Exploring the Role of Natural Clinoptilolite Zeolite in Cementitious Systems— Accelerated Carbonation and 3D Printing Applications

Cement, the binding material in concrete, contributes significantly to atmospheric CO₂ emissions during its production. Consequently, developing methods to reduce cement usage in concrete while maintaining adequate strength and durability has substantial environmental implications. Natural zeolites are being explored as supplementary cementitious materials (SCMs) due to their high pozzolanic activity, attributed to their porous aluminosilicate framework. Previous research has elucidated the fundamental impacts of this natural pozzolan on hydration reactions, densification, and strength development. But fundamental work related to the contributions of zeolite additions to the progression of curing reactions in cement composites not been evaluated in detail. To advance this understanding, in this work isothermal microcalorimetry is enrolled to measure the change in heat flow as a function of zeolite replacement. To assess the durability of the resultant composites, samples are exposed to two high CO₂ concentration environments: a) a 20% CO₂ in air concentration at ambient pressure, and b) a 100% CO₂ environment at elevated pressure. Following carbonation, the composites are assessed through mechanical testing, microCT, pH measurement, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) to determine the effects of CO₂ exposure. Experimental results confirm that zeolite replacement of cement in mortar composites can facilitate the enhancement of compressive strength that occurs by carbonation, but that it is sensitive to the replacement concentration.