Addressing Clay Mineralogy Effects on Performance of Chemically Stabilized Expansive Soils Subjected to Seasonal Wetting and Drying

Premature failures in chemically stabilized expansive soils cause millions of dollars in maintenance and repair costs. One of the reasons for these failures is the inability of existing stabilization design guidelines to consider the complex interactions between clay minerals and the stabilizers. It is vital to understand these complex interactions, as they are responsible for the strength improvement and swell/shrink reduction in these soils, in turn affecting the overall health of the infrastructure. Hence, this research study examined the longevity of chemically stabilized expansive soils subjected to wetting/drying conditions with a major focus on clay mineralogy. Eight different natural soils with varying clay mineralogy were subjected to wetting/drying durability studies after stabilizing with chemical additives including quicklime and cement. Performance indicators such as volumetric strain and Unconfined compressive strength trends were monitored at regular intervals during the wetting/drying process. It was observed that clayey soils dominant in the mineral Montmorillonite were susceptible to premature failures. It was also noted that soils dominant in other clay minerals exhibited early failures at lower additive contents. Also, an attempt was made for the first time to address the field implications of the laboratory studies by developing a correlation that predicts service life in the field based on clay mineralogy and stabilizer dosage

Effect of intrinsic microscopic properties and suction on swell characteristics of compacted expansive clays

© 2018 Elsevier Ltd The complex swelling mechanism in expansive clays during moisture ingress can be succinctly explained by an examination of their core mineralogy, microfabric, grain size and suction response. This note has attempted to investigate these influential factors on five different expansive clay samples to enable further understanding of swell behaviour. Laser diffractometry tests were performed on the expansive clays to determine the clay-sized particle structure

E-Intelligence form design and Data Preprocessing in Health Care

I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii Clinical data systems continue to grow as a result of the proliferation of features that are collected and stored. Demands for accurate and well-organized clinical data have intensified due to the increased focus on cost-effectiveness, and continuous quality improvement for better clinical diagnosis and prognosis. Clinical organizations have opportunities to use the information they collect and their oversight role to enhance health safety. Due to the continuous growth in the number of parameters that are accumulated in large databases, the capability of interactively mining patient clinical information is an increasingly urgent need to the clinical domain for providing accurate and efficient health care. Simple database queries fail to address this concern for several problems like the lack o

Evaluation of swell behaviour of expansive clays from specific moisture capacity

Current swell characterization techniques used to interpret the mechanical volume change occurring during the swelling process are not successful due to lack of inclusion of influential properties. Accurate prediction of swelling behaviour allows us to design more efficiently and with better reliability. This research aims at developing a more comprehensive framework to predict swell potential. Laboratory studies are conducted on five natural expansive soils with different degree of expansiveness. Initial studies include determination of basic soil characterization, swell strains and swell pressures at their compacted state along with their inherent mineralogy. Later, replicate samples were studied for soil water characteristic curves using standard pressure cell apparatus and filter paper techniques. The path traversed by the specimen during swelling process is representative of the soil water characteristic curve of the same specimen. Hence, studies are pursued to understand the relationship between degree of expansiveness and the specific moisture capacity relative to that particular range of suction head. Test results showed that the degree of expansion represented by swelling strain or swelling pressure is proportional to the specific moisture capacity determined during the swelling process

Evaluation of Swell Behavior of Expansive Clays from Internal Specific Surface and Pore Size Distribution

The interdependency of microsoil fabric-related properties and swell/shrink behavior of expansive soils needs to be identified to achieve a more thorough and accurate prediction of heave of expansive soils. In a recent research study, two microsize-related properties of a soil—pore size distribution and specific surface area—were identified and examined in an effort to address their synergistic effects on swelling behavior of soils. To study this aspect in detail, eight natural expansive clayey soils from known expansive soil regions were sampled and studied by using two test methods: conventional one-dimensional vertical swell tests and novel three-dimensional volumetric swell strain tests. Microinternal structural details, including pore void distribution, were obtained from mercury intrusion porosimetry (MIP) studies on compacted soil specimens. Specific surface area (SSA) details of the same soils were determined using the chemical ethylene glycol monoethyl ether (EGME) method. Attempts were made to predict macroswell properties, using both pore and surface area properties. Modeling analyses and results showed that the swelling behavior of the clays was dependent on a newly introduced parameter that accounted for both clay mineralogy constituents and internal pore distribution of the soils. The new swell property models showed accurate predictions of measured swell strains of the present soils, depicting the importance of including mineralogy and pore fabric details in a given soil

