Matching Items (4)
Filtering by

Clear all filters

150127-Thumbnail Image.png

Stabilization and imaging of cohesionless soil specimens

Description
This dissertation describes development of a procedure for obtaining high quality, optical grade sand coupons from frozen sand specimens of Ottawa 20/30 sand for image processing and analysis to quantify soil structure along with a methodology for quantifying the microstructure from the images. A technique for thawing and stabilizing…

This dissertation describes development of a procedure for obtaining high quality, optical grade sand coupons from frozen sand specimens of Ottawa 20/30 sand for image processing and analysis to quantify soil structure along with a methodology for quantifying the microstructure from the images. A technique for thawing and stabilizing frozen core samples was developed using optical grade Buehler® Epo-Tek® epoxy resin, a modified triaxial cell, a vacuum/reservoir chamber, a desiccator, and a moisture gauge. The uniform epoxy resin impregnation required proper drying of the soil specimen, application of appropriate confining pressure and vacuum levels, and epoxy mixing, de-airing and curing. The resulting stabilized sand specimen was sectioned into 10 mm thick coupons that were planed, ground, and polished with progressively finer diamond abrasive grit levels using the modified Allied HTP Inc. polishing method so that the soil structure could be accurately quantified using images obtained with the use of an optical microscopy technique. Illumination via Bright Field Microscopy was used to capture the images for subsequent image processing and sand microstructure analysis. The quality of resulting images and the validity of the subsequent image morphology analysis hinged largely on employment of a polishing and grinding technique that resulted in a flat, scratch free, reflective coupon surface characterized by minimal microstructure relief and good contrast between the sand particles and the surrounding epoxy resin. Subsequent image processing involved conversion of the color images first to gray scale images and then to binary images with the use of contrast and image adjustments, removal of noise and image artifacts, image filtering, and image segmentation. Mathematical morphology algorithms were used on the resulting binary images to further enhance image quality. The binary images were then used to calculate soil structure parameters that included particle roundness and sphericity, particle orientation variability represented by rose diagrams, statistics on the local void ratio variability as a function of the sample size, and the local void ratio distribution histograms using Oda's method and Voronoi tessellation method, including the skewness, kurtosis, and entropy of a gamma cumulative probability distribution fit to the local void ratio distribution.
ContributorsCzupak, Zbigniew David (Author) / Kavazanjian, Edward (Thesis advisor) / Zapata, Claudia (Committee member) / Houston, Sandra (Committee member) / Arizona State University (Publisher)
Created2011
149822-Thumbnail Image.png

Novel biopolymer treatment for wind induced soil erosion

Description
It is estimated that wind induced soil transports more than 500 x 106 metric tons of fugitive dust annually. Soil erosion has negative effects on human health, the productivity of farms, and the quality of surface waters. A variety of different polymer stabilizers are available on the market for fugitive…

It is estimated that wind induced soil transports more than 500 x 106 metric tons of fugitive dust annually. Soil erosion has negative effects on human health, the productivity of farms, and the quality of surface waters. A variety of different polymer stabilizers are available on the market for fugitive dust control. Most of these polymer stabilizers are expensive synthetic polymer products. Their adverse effects and expense usually limits their use. Biopolymers provide a potential alternative to synthetic polymers. They can provide dust abatement by encapsulating soil particles and creating a binding network throughout the treated area. This research into the effectiveness of biopolymers for fugitive dust control involved three phases. Phase I included proof of concept tests. Phase II included carrying out the tests in a wind tunnel. Phase III consisted of conducting the experiments in the field. Proof of concept tests showed that biopolymers have the potential to reduce soil erosion and fugitive dust transport. Wind tunnel tests on two candidate biopolymers, xanthan and chitosan, showed that there is a proportional relationship between biopolymer application rates and threshold wind velocities. The wind tunnel tests also showed that xanthan gum is more successful in the field than chitosan. The field tests showed that xanthan gum was effective at controlling soil erosion. However, the chitosan field data was inconsistent with the xanthan data and field data on bare soil.
ContributorsAlsanad, Abdullah (Author) / Kavazanjian, Edward (Thesis advisor) / Edwards, David (Committee member) / Zapata, Claudia (Committee member) / Arizona State University (Publisher)
Created2011
151072-Thumbnail Image.png

Endurance limit for HMA based on healing phenomenon using viscoelastic continuum damage analysis

