Periodic Reporting for period 1 - GEOBACTICON (The efficiency of bio-self-healing concrete within ground conditions)
Reporting period: 2018-11-01 to 2020-10-31
• What is the problem/issue being addressed?
Research to date has focused on the self-healing process in air or water environments. However, almost all structures (including bridges, buildings, tunnels, dams) are built on or in the ground. Thus, a significant amount of concrete structural elements are exposed to all sorts of ground conditions, e.g. different soil types, groundwater regimes, chemical and bacterial compositions that naturally existed within the ground. Research in this area is necessary because in underground concrete structures, cracks are invisible, surrounded by soil and their location cannot be accessed. This research helped to understand how different complicated ground conditions could influence the bio-self-healing process and whether an adjustment should be adopted by concrete designers.
• Why is it important for society?
The research vision is to reduce the expensive maintenance cost of underground infrastructures by reducing the uncertainty of the design of bio-self-healing concrete used for these structures. Therefore, the outcomes of this research are highly relevant to the construction industry and the knowledge produced by the project will have an economic, financial and societal impact in the EU and other regions.
• What are the overall objectives?
The hypothesis of this research is that the bio-self-healing process can be differently influenced by different ground conditions. Therefore, the project aims to explore the efficiency of the bio-self-healing solution in underground concrete structures. The research combined, in a novel interdisciplinary approach, several methods applied in materials/concrete, geotechnical engineering, and microbiology to conduct a series of lab-scale experiments on mortar specimens incubated within various soil environments. This allowed the investigation of the effect of several factors, including the type of soil, saturation regime and class of (chemical) exposures, on the bio-self-healing process.
Research to date has focused on the self-healing process in air or water environments. However, almost all structures (including bridges, buildings, tunnels, dams) are built on or in the ground. Thus, a significant amount of concrete structural elements are exposed to all sorts of ground conditions, e.g. different soil types, groundwater regimes, chemical and bacterial compositions that naturally existed within the ground. Research in this area is necessary because in underground concrete structures, cracks are invisible, surrounded by soil and their location cannot be accessed. This research helped to understand how different complicated ground conditions could influence the bio-self-healing process and whether an adjustment should be adopted by concrete designers.
• Why is it important for society?
The research vision is to reduce the expensive maintenance cost of underground infrastructures by reducing the uncertainty of the design of bio-self-healing concrete used for these structures. Therefore, the outcomes of this research are highly relevant to the construction industry and the knowledge produced by the project will have an economic, financial and societal impact in the EU and other regions.
• What are the overall objectives?
The hypothesis of this research is that the bio-self-healing process can be differently influenced by different ground conditions. Therefore, the project aims to explore the efficiency of the bio-self-healing solution in underground concrete structures. The research combined, in a novel interdisciplinary approach, several methods applied in materials/concrete, geotechnical engineering, and microbiology to conduct a series of lab-scale experiments on mortar specimens incubated within various soil environments. This allowed the investigation of the effect of several factors, including the type of soil, saturation regime and class of (chemical) exposures, on the bio-self-healing process.
The project began by developing a detailed research plan followed by conducting the microbiology aspects including training and preparations of bio-self-healing materials/ agents required for the planned bio cementitious mixtures. This was part of WP1 which also included engineering works preparations, the further purchasings and developments of the purpose-built experimental tool planned initially to be exploited in the next work packages. Also, within WP1 a primary investigation was conducted on bacterial cementitious mixtures under soil media incubations validating the originality of the project proposal. By the end of this phase, the first journal paper was published to disseminate the first set of experimental results.
The second phase (WP2) contains the preparation of specimens and the main testing used to evaluate the efficiency of pre-cracked bio self-healing cementitious specimens incubated in soil environment, namely clay and sand with different saturation regimes. The activities carried out included the following:
• Development of refined procedures used to evaluate the efficiency of self-healing concrete specimens within soil conditions.
