which led to an increase in the co-ordination number, scaling exponent, aggregate strength and a reduction in aggregate size. Thus aggregate strength increases with fractal dimension. It was confirmed that both restructuring and breakup/reformation could lead to the formation of small, compact aggregates. The high shear conditions simulated favoured breakup/reformation, while restructuring was expected to dominate with more flexible bonds, possibly at lower shear rates. Taking some account of hydrodynamic interactions by the inclusion of Kirkwood-Riseman theory led to an increase in the compactness of the aggregates and the co-ordination numbers, as well as a decrease in size of the aggregates. The results showed that hydrodynamic interactions can not be ignored. The explanation for the dramatic effects was that particles/microflocs on the outer edges of the aggregates broke off and reformed in a more compact way. Erosion was found to dominate in all cases, thus supporting the theory that erosion dominates at higher fractal dimensions. The shearing range simulated was found to be relatively high (equivalent to &lt200s-1 for particles of 2-5??m), producing relatively small aggregates. Hence it is proposed that under high shear conditions, erosion dominates. It was shown by extension of the DLCA algorithmic restructuring work of Meakin and Jullien (1988, 1989) that the scattering patterns observed in gently sheared aggregating systems are consistent with the interpretation that the shearing causes partial restructuring at large length scales.

Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 4, 2008) Includes bibliographical references (p. 65-69).