In many sub-tropical and tropical and regions of the world, marly soils (marls) and lime or cement stabilization of marl soils are used as a convenient and expedient means for development of foundation base courses and inexpensive wearing courses for transport purposes. The failure of many of these natural and stabilized marls to perform their function have been reported. This study uses physico-chemical (reaction) factors to explain the general basic causes for deterioration of the support capability for these types of soil. / The presence of palygorskite and sepiolite in marl soils provides it with some very unique features in its natural state, and particularly when it is stabilized with lime or cement. Formation of an expansive mineral ettringite as a transformation product of palygorskite increases the swelling potential of the stabilized soil. The exact mechanism of these failures is still not well known. Reactions between lime, alumina (released from the clay fraction of soil) and sulfates present in the soil pore fluid can cause the formation of ettringite. The possible contribution of palygorskite and sepiolite to the post-stabilization failure due to ettringite formation were investigated. / It is shown that the general geotechnical/physical criteria used to evaluate stabilized soil performance not be reliable for the evaluation of stabilized marl due to the possible formation of ettringite and its resultant behaviour. A set of physico-chemical studies, which include specific surface area measurements (SSA) and x-ray diffraction (XRD ), are needed for a more complete and realistic evaluation of the long-term stability of stabilized marl. In this study, a soil washing method for extraction of pure palygorskite or clay fraction from the soil mixture is developed and validated by XRD analysis. Based on the presented results, the pervious classification of marly soils is developed and a new classification for marly soils is proposed. / Following establishment of the significant role of palygorskite and sepiolite, through the experimental studies, the current XRD techniques for quantitative mineral analysis of clay soils are evaluated. The accuracy of these methods are investigated by preparation of a series of artificial soil mixtures. Finally, a quantitative XRD method for marly soils and ettringite is presented. / In the last part of this study, the major difference in the kinetics of ettringite when artificially formed is compared with that of a stabilized soil, and the role of sulfate, alumina, and calcium on the ettringite formation is investigated. Furthermore, for soil stabilization, the contribution of different clay minerals in ettringite formation is investigated. Among the clay minerals studied, palygorskite was found to be the most rich in alumina, providing the highest source of alumina for ettringite formation. (Abstract shortened by UMI.)
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.34667 |
| Date | January 1997 |
| Creators | Ouhadi, Vahid Reza. |
| Contributors | Yeng, R. N. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Civil Engineering and Applied Mechanics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001617722, proquestno: NQ37010, Theses scanned by UMI/ProQuest. |
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