Assessment of pore structure characteristics and tortuosity of 3D printed concrete using mercury intrusion porosimetry and X-ray tomography

Extrusion-based concrete 3D printing is being increasingly used in the construction industry. This paper gives insights into the porosity and pore structure of 3D printed concrete elements using mercury intrusion porosimetry, and X-ray micro-computed tomography. The experiments were conducted with two different cement systems; among which a Portland cement-blast furnace slag blend and a calcium sulfoaluminate cementlimestone blended system. The study reveals that the interlayer region contains larger and interconnected pores with low tortuosity, which could lead to enhanced transport of ions. Using the MIP data, surface fractal dimension and tortuosity parameters were computed. It was observed that the calcium sulfo aluminate-limestone blended system has higher pore complexity and tortuosity than the Portland cement-blast furnace slag system. Compared to mercury intrusion porosimetry, the X-ray micro-computed tomography technique was able to characterize both open and closed pores present in the printed sample at the resolution of the scanning. A significantly higher open porosity and the presence of more elongated pores with a high aspect ratio were observed in the interlayer compared to the bulk region. The current study can be useful in understanding the transport of ions through different regions in printed elements to assess its durability performance.