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

M A Karim


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.


Fly-ash, soil stabilization, optimization of fly-ash content

Full Text:



American Coal Ash Association (ACAA), 2016 Production and Use Survey Results News Release. (Accessed: 28 May 2018) https://www.acaa-usa.org/Publications/ProductionUseReports.aspx

Mahvash S, López-Querol S, and Bahadori-Jahromi A. Effect of class F fly-ash on fine sand compaction through soil stabilization. Structural Engineering, Civil Engineering 2007; 3(3): https://doi.org/10.1016/j.heliyon.2017.e00274

Environment Information System (ENVIS). Summary of Fly-ash Generation and Utilization during the Year 2011-12, 2012-13, 2013-14, 2014-15 and 2015-16, 2016-2017 First Half Year” 31/07/2017.

Caldas-Vieira F, and Feuerborn HJ. Impact of Political Decisions on Production and Use of Coal Combustion Products in Europe World of Coal Ash 2013. 2013, pg 17. Lexington, Kentucky USA: WOCA.

Naik TR, Shiw S. Singh SS, and Ramme, BW. Effect of Source of Fly-ash on Abrasion Resistance of Concrete. Journal of Materials in Civil Engineering, 2002; 14(5): 417-427. https://doi.org/10.1061/(ASCE)0899-1561(2002)14:5(417).

Pandey VC and Singh N. Impact of fly-ash incorporation in soil systems. Agr. Ecosyst. Environ. 2010; 16-27.

Yadav AK, Gaurav K, Kishor R, and Suman SK. Stabilization of alluvial soil for subgrade using rice husk ash, sugarcane bagasse ash and cow dung ash for rural roads. International Journal of Pavement Research and Technology, 2016; 10, 254–261.

White DJ, Harrington DS, and Thomas Z. Fly-ash Soil Stabilization for Non-Uniform Subgrade Soil. Volume I: Engineering Properties and Construction Guidelines” Iowa Highway Research Board, 2005, IHRB Project TR-461; FHWA Project 4.

Phanikumar BR and Sharma RS. Volume change behavior of fly-ash-stabilized clays, Journal of materials in Civil Engineering, 2007, 19(1): 67–74.

Ozdemir MA. Improvement in Bearing Capacity of a Soft Soil by Addition of Fly-ash. Procedia Engineering, Vol. 143, no. Advances in Transportation Geotechnics III, 01 Jan. 2016, 498-505. EBSCOhost, doi: 10.1016/j.proeng.2016.06.063.

Nath BD. Study on Strength Behavior of Organic Soil Stabilized with Fly-ash. International Scholarly Research Notices, 2017; 11: 5786541. EBSCOhost, doi:10.1155/2017/5786541.

Mahesh KG and Satish TB. Effect of fly-ash on Properties of Expansive soil. International Journal of Scientific and Engineering Research, 2013; 4(5): 37-40.

Georgia Power’s Plant Bowen Environmental Management System. 2016; http://www.georgiapower.com/company/research-conservation-and-stewardship/management-closures/plant-list/plant-bowen.html

Hassan AS. Unitization of High Percentage of Fly-ash in Silty Soil to Enhance the Engineering Properties for Subgrade Use [MS thesis]. Georgia (GA): Kennesaw State University; 2018, p.124.

Bhuvaneshwari S, Robinson RG, and Gandhi SR. Stabilization of Expansive Soils using Flyash. Fly-ash India 2005, New Delhi. Fly-ash Utilization Programme (FAUP), TIFAC, DST, New Delhi – 110016.

DOI: http://dx.doi.org/10.18282/ice.v0i0.91


  • There are currently no refbacks.