Scanning electron microscopy with backscattered electrons (SEM/BSE) is a powerful technique that ... more Scanning electron microscopy with backscattered electrons (SEM/BSE) is a powerful technique that allows the visualization of polished cross sections with good reproducibility and level of detail. It is widely used to study the microstructure of cement-based materials and identify different phases in the cement paste. However, in some cases it is difficult to distinguish between some phases due to a similar grey level, as in the case of slag and portlandite. Then, X-ray elements mapping is necessary to help in the differentiation according to composition, but it can be quite time consuming and tedious with standard detectors. A machine learning tool, trainable WEKA segmentation (TWS), can be used to train a classifier by means of pixel grey values and segment the different phases automatically without any assistance of compositional mapping, transforming the problem into a pixel classification issue. The trained models can be improved by adjusting each class. The application of the m...
Eco-Efficient Repair and Rehabilitation of Concrete Infrastructures
Abstract Costs related to repair works mount up as the direct costs of the repair as well as the ... more Abstract Costs related to repair works mount up as the direct costs of the repair as well as the indirect costs—resulting from traffic jams and possible loss in productivity, need to be taken into account. In addition, not all cracks are visible and accessible and thus not all cracks can be repaired manually. Therefore, self-healing of concrete cracks, in which an embedded healing mechanism is triggered upon crack appearance, is very promising. One of the investigated self-healing approaches consists of the use of embedded capsules with healing agent. Upon crack formation, the capsules crossed by the crack break and release their content into the crack resulting in immediate repair. In this chapter, self-healing through the use of encapsulated polyurethane is discussed. The resulting crack closure efficiency, regain in impermeability, mechanical properties, and durability are subsequently demonstrated. Finally, the possible extension in service life which can be obtained through the use of this self-healing technique is described.
A novel linear reservoir-vascular tubes network is presented in this work and the design efficacy... more A novel linear reservoir-vascular tubes network is presented in this work and the design efficacy is explored by testing concrete beams loaded on bending and by assessing their damage healing and mechanical recovery. The healing system is composed of additively manufactured polymer components that appear equally effective compared to conventional ceramic tubes since the 3D printed polymer-tubes instantly break upon cracking. It is shown that bulk reservoirs embedded into concrete can deviate cracks and detrimentally affect the concrete’s resistance to failure. The crack formation and re-opening is monitored by acoustic emission (AE) and digital image correlation (DIC) concluding that initial brittle cracking is shifted after healing to a pseudo-ductile crack re-opening with extended post-softening. The sealed cracks show significant strength and toughness recovery (i.e., above 80% of the original value) escorted also by an ultrasound pulse velocity (UPV) increase (up to 126% relativ...
3rd International Conference on the Application of Superabsorbent Polymers (SAP) and Other New Admixtures Towards Smart Concrete, 2019
Shrinkage in concrete structures has been the focus of many studies. Lately a lot of attention ha... more Shrinkage in concrete structures has been the focus of many studies. Lately a lot of attention has been given to autogenous shrinkage. Although it may not be prominent in ordinary concrete structures, in systems with very low water-to-cement/binder ratio (ultra-high performance concrete for example) it can become a serious issue associated with the cracking of the structure at early age. This type of shrinkage develops due to a reduction in the internal relative humidity of the material and it is also associated to the development of capillary pressure in the pore system due to receding menisci. A big challenge in studying autogenous shrinkage is determining the "time-zero". Given a lack of consensus in literature, this study aimed to investigate the influence of different estimations of time-zero: the final setting time determined by both an electronic Vicat apparatus and ultrasonic measurements; the "knee-point" in the shrinkage curve; and the capillary pressure build-up. Cement pastes with and without superabsorbent polymers (SAPs) were produced with Portland cement CEM III-B 42.5 N and superplasticizer (Glenium 51, 35% conc.). SAPs have proven to be quite effective in the mitigation of autogenous shrinkage as they can act as water reservoirs for the system. Among all methods, the capillary pressure was very suitable for all mixtures. For those containing SAPs no difference was found in picking the time-zero with any method. For the one without SAPs and lower w/c the choice of time-zero based on the setting time led to a different magnitude of autogenous shrinkage deformation in comparison to the other methods, which could be interpreted as an underestimation of the autogenous shrinkage deformation.
