Master of Science / Department of Civil Engineering / Mustaque A. Hossain / Pavement preservation by adopting low-cost maintenance techniques is increasing among transportation agencies day by day. Chip seal, also known as seal coat, is widely used as a low-cost, thin surface treatment in preventive maintenance of asphalt pavements in many states, including Kansas. Loosening of aggregate particles from chip-sealed pavement and associated windshield damage to vehicles is a common problem. Thus the Kansas Department of Transportation (KDOT) uses lightweight aggregates as cover materials for chip seals. Although this has decreased windshield damage problems extensive chip loss on seal-coated pavements in the state has been reported. In this study, lightweight aggregates along with polymer-modified asphalt emulsion were used to determine proper aggregate and emulsion application rates to minimize chip loss in chip seals. Again, lightweight aggregates were studied in the laboratory to determine the effect of moisture content and electrical charge on chip loss. Evaluation of chip seal was performed by statistical analysis based on rutting potential, chip embedment, and retention. Results show that aggregate retention and embedment depth depend on aggregate-emulsion interaction, whereas rutting depends on the type of aggregate. Proper selection of aggregate and asphalt emulsion is important to maximize aggregate retention in chip seal. Chip loss also results from a lack of compatibility between the aggregate and asphalt emulsion. Results indicate that retention of aggregate depends on the prevailing charges of aggregate and emulsion particles. Moisture condition of the aggregate does not have any effect on chip loss. A new sweep test machine has been developed to assess chip loss, and it was found to be better than the sweep test currently recommended by the American Society for Testing and Materials (ASTM).

Master of Science / Civil Engineering / Kyle Riding / The Kansas Department of Transportation (KDOT) currently practices a six-month procedure for determining freeze-thaw durability of coarse aggregate intended for use in concrete pavement. In addition to the excessive amount of time required to conduct this procedure, the testing conditions fail to replicate the accelerated rate of concrete deterioration commonly caused by deicer salt exposure in freeze-thaw environments. An experimental study was conducted in an attempt to reduce the duration of this aggregate qualification procedure. Limestone course aggregates from different quarries were used to batch concrete specimens. These specimens were subjected to curing regimes of different durations before being exposed to repeated cycles of freezing and thawing. The effects of the curing methods on freeze-thaw durability were then investigated. Another segment of this study entailed the immersion of coarse aggregate in salt brine solution prior to concrete batching. Salt-treated and non-salt-treated specimens were subjected to two different methods of freeze-thaw cycling to determine if the presence of salt could differentiate between aggregates with high and low performance. This study found that shorter curing methods, along with adjusted performance requirements, could be used to develop a shorter aggregate qualification procedure. It also found that shorter periods of time in more severe freeze-thaw conditions produced comparable concrete durability results to those of the current test method. Salt treatment of aggregates could indicate a difference in performance of aggregates when exposed to salts in freeze-thaw conditions. It could also be useful in determining frost resistance of hardened cement paste.

No description available.

No description available.

Call number: LD2668 .T4 1958 C43 / Master of Science

Concrete structures can prematurely deteriorate due to the corrosion of reinforcing steel. Corrosion can occur through chloride ingress due to exposure to aggressive media such as seawater and deicing salts. Corrosion causes over $100 billion in damage annually. There are many corrosion mitigation techniques on the market today; these techniques have limited effectiveness as demonstrated by the fact that billions of dollars are still being expended each year due to corrosion-related damage. Therefore, there is a need for innovative approaches to corrosion prevention. This research program used cinnamaldehyde (CA), a bioactive agent derived from cinnamon bark, as a method for corrosion mitigation. Although CA can prevent the corrosion of metals, its hydrophobicity has a negative effect on hydration when incorporated in cementitious systems. In order to avoid these negative consequences while harnessing the anti-corrosive properties, CA was incorporated in a cementitious mixture through the use of lightweight aggregate (LWA). Several tests were carried out to investigate the potential chemical and mechanical effects due to the addition of LWA pre-wet with CA. Promising results were observed, in which the time to corrosion was prolonged by 91 %.

Uncertainty is inherent in many novel and important applications such as market surveillance, information extraction sensor data analysis, etc. In the recent a few decades, uncertain data has attracted considerable research attention. There are various factors that cause the uncertainty, for instance randomness or incompleteness of data, limitations of equipment and delay or loss in data transfer. A probabilistic threshold range aggregate (PRTA) query retrieves summarized information about the uncertain objects in the database satisfying a range query, with respect to a given probability threshold. This thesis is trying to address and handle this important type of query which there is no previous work studying on. We formulate the problem in both discrete and continuous uncertain data model and develop a novel index structure, asU-tree (aggregate-based sampling-auxiliary U-tree) which not only supports exact query answering but also provides approximate results with accuracy guarantee if efficiency is more concerned. The new asU-tree structure is totally dynamic. Query processing algorithms for both exact answer and approximate answer based on this new index structure are also proposed. An extensive experimental study shows that asU-tree is very efficient and effective over real and synthetic datasets.

