Demonstration projects with self-healing capsule-based and bacteria-based concrete

To reduce downtime, costs and labour for repair of concrete structures, self-healing concrete has been proposed as a solution. Over the laste decade, the efficiency of different self-healing mechanisms has been tested at laboratory scale. Lately, the first demonstrators have been made in order to test the self-healing efficiency at real scale and in actual service conditions. At the one hand our team has cast real-scale concrete beams, containing previously selected polymeric capsules. As capsule wall material, poly(methyl methacrylate) (PMMA) was chosen due to its high chemical stability in contact with concrete, high survival ratio during the concrete mixing process and ability to rupture when crossed by cracks of small width. The self-healing efficiency of the concrete elements with randomly dispersed PMMA capsules was determined after crack creating by 3-point-bending tests. Secondly, an in situ demonstration project was established with microbial self-healing concrete. A mixed ureolytic culture of bacterial spores (MUC+) and the nutrients urea and calcium nitrate were mixed into the concrete in a real concrete plant. With this self-healing concrete the roof plate of a sewer inspection pit was cast. From the same batch of concrete, prisms were taken to the laboratory for crack creation of the self-healing efficiency. For cracks with an average width of 348 um, created after 6 weeks of curing, a sealing efficiency against water flow of more than 90 % was measured after 24 weeks of water immersion