Effect of Density on the Pore Size and Pore Volume of Expansive Clays

It is a well established fact that, both pore size and volume govern the density and particle size characteristics of any soil. For clayey soils, higher densities followed by lesser particle size result in low pore volumes. However, not many studies were conducted on how these pore characteristics alter with variations in density and particle size. This paper presents the results of a study conducted to understand the effect of compaction effort on the pore size and pore volume characteristics on two semi-arid expansive clays. These two clays selected represent soils with different degrees of expansivity, particle sizes and mineralogy. Mercury Intrusion Porosimetry tests were conducted to study the pore size characteristics at 100, 95, 90, 85, 80, 75 and 70% of maximum dry density (MDD) at corresponding optimum moisture content values. Both pore volume and pore size were analysed with varying density characteristcs and particle sizes. It was observed that in case of samples conducted at 100% MDD, about 50% of the pores were larger than 0.1 μm and this value increased with reduction in density. The current observations assume practical importance especially in the wake of microbial treatments for soils where the the passage of microbes depends on the pore size and more specifically pore throat size

Effect of Unit Weight on Porosity and Consolidation Characteristics of Expansive Clays

This study investigated the relationship between pore characteristics and unit weight of clayey soils. This relationship was particularly important in case of expansive soils, as the pore characteristics determine moisture flux boundaries, which in turn represent volume change behavior. Current research tried to evaluate the effect of compaction unit weight on the pore size and pore volume along with consolidation and swell characteristics on two expansive clays from semi-arid environment. The two selected clays represent soils with different degrees of expansion, particle size and mineralogy. Pore size characterization for these two soils was performed using Mercury Intrusion Porosimetry, while swell and consolidation characteristics were determined using a conventional oedometer test. Samples for both tests were compacted at different unit weights including, 100, 95, 90, 80, 75, and 70 % of maximum dry unit weight (MDUW) obtained from standard proctor. The compaction water content was kept constant for all unit weight levels. Both pore volume and pore size distribution was analyzed with varying unit weight characteristics and particle sizes. In addition, swell strains and compression indices were studied with varying unit weight of compacted specimens. It was observed that, in the case of samples compacted at 100 % MDUW, about 50 % of the pores were larger than 0.1 µm, and this value increased with reduction in unit weight. Current research is of practical importance, especially in the wake of microbial treatments for clayey soils where the passage of microbes depends on the pore size and more specifically pore throat size

Long-Term Durability Studies on Chemically Treated Reclaimed Asphalt Pavement Material as a Base Layer for Pavements

For several years reclaimed asphalt pavement (RAP) material has been used as a construction material in hot-mix asphalt (HMA) to reduce material costs and stabilize pavements. Of the 45 million tons of RAP produced every year in the United States, only 33% is being used in HMA. Recent studies have demonstrated that RAP can be used effectively in base layers when it is blended with aggregate base materials and stabilized with cement or fly ash additives. This adoption in the pavement base layer helps maximize the reutilization of RAP material and minimize its disposal in landfills, thereby making it an environmentally friendly practice. However, studies reported so far addressed only the strength and stiffness characteristics of stabilized RAP in base layers in the short term, and not many studies have addressed its long-term behavior. In this study the long-term durability of untreated as well as stabilized specimens was tested by conducting standard durability testing to replicate the moisture fluctuations in the field from seasonal variations. In addition, leachate studies were conducted to examine the effect of rainfall infiltration on the leachability of the cement or fly ash stabilizer from stabilized RAP mixtures. Durability studies revealed a very low volumetric change and good retaining strength at the end of three, seven, and 14 cycles for RAP material from the El Paso, Texas, area, and leachate tests proved that the leaching of cement or fly ash stabilizer from RAP mixes cannot be considered to be a concern for long-term performance. However, approximately 2 years of field infiltration were replicated in the laboratory in this study. Of the several RAP mixtures studied, the mixture composed of 60% RAP and 40% base material with 2% cement was identified as an effective long-term-performing mixture