Abstract
Expansive soil is a source of risk to the foundations or subgrade engineering. Stabilization of expansive soil is imperative for practical engineering. A series of laboratory experiments were performed to analyze the physical-mechanical properties and microstructures of stabilized soil. Three stabilizers used in this study are fly ash, sand, and basalt fiber. Different percentages of fly ash (0, 5, 10, 15, and 20%), sand (0, 8, 16, and 24%), and basalt fiber (0 and 0.4%) were added by weight into natural soil. Experimental results indicate that the optimum moisture content of stabilized soil increases with the increase of fly ash content for a given sand content, whereas the maximum dry density shows a decreasing trend. The variation trend of optimum moisture content and maximum dry density turns reverse with the increase of sand content for a given fly ash content. Plasticity index is decreased by both increasing fly ash content and sand content. It is found that the maximum unconfined compressive strength and optimum growth rate of strength are obtained by selected mixtures of 10% fly ash, 8% sand, and 0.4% basalt fiber contents. As the analysis of complementary effect suggests, most of the mixt treatments applied in this study have produced good results associated with the strength enhancement of expansive soil. In line with the results of SEM tests, the connection among clay particles has been enhanced through the generation of hydration products (C-S-H and AFt) of fly ash. The filling effect of sand has increased the integrality and compactness of stabilized soil. Moreover, the gripping effect between fibers and soil particles notably improves the strength of stabilized soil. The effect of sand on reinforced soil with 0.4% basalt fiber increases the interfacial force between fibers and soil particles.
Highlights
Expansive soil is a kind of high-plasticity clay with strong hydrophilic mineral components, such as montmorillonite and illite
Some researchers have investigated various methods for expansive soil stabilization. e effect of lime, cement, and fly ash on the physical-mechanical behaviors of soil samples is confirmed by the research of modified methods on expansive soils
When fly ash is added into expansive soils, the reaction with clay particles will improve the strength, consolidation, and drainage characteristics [13]
Summary
Expansive soil is a kind of high-plasticity clay with strong hydrophilic mineral components, such as montmorillonite and illite. The particular features of expansive soil will bring severe safety hazards and economic losses to expansive soil areas Given these situations, improving the physical and mechanical properties of expansive soil is indispensable for stability of foundation and subgrade engineering. E effect of lime, cement, and fly ash on the physical-mechanical behaviors of soil samples is confirmed by the research of modified methods on expansive soils. Chemical stabilization has been considered a practical and effective solution to reduce swell-shrink characteristics and improve physical-mechanical properties of expansive soil. Sand is broadly applied in civil engineering materials by its abundant source and low price Another physical stabilization of expansive soil is fiber reinforcement. In the following chapters of this paper, an experimental study has been conducted for expansive soil stabilized with fly ash, sand, and basalt fiber. is paper aims to study the effect of the noted three additives on physical-mechanical and microstructural characteristics of expansive soil which can be satisfactorily applied for construction of foundations, subgrade, road, and even driveways after reasonable and effective treatments
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