Lignosulfonate, a co-product of paper pulp production, has traditionally been used for dust suppression purpose. Although lignosulfonate has been reported as an alternative soil stabilizer because of its natural properties, its use has not been adequately investigated for soil stabilization purposes. Correspondingly, very limited field practice has been conducted in applying these laboratory attempts.

For this study, homogeneously diluted lignosulfonate was mixed with two types of silty soils in the laboratory with the goals of improving their strength and durability. Measurements and observations were obtained from six laboratory tests on untreated and lignosulfonate stabilized soils, including: (1) Proctor compaction test, (2) unconfined compressive strength (UCS) test, (3) freeze-thaw durability test, (4) wet-dry durability test, (5) scanning electron microscope (SEM) analysis, and (6) set time test. The unconfined compressive strength test results demonstrated that only a low dosage of lignosulfonate and water was required to improve the strength of sandy silt with gravel. Based on the outcomes of the durability tests, lignosulfonate improved the wet-dry resistance of both types of silty soils, and a significant improvement was noticed in freeze-thaw durability for sandy silt with clay with the addition of lignosulfonate. The SEM analysis indicated that lignosulfonate was capable of physically bonding soil particles. The set time test conveyed the strength increment of lignosulfonate itself and its mechanisms, indicating that the hardening process also contributed to increasing the stabilized soil strength.

In the field demonstration, five soil stabilizers (cement, ammonium-based lignosulfonate, chlorides, Claycrete, and Base One) were sprayed on a gravel road subgrade. Seasonal in situ tests and documentations were conducted both before and one week after the construction to monitor the performance of the stabilized section and to draw the lessons learned from the practice. Light weight deflectometer (LWD) test and dynamic cone penetration (DCP) test were performed. The construction process was documented both visually and in written form. Some critical lessons were learned, which provide recommendations for future studies and benefit relevant practitioners.

This study provides guidance for subgrade stabilization with lignosulfonate on the basis of its laboratory and field investigations.