Improvement of tikrit gypseous soil using soil replacement and additives
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Date
2015-05-01
Authors
Lamyaa Najah Snodi
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Abstract
Gypsum has posed great problems in construction that lead to reduction in shear strength and sudden collapse whenever it mixes with water or any liquid. This study investigates the characteristics of Gypseous soil from Tikrit, Iraq where the gypsum content of approximately 51 % of soil. This Gypseous soil is classified as poorly graded sand (SP) according to Unified Soil Classification System (USCS). The soils used for soil replacements method are of Silty Sand (SM) and Low plasticity Sandy Silt (ML). The percentages of soil replacement of 5 to 50 % by weight of Gypseous soil were studied. The chemical additives were added such as Styrene Butadiene Rubber (SBR) and Lime at 1.25 %, 2.5 % and 5 %, as for Geopolymer was used at 2.5 % for the improvement of this Gypseous soil. Curing times of 7, 14 and 28 days were considered for the soil replacement and some sample were used to study the leaching effect by means of studying the variation of total soluble salts (T.S.S %). Physical and engineering tests for all the soil replacement were done accordingly, the result shows that the plasticity of treated soil was increased and improved the soil workability. The compaction test result shows that as it decreases in maximum dry density, the optimum moisture content increase with greater content of additives used. The permeability coefficient and the collapsibility were found to be decreases when using soil replacement method, whereas when added chemical additives it decreases. Strength value of soil was improved for both soil replacements (SM and ML) at 10% of Gypseous soil. The results imply that Lime additives provide beneficial effect for soil stabilization and improved workability and its strength. The X-Ray Diffraction (XRD) test result confirmed the chemical interactions show that the new phases consists of new cementation products of the chemical additives with Gypseous soil.