Concrete Repair, Rehabilitation and Retrofitting II, 2008
ABSTRACT: This paper describes the effectiveness of two strategies in preventing algal growth on ... more ABSTRACT: This paper describes the effectiveness of two strategies in preventing algal growth on aerated autoclaved concrete. A first strategy comprised the use of water repellents in order to affect the bioreceptivity of the material. In the second strategy, products ...
Sustainable Construction Materials and Technologies (SCMT), 2016
Reinforcement corrosion induced by diffusion of chlorides is one of the most important damage mec... more Reinforcement corrosion induced by diffusion of chlorides is one of the most important damage mechanisms that leads to the deterioration of reinforced concrete structures. Cracking of reinforced concrete structures during their service life is almost inevitable. Cracks form preferential pathways for the ingress of chlorides and will accelerate the onset of corrosion and its propagation. In this paper, autonomous self-healing of cracks by encapsulated polyurethane is investigated as a possible method to heal cracks and reduce chloride ingress through cracks without human intervention. Cracks in concrete specimens were created in two ways: by means of thin metal plates to create standardized artificial cracks and by means of splitting tests to create realistic cracks. A crack width of 0.3 mm was chosen since most design codes limit the crack width to that value. The resistance to chloride penetration of autonomously healed concrete was evaluated by the diffusion test as described in NT Build 443. Uncracked, cracked and healed specimens were subjected to a 165 g/l NaCl solution for 7 weeks. After that period chloride profiles in the crack region and in an area further away from the crack were obtained by potentiometric titrations. From the resulting chloride profiles it was concluded that the polyurethane was very well able to seal both artificial and realistic cracks and reduce the chloride content in the crack zone significantly. At depths below the surface larger than 14 mm, healing was able to reduce the total chloride content in the crack zone by more than 70%.
Cracks in reinforced concrete are preferential ingress paths for aggressive substances such as ch... more Cracks in reinforced concrete are preferential ingress paths for aggressive substances such as chlorides. As soon as a critical amount of chlorides has reached the steel reinforcement, corrosion will occur. Therefore, crack healing is of utmost importance. However, manual crack repair is very labour intensive. Therefore, the potential of self-healing through the release of a water repellent agent from embedded capsules was compared with the effectiveness of applying this agent on the concrete surface before or after cracking and the effectiveness of injection of the agent into a crack. From the electrochemical corrosion measurements, it was shown that only uncracked samples were able to withstand 135 weekly cycles of exposure to a 33 g/L chloride solution without corrosion initiation of the reinforcement. While samples with manually injected and autonomously healed cracks resisted the exposure conditions for about 50 cycles or more, samples for which the water repellent agent was ap...
The first-generation of autonomously healed concrete elements is under construction: beams (SIM-S... more The first-generation of autonomously healed concrete elements is under construction: beams (SIM-SECEMIN project, Flanders Belgium), one-way flat slabs (MeMC, VUB, Belgium) and wall panels (Materials4Life project, UK) are designed with the embedment of encapsulated repair agent. In the presence of cracks, capsules rupture releasing the agent that fills the crack void. The released agent seals and mechanically restores the crack discontinuity. This automatic process can be repeatable using vascular networks that carry the agent and release it at different locations into concrete. The innovative design is built up following several series of laboratory-scale beam tests configured over the last decade. This paper discusses the application of numerous experimental techniques that assess the mechanical performance of autonomously healed concrete: Acoustic Emission, Ultrasound Pulse Velocity, Optical Microscopy, Digital Image Correlation, Capillary Water Absorption, Computed Tomography. The study focuses on the performance and efficiency of each method on laboratory and real-scale tests. The techniques with the most promising output are selected and combined in order to design a sensing tool that evaluates healing on real applications.
Libro de Comunicaciones / Livro das Comunicações, 2018
El impacto medioambiental ocasionado durante las últimas décadas por el sector de la construcción... more El impacto medioambiental ocasionado durante las últimas décadas por el sector de la construcción, teniendo en cuenta tanto la elevada utilización de recursos naturales como la generación de grandes volúmenes de residuos, ha fomentado el interés de dicho sector por el conocimiento y uso de los hormigones reciclados. Este tipo de material proporciona una alternativa capaz de solventar los dos costes ecológicos mencionados anteriormente, ya que el uso de residuos de construcción y demolición en la elaboración de nuevos hormigones disminuye las necesidades de deposición en el medio de dicho flujo residual, así como también reduce la demanda de nuevas extracciones. En el presente estudio se muestran las diferencias de comportamiento existentes entre un hormigón convencional (realizado con árido 100% natural) y un hormigón reciclado (50% del árido grueso natural se ha sustituido por árido reciclado mixto) cuando estos son utilizados en el sector agroganadero. Este tipo de ambientes son m...
