Characterization of Stabilization Mechanism of Pavement Foundation Material Using Polyacrylamide Additive

In Australia, synthetic polymer additives, i.e., polyacrylamide (PAM), recently have been shown to provide marked benefits for the construction and maintenance of unsealed roads over traditional cementitious additives. This study investigated the effects of using a specific synthetic polyacrylamide, currently being used in Australia, on the engineering properties of pavement foundation materials (PFM). The primary objective of the study was to understand the mechanism of stabilization in granular materials when using PAM additive. The tests were undertaken in two stages. In the first stage, the mechanism of PAM stabilization was investigated considering the changes in dry density, unconfined compressive strength (UCS), and elastic modulus of this PFM, with varying clay contents, when stabilized with PAM. In the second stage, analysis using X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests was performed to identify the changes in the matrix of the PAM-treated samples. For the PFM tested herein, results from the first stage showed that adding PAM increased its dry density, strength, and elastic modulus. Furthermore, increasing clay percentage in the PFM did not contribute significantly to increasing the adsorption of PAM onto the material's particles. The results from the second stage showed that the interaction between PAM and PFM particles occurred mainly by adsorption and physical bonding rather than chemical interaction. For the PAM-treated PFM, SEM analysis results revealed that loose particles and pore volume decreased, with a high increase in contact points between particles.