Novel production of macrocapsules for self-sealing mortar specimens using stereolithographic 3D printers
Claire Riordan, Giovanni Anglani, Barbara Inserra, Dave Palmer, Abir Al-Tabbaa, Jean-Marc Tulliani and Paola Antonaci
Abstract: The use of capsule-based technology for self-sealing and self-healing cementitious systems has been extensively investigated for both macro- and microencapsulated additions. In this study, macrocapsules, produced using a novel technique were characterised and compared, evaluating mechanical triggering, bonding with the cementitious matrix, and self-sealing efficiency upon integration into cementitious mortar specimens. Macrocapsules containing a commercially available water repellent agent were produced in two ways. Stereolithographic additive manufacturing (3D printing) was used to produce novel rigid acrylate macrocapsules as well as alumina ones. Cementitious macrocapsules produced with a rolling technique were also used as a comparison. The capsules were characterised in terms of watertightness, water uptake, and shell morphology. Following this, the capsules were integrated into cement mortar prisms and subjected to controlled cracking by three-point bending to evaluate the triggering and subsequent self-sealing effect. The results highlighted influential process parameters that can be optimised and explored for further capsule-based self-sealing in structural applications.
Reference of this article: Claire Riordan, Giovanni Anglani, Barbara Inserra, Dave Palmer, Abir Al-Tabbaa, Jean-Marc Tulliani, Paola Antonaci, Novel production of macrocapsules for self-sealing mortar specimens using stereolithographic 3D printers, Cement and Concrete Composites, Volume 142, 2023, 105216, ISSN 0958-9465
Affiliations:
Claire Riordan and Abir Al-Tabbaa: Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK
Dave Palmer: Micropore Technologies Ltd, Wilton Centre, Redcar, TS10 4RF, UK
Giovanni Anglani and Paola Antonaci: Department of Structural, Geotechnical and Building Engineering (DISEG), Politecnico di Torino, Corso Duca Degli Abruzzi 24, 10129, Turin, Italy
Barbara Inserra and Jean-Marc Tulliani : Department of Applied Science and Technology, Politecnico di Torino, INSTM R.U. Lince Laboratory, Corso Duca Degli Abruzzi 24, 10129, Turin, Italy
Corresponding author:
The full article can be found here: https://doi.org/10.1016/j.cemconcomp.2023.105216
PVDF-based coatings with CNT additions for strain monitoring of mortar substrates subjected to bending
Gabriele Milone, Jean-Marc Tulliani and Abir Al-Tabba
Abstract: Sensing coatings are rapidly entering the field of non-destructive tests. While cement-based composites are proving an excellent interaction with new/recent structures, polymer-based coatings, already employed for structural retrofitting purposes, can provide a valuable alternative. This study investigated the production, application, and use of poly(vinylidene fluoride) (PVDF) coatings. A 10w/v% PVDF-to-solvent ratio became the best trade-off between electrical conductivity and bond strength with the substrate. Different concentrations of Carbon Nanotubes (CNT) were investigated: 0.05, 0.10, 0.25, 0.50, and 0.75% by weight of PVDF. The conductive PVDF-CNT composites were brushed on the casted mortar beams with screws embedded as electrodes. The mortar beams and attached polymer coatings were then subjected to bending stress. The Gauge Factor was obtained by comparing the substrate’s strain with the coating’s electric response. The sensing intervals in the Fractional Change of Resistance-strain curves varied in relation to the CNT concentration. For instance, adding 0.50w/v% of CNT gave the highest sensitivity up to 0.2‰ strain, followed by a lower – still sufficient – gauge factor. PVDF-based coatings with CNT additions of 0.25 and 0.75w/v% witnessed a comparable sensing performance in the same strain limits, abruptly increasing and finally stabilizing to a low gauge factor. In contrast, both 0.05 and 0.10w/v% resulted in a low monitoring potential overall. The varying sensing zones experienced by the coating were attributed to the microscopical behavior of CNT within the PVDF matrix. In conclusion, the results highlighted the potentiality of polymeric coatings for sensing, monitoring, and inspection of concrete structures.
Reference of this article: PVDF-based coatings with CNT additions for strain monitoring of mortar substrates subjected to bending Gabriele Milone, Jean-Marc Tulliani and Abir Al-Tabbaa MATEC Web Conf., 378 (2023) 05001
Affiliations:
Gabriele Milone and Abir Al-Tabbaa: Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK
Jean-Marc Tulliani: Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, Turin 10129, Italy
The full article can be found here: https://doi.org/10.1051/matecconf/202337805001
Structural performance of reinforced concrete beams with self-healing cover zone
Shan He, Mladena Luković, Henk Jonkers and Erik Schlangen
Abstract: In the current study, experiments were carried out to investigate the structural performance of reinforced concrete (RC) beams with a self-healing cover zone. The cover zone consists of a 1.5-cm-thick layer of bacteria-embedded strain hardening cementitious composite (SHCC) for a combination of crack width control and crack healing. The aim is to bring together two emerging technologies (i.e., self-healing and strain-hardening) that show great potential for realizing highly efficient concrete structures. RC beam without the self-healing cover was also prepared as the control specimen for comparison purposes. The experimental program includes loading the beams to failure in four-point bending configuration and sawing the beams to segments for crack pattern analysis and crack healing. Results show that the beams with selfhealing cover exhibited a 45-60% improvement in structural capacity. The crack patterns of the hybrid beams were also largely modified. While the reference beam formed only a few major cracks, the hybrid beams formed around 40 fine cracks in the constant bending moment region with an average crack width smaller than 0.2 mm even at maximum load. By having an improved cracking behavior and an enhanced self-healing capacity, it is expected that the beams with a self-healing cover will possess an extended service life at the expense of minimal additional cost.