Concrete Repair, Rehabilitation and Retrofitting II, 2008
Abstract The ability of certain bacteria to promote the precipitation of calcium carbonate, has b... more Abstract The ability of certain bacteria to promote the precipitation of calcium carbonate, has been used advantageously for consolidation of concrete and Stone or for the desnification of sandy soils. Previous research has illustrated a reduction of the capillary permeable ...
ID No : CM-00 ABSTRACT The restoration of concrete cracks is important as they may endanger the d... more ID No : CM-00 ABSTRACT The restoration of concrete cracks is important as they may endanger the durability of the structure, however, large costs are involved in crack repair and sometimes repair is even impossible due to inaccessibility. Therefore, we attempt to heal cracks autonomously by embedding an encapsulated two-compound polyurethane-based healing agent inside the matrix. When cracks appear, the brittle capsules break and the healing agent is released. Upon contact of both compounds the healing agent starts to expand and seals the crack, so aggressive substances cannot longer enter the matrix.The restoration of concrete cracks is important as they may endanger the durability of the structure, however, large costs are involved in crack repair and sometimes repair is even impossible due to inaccessibility. Therefore, we attempt to heal cracks autonomously by embedding an encapsulated two-compound polyurethane-based healing agent inside the matrix. When cracks appear, the britt...
This research investigates the use of copper slag as supplementary cementitious materials (SCM) i... more This research investigates the use of copper slag as supplementary cementitious materials (SCM) in ultra high performance mortar (IHPM). Two secondary slag types from a plant in Belgium were utilized as SCM and were classified as a quickly cooled granulated copper slag (QCS) and a slowly cooled broken copper slag (SCS). Both materials were ground intensively using a planetary ball mill. A low water-to-binder ratio of 0.15 was chosen for the UHPM in this study. Various mortar and cement paste samples were produced with increasing copper slag content from 0 to 20 wt% in steps of 5 wt%. Particle size distribution (PSD) and specific surface area (SSA) of the copper slag were assessed using laser diffraction and the Blaine permeability test, respectively. The results obtained, showed that the strength of mortars with different copper slag proportions was comparable to or even better than the control mixture at 90 days. The increased fineness of the copper slag enhances the mortar strengt...
Autogenous healing is one of the promising paths to counteract the formation of cracks in concret... more Autogenous healing is one of the promising paths to counteract the formation of cracks in concrete. A way of promoting this autogenous healing is by limiting the cracks by means of synthetic (polyvinyl alcohol) microfibres and by providing the necessary water by means of superabsorbent polymers (SAPs) [1-3]. There are different types and sizes
Generally, it is assumed that cracks influence the durability of concrete negatively by accelerat... more Generally, it is assumed that cracks influence the durability of concrete negatively by accelerating the penetration of aggressive elements. One of those elements are chlorides, present in marine environments. In this research, the effect of the crack width on chloride penetration is investigated by means of non-steady state migration tests based on NT Build 492. Therefore, ordinary Portland cement-, high sulphate resistant- and slag concrete are used. The cracks are formed by means of steel plates with widths of 0.1, 0.2 and 0.3 mm. After the migration test, migration coefficients and penetration depths are obtained. It seems that a crack width of 0.1 mm already has an influence on chloride penetration. Nevertheless, the biggest changes are measured for a crack width of 0.3 mm. The migration coefficient at the 0.3 mm crack tip increases 47 % compared to the migration coefficient at the exposed surface, regardless the concrete type.
The paper proposes expressions for the self-repairing assessment (i.e., the recovery of the mecha... more The paper proposes expressions for the self-repairing assessment (i.e., the recovery of the mechanical properties of the material consequent to the self-healing process) obtained by processing through regression analysis the results of the four-point-bending tests performed on ECC specimens. ECC mixes design considered varying the fly ash content/cement content and the type of micro-fibers. four-point-bending tests were performed on reference specimens and pre-cracked and healed specimens, at various ages and with different loading rates. The studied parameters are the first-cracking strength, ultimate flexural strength upon strain hardening, initial tangent Young modulus and ultimate flexural tensile strain as a measurement of the multiple-cracking capability. Finally, power and logarithmic regression expressions are proposed to simulate the recovery of the self-healing parameters.
