COMPARISON OF MACROPORE STRUCTURES AND NETWORKS OF AUTOCLAVED AERATED CONCRETE BLOCKS USING MICRO-FOCUS X-RAY COMPUTED TOMOGRAPHY

Abstract

Autoclaved aerated concrete (AAC) is a lightweight cementitious material that has a unique structure characterized by a robust skeleton and pores (porous medium). The internal pore network structure of AAC highly controls mechanical and mass transport properties. This study aimed to identify the pore network structure of AAC (typical meso- and macropores with diameter >10 μm) and to correlate the pore characteristics with mass transport parameters of AAC such as gas diffusivity (Dp/D0), air permeability (ka), and saturated hydraulic conductivity (Ks) using three different AAC blocks. First, the three-dimensional macropore structure and network of 10 cm cubes of AAC blocks were visualized by microfocus X-ray computed tomography (MFXCT), and then pore structural parameters such as effective pore radius, coordination number, and tortuosity in the z direction were analyzed using a three-dimensional medial axis technique. Next, mass transport parameters were measured using 100 cm3 core samples taken from AAC blocks. Based on measured pore structural parameters with a scanning resolution of 12 μm, clear differences in macropore networks were observed among tested samples: the AAC blocks from Vietnam had less tortuous macropores with smaller and narrower range of radii compared to Japanese AAC sample. In collaboration with predictive models for mass transport parameters, Dp/D0, ka, and Ks were estimated by using the pore structural parameters from MFXCT and compared to measured values. The estimated Dp/D0 and ka values fit the measured values for all tested samples well, but the estimated ka and Ks from MFXCT under- or overestimated the measured values.