Tomography-based investigation on the early-time capillary imbibition in stained foam concrete

In this study, the vertical imbibition of water from foam concretes upward were studied with the assistance of staining, which illustrated the way contrast material spread in specimens during CT scans. The 20 x 20 mm2 bottom face of dried rectangular concrete was adopted, and the test was limited to the first 2.5 h. Using cesium (Cs) or iodine (I) as the staining agent, a new-developed X-ray attenuation method (XRAM) was used to obtain the spatial distribution of water. The result showed that Cs and I are equally trustable in tracing water during the early-time imbibition. Besides, two regions, namely "saturated verge" (near the imbibing face) and "unsaturated transport region" (from an inner area), could be recognized from the imbibition path regarding their variant evolving patterns. The saturated verge from the inlet was of constant width, while the scale of the unsaturated transport region kept increasing during imbibition, and the imbibing rate was similar for all specimens in this study. Moreover, even though the imbibition progress in this study was confirmed a diffusion-controlling progress, a broad imbibition front was revealed from the averaged 1D water content profile, which was mainly attributed to the irregular-shaped "saturated verge".