Transport of water through strain-hardening cement-based composite (SHCC) applied on top of cracked reinforced concrete slabs with and without hydrophobization of cracks – Investigation by neutron radiography

• Capillary suction and drying kinetics of cracked RC/SHCC systems are studied.
• Water migration was non-destructively visualized and quantified by neutron radiography.
• Hydrophobization inhibits moisture ingress into cracks in the RC substrate efficiently.
• Crack widths affect drying kinetics substantially.

Composite specimens of steel-reinforced concrete (RC) strengthened with strain-hardening cement-based composite (SHCC) were characterized according to their water uptake and drying kinetics by neutron radiography imaging. The specimens were cracked in well-defined patterns, and some cracks were hydrophobized at the RC/SHCC interface. Qualitative and quantitative image evaluation revealed that capillary suction was very intense; within 1.2 min the cracks in both SHCC and RC filled with water completely, deep into the interior. Capillary transport through the matrices followed and led to moisture distribution throughout the body up to an elapsed time of 27 h. When drying, only macro-sized cracks emptied within about 1 h. Up until 46 h the original water frontier progressed further into the matrix. In parallel the specimen dried from its bottom face.Hydrophobization of cracked areas prior to application of SHCC proved a highly efficient measure to inhibit long-term ingress of water deep into the structure.