Performance of the one-part geopolymer stabilized soft clay under acids attack

Abstract

The evolution of globalization and rapid industrialization, coupled with intensive human activities, leads to a significant release of acidic gases and particles (e.g., NOX and SO2) is unavoidable. These emissions eventually result in dry and wet acid depositions due to atmospheric circulation. This infiltration of acidic elements alters the chemical properties of water systems, thereby deteriorating ground stability. The economically developed soft clay areas face considerable threats from these acid environmental attacks. This study focused on employing a ''one-part'' geopolymer (OPG) comprising ground granulated blast furnace slag (GGBFS), fly ash (FA), and solid sodium hydroxide (NH) to stabilize the soft clay. Simultaneously, the deterioration behavior of OPG stabilized soft clay under two different acids (HNO3 and H2SO4) with various pH values (pH of 2, 4, and 6) and varied immersion periods up to 240 days was evaluated including the mass loss, neutralization depth (ND), pH value, and unconfined compressive strength (UCS). Additionally, scanning electron microscopy (SEM) and X-ray energy spectrometry (EDS) characterized the evolution of microstructure and hydrate composition of OPG-stabilized soft clay post varied acid immersion. The results highlighted the superior acid resistance of the stabilized soft clay with an 80:20 GGBFS/FA ratio compared to other ratios. The presence of significant hydration products, such as calcium silicate hydrates (C-S-H), calcium aluminate (aluminosilicate) hydrates (C-A-(S)-H), and sodium aluminosilicate hydrates (N-A-S-H), was observed in the OPG stabilized soft clay. In addition, the contents of Si in the OPG played a significant role in enhancing the acid resistance of the OPG stabilized soft clay. Based on these experimental results, two proposed mechanisms detailed the deterioration and acid resistance of the OPG stabilized soft clay under HNO3 and H2SO4 attack. The findings of this study contribute to advancing scientific comprehension concerning the acid resistance of the OPG stabilized soft clay in ground improvement practices.