Carbon reduction in deep mixing method grouts using Calcium-Silica-Hydrate (CSH) nano particles

Deep Mixing Methods (DMMs) are a versatile solution for ground improvement that can be used to increase bearing capacity, reduce settlement, and mitigate liquefaction. However, DMMs are cement-intensive, as a single project can consume over 100,000 tons of ordinary portland cement (OPC). This makes DMMs carbon-intensive, as OPC production has been estimated to contribute to 8% of the world’s annual CO2e production. New technologies, including calcium-silica-hydrate nanoparticles and Type IL cement, can be used to reduce the carbon footprint in DMMs by reducing the amount of OPC that is required to achieve equivalent strengths. A laboratory study was conducted using Type IL (10) cement grout with and without dosing of a calcium-silica-hydrate nanoparticle blended with a clayey sand (SC). Unconfined compressive strength (UCS) testing revealed late strength gains in excess of 60% over the baseline. UCS testing was performed on specimens after up to one year of curing to determine long-term strength gain. Scanning electron microscopy (SEM) was also performed on specimens during peak strength gain. Initial testing indicates that CSH nanoparticles can be used with Type I-L cement to reduce binder factors in DMM applications while yielding higher than baseline conditions. Additionally, a roadmap to implementation is provided with stakeholder involvement. Stakeholders are critical in the process of carbon reduction and have key roles as collaborators in the roadmap to implementation.