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.

The City of Saskatoon is responsible for maintaining approximately 1,100 km of roads including locals, collectors, arterials, and freeways. With the aged state of the road infrastructure, increasing budget constraints limit the City’s ability to maintain existing road infrastructure to an acceptable level of service and to construct new road infrastructure. The infrastructure demands related to urban growth within the City of Saskatoon have caused a shrinking aggregate supply and increasing aggregate demand. In turn, growing demand and dwindling resources for aggregate are resulting in rapid increases to road construction costs. Aggregate sources are a non-renewable resource in Saskatchewan. Therefore, road designers do not have an endless supply of quality aggregates. With limitations of the road building industry and the foreseeable economic growth projected for the City of Saskatoon, it is reasonable to expect that the unit costs of providing conventional pavement structures will continue to increase in Saskatoon. Presently, the primary conventional road building materials include well graded granular base material, subbase, crushed rock and a wearing surface of either conventional hot mix asphalt concrete (HMAC) or Portland cement concrete (PCC). To ensure long term pavement performance, quality aggregate sources are needed in all road design structural layers. Recent years have seen an increased need for substructure drainage systems, therefore increasing the need for high quality crushed rock. City of Saskatoon, like other urban centers, generates significant stock piles of concrete rubble annually. The primary objective of this research was to compare PCC material properties to those of conventional granular materials under realistic field state conditions. The second objective of this research was to validate the economic feasibility of using recycled PCC material within City of Saskatoon road structure through test section design and field test sections’ structural performance. Conventional and mechanistic material characterization was completed for recycled PCC well graded base course and recycled PCC drainage rock derived from PCC rubble, as well as conventional City granular base and drainage rock aggregates from typical City of Saskatoon stockpiles. Conventional testing completed on the samples included physical properties as required by COS aggregate specifications. Micro-Deval testing was also completed to compare the mechanical breakdown of the aggregates tested. Based on the results of the conventional tests performed, the recycled PCC well graded base and the recycled PCC drainage rock were found to meet COS base and drainage rock specifications, respectively. The recycled PCC well graded base material, recycled PCC drainage rock, COS granular base, and recycled PCC well graded base stabilized with different percentages of cement and slow setting type one (SS-1) asphalt emulsion were the research materials mechanistically tested. These materials were mechanistically tested using triaxial frequency sweep characterization to derive the mechanistic material constitutive relations across all the materials. Five repeat samples were gyratory compacted and tested at room temperature using the rapid triaxial testing. To characterize climatic durability, all the samples were moist cured for 28 days, characterized using the rapid triaxial test; then vacuum saturated and then characterized again using the rapid triaxial test. The mechanistic properties measured for the PCC material showed better climatic durability compared to those measured for the virgin aggregates, particularly after climatic durability testing. Prior to vacuum saturation, the conventional COS granular base had a peak dynamic modulus of 457 MPa. Under the same testing conditions, recycled PCC well graded base unstabilized had a stiffness of 1081 MPa; the stabilized PCC samples with two percent cement had a dynamic modulus of 1542 MPa. The radial micro strain and Poisson’s ratio were reduced for well graded PCC materials both unstabilized and stabilized compared to the conventional COS granular base. The conventional granular base had a peak radial micro strain of 194 compared to the untreated recycled PCC well graded base peak radial micro strain of 54 at the same testing parameters of low stress state at a testing frequency of 10 Hz prior to vacuum saturation. The conventional COS granular base samples failed under high deviatoric stress state at a 0.5 Hz testing frequency prior to vacuum saturation, whereas the PCC materials survived all testing frequencies and stress states. However, after vacuum saturation, the unstabilized recycled PCC well graded base samples failed under high stress state under a 10 Hz testing frequency. To validate field structural performance, two road structures within the City of Saskatoon were used as test sections in which recycled PCC drainage rock was used as a structural drainage layer. The first test section was constructed in the east bound lane of Marquis Drive, and the second was completed at the University of Saskatchewan. Prior to construction of both the Marquis Drive and North Road test sections, both sections were tested for peak surface deflections using the heavy weight deflectometer. Segment 1 of Marquis Drive had an average pre construction surface deflection of 1.85 mm under a primary weight limit. Section 1 of North Road had an average pre construction surface deflection of 1.17 mm under primary weight limit. After construction was complete on both test sections using recycled materials including a PCC drainage layer, HWD testing showed post construction peak deflections were significantly lower than the deflections measured pre construction. Recycled PCC well graded base material performed well in mechanistic laboratory analysis. However, the material was not field tested in this research. Mechanistic laboratory and field analysis indicated that recycled PCC drainage rock aggregates met structural performance requirements. The capital cost analysis showed that using recycled PCC drainage rock can reduce the overall cost of road rehabilitation projects when compared to using conventional virgin aggregates, particularly crushed drainage rock. The Marquis Drive section had a cost savings of $89,000, and the University of Saskatchewan section had a cost savings of $75,800 when recycled materials were used in lieu of virgin aggregates to rehabilitate the pavement structure. In addition, no PCC was disposed of in the landfill, saving the City of Saskatoon tipping fees and extending the life of the landfill. This research showed that the crushed PCC rubble is both technically and economically feasible to use as high quality aggregates in City of Saskatoon streets. Based on the findings of this research, the City of Saskatoon should pursue the use of recycled PCC rubble aggregates in urban road construction.

