Nondestructive test for visualization of water movement in concrete using neutron imaging

Water penetration in concrete has been introduced into Japanese Standard Specifications for Concrete Structures ‘Design’ in 2018. This clearly shows that water ingress through surfaces can affect steel corrosion. Test method for water penetration rate coefficient of concrete subjected to water in short term was indicated at the same time. In 2022, Specifications ‘Maintenance’ has involved this coefficient to estimate progress of steel corrosion. The proposed test method can be useful for maintenance on the one hand and has a problem on the other. The test is performed in destructive way and needs nine circular specimens (100 mm in diameter and 200 mm in height). The aim of this research is to develop nondestructive test method which can visualize water movement in concrete. Neutron imaging is chosen to attain this goal and is conducted at the RIKEN Accelerator-driven compact Neutron Source, RANS. For incident neutrons, transmittance is changed by the element distributed to the transmission direction and the volume. Especially, hydrogen strongly scatter incident neutrons and water is imaged as shades.