• Experimental testing for evaluating the efficiency of bacterial self-healing of mortar specimens incubated in clay soil with different chemical exposure conditions and saturation regimes.
• Experimental testing for the evaluation of the efficiency of bacterial self-healing of mortar specimens incubated in sand soil with different chemical exposure conditions and saturation regimes.
At the end of each testing phase, the experimental data were analysed and interpreted (as part of WP3). Based on the analysis and interpretation, the relevant recommendation was developed to support a framework for the industrial application of bio-self-healing concrete technology for underground structures
From a design perspective, the work revealed that the bio self-healing technique can generally benefit concrete structures embedded within all types of soils under all conditions (adopted in the experiments); however, on the other hand, the study emphasises the need to consider the groundwater regime as well as acidity and sulphate of the ground. More broadly, it was found from the research work of this project growing evidence suggesting that the performance of bio-concrete within the ground is challenged by various unconventional issues. These include the effect of soil bacteria, soil particle infiltration within cracks, pore-water pressure, capillary pressure of cracks, chemical exposures and crack orientation and pattern created in interaction with engineered and natural ground.
The results were disseminated gradually through 2 journal papers, 3 conference papers, and 2 presentations, which were well received by the industrial and scientific communities. However, there has been a limitation on some planned dissemination activities due to the pandemic. In particular, it was not possible to participate in some international conferences and events as these have been either postponed or cancelled.
The second phase (WP2) contains the preparation of specimens and the main testing used to evaluate the efficiency of pre-cracked bio self-healing cementitious specimens incubated in soil environment, namely clay and sand with different saturation regimes. The activities carried out included the following:
• Development of refined procedures used to evaluate the efficiency of self-healing concrete specimens within soil conditions.
• Experimental testing for evaluating the efficiency of bacterial self-healing of mortar specimens incubated in clay soil with different chemical exposure conditions and saturation regimes.
• Experimental testing for the evaluation of the efficiency of bacterial self-healing of mortar specimens incubated in sand soil with different chemical exposure conditions and saturation regimes.
At the end of each testing phase, the experimental data were analysed and interpreted (as part of WP3). Based on the analysis and interpretation, the relevant recommendation was developed to support a framework for the industrial application of bio-self-healing concrete technology for underground structures
From a design perspective, the work revealed that the bio self-healing technique can generally benefit concrete structures embedded within all types of soils under all conditions (adopted in the experiments); however, on the other hand, the study emphasises the need to consider the groundwater regime as well as acidity and sulphate of the ground. More broadly, it was found from the research work of this project growing evidence suggesting that the performance of bio-concrete within the ground is challenged by various unconventional issues. These include the effect of soil bacteria, soil particle infiltration within cracks, pore-water pressure, capillary pressure of cracks, chemical exposures and crack orientation and pattern created in interaction with engineered and natural ground.
The results were disseminated gradually through 2 journal papers, 3 conference papers, and 2 presentations, which were well received by the industrial and scientific communities. However, there has been a limitation on some planned dissemination activities due to the pandemic. In particular, it was not possible to participate in some international conferences and events as these have been either postponed or cancelled.
This research project has initiated interdisciplinary research work that enabled the senior researcher and the other members of the research team to tackle fundamental aspects of bio-concrete-ground interaction, including an understanding of both the biological aspects and the ground and structural engineering. The interdisciplinary nature of the project has added great value to the senior researcher’s skills and experience, which has enhanced his potential and future career prospects. Despite the lockdown, the senior researcher was able to acquire new scientific knowledge on bacteria strains as well as experimental skills in Microbiology equipment such as Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDX). These skills were valuable and have been recognised by the beneficiary institution, which offered him to continue to use the university facilities as a visiting researcher for three years after the end of the project. This will further enhance the potential and future career prospects of the senior researcher, who is planning to publish further 2 journal papers. The impact of this on the university will be key in the participation of the Research Excellence Framework (REF).