Direct ink writing of vascularized self-healing cementitious composites
Zhi Wan, Yading Xu, Shan He, Yu Chen, Jinbao Xie and Branko Šavija
Abstract: Direct ink writing of cementitious materials can be an alternative way for creating vascular self-healing concrete by intentionally incorporating hollow channels in the cementitious matrix. In this study, a 3D-printable fibre reinforced mortar was first developed. Three groups of specimens were fabricated using direct ink writing, where the two top and bottom printing layers were printed with different printing directions. The macrostructure of the hardened specimens was studied using CT scanning. Four-point bending tests were carried out to investigate the initial flexural strength and the strength recovery after healing with injected epoxy resin. Furthermore, water permeability test was used to evaluate the healing potential of the samples. The results from CT scanning show that printing direction influences the actual volumes of hollow channels and the volume of small pores which are a consequence of the deposition process. The hollow channels of all samples were squeezed by the upper layers during the printing process, and the longitudinally printed samples were the most affected. When printing direction changes from longitudinal to transverse, the initial flexural strength decreases. Similarly, the average permeability of the cracked samples increases when the printing direction changes from longitudinal to transverse. Although the healing effectiveness regarding flexural strength is remarkable for all specimens, it was only possible to perform a single healing process as hollow channels were then blocked by the epoxy resin. The rough surface of the hollow channels is inferred to make it difficult to extract the epoxy resin out of the specimens.
Reference of this article: Zhi Wan, Yading Xu, Shan He, Yu Chen, Jinbao Xie, Branko Šavija, Direct ink writing of vascularized self-healing cementitious composites, Cement and Concrete Composites, Volume 144, 2023, 105295, ISSN 0958-9465,
Affiliations:
Zhi Wan, Yading Xu, Shan He, Yu Chen, Jinbao Xie and Branko Šavija: Microlab, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, the Netherlands
The full article can be found here: https://doi.org/10.1016/j.cemconcomp.2023.105295
An enhanced lattice beam element model for the numerical simulation of rate-dependent self-healing in cementitious materials
Sina Sayadi, Ze Chang, Shan He, Erik Schlangen, Iulia C. Mihai and Anthony Jefferson
Abstract: This paper describes the development of a discrete lattice model for simulating structures formed from self-healing cementitious materials. In particular, a new approach is presented for simulating time dependent mechanical healing in lattice elements. The proposed formulation is designed to simulate the transient damage and healing behaviour of structures under a range of loading conditions. In addition, multiple and overlapping damage and healing events are considered. An illustrative example demonstrates the effects of varying the healing agent curing parameters on the computed mechanical response. The model is successfully validated using published experimental data from two series of tests on structural elements with an embedded autonomic self-healing system. The meso-scale model gives detailed information on the size and disposition of cracking and healing zones throughout an analysis time history. The model also provides an accurate means of determining the volume of healing agent required to achieve healing for all locations within a structural element. The importance of the information provided by the model for the design of self-healing cementitious material elements is highlighted.
Reference of this article: Sina Sayadi, Ze Chang, Shan He, Erik Schlangen, Iulia C. Mihai, Anthony Jefferson, An enhanced lattice beam element model for the numerical simulation of rate-dependent self-healing in cementitious materials, Engineering Fracture Mechanics, Volume 292, 2023, 109632, ISSN 0013-7944,
Affiliations:
Sina Sayadi, Iulia C. Mihai and Anthony Jefferson: School of Engineering, Cardiff University, Cardiff CF24 3AA, UK
Ze Chang, Shan He and Erik Schlangen: Faculty of Civil Engineering and Geosciences, TUDelft, Delft 2628 CN, the Netherlands
The full article can be found here: https://doi.org/10.1016/j.engfracmech.2023.109632
Self-Waterproofing Performance of Repair Mortars With Inorganic Healing Agents
Padmapriya Arul Kumar, Sripriya Rengaraju & Abir Al-Tabbaa
Abstract: In Europe, about 55% of concrete bridges are about 50 years old and require non-structural rapid repair strategies to reinstate the aesthetic and durability performances. Existing strategies focus primarily on superficial restoration that continues to demonstrate premature deterioration due to inevitable micro-crack formations that further propagate to macro-cracks leading to the ingress of moisture along with harmful ions. In this study, the benefits of self-healing technology to control moisture ingress at the microscale were investigated. For this, tailored microcapsule with inorganic healing agent, specifically, commercially available water-repellent agent (SIKAGARD 705L) was added to mortar with two types of commonly used binders namely CEMI 52.5N and CEMI 52.5R. The compatibility assessment in terms of capsule integration, fresh and hardened properties was done. The baseline healing efficiency of the mortars without any healing additions was obtained to understand the autogenous healing capacity of the reference mortars. Subsequently, the reference mortar mixes were compared with mixes containing varying fractions of microcapsules (3, 5, and 10%) for autonomous healing efficiency with capillary absorption as the main durability function. The healing efficiency was further investigated for two different crack mouth widths (350 μm); representative of non-structural residual crack widths. In mortars with microcapsules, a maximum reduction of sorptivity coefficients up to 82% and 78% with CEMI 52.5N and CEMI 52.5R mortars, respectively, for specimens cracked after 7 days of curing was observed. Subsequently, a synergetic effect of autogenous healing action and autonomous water-repellent action for durability recovery was identified and proved useful for repair mortar applications. The healing agent investigated, capsule content, and healing environment considered in the current study lay a foundation for further optimisation to improve the performance and to suit different applications.