Thesis (MEngSc)--University of Melbourne, Dept. of Chemical and Biomolecular Engineering, 2010. / Typescript. Includes bibliographical references (p. 105-110)

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Three main objectives have been set for this research. The first is to develop an accurate method for measuring the dielectric constant of PCC using a capacitor probe (C-Probe) that has been recently developed at Virginia Tech and validate it for field application to detect internal PCC flaws such as delamination. The C-Probe consists of two flexible conducting plates, connected to a Network Analyzer, with a specific separation between them. The second is to optimize the C-Probe design configuration for different PCC slab thicknesses. The third objective is to develop a predictive model that correlates the bulk dielectric constant of PCC with its critical parameters (cement, aggregate, and air content). Five calibration methods have been developed and evaluated for the C-Probe to measure the dielectric properties of PCC. This evaluation has demonstrated that open, short, Teflon material (OSM) calibration method is the most appropriate one for the C-Probe. The selected calibration method was used to validate the C-Probe fixture for field application by measuring 1.5 x 1.5 m PCC slabs prepared with different mix properties, thicknesses, and induced deterioration. The C-Probe has been proved to detect induced voids in the PCC slabs. In addition, the effect of steel reinforcement on measurements can be mastered by controlling the penetration of electromagnetic (EM) field in the PCC slabs. The effective penetration depth of the EM field for different C-Probe design configuration was optimized by computer simulation. The results have been used to develop a predictive model that correlates the effective penetration depth with the plates' size, separation between them, and the dielectric constant of the PCC under test. Thus, an optimum design for different desired penetration depth was achieved. Two experimental designs were developed to identify the critical parameters that affect the bulk dielectric constant of PCC. A computer simulation was used to identify the significance of each parameter. A predictive model has been developed to correlate the PCC bulk dielectric constant to the critical parameters. The estimated dielectric constant of PCC using the predictive model was correlated to that obtained by other theoretical mixture models; the predictive model has found to correlate well with Looyenga theoretical mixture model. / Ph. D.

Most engineering as well as pavement materials are composites composed of two or more components to obtain a variety of solid properties to support internal and external loading. The composite materials rely on physical or chemical properties and volume fraction of each component. While the properties can be identified easily, the volume fraction is hard to be estimated due to the volumetric variation during the performance in the field. Various test procedures have been developed to measure the volume fractions; however, they depend on subjective determination and judgment. As an alternative, electromagnetic technique using dielectric constant was developed to estimate the volume fraction. Empirical and mechanistic approaches were used to relate the dielectric constant and volume fraction. While the empirical models are not very accurate in all cases, the mechanistic models require assumptions of constituent dielectric constants. For those reasons, the existing approaches might produce less accurate estimate of volume fraction. In this study, a mechanistic-based approach using the self consistent scheme was developed to be applied to multiphase materials. The new approach was based on calibrated dielectric constant of components to improve results without any assumptions. Also, the system identification was used iteratively to solve for dielectric parameters and volume fraction at each step. As the validation performed to verify the viability of the new approach using soil mixture and portland cement concrete, it was found that the approach has produced a significant improvement in the accuracy of the estimated volume fraction.

