Using Neutron Radiography to Assess Parameters Associated with Water Permeability Testing

Abstract

Abstract This study uses neutron radiography to evaluate specimen preparation and test parameters that impact the depth of water penetration in concrete tested under water pressure. First, the impact of the boundary conditions (i.e., the dissipation of pressure that may build up at the lower side of the specimen) on the water penetration throughout the specimen depth was studied. Second, the impact of predrying the specimens (at 65°C) was examined. Third, the depth of water penetration is often measured by splitting the specimen at the end of the permeability test. The use of visual assessment to quantify the depth of water penetration was compared with neutron radiography measurements to determine the accuracy of visual inspection. It was concluded that care should be taken while designing the permeability apparatus to allow pressure dissipation at the lower section of the specimen. The predrying of the specimens at 65°C significantly impacts the permeability and microstructure of the concrete specimens. Finally, water can be seen by the eye when it fills voids with a pore radius greater than 46 nm (i.e., a relative humidity higher than 98.2 ± 0.5 % range, in concrete specimens with a water-to-cement ratio of 0.42 and an air content of 2.5 % content).