Stabilization of a soft marine clay using halloysite nanotubes: A multi-scale approach

Abstract

Halloysite nanotubes are novel 1D natural nanomaterials which are widely used in reinforcing polymer, adsorbents for pollution remediation, and nanoreactors for biocatalyst; owing to their high mechanical strength, thermal stability, high aspect ratio, nature-friendly, cost-effectiveness, and abundance. However, the use of halloysite nanotubes as a stabilizing agent for soft soils is currently not clear. This paper explores the possibility of stabilizing a soft marine clay by adding halloysite nanotubes. Laboratory investigations were conducted on marine clay treated with three different types of halloysite nanotubes [Matauri Bay (MB-Hal), UltraHallopure (UHP-Hal), and Dragonite (DG-Hal)] and combined under 5% by dry clay mass. Test results revealed notable improvements in the properties of the marine clay. The addition of halloysite nanotubes resulted in an increase in the clay and silt-sized contents and a decrease in the sand-sized content. The plasticity and hydraulic conductivity of the clay decreased upon treatment with the halloysite nanotubes. Moreover, the unconfined compressive strength (UCS) of the treated-clay recorded ascending values with increasing curing time. The percentage increase of the UCS for the 14-days cured DG-Hal, MB-Hal, and UHP-Hal treated-clay samples over the untreated-clay were 67%, 62%, and 51%, respectively. Microstructural study reveals that the stabilization process modified the porous network of the clay. The pores of the clay were filled by the halloysite nanoparticles. DG-Hal treated sample recorded the highest strength and lowest hydraulic conductivity for all curing durations relative to MB-Hal and UHP-Hal treated clay samples. Obtained changes in the plasticity, strength, and hydraulic conductivity of the treated samples indicates that halloysite nanotubes can be used as an effective stabilizing agent for soft soils. However, it is recommended to investigate the effect of different percentages of halloysite nanotubes to stabilize soft soils.