Optimization of Soil to Fly-Ash Mix Ratio for Enhanced Engineering Properties of Clayey Sand for Subgrade Use

Abstract

A laboratory investigation was carried out to determine the optimum soil to fly ash mix ratio to enhance the engineering properties of clayey sand that can potentially be used as a road subgrade. Grain size distribution and Atterberg limits tests were conducted to classify the soil and to study the effects of the fly ash on the soil plasticity. The Proctor test was conducted to determine the optimum moisture content and maximum dry density of soil--fly ash mixtures with arbitrarily selected 0%, 40%, 50%, and 60% fly ash content. A higher percentage was selected to find the highest optimum fly ash content to maximize the beneficial use. Unconfined compression and consolidation tests were conducted with air-dry arbitrarily selected curing periods of 0, 2, 8, and 28 days to determine the strength and to predict the settlement and the volume change behavior. It can be concluded from the trend analysis that a fly ash content range of 32–50% appeared to be optimum that is expected to perform better as subgrade materials for a curing period range of 16–19 days. However, experimental data showed a fly ash content of 50% was the optimum for a curing period of 8 days. The settlement and the volume change behavior improved at least 44% with increased fly ash content.

Enhancing Subgrade Efficiency with Industrial Ash & Geotextile Combinations for Economical Pavement Solutions

“…The maximum compaction after mixing the 50% y ash of class F with clayey sand (SC). Also increase in 50% y ash content for a curing period of 8 days, there was at least a 44% improvement in settlement and volume change behavior (7).…”

Study of copper adsorption in some calcareous soils and calcium carbonate in North of Iraq

“…The soil texture plays a crucial role in retaining and releasing trace elements. Soils with a coarse texture have a lesser propensity for sorbing trace elements than soils with a fine texture (Karim, 2020; Karim, 2018; Lü et al, 2017) [13,14,19] .…”

Geotechnical Characteristics of Fine-Grained Soils Stabilized with Fly Ash, a Review

“…Table A4 (Appendix A) shows the UCS of fly ash-stabilized soils determined by many investigators and Figure 4 summarizes the mechanism of strength improvement in fine-grained soils stabilized with class C and class F fly ash based on the literature. It has been shown that the strength of soil stabilized with class C or class F fly ash shows an increase [3,10,16,27,33,35,88,98,101,[103][104][105][106][107][108][109][110][111][112][113][114]. However, several researchers have pointed out that there is an optimum level of fly ash addition to stabilize soil [51,60,104,115].…”

“…Many consolidation characteristics such as compression index (C c ), coefficient of volume compressibility (m v ), coefficient of consolidation (c v ), pre-consolidation pressure, and permeability or hydraulic conductivity (k) were studied using one-dimensional consolidation tests [35,81,83,111,119,[121][122][123]. Compression indices of the unstabilized soil and stabilized soil with different percentages of fly ash are shown in Table A6 (Appendix A).…”

“…Fly ash-stabilized soil can be used as an effective material in geotechnical applications due to its enhanced geotechnical characteristics [33][34][35][36].…”