Al2O3/SO3 molar ratio of PG-CAC-based binders on the macro-micro properties of cement-treated waste dredged clay

Abstract

The binders promoting the generation of ettringite (AFt) are very suitable for stabilizing waste dredged clay (DC) with high water content, while the variability of components may lead to uncertain workability. In this study, a series of unconfined compression tests were conducted on the DC stabilized by the ternary hydration system consisting of ordinary Portland cement, recycled phosphogypsum and calcium aluminate cement, the effects of the Al2O3/SO3 molar ratio (m) on the mechanical properties were evaluated accordingly. Subsequently, a series of microstructure tests and mineralogical tests were performed to further reveal the influence of m on the mechanism of stabilized DC. The results demonstrate that at the same binder content, the unconfined compression strength (UCS, qu) shows a linear increase with m. The compactness of cement-treated DC was improved by the main generation of ettringite, while excessive ettringite may cause expansion and destroy the existing cementation. As m increases, the excessive Al2O3 promotes the generation of C-(A)-S-H and C-A-H after generating enough AFt, which not only cements the soil particles with the cementation effect, but also repairs cracks induced by the AFt expansion. The collaborative effects of the filling and cementation result in an improvement of qu from 11.2% to 129.5% when m increases from 0.133 to 1.414. It can be anticipated from the study that controlling m around 0.55 will play an important role in stabilizing the DC, thus further promoting the co-utilization of recycled DC and phosphogypsum.