Applying Multiwall Carbon Nanotubes for Soil Stabilization

Abstract

The chemical stabilization of a soil is a technique where the soil is mixed with cementitious material in order to improve its mechanical behavior. The chemical stabilization is dependent on a wide range of parameters, being the most important ones associated to the soil properties and cementitious material characteristics. The nanoparticles are not a cementitious material but once introduced in a soil they are expected to reduce the interparticles’ spacing, which will promote the construction of a stronger and stiffer soil skeleton matrix together with the cementitious material, therefore improving the mechanical properties of the soil. Thus, optimization of nanoparticles distribution is required to obtain a final material with the best characteristics at a competitive cost. In order to maximize the benefits of the nanoparticles (multiwall carbon nanotubes, MWCNT) added to a stabilized soil it is crucial to overcome the problems related with particle agglomeration. Thus, it was defined a strategy which comprises the characterization of the MWCNT (zeta potential and size), the definition of the aqueous medium with surfactant addition (a plycarboxylate-based surfactant was tested), the characterization of the surfactant (viscosity, molecular weight, zeta potential and molecule size) and the application of energy (with a particular power and during a specific time) to promote the particles’ dispersion. The quality of the suspension, in terms of particles’ dispersion, was evaluated trough the analysis of the particle size distribution given by dynamic light scattering (DLS). After, a series of performance tests (unconfined compression strength, UCS) test with the soil were conducted over samples with 7 of curing time. The preliminary results of the performance tests have shown the high potential of adding multiwall carbon nanotubes to a chemically stabilized soil. The results have also pointed out the importance of the nanoparticle homogenization process where the presence of the surfactant has a major role.