Physicochemistry of Pozzolanic Stabilization of a Class A-2-7 Lateritic Soil

Authors: Ahmed O. Apampa, Yinusa A. Jimoh

Abstract:

The paper examines the mechanism of pozzolan-soil reactions, using a recent study on the chemical stabilization of a Class A-2-7 (3) lateritic soil, with corn cob ash (CCA) as case study. The objectives are to establish a nexus between cation exchange capacity of the soil, the alkaline forming compounds in CCA and percentage CCA addition to soil beyond which no more improvement in strength properties can be achieved; and to propose feasible chemical reactions to explain the chemical stabilization of the lateritic soil with CCA alone. The lateritic soil, as well as CCA of pozzolanic quality Class C were separately analysed for their metallic oxide composition using the X-Ray Fluorescence technique. The cation exchange capacity (CEC) of the soil and the CCA were computed theoretically using the percentage composition of the base cations Ca²⁺, Mg²⁺ K⁺ and Na²⁺ as 1.48 meq/100 g and 61.67 meq/100 g respectively, thus indicating a ratio of 0.024 or 2.4%. This figure, taken as the theoretical amount required to just fill up the exchangeable sites of the clay molecules, compares well with the laboratory observation of 1.5% for the optimum level of CCA addition to lateritic soil. The paper went on to present chemical reaction equations between the alkaline earth metals in the CCA and the silica in the lateritic soil to form silicates, thereby proposing an extension of the theory of mechanism of soil stabilization to cover chemical stabilization with pozzolanic ash only. The paper concluded by recommending further research on the molecular structure of soils stabilized with pozzolanic waste ash alone, with a view to confirming the chemical equations advanced in the study.

Keywords: Cation exchange capacity, corn cob ash, lateritic soil, soil stabilization.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1125823

References:

[1] M. D. Gidigasu, Laterite Soil Engineering. Elsevier Scientific Publishing Company. Amsterdam, 1976. pp 3 -4.
[2] M. Alhassan, Potentials of rice husk ash for soil stabilization. A.U. Journal of Technology, 2008, pp 246 – 250. Available at www.journal.au.edu/au_techno. (November 26 2011)
[3] Y.A. Adama, and Y.A. Jimoh, Production And Classification of Locust Bean Pod Ash (LBPA) as a Pozzolan, 2011. Available at www.engineeringcivil.com (29 January 2012)
[4] Y.A. Jimoh, and O.A. Apampa, An evaluation of the influence of corn cob ash on the strength parameters of lateritic soils. IISTE Civil and Environmental Research, Vol.6, No. 5, 2014. New York, United States, 2014.
[5] C.A. O’Flaherty, Highway Engineering Vol 2: Edward Arnold Publishers Limited, London. Second Edition, 1974.
[6] C.A. O’Flaherty, Highways: The Location, Design, Construction & Maintenance of Pavements. Elsevier Publishers. New Delhi, India, 2002.
[7] S.M. Agus, and H. Gendut, Influence of Rice Husk Ash and Lime on Engineering Properties of Clayey Subgrade, 2002. Available at www.ejge.com/2003. (May 12 2012)
[8] S.A. Ola, “Clay Mineralogy and Clay Water System” in Essentials of Geotechnical Engineering, S.A. Ola Ed., University Press Plc. Ibadan, Nigeria, 2013, pp 24 -40.
[9] P.L. Capper, and W.F. Cassie, The Mechanics of Engineering Soils. 6th edition. John Wiley and Sons Inc., New York, 1976.
[10] N.O. Adebisi, G.O., Adeyemi, O.S., Oluwafemi, and S.P. Songca, Important Properties of Clay Content of Lateritic Soils for Engineering Project. Canadian Center for Science and Education, Journal of Geography and Geology, Vol. 5, No.22, 2013, p 99-115.
[11] D.A. Alao, Geology and Engineering Properties of Laterites from Ilorin, Nigeria. Engineering Geology, Journal, Elsevier Science Publishers, Amsterdam, Vol 19, 1983 p 111 – 118,.
[12] C. Ma, and R.A. Eggleton, Cation Exchange Capacity of Kaolinite. Journal of Clays and Clay Minerals. Vol. 47, No 2, 1999. pp 174 – 180.
[13] M. Astera, Cation Exchange Capacity Simplified. Online publication 2007. Available at www.soilminerals.com (10 January 2015)
[14] Nigerian General Specifications (Roads and Bridges) Volume II, 1997. Federal Ministry of Works, Lagos, Nigeria.
[15] Midwestlabs, Calculating Cation Exchange Capacity and Percent Base Saturation. Online publication 2012. Available at www.midwestlabs.com (30 April 2015)
[16] D.B. Mengel, Fundamentals of soil cation exchange capacity. Publication of Purdue University Cooperative Extension Service, West Lafayette, USA, 2012.
[17] H.J.H. Brouwers, and R.J. Van Eijk, Chemical reactions of fly ash. Proceedings of the 11th International Congress on the Chemistry of Cement, Durban, South Africa 11-16 May 2003, pp 791 – 800.
[18] T. Zhang, L. Vandeperre, and R.C. Cheeseman, Formation of magnesium silicate hydrate (M-S-H) cement pastes using sodium heametaphosphate. Cement and Concrete Research vol 65, November 2014, 2014, p 8 – 14.
[19] J. Wei, Y. Chen, and Y. Li. The Reaction Mechanism between MgO and Microsilica at Room Temperature. Journal of Wuhan University of Technology – Mater. Sci. Ed. Vol 21, issue 2, June 2006, pp 8 – 14.