Abstract
ABSTRACT Development and commercialization of self-healing concrete is hampered due to a lack of standardized test methods. Six inter-laboratory testing programs are being executed by the EU COST action SARCOS, each focusing on test methods for a specific self-healing technique. This paper reports on the comparison of tests for mortar and concrete specimens with polyurethane encapsulated in glass macrocapsules. First, the pre-cracking method was analysed: mortar specimens were cracked in a three-point bending test followed by an active crack width control technique to restrain the crack width up to a predefined value, while the concrete specimens were cracked in a three-point bending setup with a displacement-controlled loading system. Microscopic measurements showed that with the application of the active control technique almost all crack widths were within a narrow predefined range. Conversely, for the concrete specimens the variation on the crack width was higher. After pre-cracking, the self-healing effect was characterized via durability tests: the mortar specimens were tested in a water permeability test and the spread of the healing agent on the crack surfaces was determined, while the concrete specimens were subjected to two capillary water absorption tests, executed with a different type of waterproofing applied on the zone around the crack. The quality of the waterproofing was found to be important, as different results were obtained in each absorption test. For the permeability test, 4 out of 6 labs obtained a comparable flow rate for the reference specimens, yet all 6 labs obtained comparable sealing efficiencies, highlighting the potential for further standardization.
Highlights
Self-healing concrete has a great potential as a building material as it is able to heal its own defects without external human intervention
This paper reports on the comparison of tests for mortar and concrete specimens with polyurethane encapsulated in glass macrocapsules
After pre-cracking, the self-healing effect was characterized via durability tests: the mortar specimens were tested in a water permeability test and the spread of the healing agent on the crack surfaces was determined, while the concrete specimens were subjected to two capillary water absorption tests, executed with a different type of waterproofing applied on the zone around the crack
Summary
Self-healing concrete has a great potential as a building material as it is able to heal its own defects without external human intervention. These defects are a common phenomenon in concrete and manifest as cracks caused by e.g. mechanical loading or restrained shrinkage. In most cases the formation of cracks does not pose an immediate risk for the structural behaviour of concrete elements. These cracks may significantly accelerate the degradation of the elements, and might thereby reduce the service life and the sustainability. Structures which can operate longer without being replaced have a significant environmental benefit, considering that the construction sector has a large share in the global CO2 emissions [1]
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