Description

Perpetual Pavements, if properly designed and rehabilitated, it can last longer than 50 years without major structural rehabilitation. Fatigue endurance limit is a key parameter for designing perpetual pavements to mitigate bottom-up fatigue cracking. The endurance limit has not been implemented in the Mechanistic Empirical Pavement Design Guide software, currently…

Perpetual Pavements, if properly designed and rehabilitated, it can last longer than 50 years without major structural rehabilitation. Fatigue endurance limit is a key parameter for designing perpetual pavements to mitigate bottom-up fatigue cracking. The endurance limit has not been implemented in the Mechanistic Empirical Pavement Design Guide software, currently known as DARWin-ME. This study was conducted as part of the National Cooperative Highway Research Program (NCHRP) Project 9-44A to develop a framework and mathematical methodology to determine the fatigue endurance limit using the uniaxial fatigue test. In this procedure, the endurance limit is defined as the allowable tensile strains at which a balance takes place between the fatigue damage during loading, and the healing during the rest periods between loading pulses. The viscoelastic continuum damage model was used to isolate time dependent damage and healing in hot mix asphalt from that due to fatigue. This study also included the development of a uniaxial fatigue test method and the associated data acquisition computer programs to conduct the test with and without rest period. Five factors that affect the fatigue and healing behavior of asphalt mixtures were evaluated: asphalt content, air voids, temperature, rest period and tensile strain. Based on the test results, two Pseudo Stiffness Ratio (PSR) regression models were developed. In the first model, the PSR was a function of the five factors and the number of loading cycles. In the second model, air voids, asphalt content, and temperature were replaced by the initial stiffness of the mix. In both models, the endurance limit was defined when PSR is equal to 1.0 (net damage is equal to zero). The results of the first model were compared to the results of a stiffness ratio model developed based on a parallel study using beam fatigue test (part of the same NCHRP 9-44A). The endurance limit values determined from uniaxial and beam fatigue tests showed very good correlation. A methodology was described on how to incorporate the second PSR model into fatigue analysis and damage using the DARWin-ME software. This would provide an effective and efficient methodology to design perpetual flexible pavements.
ContributorsZeiada, Waleed (Author) / Kaloush, Kamil (Thesis advisor) / Witczak, Matthew W. (Thesis advisor) / Zapata, Claudia (Committee member) / Mamlouk, Michael (Committee member) / Arizona State University (Publisher)
Created2012
149502-Thumbnail Image.png

Evaluation of the effects of aging on asphalt rubber

Description
Oxidative aging is an important factor in the long term performance of asphalt pavements. Oxidation and the associated stiffening can lead to cracking, which in turn can lead to the functional and structural failure of the pavement system. Therefore, a greater understanding of the nature of oxidative aging in asphalt…

Oxidative aging is an important factor in the long term performance of asphalt pavements. Oxidation and the associated stiffening can lead to cracking, which in turn can lead to the functional and structural failure of the pavement system. Therefore, a greater understanding of the nature of oxidative aging in asphalt pavements can potentially be of great importance in estimating the performance of a pavement before it is constructed. Of particular interest are the effects of aging on asphalt rubber pavements, due to the fact that, as a newer technology, few asphalt rubber pavement sections have been evaluated for their full service life. This study endeavors to shed some light on this topic. This study includes three experimental programs on the aging of asphalt rubber binders and mixtures. The first phase addresses aging in asphalt rubber binders and their virgin bases. The binders were subjected to various aging conditions and then tested for viscosity. The change in viscosity was analyzed and it was found that asphalt rubber binders exhibited less long term aging. The second phase looks at aging in a laboratory environment, including both a comparison of accelerated oxidative aging techniques and aging effects that occur during long term storage. Dynamic modulus was used as a tool to assess the aging of the tested materials. It was found that aging materials in a compacted state is ideal, while aging in a loose state is unrealistic. Results not only showed a clear distinction in aged versus unaged material but also showed that the effects of aging on AR mixes is highly dependant on temperature; lower temperatures induce relatively minor stiffening while higher temperatures promote much more significant aging effects. The third experimental program is a field study that builds upon a previous study of pavement test sections. Field pavement samples were taken and tested after being in service for 7 years and tested for dynamic modulus and beam fatigue. As with the laboratory aging, the dynamic modulus samples show less stiffening at low temperatures and more at higher temperatures. Beam fatigue testing showed not only stiffening but also a brittle behavior.
ContributorsReed, Jordan (Author) / Kaloush, Kamil (Thesis advisor) / Mamlouk, Michael (Committee member) / Zapata, Claudia (Committee member) / Arizona State University (Publisher)
Created2010