Investigation of x-ray computed tomography for Portland cement phase quantification

Cementitious materials are often characterized through the use of advanced analytical techniques to understand the macro-, micro-, and nano-scale properties, including phase formation during hydration, and subsequent potential deterioration mechanisms which can affect service life. A major limitation with using such analytical techniques to quantify solid phases in cementitious systems is that many techniques are destructive in nature. If one wants to monitor changes over time, samples must be extracted from different locations of the same sample, or from a different sample, at different times. This limitation can hinder the ability continually monitor the desired property. One method to extract quantifiable information non-destructively is x-ray computed tomography (x-ray CT). X-ray CT is a non-destructive, non-contact technique that uses computer-processed x-rays to produce three-dimensional tomographic images of specific zones of a sample. This technique has been successfully used in many different aspects of research, including medicine, geo-sciences, and materials science. The use of x-ray CT has been applied to cementitious systems but has been predominately limited to qualitative or semi-quantitative analysis. Quantification of cementitious properties has been hindered through two means, spatial resolution and low contrast between solid phases, including the unhydrated and hydrated phases. This low contrast has often led to quantification of void space within the cementitious sample. The work presented in this dissertation addresses methods to resolve the expected low contrast in x-ray CT images on cementitious and the potential for segmentation of the four main hydration products found in portland cement. This was achieved through an investigation of different image segmentation algorithms and a creative use of contrast agents to be bound into specific hydration products using a synchrotron x-ray CT. Advancements in x-ray CT optics and data collection are continually improving image resolution, therefore it is not discussed in this dissertation. Published literature on the use of x-ray CT in cementitious materials often does not include a thorough description of the image processing procedures used for analysis. The use of arbitrary, histogram-based threshold values can lead to biased segmentation and misclassification of the voxels in the image volume. Presented in this dissertation is a method to deconstruct the greyscale values of a histogram into individual Gaussian curves in an unbiased manner. The greyscale values of laboratory synthesized calcium-silicate-hydrate (C-S-H), calcium hydroxide (CH), monosulfate (AFm), and ettringite (AFt) were determined to provide a baseline for threshold values. Pure phase, binary, and quaternary mixture samples of the four aforementioned phases were studied. A Gaussian probability density function was applied to each phase and proportioned to the known mass of each phase in the binary and quaternary mixtures. Intersections of the Gaussian curves was determined as the threshold value. Quantification of binary mixtures was successfully done with exception to C-S-H and AFm mixtures. Low contrast between the phases was observed leading to difficulties accurately quantifying such mixtures. Similar success was observed in quaternary mixtures of phases. However, difficulties in segmentation were compounded segmenting AFm, C-S-H, and CH in these mixtures. One method to resolve low contrast is to incorporate the use of contrast agents. Success in the medical field, and other limited successes in geo-sciences, provided the motivation to determine methods to incorporate contrast agents into portland cement hydrates. Literature reports a myriad of ions which can be incorporated into the structure of C-S-H, AFm, and AFt through various mechanisms, including substitution and absorption. Due to the limitations in segmenting AFm and C-S-H in their pure form, investigations for incorporating contrast agents to improve segmentation was done. Iodine was selected as the contrast agent to be substituted for the sulfate ion in AFm. Dual energy scans above and below the absorption edge of iodine was done, and the use of image subtraction allowed for quick and accurate segmentation of the C-S-H and modified AFm phases. However, difficulties segmenting C-S-H and CH were observed in quaternary mixtures of AFt, CH, C-S-H, and a modified AFm using the Gaussian deconstruction method to determine threshold values for segmentation. Lastly, due to the difficulties achieving consistent results during segmentation when using histogram-based threshold values, a study determining the feasibility of local segmentation algorithms was done on binary and quaternary mixtures of the four phases. These algorithms often result in more desirable results by accounting for the spatial arrangement of the greyscale values throughout the image volume. Two local segmentation algorithms, watershed and Bayesian Markov random fields, were compared to the Gaussian deconstruction method. Results indicated both local segmentation algorithms resulted in more accurate quantification of the four phases, thus providing promise for future applications to hydrating portland cement