Reference of this article: Self-Waterproofing Performance of Repair Mortars With Inorganic Healing Agents Padmapriya Arul Kumar, Sripriya Rengaraju and Abir Al-Tabbaa MATEC Web Conf., 378 (2023) 03001
Affiliations:
Padmapriya Arul Kumar, Sripriya Rengaraju and Abir Al-Tabbaa : Department of Engineering, University of Cambridge, United Kingdom
Corresponding author:
The full article can be found here: https://doi.org/10.1051/matecconf/202337803001
A statistical comparison between calculated and experimentally evaluated crack spacing measures given in practise codes for the design of reinforced concrete elements made with self-healing concrete
Kiran Dabral, Esteban Camacho, Juan Ángel López Martínez, Maria Cruz Alonso & Pedro Serna
Abstract: Available design codes provide formulations to evaluate the maximum spacing between the cracks, which then is used to calculate the crack width in concrete structures. This paper discusses the parameters controlling the crack spacing and develops an experimental test program on a set of industrial-scale reinforced concrete elements cast with self-healing concretes to be tested under flexural actions. This study provides a wide picture of the limits of maximum, minimum, and average spacing occurring in the beams. A comparison is highlighted between the calculated and experimentally evaluated measures. It was observed that the provisions given in Eurocode 2 and Model code 2010 present a good approach for the calculation, always with a small degree of overestimation for concrete without fibres. On the other hand, the values calculated using recommendations from NFP 18-710, the overestimation is higher. The influence of loading levels seems to not affect the number of cracks with an increase in concrete cover. The experimentally evaluated ranges to relate maximum and minimum spacing with the average value in a loaded region are given. No influence of using self-healing agents was detected.
Reference of this article: A statistical comparison between calculated and experimentally evaluated crack spacing measures given in practise codes for the design of reinforced concrete elements made with self-healing concrete Kiran Dabral, Esteban Camacho, Juan Ángel López Martínez, Maria Cruz Alonso and Pedro Serna MATEC Web Conf., 378 (2023) 06006
Affiliations:
Kiran Dabral, Esteban Camacho and Juan Ángel López Martínez : RDC Research and Development Concrete, 46055 València, Spain
Maria Cruz Alonso: Universitat Politècnica de València, 46022 València, Spain
Pedro Serna: Eduardo Torroja Institute of Construction Science (IETcc-CSIC), 28033 Madrid, Spain
Corresponding author:
The full article can be found here: https://doi.org/10.1051/matecconf/202337806006
EFFECT OF AUTOGENOUS SELF-HEALING ON HIGH TEMPERATURE EXPOSED ULTRA HIGH-PERFORMANCE CONCRETE
Niranjan Prabhu Kannikachalam, Ahmed M. E. M. Alhadad, Francesco Lo Monte, Enrico Maria Gastaldo Brac, Roberto Rosignoli, Nele De Belie & Liberato Ferrara
Abstract: Mechanical properties of Ultra High-Performance Concrete (UHPC) degrade when exposed to elevated temperatures, even more than ordinary concretes due to its dense microstructure. Concerning, in particular, the special application of nuclear power plants, in which UHPC can find a promising use, concrete can be subjected to moderately high temperature (usually lower than 400 °C) along the working life, this making of interest the study on the influence and persistence of UHPC's innate self-healing capabilities over the thermal degradation. In this context, the paper focuses on an experimental study of UHPC recovery ability by autogenous self-healing after being exposed to high temperatures. The UHPC specimens have been made with hybrid fibers, that is, polypropylene and steel fibers, and have been pre-cracked up to a cumulative crack width of 0.3 mm under 4-point flexural test. The pre-cracked specimens have been exposed to a temperature of 200 °C or 400 °C, with a heating rate of 1 °C / minute from room temperature and kept at the target temperature for two hours, with a following slow cooling at a rate of
Reference of this article:Effect of autogenous self-healing on high temperature exposed ultra high-performance concrete, Niranjan Prabhu Kannikachalam; Ahmed M. E. M. Alhadad; Francesco Lo Monte; Enrico Maria Gastaldo Brac; Roberto Rosignoli; Nele De Belie and Liberato Ferrara, IFireSS 2023 – International Fire Safety Symposium Rio de Janeiro, Brazil, 21st-23rd June 2023 pages 667 till 676
Affiliations:
Niranjan Prabhu Kannikachalam, Ahmed M. E. M. Alhadad, Francesco Lo Monte, Enrico Maria Gastaldo Brac, Roberto Rosignoli and Liberato Ferrara: Department of Civil and Environmental Engineering, Politecnico di Milano, Italy
Niranjan Prabhu Kannikachalam and Nele De Belie: Department of Structural Engineering and Building Materials; Magnel-Vandepitte Laboratory, Ghent University, Belgium