A comprehensive series of tests, including dynamic triaxial, monotonic triaxial and unconfined compressive strength (UCS) tests, were carried out on reconstituted landfill waste material buried for over twenty years in a closed landfill site in Sydney, Australia. Waste materials collected from the landfill site were treated with varying percentages of cement, and both treated and untreated specimens were investigated to evaluate the influence of cement treatment. The study examined the dynamic properties of cement-treated landfill waste, including cumulative plastic deformation, resilient modulus, and damping ratio, and also analysed the impact of cyclic loading on post-cyclic shear strength in comparison to pre-cyclic shear strength. The UCS tests and monotonic triaxial tests demonstrated that untreated specimens subjected to monotonic loading exhibited a progressive increase in strength with rising axial strain, whereas cement-treated specimens reached a peak strength before experiencing a decline. During cyclic loading, with the inclusion of cement, a significant reduction in cumulative plastic deformation and damping ratio was observed, and this reduction was further enhanced with increasing cement content. Conversely, the resilient modulus showed substantial improvement with the addition of cement, and this enhancement was further amplified with increasing cement content. The formation of cementation bonds between particles curtails particle movement within the landfill waste material matrix and prevents interparticle sliding during cyclic loading, leading to lower plastic strains and damping ratio while increasing resilient modulus. Post-cyclic monotonic testing revealed that cyclic loading caused the partial breakage of the cementation bonds, resulting in reduced shear strength. This reduction was higher on samples treated with lower cement content. Overall, the findings of the research offer crucial insights into the possibility of cement-treated landfill waste as a railway subgrade, laying the groundwork for informed design decisions in developing transport infrastructure over closed landfill sites while using landfill waste materials available on site.

Cementation, even in small amounts, tends to alter the mechanical properties of soil significantly. Ordinary Portland Cement (OPC) is a widely used binding admixture, but there has been an increasing need for replacement owing to its carbon footprint. One such alternative is Calcium Sulfoaluminate cement (CSA), which has higher initial strength gain and lower carbon footprint than OPC. Since existing strength prediction models available from literature were developed for conventional cement types such as OPC and Portland Blast Furnace Cement (PBFC), those are not applicable for predicting the strength evolution of soil treated by other types of cements (e.g., underpredicting the initial strength of CSA treated sand). It is because the prediction models available are generally either soil-specific or cement-specific. This paper proposes a unified strength prediction model that works irrespective of cement and/or soil types by introducing a slope parameter that controls time-dependent strength gain. The proposed model is validated by data collected from literature on various soils and cement types. The three-parameter model demonstrates strong applicability for predicting the strength evolution over a wide range of water-to-cement ratios.