The use of recycled concrete aggregates in Portland cement concrete and granular road base or sub-base works has increased steadily all over the world in order to conserve the limited natural aggregate deposits. The recycling of the demolished concrete aggregate for the use in concrete or granular pavement works will not only help to protect the environment but also an economical benefit to the user. The main drawback for the bulk utilization of demolished or recycled aggregate is its characterization and proper quality control during its production. The overall objective of this research was to characterize recycled concrete aggregates (RCA) obtained from a demolished foundation structure and to determine its suitability for Portland Cement Concrete (PCC) works and use as a granular road base or sub-base material. Tests were carried out on RCA samples to determine whether it meets the specification for concrete aggregate material or a granular road base and sub-base materials. Several concrete mixes consisting of 10, 20, 30, 40, 60, and 80 % replacement of natural coarse aggregates (NCA) with RCA were prepared and tested for compressive strength after curing periods of 7, 14, and 28 days. The compressive strength of concrete made with various percentages of RCA decreased with increasing RCA content but it increased with curing period for all concrete mixes. The durability parameters of the natural aggregates and RCA samples were investigated by using sulfate soundness, rapid freeze-thaw and micro-deval tests to ascertain their chemical and abrasive resistance. The California Bearing Ratio (CBR) of RCA base was also compared with that of a natural road base material to determine its suitability for road base or sub-base works. In this study, the flakiness and elongation indices of the RCA were found to be better than that of conventional natural aggregates. The RCA base material had lower maximum dry density, higher optimum moisture content, and low California Bearing Ratio (CBR) value compared to the natural crushed rock base (NCRB) material but was found to be a relatively good road base material.

The use of electromagnetic waves as a nondestructive evaluation technique to evaluate Portland cement concrete (PCC) structures is based on the principle that a change in the structure, composition, or properties of PCC results in a change in its dielectric properties. The coaxial transmission line is one of the few devices that can measure the dielectric properties of PCC at a frequency range of 100-1000 MHz. A coaxial transmission line developed at Virginia Tech was used to study the effect of moisture, type of aggregate, water/cement ratio, curing period, admixture type (microsilica, superplasticizer, and shrinkage admixture), and chloride content on the dielectric properties of PCC. Measurements were conducted in the time domain and converted to the frequency domain using Fast Fourier Transform. The research found that an increase in the moisture content of PCC resulted in an increase in the dielectric constant. Mixes containing limestone aggregate had a greater dielectric constant than those containing granite. The dielectric constant decreased with curing period due to the reduction in free water availability. Mixes containing higher water/cement ratios exhibited a higher dielectric constant, especially in the initial curing period. The admixtures did not significantly affect the dielectric constant after one day of curing. After 28 days of curing, however, all three admixtures had an effect on the measured dielectric constant as compared to control mixes. Chloride content had a significant effect on the loss part of the dielectric constant especially during early curing. A relationship was also established between the chloride permeability (based on conductance measurements) of PCC and its dielectric constant after 75 days of moist curing. / Master of Science

Portland cement concrete (PCC) structures deteriorate with age and need to be maintained or replaced. Early detection of deterioration in PCC (e.g., alkali-silica reaction, freeze/thaw damage, or chloride presence) can lead to significant reductions in maintenance costs. However, it is often too late to perform low-cost preventative maintenance by the time deterioration becomes evident. Non-destructive evaluation (NDE) methods are potentially among the most useful techniques developed for assessing constructed facilities. They are noninvasive and can be performed rapidly. Portland cement concrete can be nondestructively evaluated by electrically characterizing its complex dielectric constant. The real part of the dielectric constant depicts the velocity of electromagnetic waves in PCC. The imaginary part describes the conductivity of PCC and the attenuation of electromagnetic waves, and hence the losses within the PCC media. Dielectric properties of PCC have been investigated in a laboratory setting using a parallel plate capacitor operating in the frequency range of 0.1MHz to about 40MHz. This capacitor set-up consists of two horizontal-parallel plates with an adjustable separation for insertion of a dielectric specimen (PCC). While useful in research, this approach is not practical for field implementation In this research, a capacitance probe has been developed for field application. The probe consists of two planar conducting plates and is made of flexible materials for placement on exposed surfaces of the specimens to be tested. The calibration method of both capacitive systems has been extensively studied to minimize systematic errors in the measurement process. These two measurement systems will be discussed and compared to one another on the basis of sensitivity and measurement repeatability. / Master of Science