Measuring the water absorption capacity of superabsorbent polymers in soils

¹ Department of Civil and Environmental Engineering, Institute of Science Tokyo, Meguro, Tokyo, Japan
² Department of Geoscience and Engineering, Delft University of Technology, Delft, The Netherlands
³ Technica Goudou Co., Ltd, Kobe, Hyogo, Japan

Abstract

Superabsorbent polymers (SAPs) are used to remove excess water from liquid excavated soils and dredged soils. They are also used to improve soil water retention for agricultural purposes. The pore water of SAP-treated soils exists in two forms: absorbed and free water. Measuring the amount of absorbed water is crucial for assessing the hydro-mechanical behaviour of SAP-treated soils, as only free water contributes to suction-induced interparticle forces and water paths; however, methods for separating these two forms of water have not been established. This study presents an experimental methodology to estimate the water absorption capacity of SAP in soils. A centrifugal force smaller than the SAP absorption force was used to extract free water from the SAP-treated soil. Sandy soil treated with various SAP dosages and water contents was tested. The amount of absorbed water increased with higher dosage at a constant initial water content until it reached the maximum value. Based on the experimental results, a three-dimensional equation has been established to describe the relationship among the absorbed water content, SAP dosage, and initial water content. Regression analysis showed that the proposed equation effectively fitted the experimental data and provided a reliable prediction of absorbed water content for the tested material. The proposed experimental methodology and prediction method are useful for evaluating the mechanical and hydraulic properties of SAP-treated soil and for determining the optimal SAP dosage for soil with various initial water contents.