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.

Cell surface properties are crucial to the mechanisms by which groups of cells organize themselves during embryogenesis, cancer metastases and tissue engineering. Measured surface tension values provide a quantitative basis for predicting a range of cell behaviors including sorting of embryonic cells, self-organization of pancreatic islet cells and invasive potential of tumor cells. Tissue surface tensions are a measurement of the tension that acts along the interface between a cell aggregate and its surrounding media and it is typically measured by compressing an aggregate of cells. In this study a novel apparatus is used to measure the surface tensions of aggregated embryonic chick cells from heart, liver, neural retina and mesencephalon tissues. These surface tension values are consistent with the known engulfment behavior of the cells involved and are in close agreement with measurements made previously by other means. It has been suggested that surface tensions and cell rearrangement patterns are a direct result of adhesion forces between cells arising from cadherins. However, cadherin binding alone is insufficient to account for observed engulfment phenomena and recent experimental evidence suggests that actin dynamics are involved. A cell surface property referred to as interfacial tension or cortical tension takes into account both adhesion forces and forces derived from actin microfilaments and could shed new light on the mechanisms involved in cell interactions. Computer simulations indicate that the interfacial tension between cells can be measured through a modified compression test experiment. In this cell aggregate compression study, cell shapes as well as the aggregate profile are measured in addition to the compression force in attempts to measure cell interfacial tensions.

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.

Cell surface properties are crucial to the mechanisms by which groups of cells organize themselves during embryogenesis, cancer metastases and tissue engineering. Measured surface tension values provide a quantitative basis for predicting a range of cell behaviors including sorting of embryonic cells, self-organization of pancreatic islet cells and invasive potential of tumor cells. Tissue surface tensions are a measurement of the tension that acts along the interface between a cell aggregate and its surrounding media and it is typically measured by compressing an aggregate of cells. In this study a novel apparatus is used to measure the surface tensions of aggregated embryonic chick cells from heart, liver, neural retina and mesencephalon tissues. These surface tension values are consistent with the known engulfment behavior of the cells involved and are in close agreement with measurements made previously by other means. It has been suggested that surface tensions and cell rearrangement patterns are a direct result of adhesion forces between cells arising from cadherins. However, cadherin binding alone is insufficient to account for observed engulfment phenomena and recent experimental evidence suggests that actin dynamics are involved. A cell surface property referred to as interfacial tension or cortical tension takes into account both adhesion forces and forces derived from actin microfilaments and could shed new light on the mechanisms involved in cell interactions. Computer simulations indicate that the interfacial tension between cells can be measured through a modified compression test experiment. In this cell aggregate compression study, cell shapes as well as the aggregate profile are measured in addition to the compression force in attempts to measure cell interfacial tensions.

The performance of hot mix asphalt, Portland cement concrete, unbound base, and subbase layers in a pavement are significantly affected by aggregate shape characteristics. Classification of coarse and fine aggregate shape properties such as shape (form), angularity, and texture, are important in predicting the performance of pavements. Consequently, there is a need to implement a system that can characterize aggregates without the limitations of the current aggregate classification standards. The Aggregate Image Measurement System (AIMS) was developed as a comprehensive and capable means of measuring aggregate shape properties. A new design of AIMS will be introduced with several modifications to improve the operational and physical components. The sensitivity, repeatability, and reproducibility are analyzed to evaluate the quality of AIMS measurements. The sensitivity of AIMS is evaluated and found to be good for several operational and aggregate parameters. Important operational and environmental factors that could affect the AIMS results are identified and appropriate limits are recommended. AIMS is able to control normal variations in the system without affecting the results. A comprehensive analysis is conducted to determine the repeatability and reproducibility of AIMS for multiple users and laboratories. Single-operator and multi-laboratory precision statements are developed for the test method in order to be implemented into test standards.

