New self-healing system for cracks repairing

Macrocapsules with an expanding mineral powder were set-up for sealing cracks into cementbased materials. The expanding mineral powder was composed of a commercial fast setting cement mortar, sodium polyacrylate and a commercial product used to produce sparkling water (based on sodium acid carbonate, malic acid and tartaric acid). An optimal proportioning of these components was determined as 10:1:1, respectively. These compounds were first mixed with polyethylene glycol and cast into cylindrical moulds. Then, the mix was heated at 230°C in an oven and the cylinders were demoulded thereafter. The obtained products could be delicately handled and were coated with an epoxy resin to produce waterproofed macrocapsules, while some uncoated cylinders were mixed with water and kept in closed containers for 14 days. Brazilian tests were performed on these hydrated cylinders to determine their indirect tensile strength. Finally, the coated macrocapsules were incorporated into mortar prisms, that were pre-cracked in three-point bending test after 14 days. The prisms were kept under water for 8 days and showed a sealing efficiency of 98.7% with a water flow of 3.8 g/min, which decreased to 3.5 g/min after 18 days of water curing. The same samples were stored 10 more days under water to reach an overall healing time of 28 days, after which they were subjected again to a three-point bending test to assess the recovery of the mechanical properties in flexion. The average recovered flexural strength was (10.6 ±4.5)%.