Stabilisation of Kuttanad Soil Using Calcium and Sodium Lignin Compounds

Kuttanad region in Kerala is the lowest lying area in India with an elevation of one metre above mean sea level. Soil in this region is characterised by low bearing capacity, hence, construction works on Kuttanad soil is often problematic and expensive. Traditionally, stabilisation in Kuttanad soil is done by hydrated lime, Portland cement, fly ash, etc. Stabilisation of weak soil with industrial by-products is commonly adopted nowadays because of its economical as well as environmental benefits. One such material is lignin; chemically called as lignosulphonates produced as a by-product in paper pulping industry. Lignin compounds are available in different chemical compositions based on the cellulose separator used during pulping process. This paper presents in detail the effectiveness of stabilising Kuttanad soil using sodium as well as calcium forms of lignin. The effect of lignin on compaction characteristics, consistency limits, unconfined compressive strength and CBR were studied using a series of laboratory tests and the optimum percentage of additive was found out. A comparative study has also been done with the two compounds to identify which one has the best stabilisation capacity.