The skid resistance of asphalt pavement is a major characteristic that determines the driving safety on a road, especially under wet surface conditions. Skid resistance is primarily a function of the microtexture and macrotexture of a pavement surface. Microtexture is influenced by aggregate surface characteristics and is required to disrupt the continuity of surface water film and attain frictional resistance between the tire and the pavement surface. Macrotexture is affected mostly by mixture design or aggregate gradation and contributes to skid resistance by providing drainage paths of water that can be otherwise trapped between a tire and a pavement surface. The increase in macrotexture contributes to preventing hydroplaning and improving wet frictional resistance, particularly at high speeds. While much research has been conducted in the past to identify material factors that affect skid resistance, there is still a need to develop a model for predicting asphalt pavement skid resistance as a function of mixture characteristics and traffic level. The purpose of this study was to develop such a model based on extensive laboratory experiments and field measurements involving different mixture types and aggregate sources. The model incorporates functions that describe the resistance of aggregates to polishing and aggregate size distribution. The aggregate resistance to polishing was quantified by measuring aggregate texture using the Aggregate Imaging System (AIMS) before and after polishing in the Micro-Deval device. The analysis in this dissertation demonstrates how this model can be used to design mixtures and classify aggregates that provide desirable skid resistance levels.

This research is intended to contribute toward the understanding, development, and implementation of a more fundamental design process for bituminous pavement materials, utilizing thermodynamic properties of the materials involved. The theory developed by van Oss, Chaudhury and Good forms the basis of this research. Optimization of techniques to characterize surface energy, as well as consideration and evaluation of additional factors that influence adhesion in the presence of water, are pursued. A synthesis of theories and mechanisms of bitumen-aggregate adhesion is presented, and existing and potential techniques for surface energy characterization are reviewed to establish firm background knowledge on this subject. The Wilhelmy plate technique was scrutinized and improved methodologies and analysis procedures are proposed. Inverse gas chromatography (IGC) is introduced as an alternative technique. A reasonable comparison of total surface energy values form these techniques with mechanical surface tension values were found. Results suggest that bitumen surface energies do not vary substantially. Inability of these techniques to detect the effect of a liquid additive is rationalized by the ‘potential’ surface energy concept. Suggestions for a more realistic characterization of bitumen polar surface energy components are presented. A static gravimetric sorption technique was employed to characterize aggregate surface energies. Dynamic vapor sorption was identified as a candidate alternative technique for aggregate surface energy characterization. A study on the effect of pH on surface energy components of water revealed that this effect is practically negligible. Calculation of the free energy of electrostatic interaction (DGEL) indicated that this term contributes less than 1% to the total free energy of adhesion. Despite this finding, it is shown that DGEL alone is able to distinguish moisture sensitive mixtures. The significance of electrical phenomena at the interface is elucidated through another mechanism following the work of M.E. Labib. The relationship between pH and electron donor-acceptor properties of aggregate surfaces is presented. The Labib approach potentially offers the solution to quantify the effect of pH on adhesion. In addition, it should be possible to resolve issues with the acid-base scale proposed by the founders of the current theory, by replacing it with a more absolute donor-acceptor scale.

Shape, texture, and angularity are among the properties of aggregates that have a significant effect on the performance of hot-mix asphalt, hydraulic cement concrete, and unbound base and subbase layers. Consequently, there is a need to develop methods that can quantify aggregate shape properties rapidly and accurately. In this study, an improved version of the Aggregate Imaging System (AIMS) was developed to measure the shape characteristics of both fine and coarse aggregates. Improvements were made in the design of the hardware and software components of AIMS to enhance its operational characteristics, reduce human errors, and enhance the automation of test procedure. AIMS was compared against other test methods that have been used for measuring aggregate shape characteristics. The comparison was conducted based on statistical analysis of the accuracy, repeatability, reproducibility, cost, and operational characteristics (e.g. ease of use and interpretation of the results) of these tests. Aggregates that represent a wide range of geographic locations, rock type, and shape characteristics were used in this evaluation. The comparative analysis among the different test methods was conducted using the Analytical Hierarchy Process (AHP). AHP is a process of developing a numerical score to rank test methods based on how each method meets certain criteria of desirable characteristics. The outcomes of the AHP analysis clearly demonstrated the advantages of AIMS over other test methods as a unified system for measuring the shape characteristics of both fine and coarse aggregates. A new aggregate classification methodology based on the distribution of their shape characteristics was developed in this study. This methodology offers several advantages over current methods used in practice. It is based on the distribution of shape characteristics rather than average indices of these characteristics. The coarse aggregate form is determined based on three-dimensional analysis of particles. The fundamental gradient and wavelet methods are used to quantify angularity and surface texture, respectively. The classification methodology can be used for the development of aggregate shape specifications.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 506-525). Available also in a digital version from Dissertation Abstracts.

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.