Study of micro-cracks in cement-based materials with NMR relaxometry and ultrasound

Reinforced concrete structures require regular assessment of their structural integrity. The effects of mechanical loading and environmental effects on concrete structures produce micro-cracks, reducing the overall strength and stiffness while increasing their permeability to aggressive species. Water carrying aggressive species such as chloride ions can then travel through these small channels, reaching the reinforcing steel and causing corrosion. It can also be a starting point for larger cracks. This is particularly important since it may significantly reduce the service life of the structures. In this paper, two nondestructive testing techniques were used for micro-cracking assessment: i) NMR relaxometry and ii) Through-transmission ultrasound waves.