Optimization of Fly-Ash to Soil Mix Ratio and Curing Period for Subgrade Use

Abstract

A laboratory study was conducted to determine the optimum fly-ash to soil ratio that can be used as a road subgrade to improve strength and compactability. Proctor compaction, grain size distribution, Atterberg limits, and unconfined compression tests were conducted. Proctor compaction test was conducted to determine the optimum moisture content and maximum dry density of soil samples with 0%, 40%, 50%, and 60% fly-ash content. Atterberg limits and grain size distribution tests were conducted to classify the soil. Unconfined compression test was conducted with air-dry curing periods of 0, 2, 8, and 28 days to determine the strength. Curing periods help understand the strength gained with time. It is obvious from the study that the optimum soil to fly-ash mixture was a mixture of soil and 50% fly-ash which is expected to perform better as subgrade materials for a curing period of 8 days; however, a mixture of soil with 40% fly-ash content could also be used as a viable alternative for the same curing period.