Characterization of distributed damage and self-healing in cementitous materials based on time-dependent 3-D x-ray computed microtomography (Micro-CT)

Characterization of distributed damage and self-healing in cementitous materials based on time-dependent 3-D x-ray computed microtomography (Micro-CT)

Fan, S.
Li, M.

2013-06-16

Concrete cracking is inevitable, and can be the result of one or a combination of factors such as dry shrinkage, thermal contraction, fatigue, and embedded steel corrosion. The presence of cracks leads to further deterioration, service life reduction of concrete infrastructure, and frequent maintenance and repairs. These challenges can be potentially addressed with innovative self-healing cementitious materials, which can autogenously regain material transport properties as well as mechanical characteristics after the damage self-healing process. For the development of self-healing cementitious materials, it is crucial to precisely characterize the extent and quality of self-healing due to a variety of factors. X-ray computed microtomography (Micro-CT) was adopted in this study to derive threedimensional tomographic data of micro-cracks before and after healing in engineered cementitious composite (ECC) materials. This method is a non-destructive visualizing technique that allows digitalization and monitoring of the interior characteristics of solid objects. ECC specimens were pre-damaged under bending to form multiple micro-cracks, and then exposed to wet-dry cycles to allow potential self-healing to occur. Micro-CT was then employed to build 3-D tomography models of the samples. The 3-D microcrack geometry, width and area were quantified. The extent of selfhealing was then determined. The results were further combined with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) to characterize crystalline and chemical properties of the self-healing products. This study showed that Micro-CT is a suitable advanced technique to directly quantify self-healing potential in solid materials. The Micro-CT results revealed that selfhealing extent of ECC is strongly influenced by crack width. For a bending crack with surface crack width of 30 ?m, 55.3% of the crack volume was healed after 5 wet-dry cycles. For a bending crack with surface crack width of 100 ?m , only 7% of the crack volume was healed after 5 wet-dry cycles. Hence, controlling microcrack width to under 30 ?m is a necessary condition for achieving early, robust self-healing in ECC.

x-ray computed microtomography
nondestructive
damage
self-healing
engineered cementitious composites

http://resolver.tudelft.nl/uuid:f08e4b47-7418-440d-b6be-42ab3160d0de

Conference proceedings

conference paper

(c) 2013 Fan, S.; Li, M.