Interfacial mechanical bond characterization between cement pastes and porous aggregates through a coupled XCT and DVC technique

Abstract

Interfacial transition zone (ITZ) between cement matrix and porous aggregates plays an important role in affecting overall behavior of lightweight aggregate concrete (LWAC) due to mechanical interlocking effect. However, existing characterization techniques could not assess interfacial bond performance of LWAC in a three-dimensional and non-destructive way. The present study proposed a novel technique involving both in-situ X-ray computed tomography (XCT) and digital volume correlation (DVC) to quantitatively assess interfacial bond behavior between cement pastes and porous aggregates. In the test program, samples with various interfacial conditions were loaded to generate necessary displacement differences among different constituents. Volumetric deformations traced by XCT were transformed into volumetric strain components through DVC computation. Furthermore, cement-aggregate interactions were evaluated by analysis of XCT results. Eventually, strain profiles were used to characterize mechanical bond properties of the interfaces. Through the investigations, it was found that not all the penetrated cement paste could contribute to interfacial bond and that the proposed method could evaluate the effective area providing mechanical interlocking. The test results also showed that overall concrete strength could not represent the strength of ITZ.