Abstract
Soils at many sites do not always have enough strength to bear the structures constructed over them and some of the soil may need to be stabilized in order to improve their geotechnical properties. In this paper, routine laboratory tests were critically carried out to investigate the efficacy of lignin in improving the strength behaviour of the soils. Two different soil samples (laterite and kaolin) were studied and mixed with different proportions of lignin (2% and 5% of dry weight of soil), respectively. Unconfined Compressive Strength (UCS) characteristics evaluated in this study were done on samples at their maximum dry density and optimum moisture content (obtained from compaction tests). The UCS tests on all the specimens were carried out after 0, 7, 15, 21 and 30 days of controlled curing. The research results showed that the addition of lignin into kaolin reduced its maximum dry density while giving progressively higher optimum moisture content. Contrarily, with the laterite soil, both maximum dry density and optimum moisture content simultaneously increased when lignin was added into the soils. The UCS results showed that the the stabilized laterite with 2% lignin continued to gain strength significantly at a fairly steady rate after 7 days. Unfortunately, lignin did not show a significant effect in kaolin.
Highlights
In most tropical countries, the road network consists of paved and unpaved roads [1]
The dispersion of the clay fraction benefits stability of the soil-aggregate mix by: a) plugging voids and improving water tightness and reducing frost susceptibility, b) eliminating soft spots caused by local concentrations of binder soil, c) filling voids with fines increasing density, and d) increasing the effective surface area of the binder fraction which results in a greater contribution to strength [7]
It can be seen that the both laterite and kaolin mixed with 5% lignin gives the lowest optimum moisture content (OMC) of 15% and 20% and highest maximum dry density (MDD) of 1.85 Mg/m3 and 1.54 Mg/m3, respectively.If compared the curve trend with standrad proctor and modified poctor test, it was found that the more amount lignin were added the higher MDD is recorded of stabilize soil
Summary
The road network consists of paved and unpaved roads [1]. Lignin as soil additive causes dispersion of the clay fraction of some soils, resulting in the shear strength increase of the soil [3]. The dispersion of the clay fraction benefits stability of the soil-aggregate mix by: a) plugging voids and improving water tightness and reducing frost susceptibility, b) eliminating soft spots caused by local concentrations of binder soil, c) filling voids with fines increasing density, and d) increasing the effective surface area of the binder fraction which results in a greater contribution to strength [7]. Adding lignin to clayey soils increases the soil stability by causing dispersion of the clay fraction [2]. Lignin based stabilizers such as ammonium persulfatelignin,sodium bichromate-lignin etc. Detailed data analysis of laboratory test results in comparing treated soils with untreated soils under different moisture conditions and different percentage of lignin were presented
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