Abstract
The stabilization of soil through the addition of fly ash has been shown to be an effective alternative for improving the strength and stiffness of soil through the resulting chemical reactions. The chemical reaction that occurs dissociates the lime (CaO) in the fly ash, and the establishment of cementitious and pozzolanic gels (consisting of calcium silicate hydrate (CSH) gel and calcium aluminate hydrate (CAH) gel) binds the soil particles and increases the strength and stiffness of the soil. Investigations into the mechanical properties of sands stabilized with fly ash (fly-ash-stabilized sands) were conducted through a series of unconfined compressive strength (UCS) and direct shear strength tests for various fly ash percentages, curing times, grain sizes, degrees of saturation during sample preparation, and content of fines. It was found that the mechanical properties—UCS and direct shear strength (DSS)—of fly-ash-stabilized sands increased with both increasing fly ash content in the specimen and curing time, but decreased with increasing grain size, degree of saturation during sample preparation, and content of fines. The results indicated that fly-ash-stabilized sands required more than a month to attain their optimum performance with regard to binding sand particles.
Highlights
The chemical stabilization of cohesionless soil using a grouting technique is the most common method used for liquefaction mitigation of the ground below existing buildings
Tests were conducted on two different kinds of sand—fine and coarse—under either natural or clean conditions, with different fly ash contents, curing times, and degrees of saturation during sample preparation
The reviewed parameters were fly ash percentages (5–30%), curing times (7–56 days), grain sizes (0.075–0.25 mm and 0.6–2 mm), degree of saturation during sample preparation (30%, 50%, and 100%), and content of fines (2.88% and 1.33%). This investigation was conducted to study the effects of those parameters on the mechanical behavior of sands stabilized with fly ash
Summary
The chemical stabilization of cohesionless soil using a grouting technique is the most common method used for liquefaction mitigation of the ground below existing buildings. Soil stabilization with fly ash can reduce environmental pollution, and costs of materials are relatively inexpensive [15,16,17]. Soil stabilization with fly ash has been proposed as an effective alternative for strength and stiffness improvement through chemical reactions [18,19], because certain types of fly ash contain lime (CaO) and pozzolan consisting of, for example, silica (SiO2 ) and alumina (Al2 O3 ). When fly ash is mixed with soil in the presence of water, chemical reactions occur [20]. These chemical reactions dissociate the lime (CaO) in the fly ash and establish cementitious and pozzolanic gels consisting of calcium silicate hydrate (CSH)
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