Date of Award

8-1-2019

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Kolay, Prabir

Abstract

Soft soil stabilization frequently uses cement, lime, fly ash, etc., but very limited studies were conducted on the long-term durability of stabilized soil. The present research work deals with the long-term durability of commercially available soil (i.e., EPK clay) stabilized with ordinary Portland cement and polypropylene fiber using a realistic approach, where the effect can be noticed in each weathering cycle. In the present study, two different tests (i.e., wetting-drying and freezing-thawing) were conducted to analyze the long-term durability of stabilized soil. Cycles of higher temperature followed by rainfall, which generally occurs in southern states of the US, were analyzed by the wetting-drying test; and on the other hand, cycles of freezing temperature followed by normal temperature, which generally occurs in northern states of the US and Canada, were analyzed by the freezing-thawing test. For the mid-continental region where freezing, normal, and higher temperature followed by rainfall are expected to occur, hence both the test method i.e., wetting-drying and freezing-thawing, were suggested. Laboratory experimental investigations were conducted to find the percentage loss of stabilized soil during wetting-drying and freezing-thawing tests, which were used as a durability indicator for cement and cement-fiber stabilized soil. Stabilized samples were subjected to harsh environmental conditions in a laboratory set up, and their deterioration was observed and studied after each wetting-drying and freezing-thawing cycle. In the real world, stabilized soil encounters seasonal cycles of monsoon and summer in long run of its service life which was simulated in rapid weathering cycles in laboratory setup. EPK clay samples were stabilized with different percentages of cement, and a mix of cement-fiber combination and were subjected to 12 cycles of wetting-drying and freezing-thawing cycles separately to determine the percentage loss of soil in accordance with the ASTM standards. Finally, based on percentage loss of soil of those stabilized samples which survived up to 12 cycles of weathering action, the optimum content of stabilizing agent was determined for wetting-drying and freezing-thawing tests. Results of wetting-drying tests indicate that EPK clay stabilized with ordinary Portland cement and fiber combination survived up to 12 cycles, but only 10% cement + 0.5% fiber was durable against wetting-drying based on percentage loss. For all the samples stabilized with 10% cement + 0.5% fiber combination, the percentage loss of soil when subjected to durability test was less than 7%, which satisfy the Portland Cement Association’s (PCAs) durability specification. The results of freezing-thawing tests indicate that the EPK clay stabilized with 10% cement, 5% cement + 0.5% fiber, and 10% cement + 0.5% fiber survived up to 12 cycles and were durable against freezing-thawing based on percentage loss of soil i.e., less than 7% which satisfy the Portland Cement Association’s durability specification.

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