The Reaction Products of Lime Treated Tropical Clay Soils and Their Impact on Strength Development


Adil A. M Elhassan

Sudan University of Science and Technology, Faculty of Engineering, Department of Civil Engineering
Corresponding author; e-mail:

Ahmed M. Elsharief

Building and Road Research Institute, University of Khartoum
Address: Khartoum, P.O.Box 321, Sudan

Awad E. M. Mohamed

Building and Road Research Institute, University of Khartoum, Khartoum, P.O.Box 321, Sudan



Comprehensive laboratory investigations have been performed to study the mineralogy, microstructure and reaction products of three tropical clay soils treated with hydrated lime and their impact on the development of the treated soils strength with time. Soil 1 is a highly plastic montmorillonitic clay soil; Soil 2 is a low plastic lateritic clay soil whereas Soil 3 is highly plastic clay of mixed clay minerals. Optimum lime content (OLC) was added to the three soils and the tests conducted on the natural and treated soils included Atterberg limits, 1-dimensional consolidation, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Unconfined Compression Strength (UCS). The XRD was performed after 1 day, 7 days and 360 days of curing, The SEM after 360 days and the UCS in the short and long term (from 0.5 hours to 360 days). The three soils reacted with lime causing aggregation of the mix and formation of new reaction products. The reaction products formed depended on the clay mineralogy and curing time. Calcium silicate hydrates (CSH) was formed in the short and long term for Soil 1. Calcium aluminates hydrates (CAH) was the main reaction product after 7 days of curing for the kaolinitic clay (Soil 2) and CSH appeared in small quantity later (360 days). The reaction products CSH, CAH and calcium aluminates silicate hydrates (CASH) appeared in the mixed clay mineral (Soil 3). An evaluation of the reaction products and strength data has shown that the contribution of CSH to strength development seized after 56 days. The increase of strength with time was noticed for Soil 2 and Soil 3 and was attributed to the compound CAH.

Keywords: Hydrated Lime, XRD, SEM, reaction products, strength development.

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