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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. ispartof: pages:180-185 ispartof: Proceedings Resilient Materials 4 Life 2020 (RM4L2020) pages:180-185 ispartof: Resilient Materials 4 Life 2020 (RM4L2020) location:Cardiff, UK date:20 Sep - 22 Sep 2021 status: published

Recently, researchers have focussed on the development of self-healing strategies in order to guarantee high performance regarding the durability of concrete structures. Exposing self-healing concrete to extreme conditions and evaluating its behaviour is the first step in understanding how the self-healing mechanism performs under these conditions. Nevertheless, there are limited studies subjecting self-healing concretes to harsh conditions combining extreme low temperatures and salt attacks. Therefore, we concentrate in this study on freezing and thawing conditions with de-icing salts, specifically with sodium chloride. It is an innovative assessment of self-healing concrete including commercially manufactured bacteria as healing agent. The objective is to ensure that autonomous crack healing occurs, restricting chloride ingress, extending the service life, and reducing the effect of degradation. The study presents the influence of the exposure conditions through permeability tests, microscopic investigations, scaling analyses, and chloride penetration. The permeability tests showed complete sealing after freezing and thawing cycles. Nevertheless, the healing products were removed together with material that was scaled off the surface due to cyclic freezing and thawing. The bacteria enhanced the properties of the concrete, resulting in less scaling and chloride penetration. However, chloride penetration through the crack cannot be prevented., This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sk��odowska-Curie grant agreement No 860006. The healing agent was provided by Basilisk and TU Delft, the latter being a beneficiary of SMARTINCS. T. Van Mullem and N. De Belie acknowledge the support of the grant (21SCIP C158977-02) from the Construction Technology Research Program funded by the Ministry of Land, Infrastructure and Transport of the Korean government., {"references":["Z. Liu and W. Hansen, \"Effect of hydrophobic surface treatment on freeze-thaw durability of concrete,\" Cem. Concr. Compos., vol. 69, pp. 49–60, May 2016, doi: 10.1016/j.cemconcomp.2016.03.001","M. J. Al-Kheetan, M. M. Rahman, S. H. Ghaffar, M. Al-Tarawneh, and Y. S. Jweihan, \"Comprehensive investigation of the long-term performance of internally integrated concrete pavement with sodium acetate,\" Results Eng., vol. 6, no. March, p. 100110, Jun. 2020, doi: 10.1016/j.rineng.2020.100110","M. Pigeon, J. Marchand, and R. Pleau, \"Frost resistant concrete,\" Constr. Build. Mater., vol. 10, no. 5, pp. 339–348, Jul. 1996, doi: 10.1016/0950-0618(95)00067-4","L. Basheer and D. J. Cleland, \"Freeze–thaw resistance of concretes treated with pore liners,\" Constr. Build. Mater., vol. 20, no. 10, pp. 990–998, Dec. 2006, doi: 10.1016/j.conbuildmat.2005.06.010","R. Mors and H. M. Jonkers, \"Bacteria-based self-healing concrete: evaluation of full scale demonstrator projects,\" RILEM Tech. Lett., vol. 4, pp. 138–144, Apr. 2020, doi: 10.21809/rilemtechlett.2019.93","K. J. Shin, W. Bae, S.-W. Choi, M. W. Son, and K. M. Lee, \"Parameters influencing water permeability coefficient of cracked concrete specimens,\" Constr. Build. Mater., vol. 151, pp. 907–915, Oct. 2017, doi: 10.1016/j.conbuildmat.2017.06.093"]}

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. ispartof: Science And Technology Of Advanced Materials vol:21 issue:1 pages:661-682 ispartof: location:United States status: Published online

Extreme environments are aggressive for concrete structures, hence a performance-based design is crucial to guarantee the durability during the service life. Nonetheless, there is a knowledge gap regarding the influence of cracks on standard and self-healing concrete. This research focuses on monitoring cracked self-healing concrete with two commercial healing agents: a bacteria-based healing agent (BAS) and a crystalline admixture (CA). After crack formation and a healing process of three months in wet/dry conditions (4 days/3 days), several extreme conditions were considered: (1) submerged in artificial seawater, (2) submerged in a solution with 33 g/L sodium chloride and (3) freeze-thaw (FT) cycling with de-icing salts. Microscopic images were used to quantify the healing efficiency of the two different healing agents, while chloride ingress and scaling were measured to determine durability. The results of the microscopic measurements indicated significant healing efficiency for both healing agents after the healing regime reaching 72% for CA, and 67% for BAS. After exposure to a marine environment, this efficiency increased to 95% and 92%, respectively. The uncracked BAS samples achieved a scaling reduction of 93% under FT exposure relative to the uncracked REF samples, while this was 49% for the CA samples. In cracked samples, scaling was reduced by 50% for BAS and 24% for CA, relative to the cracked REF samples. In all tested conditions, the BAS samples partially prevented the chloride ingress through the crack, while CA samples showed a great reduction. Overall, both healing agents reduced the degradation and could decrease the chloride ingress.

The development of circular economy models for the construction sector brings important challenges and opportunities to research and particularly to make knowledge transfer, for example through public policies. Santiago de Cali, third major city of Colombia (South America), is developing a circular economy model policy, which is mainly based on waste valorisation. Among others, the model includes a family of eco-concrete products that replaces Portland cement by blast furnace slag and fly ash coming from local industries. Therefore, the aim of this research is to develop scientific based recommendations to stakeholders for the selection of different concrete products (i.e. beams, columns, slabs) using blast furnace slag and fly ash (eco-concretes). Considering that life cycle assessment (LCA) is the most employed tool for consolidating, comparing, and assessing sustainability impacts [1], the LCA of these concrete products for the design of a sustainable residential house was performed. The LCA software Building for Environmental and Economic Sustainability (BEES) developed by the National Institute of Standards and Technology (NIST) was selected for the study. Results include a discussion on the environmental impacts. Furthermore, a methodology for the selection of sustainable building materials is presented.