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Novel active crack width control technique to reduce the variation on water permeability results for self-healing concrete

Tim Van Mullem (UGent) , Elke Gruyaert (UGent) , Brenda Debbaut (UGent) , Robby Caspeele (UGent) and Nele De Belie (UGent)
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Abstract
An important characteristic of self-healing concrete is its ability to regain liquid tightness after it has been damaged. This ability can be tested using water permeability setups. However, a lack of standardized test methods makes it difficult to compare results between different studies. Additionally, the large variation on crack widths between specimens results in a large spread of the permeability results. This , together with all other factor (e.g. internal crack geometry) contributing to the variability of permeability results, should be clearly assessed in order to develop a standardized permeability test. In this study a new active crack width control technique has been developed to significantly reduce the variation on the crack width within a series of specimens, resulting in more consistent permeability results. By analysing permeability results of specimens from test series with different nomina crack widths the factors contributing to variability could be assessed. The two main contributors are the variability on the mean crack width at the crack mouth and the variability on the internal crack geometry. The variability of the mean crack width can induce a 3 times higher variability of the permeability results. In contrast to the crack width, the internal geometry of a crack cannot be determined directly, yet it can cause a difference in permeability of more than 25% for specimens with an identical nominal surface crack width. It can be concluded that when crack widths are actively controlled, the main source of variability on permeability results is the internal geometry which cannot be controlled, regardless of the chosen cracking technique. In order to reduce the variance on the mean permeability, it is proposed to use at least six specimens per series.
Keywords
General Materials Science, Civil and Structural Engineering, Building and Construction

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Chicago
Van Mullem, Tim, Elke Gruyaert, Brenda Debbaut, Robby Caspeele, and Nele De Belie. 2019. “Novel Active Crack Width Control Technique to Reduce the Variation on Water Permeability Results for Self-healing Concrete.” Construction and Building Materials 203: 541–551.
APA
Van Mullem, T., Gruyaert, E., Debbaut, B., Caspeele, R., & De Belie, N. (2019). Novel active crack width control technique to reduce the variation on water permeability results for self-healing concrete. CONSTRUCTION AND BUILDING MATERIALS, 203, 541–551.
Vancouver
1.
Van Mullem T, Gruyaert E, Debbaut B, Caspeele R, De Belie N. Novel active crack width control technique to reduce the variation on water permeability results for self-healing concrete. CONSTRUCTION AND BUILDING MATERIALS. Elsevier ; 2019;203:541–51.
MLA
Van Mullem, Tim et al. “Novel Active Crack Width Control Technique to Reduce the Variation on Water Permeability Results for Self-healing Concrete.” CONSTRUCTION AND BUILDING MATERIALS 203 (2019): 541–551. Print.
@article{8607312,
  abstract     = {An important characteristic of self-healing concrete is its ability to regain liquid tightness after it has been damaged. This ability can be tested using water permeability setups. However, a lack of standardized test methods makes it difficult to compare results between different studies. Additionally, the large variation on crack widths between specimens results in a large spread of the permeability results. This , together with all other factor (e.g. internal crack geometry) contributing to the variability of permeability results, should be clearly assessed in order to develop a standardized permeability test. In this study a new active crack width control technique has been developed to significantly reduce the variation on the crack width within a series of specimens, resulting in more consistent permeability results. By analysing permeability results of specimens from test series with different nomina crack widths the factors contributing to variability could be assessed. The two main contributors are the variability on the mean crack width at the crack mouth and the variability on the internal crack geometry. The variability of the mean crack width can induce a 3 times higher variability of the permeability results. In contrast to the crack width, the internal geometry of a crack cannot be determined directly, yet it can cause a difference in permeability of more than 25\% for specimens with an identical nominal surface crack width. It can be concluded that when crack widths are actively controlled, the main source of variability on permeability results is the internal geometry which cannot be controlled, regardless of the chosen cracking technique. In order to reduce the variance on the mean permeability, it is proposed to use at least six specimens per series.},
  author       = {Van Mullem, Tim and Gruyaert, Elke and Debbaut, Brenda and Caspeele, Robby and De Belie, Nele},
  issn         = {0950-0618},
  journal      = {CONSTRUCTION AND BUILDING MATERIALS},
  language     = {eng},
  pages        = {541--551},
  publisher    = {Elsevier },
  title        = {Novel active crack width control technique to reduce the variation on water permeability results for self-healing concrete},
  url          = {http://dx.doi.org/10.1016/j.conbuildmat.2019.01.105},
  volume       = {203},
  year         = {2019},
}

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