Scanning electron microscopy with backscattered electrons (SEM/BSE) is a powerful technique that ... more Scanning electron microscopy with backscattered electrons (SEM/BSE) is a powerful technique that allows the visualization of polished cross sections with good reproducibility and level of detail. It is widely used to study the microstructure of cement-based materials and identify different phases in the cement paste. However, in some cases it is difficult to distinguish between some phases due to a similar grey level, as in the case of slag and portlandite. Then, X-ray elements mapping is necessary to help in the differentiation according to composition, but it can be quite time consuming and tedious with standard detectors. A machine learning tool, trainable WEKA segmentation (TWS), can be used to train a classifier by means of pixel grey values and segment the different phases automatically without any assistance of compositional mapping, transforming the problem into a pixel classification issue. The trained models can be improved by adjusting each class. The application of the m...
Eco-Efficient Repair and Rehabilitation of Concrete Infrastructures
Abstract Costs related to repair works mount up as the direct costs of the repair as well as the ... more Abstract Costs related to repair works mount up as the direct costs of the repair as well as the indirect costs—resulting from traffic jams and possible loss in productivity, need to be taken into account. In addition, not all cracks are visible and accessible and thus not all cracks can be repaired manually. Therefore, self-healing of concrete cracks, in which an embedded healing mechanism is triggered upon crack appearance, is very promising. One of the investigated self-healing approaches consists of the use of embedded capsules with healing agent. Upon crack formation, the capsules crossed by the crack break and release their content into the crack resulting in immediate repair. In this chapter, self-healing through the use of encapsulated polyurethane is discussed. The resulting crack closure efficiency, regain in impermeability, mechanical properties, and durability are subsequently demonstrated. Finally, the possible extension in service life which can be obtained through the use of this self-healing technique is described.
A novel linear reservoir-vascular tubes network is presented in this work and the design efficacy... more A novel linear reservoir-vascular tubes network is presented in this work and the design efficacy is explored by testing concrete beams loaded on bending and by assessing their damage healing and mechanical recovery. The healing system is composed of additively manufactured polymer components that appear equally effective compared to conventional ceramic tubes since the 3D printed polymer-tubes instantly break upon cracking. It is shown that bulk reservoirs embedded into concrete can deviate cracks and detrimentally affect the concrete’s resistance to failure. The crack formation and re-opening is monitored by acoustic emission (AE) and digital image correlation (DIC) concluding that initial brittle cracking is shifted after healing to a pseudo-ductile crack re-opening with extended post-softening. The sealed cracks show significant strength and toughness recovery (i.e., above 80% of the original value) escorted also by an ultrasound pulse velocity (UPV) increase (up to 126% relativ...
3rd International Conference on the Application of Superabsorbent Polymers (SAP) and Other New Admixtures Towards Smart Concrete, 2019
Shrinkage in concrete structures has been the focus of many studies. Lately a lot of attention ha... more Shrinkage in concrete structures has been the focus of many studies. Lately a lot of attention has been given to autogenous shrinkage. Although it may not be prominent in ordinary concrete structures, in systems with very low water-to-cement/binder ratio (ultra-high performance concrete for example) it can become a serious issue associated with the cracking of the structure at early age. This type of shrinkage develops due to a reduction in the internal relative humidity of the material and it is also associated to the development of capillary pressure in the pore system due to receding menisci. A big challenge in studying autogenous shrinkage is determining the "time-zero". Given a lack of consensus in literature, this study aimed to investigate the influence of different estimations of time-zero: the final setting time determined by both an electronic Vicat apparatus and ultrasonic measurements; the "knee-point" in the shrinkage curve; and the capillary pressure build-up. Cement pastes with and without superabsorbent polymers (SAPs) were produced with Portland cement CEM III-B 42.5 N and superplasticizer (Glenium 51, 35% conc.). SAPs have proven to be quite effective in the mitigation of autogenous shrinkage as they can act as water reservoirs for the system. Among all methods, the capillary pressure was very suitable for all mixtures. For those containing SAPs no difference was found in picking the time-zero with any method. For the one without SAPs and lower w/c the choice of time-zero based on the setting time led to a different magnitude of autogenous shrinkage deformation in comparison to the other methods, which could be interpreted as an underestimation of the autogenous shrinkage deformation.
