Application of biomass by-product lignin stabilized soils as sustainable Geomaterials: A review.

Due to the increasing concerns on environmental pollution, fossil energy shortage, and sustainable development, the recycling of industrial by-products had become a popular practice worldwide. Chemical stabilization of problematic soils with biomass by-product lignin was being considered as one of the viable answers to the consumption of such lignin stockpiles and the reduction of environmental loading. This paper summarized the production and physicochemical properties of by-product lignin collected from paper mills and reviewed the state of the art of this lignin stabilized soils as engineering materials. In addition, the potential focuses requiring further study to promote lignin stabilization technology were expected. The results showed that physicochemical properties of by-product lignin were mainly controlled by plant biomass and production technology, which should be clearly examined before field application. By-product lignin exhibited a satisfactory performance of improving engineering properties of both cohesive soils and noncohesive soils with respect to strength, erosion resistance, and durability. The precipitated cementing materials bonded particles and filled pores in the soil matrix, while their formation mechanism had not clearly explored yet. By-product lignin stabilized soils suffered from performance deterioration as exposed to moisture intrusion and wetting-drying cycle. The formed bonding among soil particles was essential in affecting the mechanical responses and durability of stabilized soils. The desirable construction procedure and protective measure were encouraged to be established for safety applications of the stabilized soils. Additional researches were recommended to by-product lignin optimization/modification, dynamic behaviors of stabilized soils, and application in some special soils. The outcomes of this review are invaluable in facilitating application of biomass by-product lignin for stabilizing problematic soils in engineering constructions.