Application of pH- sensitive hydrogels for concrete applications

1. Application of pH-sensitivehydrogels for concrete applications Arn Mignon, Sandra Van Vlierberghe, Peter Dubruel, Nele De Belie

2. Using specific types of hydrogels as self-sealing materials for cracks in concrete Crosslinked hydrogel network is synthesized Acrylic acid and acrylamide used as monomers / N,N'- Methylenebisacrylamide as crosslinker Swelling capacity is tested for whole pH-range Max. swellingdegree: 450 timesitsownweightat pH 12

3. Dynamic Vapour Sorption and microscopy help understanding the hydrogel properties Measurements are done with Dynamic Vapour Sorption, which uses sorption and desorption steps The hydrogel has a moisture uptake capacity of more than 92 % its weight The hydrogel is added to mortar: (0.5 m% and 1 m% vs. cement weight) Significant swelling is seen when water is poured over the surface

4. Water permeability tests prove the worth of the used hydrogels Water permeability factor k indicates the sealing capacity of cracks k (1 m% hydrogel) 10 times smaller than k (reference) at first measuring days Small cracks (< 220 µm) heal completely with and without the hydrogel The hydrogels are fulfilling their anticipated task especially in thefirst weeks after crack initiation