Abstract
Concrete cracking can result in a significant reduction of the durability and the service life due to the ingress of aggressive agents Self-healing concrete is able to heal cracks without external intervention, thereby mitigating the need for manual repair. In the assessment of the healing efficiency of self-healing concrete the to-be-healed crack width is an important parameter and different researchers have emphasised that the variability of the crack width significantly hampers an accurate assessment of the healing efficiency. With two new crack control techniques the variability of the crack width was reduced in order to decrease the variability on the calculated healing efficiency. This paper reports on the application of these techniques for the assessment of self-healing mortar containing encapsulated polyurethane. The healing potential was investigated by looking at the degree of sealing using a water flow test setup. It was observed that by using a crack control technique the variability on the crack width can indeed be reduced. Nonetheless, this does not translate in an equivalent reduction on the variability of the healing efficiency. This indicates that other factors contribute to the variability of the healing efficiency.
Highlights
Reinforced concrete is a commonly used construction material
This paper reports on two different crack width control techniques to reduce the variance in crack width when a 3-point bending test is applied, in an attempt to reduce the variability on the sealing results
For one specimen it was not possible to measure the crack width as the crack face was completely covered by the healing agent
Summary
Reinforced concrete is a commonly used construction material. Due to the low tensile strength, concrete can crack and these formed cracks provide a transport path for harmful substances to migrate into the concrete matrix and result in corrosion of the reinforcement. In order to test the sealing capacity of self-healing concrete a crack first needs to be induced, after which the actual testing can be performed These tests are very sensitive to the variance in crack width [1,2,3]. In order to have a low variance in crack width standardised cracks are sometimes used, such as: non-through going cuts [4], cast-in metal plates to be pulled out after the initial setting of the concrete creating a non-through going cut [5], cracking the specimens in two halves and reattaching them [6], These cracks do not have a geometry which is commonly found in reality. This allows to limit the variance as a result of the healing mechanism as much as possible
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