Watershed response to western juniper control

Western juniper (Juniperus occidentalis) encroachment has been associated with increased soil loss and reduced infiltration resulting in the loss of native herbaceous plant communities and the bird and animal species that rely on them. Hydrologically, however, change in water yield has been linked with the amount of annual precipitation a site received. Studies published in the 1970’s and 1980’s, suggest that a minimum 4500 mm (18 inches) of annual precipitation was necessary before an increase in water yield manifested itself following vegetation manipulation. In 1993, a paired watershed study was initiated in the Camp Creek drainage, a tributary of the Crooked River of central Oregon, to evaluate the impacts of cutting western juniper on the hydrologic function of those sites. The study involved a paired watershed approach using watersheds of approximately 110 hectares (270 acres) each to evaluate changes in a system’s water budget following the reduction of western juniper. The 30 year average annual precipitation for the area is 3500 mm (13.75) and during the study period, annual precipitation ranged from 80 percent to 129 percent of average. In 2005, following 12 years of pretreatment monitoring in the 2 watersheds (Mays and Jensen) all post-European aged juniper (juniper .05), increased days of recorded ground water by an average of 41 days (alpha > .05) and increased the relative availability of late season soil moisture at soil depths of .76 m (27 inches) (alpha > 0.1). Ephemeral channel flow did not show a predictable trend during 2 years of post treatment measurements. Channel flow is dependent on spring snow melt and severe summer thunderstorm activity. When winter soils were greater than 0 degrees Celsius (32 degrees F), the source of channel flow in Mays was observed to be seepage from the channel banks. Channel flow in Jensen appeared to be a result of rock forcing subsurface flows to the surface. Vegetative responses showed significant increases in perennial forb canopy cover (alpha > .01) and annual forb and annual grass basal cover (alpha > .05). Increases were also found in reduction of percent bare ground and increase in shrub cover, but were not significant. A statistically insignificant decrease in perennial grass cover was noted in the treated watershed however a large amount of reproductive culms were noted in the treated watershed in 2007 compared to the control watershed. Hillslope erosion and channel morphology showed no predictable trend following treatment. Inherent differences in channel morphology between the two watershed prior to treatment existed. This difference may be a product of the two channels being at different evolutionary or successional stages relative to each other and thus indicating that channel recovery would be different for each watershed. The Camp Creek project illustrated that for this system, managing vegetation for water yield may be obtainable at a much lower precipitation threshold than what was previously reported in the literature

Ecohydrologic Connections in Semiarid Watershed Systems of Central Oregon USA

An improved understanding of ecohydrologic connections is critical for improving land management decisions in water-scarce regions of the western United States. For this study, conducted in a semiarid (358 mm) rangeland location in central Oregon, we evaluated precipitation-interception-soil moisture dynamics at the plot scale and characterized surface water and groundwater relations across the landscape including areas with and without western juniper (Juniperus occidentalis). Results from this study show that juniper woodlands intercepted up to 46% of total precipitation, altering soil moisture distribution under the canopy and in the interspace. Results indicate that precipitation reaching the ground can rapidly percolate through the soil profile and into the shallow aquifer, and that strong hydrologic connections between surface and groundwater components exist during winter precipitation and snowmelt runoff seasons. Greater streamflow and springflow rates were observed in the treated watershed when compared to the untreated. Streamflow rates up to 1020 L min(-1) and springflow rates peaking 190 L min(-1) were observed in the watershed where juniper was removed 13 years ago. In the untreated watershed, streamflow rates peaked at 687 L min(-1) and springflow rates peaked at 110 L min(-1). Results contribute to improved natural resource management through a better understanding of the biophysical connections occurring in rangeland ecosystems and the role that woody vegetation encroachment may have on altering the hydrology of the site

Western juniper : its impact and management in Oregon rangelands

This publication acquaints you with the biology and ecology of western juniper and how the tree affects the landscapes it occupies.Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalo

The effect of western juniper on the estrous cycle in beef cattle

Numerous evergreen trees and shrubs contain labdane acids, including isocupressic acid, which can cause late-term abortions in cattle. Recent research has shown that the bark from western juniper trees can also cause late-term abortions in cattle. Additionally, ranchers have observed that cattle in western juniper-infested rangelands tend to have decreased conception rates. The objective of this study was to determine if western juniper alters the estrous cycle of cattle. Fourteen heifers (10 treated and 4 control) were monitored for 74 days for signs of normal estrous behavior, with a 21 day feeding trial with western juniper bark from days 28-48, after which the cattle were bred naturally with a bull. The cattle were checked for pregnancy 30 days after all cattle had been bred. The data from this study indicate that exposure to western juniper bark does not affect normal estrus, estrous cycle or conception rates of cattle.Keywords: Cattle, Isocupressic acid, Estrus, Abortion, Western juniper, Estrous cycl

