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

M A Karim,Adam Kaplan,Ahmed Sami Hassan

doi:10.3390/app10207038

M A Karim, Adam Kaplan + Show 1 more

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https://doi.org/10.3390/app10207038

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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.

Highlights

The industrial revolution and the significant technological developments of the last century have allowed people to use more energy than previous generations
This study explored the possibility of using a higher percentage of fly ash in soil to enhance the engineering properties that can be used in subgrade construction and in other engineering applications
The specific gravity of the clayey sand decreased as the percentage of fly ash content in the mixture increased because the specific gravity of the fly ash was lower than the specific gravity of the original soil

Summary

Introduction

The industrial revolution and the significant technological developments of the last century have allowed people to use more energy than previous generations. The electric energy in the United States is generated using a variety of resources. According to the American Coal Ash Association (ACAA), nearly 38 million tons of fly ash were generated in 2016 and about 22 million tons (57%) were reused in beneficial applications, including concrete production, flowable fill, embankments, agriculture, mining applications, road pavement, soil amendments, material recovery, and waste stabilization, while the rest of the production was sent to disposal basins [1]. Fly ash has a broad range of applications within the construction industry [2]. The application of fly ash as a partial replacement for Portland cement in concrete is widely used, with considerable volumes. In road base and sub-base material, the utilization was 1%, with structural fills and embankments using over 5% [2]

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