Concrete Repair, Rehabilitation and Retrofitting II, 2008
ABSTRACT: This paper describes the effectiveness of two strategies in preventing algal growth on ... more ABSTRACT: This paper describes the effectiveness of two strategies in preventing algal growth on aerated autoclaved concrete. A first strategy comprised the use of water repellents in order to affect the bioreceptivity of the material. In the second strategy, products ...
Sustainable Construction Materials and Technologies (SCMT), 2016
Reinforcement corrosion induced by diffusion of chlorides is one of the most important damage mec... more Reinforcement corrosion induced by diffusion of chlorides is one of the most important damage mechanisms that leads to the deterioration of reinforced concrete structures. Cracking of reinforced concrete structures during their service life is almost inevitable. Cracks form preferential pathways for the ingress of chlorides and will accelerate the onset of corrosion and its propagation. In this paper, autonomous self-healing of cracks by encapsulated polyurethane is investigated as a possible method to heal cracks and reduce chloride ingress through cracks without human intervention. Cracks in concrete specimens were created in two ways: by means of thin metal plates to create standardized artificial cracks and by means of splitting tests to create realistic cracks. A crack width of 0.3 mm was chosen since most design codes limit the crack width to that value. The resistance to chloride penetration of autonomously healed concrete was evaluated by the diffusion test as described in NT Build 443. Uncracked, cracked and healed specimens were subjected to a 165 g/l NaCl solution for 7 weeks. After that period chloride profiles in the crack region and in an area further away from the crack were obtained by potentiometric titrations. From the resulting chloride profiles it was concluded that the polyurethane was very well able to seal both artificial and realistic cracks and reduce the chloride content in the crack zone significantly. At depths below the surface larger than 14 mm, healing was able to reduce the total chloride content in the crack zone by more than 70%.
Cracks in reinforced concrete are preferential ingress paths for aggressive substances such as ch... more Cracks in reinforced concrete are preferential ingress paths for aggressive substances such as chlorides. As soon as a critical amount of chlorides has reached the steel reinforcement, corrosion will occur. Therefore, crack healing is of utmost importance. However, manual crack repair is very labour intensive. Therefore, the potential of self-healing through the release of a water repellent agent from embedded capsules was compared with the effectiveness of applying this agent on the concrete surface before or after cracking and the effectiveness of injection of the agent into a crack. From the electrochemical corrosion measurements, it was shown that only uncracked samples were able to withstand 135 weekly cycles of exposure to a 33 g/L chloride solution without corrosion initiation of the reinforcement. While samples with manually injected and autonomously healed cracks resisted the exposure conditions for about 50 cycles or more, samples for which the water repellent agent was ap...
The first-generation of autonomously healed concrete elements is under construction: beams (SIM-S... more The first-generation of autonomously healed concrete elements is under construction: beams (SIM-SECEMIN project, Flanders Belgium), one-way flat slabs (MeMC, VUB, Belgium) and wall panels (Materials4Life project, UK) are designed with the embedment of encapsulated repair agent. In the presence of cracks, capsules rupture releasing the agent that fills the crack void. The released agent seals and mechanically restores the crack discontinuity. This automatic process can be repeatable using vascular networks that carry the agent and release it at different locations into concrete. The innovative design is built up following several series of laboratory-scale beam tests configured over the last decade. This paper discusses the application of numerous experimental techniques that assess the mechanical performance of autonomously healed concrete: Acoustic Emission, Ultrasound Pulse Velocity, Optical Microscopy, Digital Image Correlation, Capillary Water Absorption, Computed Tomography. The study focuses on the performance and efficiency of each method on laboratory and real-scale tests. The techniques with the most promising output are selected and combined in order to design a sensing tool that evaluates healing on real applications.
Libro de Comunicaciones / Livro das Comunicações, 2018
El impacto medioambiental ocasionado durante las últimas décadas por el sector de la construcción... more El impacto medioambiental ocasionado durante las últimas décadas por el sector de la construcción, teniendo en cuenta tanto la elevada utilización de recursos naturales como la generación de grandes volúmenes de residuos, ha fomentado el interés de dicho sector por el conocimiento y uso de los hormigones reciclados. Este tipo de material proporciona una alternativa capaz de solventar los dos costes ecológicos mencionados anteriormente, ya que el uso de residuos de construcción y demolición en la elaboración de nuevos hormigones disminuye las necesidades de deposición en el medio de dicho flujo residual, así como también reduce la demanda de nuevas extracciones. En el presente estudio se muestran las diferencias de comportamiento existentes entre un hormigón convencional (realizado con árido 100% natural) y un hormigón reciclado (50% del árido grueso natural se ha sustituido por árido reciclado mixto) cuando estos son utilizados en el sector agroganadero. Este tipo de ambientes son m...