Fracture mechanics is applied to study the behavior of concrete containing expanded polystyrene (EPS) aggregate replacement. The EPS replaces a portion of the normal weight fine aggregate. Previous research has shown EPS aggregate replacement changes the failure mode in compression from a typical instantaneous failure, as in normal weight concrete (NWC), to a more gradual dissipation of load carrying capacity. This behavior is investigated through the use of fracture mechanics. The fracture energy, critical stress intensity factor and characteristic length of EPS concrete, NWC and fiber reinforced concrete (FRC) are experimentally determined. The two types of tests used to study these properties are the three point bending test recommended by the RILEM technical committee and a wedge splitting test developed recently. The conclusions derived from this research demonstrate that EPS aggregate replacement increases the size of the fracture process zone in front of the crack tip. This increase in size changes the failure mode of concrete allowing it to maintain load after reaching peak load and absorb more energy during the fracture process.

Grasslands throughout the world including those in British Columbia have been severely reduced and altered by agricultural production and inappropriate livestock grazing practices. Ongoing degradation of rangelands is a worldwide problem, currently affecting about 680 million hectares of rangelands. Studies on development and application of criteria and indicators for forests and grasslands are often lacking, or have been done on a limited number of sites with relatively narrow ranges of climate and soil type. This study aims to (i) quantify the relationships among soil/vegetation properties known to be affected by grazing to easily-assessed indicators, used in the existing health assessment systems, that do not require laboratory analyses or time consuming measurement, and (ii) to evaluate impacts of grazing on soil aggregate stability on the rough fescue grasslands of the southern interior of British Columbia. During the growing seasons of 2006 and 2007, soil and vegetation properties were measured on nine open grassland sites with a potential natural plant community dominated by rough fescue (Festuca campestris Rydb.) in the southern interior of British Columbia. Each site had at least one area excluded from grazing and all units were classified into different seral stages according to the amount of rough fescue present on the land. Rough fescue cover was found to be a useful indicator of the presence of functioning recovery mechanisms. Percent exposed mineral soil was found to be a sensitive indicator of the degree of soil stability and watershed function, as well as an indicator of the integrity of nutrient cycles and energy flows in rough fescue grasslands. Percent Junegrass cover was not as sensitive an indicator as percent exposed mineral soil, but has general overall strength with many health measures.. Only the 1-2 mm aggregate size class was closely related to most soil and vegetation properties, showing that it is more sensitive than the other aggregate stability parameters to soil and vegetation properties. The results from this study can help rangeland managers and ranchers in determining the rangeland health in their area as well as help researchers understand that only a certain number of parameters need to be assessed.

Abstract, <br /> The interest in using recycled construction materials is derived from the growth in construction and demolition waste due to rehabilitation and natural and technological disasters. The driving force for recycling concrete is three-fold: preserving natural resources, utilizing the growing waste and saving energy and money. While some waste concrete is currently being crushed and used for grading and base material for highways, it has not been used as the aggregate in new concrete in Canada, largely because of the plentiful supply of good quality virgin material. However, crushed concrete is being used in new concrete in other parts of the world where the local aggregate is inferior, and there is now a push within the Canadian cement and concrete sector to improve the industry sustainability, one aspect of which is recycling of materials. <br /><br /> The research done to date has emphasized the influence of recycled concrete aggregate (RCA) on the workability and strength of the new concrete with little attention being paid to the behaviour in service. In contrast, the present study is focused on the durability of concrete containing RCA in reinforced structures. Since the most common cause of failure of reinforced concrete structures in this part of the world is corrosion of the reinforcement by de-icing salts, the focus of the project is on this aspect of durability. The project involves a comparative study of the durability of three concrete mixtures containing, as coarse aggregate: <ol> <li>new clean recycled concrete aggregate (NC-RCA) obtained by crushing the excess concrete returned to the ready mix yard; </li> <li>old de-icing salt contaminated, recycled concrete aggregate ( OC-RCA) from a demolished bridge over Highway 401 in Ontario; </li> <li>natural aggregate as a control material. </li> </ol> These three materials were crushed and sieved to give the same grading for each mix. Natural sand was used as fine aggregate. The mixes were adjusted to account for the different water absorption characteristics of the aggregates but were otherwise identical. Prism specimens with a centrally placed reinforcing bar, cylindrical specimens and non-reinforced slabs were cast from each of the concretes. After curing, the reinforced prisms were exposed to a saturated de-icing salt solution for two of every four weeks. For the second two week period, they were allowed to dry in the laboratory atmosphere or, to accelerate the process, dried at 32°C in a low humidity (18%) chamber. <br /><br /> The electrochemical corrosion behaviour of the steel was monitored using linear polarization resistance and cyclic polarization techniques. In addition, the physical properties of the materials were assessed. For the aggregates, water absorption, chloride content and susceptibility to abrasion were determined. For the concretes, compressive strength, salt scaling resistance and chloride permeability were measured and microscopic observation of the interfacial zones between the aggregate and the new cement paste were conducted. <br /><br /> On the basis of the results, it is concluded that the durability and the strength of the RCA concrete is very dependent on the age of the RCA aggregate. Water and chloride permeability, and, salt scaling and reinforcing steel corrosion resistance of concrete made with a very well hardened old RCA were comparable with or better than those of in normal concrete. Concrete incorporating new RCA exhibited inferior properties and consequently, it is recommended that, the OC-RCA concrete can be used as a sustainable material in structural applications.