Shrinkage of self-compacting concrete. A comparative analysis

Self-compacting concrete (SCC) is a concrete type that does not require vibration for placing and compacting. SCC possesses special technical features and properties that recommend its application in many jobs. Nevertheless, in some situations, it has been observed an inadequate behaviour of the material at early ages due to shrinkage. The existing shrinkage prediction models were developed for standard concrete. In this paper three SCC mixtures, with different compressive strength, are studied in terms of autogenous and total shrinkage. The results are compared with the Eurocode 2 model. For the studied mixtures it was found that this model underestimates the autogenous shrinkage, while the total shrinkage is generally overestimated.Fundacao para a Ciencia e a Tecnologia (FCT), Portugal [UID/MULTI/00308/2013]info:eu-repo/semantics/publishedVersio

Treatment of Benign Paroxysmalvertigo: Necessity of Post-Maneuver Prohibition

Benign paroxysmal positional vertigo (BPPV), characterized by a history of brief attacks of intense positional vertigo and rotary nystagmus, results from otoconial migration into the semicircular canals, making the sensory structures in the canal gravity sensitive. Treatment methods include positioning maneuvers, which return the otoconia back into the otolith, and typically include a variety of activity limitations for the subsequent 24-48 hours. Previous studies suggest BPPV treatment can be successful without any limitations of the patient post- therapy. The purpose of this study was to determine the necessity of post-maneuver restrictions on BPPV patients treated with the Canalith Repositioning Maneuver. Twenty participants were identified as having BPPV of the posterior canal and treated with the Canalith Repositioning Maneuver. During post-maneuver instruction, the ten participants assigned to the restricted group were provided with typical instructions. Ten participants assigned to the non-restricted group were given no post-maneuver restrictions. At the one-week post-treatment follow-up, all patients were free of vertigo and/or nystagmus. Results indicated that given two groups of subjects matched for age, gender, and symptoms, post-maneuver restrictions are not necessary for successful outcome using the CRM to treat posterior-canal BPPV

Internal curing of high-performance concrete for bridge decks

High performance concrete (HPC) provides a long lasting, durable concrete that is typically used in bridge decks due to its low permeability, high abrasion resistance, freeze-thaw resistance and strength. However, this type of concrete is highly susceptible to the deleterious effects of both autogenous and drying shrinkage. Both types of shrinkage occur when water leaves small pores , (< 50 nm) in the paste matrix to aid in hydration or is lost to the surrounding environment. Autogenous deformation (self-desiccation) occurs as the internal relative humidity decreases due to hydration of the cementitious material. Drying (and subsequent shrinkage) occurs when water is lost to the environment and continues until the internal relative humidity is equivalent to the ambient relative humidity. Typically, the magnitude of autogenous shrinkage is less than that of drying shrinkage. These two types of shrinkage do not act independently, and the total shrinkage is the aggregation of the two shrinkage mechanisms. It is imperative to minimize the amount of shrinkage in restrained members, such as bridge decks, to reduce the cracking potential. Various methods have been researched to minimize both types of shrinkage. Two methods to that have been reported to reduce shrinkage were selected for further research; internal curing using pre-soaked lightweight fine aggregate (LWFA) and shrinkage reducing admixtures (SRAs). The purpose of this study was to determine the long-term drying shrinkage performance of these two methods while reducing the external curing duration of 14 days for new bridge deck construction as specified by the Oregon Department of Transportation. In addition to monitoring drying shrinkage, durability testing was performed on concrete specimens to ensure these shrinkage mitigation methods performed at levels similar to concrete with the current mixture design. Freeze-thaw testing, permeability testing and restrained drying shrinkage testing were conducted. It was concluded that the combination of SRAs and pre-soaked LWFA was the most effective method to reduce longterm drying shrinkage for all curing durations (1, 7, and 14 day). Additionally, for durability testing, it was found that the use of SRAs performed the best in freeze-thaw testing, chloride permeability and restrained shrinkage