Evaluation of test methods for self-healing concrete with macrocapsules by inter-laboratory testing
2021
Self-healing of concrete is a promising way to increase the service life of structures. Innovative
research is being performed, yet it is difficult to compare results due to a lack of standardised
test methods. In the framework of the COST action SARCOS (CA15202) [1] six different interlaboratory
tests are being executed, in which different test methods are being evaluated for
six self-healing approaches. Here, the results of the inter-laboratory test concerning mortar
and concrete with macrocapsules filled with a polyurethane healing agent will be discussed.
The specimens were manufactured in one laboratory and then shipped to the other five
participating laboratories. All six laboratories evaluated two test methods: a water
permeability test and a capillary water absorption test. For the water permeability test, mortar
specimens were cracked and afterwards their crack width was controlled using an active
control technique. Due to the active crack control, the crack width of 90% of the samples
deviated by less than 10 μm from the target of 300 μm. This made it more straightforward to
compare the permeability test results, which indicated a similar sealing efficiency for several
of the laboratories. For the capillary water absorption test, concrete specimens were cracked
in a crack-width-controlled three-point bending test setup without active control after
unloading. Compared to the water permeability specimens, there was a lot more variation on
the crack width of the capillary water absorption specimens. The variability on the crack width
and differences in quality of waterproofing resulted in diverging findings in the capillary water
absorption test.
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