Concrete Repair, Rehabilitation and Retrofitting II, 2008
Abstract The ability of certain bacteria to promote the precipitation of calcium carbonate, has b... more Abstract The ability of certain bacteria to promote the precipitation of calcium carbonate, has been used advantageously for consolidation of concrete and Stone or for the desnification of sandy soils. Previous research has illustrated a reduction of the capillary permeable ...
ID No : CM-00 ABSTRACT The restoration of concrete cracks is important as they may endanger the d... more ID No : CM-00 ABSTRACT The restoration of concrete cracks is important as they may endanger the durability of the structure, however, large costs are involved in crack repair and sometimes repair is even impossible due to inaccessibility. Therefore, we attempt to heal cracks autonomously by embedding an encapsulated two-compound polyurethane-based healing agent inside the matrix. When cracks appear, the brittle capsules break and the healing agent is released. Upon contact of both compounds the healing agent starts to expand and seals the crack, so aggressive substances cannot longer enter the matrix.The restoration of concrete cracks is important as they may endanger the durability of the structure, however, large costs are involved in crack repair and sometimes repair is even impossible due to inaccessibility. Therefore, we attempt to heal cracks autonomously by embedding an encapsulated two-compound polyurethane-based healing agent inside the matrix. When cracks appear, the britt...
This research investigates the use of copper slag as supplementary cementitious materials (SCM) i... more This research investigates the use of copper slag as supplementary cementitious materials (SCM) in ultra high performance mortar (IHPM). Two secondary slag types from a plant in Belgium were utilized as SCM and were classified as a quickly cooled granulated copper slag (QCS) and a slowly cooled broken copper slag (SCS). Both materials were ground intensively using a planetary ball mill. A low water-to-binder ratio of 0.15 was chosen for the UHPM in this study. Various mortar and cement paste samples were produced with increasing copper slag content from 0 to 20 wt% in steps of 5 wt%. Particle size distribution (PSD) and specific surface area (SSA) of the copper slag were assessed using laser diffraction and the Blaine permeability test, respectively. The results obtained, showed that the strength of mortars with different copper slag proportions was comparable to or even better than the control mixture at 90 days. The increased fineness of the copper slag enhances the mortar strengt...
Autogenous healing is one of the promising paths to counteract the formation of cracks in concret... more Autogenous healing is one of the promising paths to counteract the formation of cracks in concrete. A way of promoting this autogenous healing is by limiting the cracks by means of synthetic (polyvinyl alcohol) microfibres and by providing the necessary water by means of superabsorbent polymers (SAPs) [1-3]. There are different types and sizes
Generally, it is assumed that cracks influence the durability of concrete negatively by accelerat... more Generally, it is assumed that cracks influence the durability of concrete negatively by accelerating the penetration of aggressive elements. One of those elements are chlorides, present in marine environments. In this research, the effect of the crack width on chloride penetration is investigated by means of non-steady state migration tests based on NT Build 492. Therefore, ordinary Portland cement-, high sulphate resistant- and slag concrete are used. The cracks are formed by means of steel plates with widths of 0.1, 0.2 and 0.3 mm. After the migration test, migration coefficients and penetration depths are obtained. It seems that a crack width of 0.1 mm already has an influence on chloride penetration. Nevertheless, the biggest changes are measured for a crack width of 0.3 mm. The migration coefficient at the 0.3 mm crack tip increases 47 % compared to the migration coefficient at the exposed surface, regardless the concrete type.
The paper proposes expressions for the self-repairing assessment (i.e., the recovery of the mecha... more The paper proposes expressions for the self-repairing assessment (i.e., the recovery of the mechanical properties of the material consequent to the self-healing process) obtained by processing through regression analysis the results of the four-point-bending tests performed on ECC specimens. ECC mixes design considered varying the fly ash content/cement content and the type of micro-fibers. four-point-bending tests were performed on reference specimens and pre-cracked and healed specimens, at various ages and with different loading rates. The studied parameters are the first-cracking strength, ultimate flexural strength upon strain hardening, initial tangent Young modulus and ultimate flexural tensile strain as a measurement of the multiple-cracking capability. Finally, power and logarithmic regression expressions are proposed to simulate the recovery of the self-healing parameters.
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