Curing of Sand Stabilized with Alkali Lignin

Lignin and its derivatives from industrial wastes of paper pulp and biofuel production has been used as a soil stabilizer for various applications. This paper discussed the curing process of alkali lignin extracted from paper pulp residuals when it was used treated poorly graded sand (SP). Soil specimens treated by different dosages of lignin were cured in air and heat (i.e., an environment with elevated temperatures), respectively. It was found out that with higher dosage of alkali lignin the unconfined compressive strength (UCS) increased to 5,000 kPa at a lignin dosage of 8% if cured in heat, but increased monotonically with lignin dosage if cured in air. The UCS of air cured specimens showed strong correlation with moisture content, namely, higher initial moisture content led to low UCS. For heat curing, the ultimate UCS was not sensitive to temperature from 30 to 100 °C as it reached the same value given sufficient curing duration. This study overall proves that alkali lignin could be a good soil stabilizer.