Abstract
Expansive soil shows frequent volume changes with the changes in the moisture content, causing severe problems to the civil engineering structures. Consequently, the measurements of swelling properties including free swell index and swelling pressure are extremely important. Several attempts are being made all over the world to control the swell-shrink behavior of expansive soils. Many researches have investigated how to overcome the problems of such soils by means of using different additives such as cement, lime, steel fibers, stone dust and fly ash. This study is directed towards the improvement of expansive soil with a new, inexpensive and environmentally friendly additive. In this study, the effect of using micro silica fume to stabilize the soil was investigated through a laboratory study. Test results showed that, the micro silica fume can considerably decrease the free swell index value by 69% at 25% micro silica fume content. Also, the swelling pressure is reduced from 410 kN/m2 to nearly 330 kN/m2 and 302 kN/m2 at micro silica fume content of 5% and 25%, respectively. This demonstrates the effectiveness of the proposed addition in the expansive soils improvement. This improvement technique can be used in different civil engineering construction projects including slope stabilization and road embankments.
Highlights
Swelling soils is the generic description of all soils containing montmorillonite mineral
As can be seen from this figure, the percentage of smectite present inside the expansive soil remains the same with increasing the micro silica fume content till 25%
This indicates that there is no changes in the mineralogical characteristics of the treated soil due to the fact that adding micro silica fume is only physical mixing without any effect on the crystalline structure of the expansive soil
Summary
Swelling soils is the generic description of all soils containing montmorillonite mineral. High plastic clays are defined as fine-grained clays with a plasticity index greater than 35% This soil type is prone to remarkable volumetric changes due to changes in the moisture content. Direct measurements of the swelling potential using laboratory and/or field tests, are essential once a soil shows indications of swelling behavior. Improvement methods such as soil replacement, compaction control and chemical stabilization showed significant reduction in the swelling potential. Several researchers proposed different techniques to improve the geotechnical properties of expansive soils by adding dust shield polymer [6], waste tire rubber [7], nanoclay [8] and egg shell powder mixed with plastic wastes [9] and with corn cob ash [10]
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