Development of Carbon Sequestering 3D-Printable Stabilized Earth Materials (2025-06)¶

Stabilized 3D-printable earth-based building products can be developed by utilizing excavated soil containing non-expansive clays. Further reduction in embodied carbon and improvement in engineering properties can be attained by sequestering carbon dioxide in the 3D-printable materials via accelerated carbon curing (ACC). This research aims to utilize kaolinite-rich lateritic soil as a 25% and 50% replacement of natural sand in 3D-printable formulations and investigate the influence of ACC on compressive strength, shrinkage, and resistance to acid-induced degradation. A combination of Portland cement (OPC) and class F fly ash (FA) have been used as stabilizers, where FA is used to replace 30% of OPC. Experimental findings suggest that a combination of FA and clay (mainly kaolinite) in the used soil imparts improvement in thixotropy by 18–30% and enhances flow retention compared to the control (without soil or FA). Furthermore, the structural build-up after extrusion is enhanced due to the flocculation of clay at rest. As a result, OPC-FA-soil mixes demonstrated substantially better buildability, evident from a printed height of 1.20 m compared to 0.48–0.54 m for OPC-sand (CC0) and OPC-FA-sand (CF30) mixes. The wet compressive strength of the 3D-printed materials is enhanced by 29–47% due to CO2 curing, depending on the loading direction, ascribed to the matrix densification by calcium carbonate crystals Carbon sequestration mitigates the loss in strength and mass of 3D-printed materials by 20–45% after exposure to sulfuric acid (pH of 0.5) for 56 days. This is attributed to reduced porosity and better neutralization capacity of calcium carbonate in low pH environments. In summary, the technology presents a potential pathway to develop low-carbon, durable, and resilient 3D-printed stabilized earth constructions.