Reference of this article: Structural performance of reinforced concrete beams with self-healing cover zone Shan He, Mladena Luković, Henk Jonkers and Erik Schlangen MATEC Web Conf., 378 (2023) 08004
Affiliations:
Shan He, Henk Jonkers and Erik Schlangen: Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft 2628 CN, the Netherlands
Mladena Luković: Concrete Structures, Faculty of Civil Engineering and Geosciences, Delft University of Technology, 2628 CN, Delft, The Netherlands
The full article can be found here: https://doi.org/10.1051/matecconf/202337808004
Strain Hardening Cementitious Composite in Reinforced Concrete Cover Zone for Crack Width Control
Shan He, Mladena Luković and Erik Schlangen
Abstract: In the current study, experiments were carried out to investigate the cracking behaviour of reinforced concrete beams consisting of 1-cm-thick layer of Strain Hardening Cementitious Composite (SHCC) in the concrete cover zone. The hybrid SHCC/concrete beams with different types of interfaces were tested and compared with control reinforced concrete beams without a SHCC layer. A new SHCC/concrete interface that features a weakened chemical adhesion but an enhanced mechanical bonding was also developed to facilitate the activation of SHCC. The beams were tested in four-point bending configuration, while Digital Image Correlation (DIC) was used to evaluate crack pattern development and crack widths. Results show that hybrid beams possessed similar load bearing capacity but exhibited an improved cracking behaviour as compared to the control beam. The maximum crack width of the best performing hybrid beams exceeded 0.3 mm at approximately 53.3 kN load, whereas in the control beam it exceeded 0.3 mm at only 32.5 kN load. It is thus expected that the hybrid beams developed in the current study will possess an improved durability and enhanced self-healing potential as a result of having smaller cracks, leading to an extended service life at the expense of minimal additional cost.
Reference of this article: He, S., Luković, M., Schlangen, E. (2023). Strain Hardening Cementitious Composite in Reinforced Concrete Cover Zone for Crack Width Control. In: Ilki, A., Çavunt, D., Çavunt, Y.S. (eds) Building for the Future: Durable, Sustainable, Resilient. fib Symposium 2023. Lecture Notes in Civil Engineering, vol 349. Springer, Cham.
Affiliations:
Shan He and Erik Schlangen: Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft 2628 CN, the Netherlands
Mladena Luković: Concrete Structures, Faculty of Civil Engineering and Geosciences, Delft University of Technology, 2628 CN, Delft, The Netherlands
The full article can be found here: https://doi.org/10.1007/978-3-031-32519-9_115
Distribution of porosity surrounding a microfiber in cement paste
Shan He, Yu Chen, Minfei Liang, En-Hua Yang and Erik Schlangen
Abstract: This study investigates the microstructural changes of cement paste due to the inclusion of polymeric microfiber at different water-to-cement (w/c) ratios. A procedure to quantify the porosity of epoxy impregnated interfacial transition zone (ITZ) is also presented. Results show that the microstructures of the ITZ beneath and above a microfiber, with respect to the gravity direction, are largely different. Though the ITZ at both sides of the fiber are more porous than the bulk matrix, the porosity of the lower ITZ (i.e., the ITZ beneath a fiber) is significantly higher than the upper side (i.e., the ITZ above a fiber). This difference can be attributed to the combined effects of fiber on the initial packing of surrounding cement grains and on the settlement of the fresh mixture. The porosity gradients of the upper ITZs are found to be nearly identical for all the tested w/c ratios, while the porosity gradients of the lower ITZs become steeper when the w/c is higher. The lower side is also found to be the preferred location for the precipitation of calcium hydroxide crystals. Results of energy-dispersive X-ray spectroscopy (EDS) and nano-indentation analyses confirm that the chemical and mechanical properties of the ITZ are also asymmetric.
Reference of this article: Shan He, Yu Chen, Minfei Liang, En-Hua Yang, Erik Schlangen, Distribution of porosity surrounding a microfiber in cement paste, Cement and Concrete Composites, Volume 142, 2023, 105188, ISSN 0958-9465,
Affiliations:
Shan He, Yu Chen, Minfei Liang and Erik Schlangen: Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft 2628 CN, the Netherlands
En-Hua Yang: School of Civil and Environmental Engineering, Nanyang Technological University, Singapore, 639798, Singapore
The full article can be found here: https://doi.org/10.1016/j.cemconcomp.2023.105188