Strength Characteristics of Compacted Fly Ash Treated Expansive Soil due to Wetting-Drying Cycles Repetition

Due to high swelling-shrinkage caused by climate change, expansive soil is a significant problem in light construction, road embankments, and slope stability (wet and dry). The physical and mechanical properties of the soil are affected by repeated drying and wetting cycles, particularly changes in volume, negative pore water pressure (suction), and compressive strength. Fly ash is used to increase soil strength and reduce plasticity caused by swelling to address this issue. Because of its chemical properties, fly ash is an excellent choice for low-cost soil improvement. The purpose of this investigation is to determine the static mechanical properties of expansive soil fly ash stabilization under Proctor standard compaction conditions. Mechanical properties were investigated due to changes in soil moisture content, saturation, suction, and compressive strength caused by repeated drying and wetting cycles. The soil's suction was measured using Whatman #42 filter paper, and the soil's compressive strength was tested using a free compression test. According to the findings, the fly ash mixture altered the expansion and shrinkage behavior of expansive soils by lowering the consistency limit. At the same moisture content, the addition of 5% to 15% fly ash increases the compressive strength of the soil significantly. Compressive strength (qu) and stress-strain modulus (Ei) decreased in 1-4 cycle cycles, and after four cycles, changes in compressive strength and stress-strain modulus were very small or insignificant. The proposed method effectively reduces the loss of expansive soil strength caused by environmental changes (wetting-drying). As a result, it contributes significantly to the development of materials to reduce structural damage in expansive soils.