After several years of research in the Magnel Laboratory (Belgium) to obtain concrete with self-healing properties, the most promising mechanisms were tested on a larger scale. Instead of small mortar samples with self-healing properties, real-scale self-healing concrete beams (150 mm × 250 mm × 3000 mm) were made and the efficiency of autonomous crack repair was evaluated over time after loading the beams in four-point bending. In addition to a reference beam without self-healing properties, a

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... beam with encapsulated polyurethane and a beam containing superabsorbent polymers were investigated. While for the beam with polyurethane, crack repair is obtained as the healing agent is released as soon as cracks damage the embedded capsules, the superabsorbent polymers absorb water which intrudes into the cracks, immediately blocking the crack through swelling and later on by continued hydration and precipitation of calcite. The efficiency of both self-healing approaches was compared by measuring the reduction in water ingress into the cracks and by measuring the crack width reduction over time.