Concrete keeps being the leading structural material due to its low
production cost and its great structural design flexibility. However, concrete is prone
to various ambient and operational loads which are responsible for crack initiation
and extension, leading to decrease of its anticipated operational service life. The
current study is focusing on the use of ultrasonic wave propagation techniques based
on low-cost and aggregate-size embedded piezoelectric transducers for the online
monitoring of the damage state and the healing performance in concrete structures
with an autonomous healing system in the form of encapsulated polyurethane-based
healing agent embedded in the matrix of concrete. The crack formation triggers the
autonomous healing mechanism which promises material recovery and extension of
the operational service life. The proposed technique is applied on large-scale, steel
reinforced, concrete beams (150mm × 250 mm × 3000 mm), subjected to four-point
bending. After the capsules are broken and the healing agent is released, which
results in filling of the crack void, and polymerized, the concrete beams are
reloaded. The results demonstrate the ability of the monitoring system to detect the
initiation and propagation of the cracking as well as to assess the performance of the
self-healing system
