One-dimensional compression and swelling of compacted fly ash

Abstract

The aim of the paper is to prove that the compressibility and swelling of compacted fly ash in both unsaturated and fully saturated conditions are dependent on the moisture content at the compaction and on the compaction energy, as in the case of cohesive soils. The studies have been conducted on samples compacted at various water contents in conventional oedometers and the Rowe hydraulic consolidation cell and in California bearing ratio moulds (swelling tests). The one-dimensional compressibility of saturated fly ash is much higher than that of unsaturated fly ash. Deformation of unsaturated samples increases with moisture at compaction, and the samples compacted with greater effort are less compressible. The consolidation of the saturated samples decreases with their moisture content at compaction and at the reduction of the compaction energy. The swelling of ash samples decreases as the moisture during compaction increases and when compaction energy is lower. The highest swelling was obtained for the fly ash with the highest optimum water content.

Effect of Bentonite Addition on the Properties of Fly Ash as a Material for Landfill Sealing Layers

“…As the water flows, the sample degree of saturation increases, but it is not certain that the back pressure value used to test partially saturated sample is sufficient to fully saturate the sample. It is shown that the condition of full and partial saturation is also important in determining compression and settlement characteristics of the compacted fly ash [50]. Figure 10 shows the dependency of hydraulic conductivity on effective stress at hydraulic gradient i = 32 of fly ash, fly ash-bentonite mixes and cohesive soil.…”

Characteristics of Compacted Fly Ash as a Transitional Soil

“…Non-plastic silty soils behave like pure sands. Soils macroscopically evaluated as non-cohesive and not demonstrating plasticity may however exhibit properties of cohesive soils, with changes occurring not only in strength characteristics but also in deformation and filtration, which was found in the example of fly ash [6][7][8]. The phenomenon of cohesion resistance in non-cohesive soils is the result of suction in the soil, which is often associated with capillary suction.…”

“…The authors' earlier work [6][7][8] has shown that compacted non-plastic fly ash should always be evaluated considering the moisture content at compaction, as in the case of cohesive soils. The aim of the work is to show how the variable content of fine particles in fly ash influences the diversification of its mechanical parameters, which will be shown in the example of the California Bearing Ratio (CBR) of ash as a parameter that is strictly dependent on the initial compaction [6,7].…”

“…The author's research [6][7][8] has shown that compacted fly ash, despite the macroscopic similarity to non-cohesive soils, should always be assessed taking into account the moisture content at compaction (at a given compaction effort) as with compacted cohesive soils; not only providing the value of the compaction index, because all specified mechanical parameters and hydraulic conductivity are strictly dependent on the moisture content of the fly ash at compaction.…”

Water Content–Density Criteria for Determining Geomembrane–Fly Ash Interface Shear Strength

“…In previous research it has been frequent practice to present the shear strength values of interface contact only for mineral soil compacted at water content closed to optimum. The permeability and mechanical properties of compacted non-cohesive fly ash and fly ash/bottom ash mixture are dependent on moisture content during compaction, w, as are properties of cohesive mineral soils [14]. Consequently, different values are obtained for w on either side of the wopt on a compaction curve, for the same dry densities, ρd.…”