Статті в журналах: "Cementitious capsule"

1

Huang, Haoliang, and Guang Ye. "Numerical Studies of the Effects of Water Capsules on Self-Healing Efficiency and Mechanical Properties in Cementitious Materials." Advances in Materials Science and Engineering 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/8271214.

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In this research, self-healing due to further hydration of unhydrated cement particles is taken as an example for investigating the effects of capsules on the self-healing efficiency and mechanical properties of cementitious materials. The efficiency of supply of water by using capsules as a function of capsule dosages and sizes was determined numerically. By knowing the amount of water supplied via capsules, the efficiency of self-healing due to further hydration of unhydrated cement was quantified. In addition, the impact of capsules on mechanical properties was investigated numerically. The amount of released water increases with the dosage of capsules at different slops as the size of capsules varies. Concerning the best efficiency of self-healing, the optimizing size of capsules is 6.5 mm for capsule dosages of 3%, 5%, and 7%, respectively. Both elastic modulus and tensile strength of cementitious materials decrease with the increase of capsule. The decreasing tendency of tensile strength is larger than that of elastic modulus. However, it was found that the increase of positive effect (the capacity of inducing self-healing) of capsules is larger than that of negative effects (decreasing mechanical properties) when the dosage of capsules increases.

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2

Kim, Yong Jic, Yun Wang Choi, and Sung-Rok Oh. "A Study on the Healing Performance of Solid Capsules for Crack Self-Healing of Cementitious Composites." Crystals 12, no. 7 (July 17, 2022): 993. http://dx.doi.org/10.3390/cryst12070993.

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The purpose of this study is to investigate the healing performance of solid capsules made of cement as a basis for manufacturing self-healing capsules that can heal cracks in cementitious composites. The solid capsules were mixed with 5%, 10%, and 15% concentrations on the cement. The self-healing performance of cementitious composites with solid capsules was investigated through three evaluations. First, the mechanical strength-healing performance was evaluated through a re-loading test. Second, the durability-healing performance was evaluated through a permeability test. Finally, the crack-healing performance was examined by observing the crack widths. Through evaluation of the healing performance of the solid capsules, the healing performance of the compressive strength was found to be high when the capsule proportion was 10% and its size was within the range of 300 μm to 850 μm. Furthermore, the splitting tensile strength showed a high healing performance when the capsule proportion mixed was 15% and its size was 850 μm. In the case of the permeability test, a capsule size of 850 μm showed a healing effect greater than 95%. Cracks with a width of up to 200 μm tended to heal using capsules with a size of 600 μm to 850 μm.

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3

Reda, Mouna A., and Samir E. Chidiac. "Performance of Capsules in Self-Healing Cementitious Material." Materials 15, no. 20 (October 19, 2022): 7302. http://dx.doi.org/10.3390/ma15207302.

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Encapsulation is a very promising technique that is being explored to enhance the autonomous self-healing of cementitious materials. However, its success requires the survival of self-healing capsules during mixing and placing conditions, while still trigger the release of a healing agent upon concrete cracking. A review of the literature revealed discontinuities and inconsistencies in the design and performance evaluation of self-healing cementitious material. A finite element model was developed to study the compatibility requirements for the capsule and the cementing material properties while the cement undergoes volume change due to hydration and/or drying. The FE results have provided insights into the observed inconsistencies and the importance of having capsules’ mechanical and geometrical properties compatible with the cementitious matrix.

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4

H. Mahdi, Zainab, Esraa Y. Al Goody, and Tabarek J. Qasim. "Self-Repairing Technique Based on Microcapsules for Cementitious Composites- A Review." Journal of Engineering 28, no. 2 (February 1, 2022): 63–80. http://dx.doi.org/10.31026/j.eng.2022.02.05.

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Self-repairing technology based on micro-capsules is an efficient solution for repairing cracked cementitious composites. Self-repairing based on microcapsules begins with the occurrence of cracks and develops by releasing self-repairing factors in the cracks located in concrete. Based on previous comprehensive studies, this paper provides an overview of various repairing factors and investigative methodologies. There has recently been a lack of consensus on the most efficient criteria for assessing self-repairing based on microcapsules and the smart solutions for improving capsule survival ratios during mixing. The most commonly utilized self-repairing efficiency assessment indicators are mechanical resistance and durability. On the other hand, Nondestructive methods have been widely used to visualize and assess cementitious composites, self-repairing behavior. However, certain issues remain, such as crack spread behavior, repairing agent kinetics on discrete crack surfaces, and the influence of inserted capsules on the mechanical characteristics of self-repaired cementitious composites, all of which require more investigations.

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5

Imad Mohammed, Abdulmohaimen, Ahmed Awadh Ba Rahman, Noor Azline Mohd Nasir, Nabilah Abu Bakar, and Nor Azizi Safiee. "Evaluation of the Compatibility of Modified Encapsulated Sodium Silicate for Self-Healing of Cementitious Composites." Applied Sciences 11, no. 22 (November 17, 2021): 10847. http://dx.doi.org/10.3390/app112210847.

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Healing agent carriers play a significant role in defining the performance of the autonomous self-healing system. Particularly, the ability to survive during the mixing process and the release of the healing agent when cracks occur without affecting the mechanical properties of the cementitious composite. Up to now, these issues are still a concern since glass capsules are unable to survive the mixing process, while some types of microcapsules were reported to cause a decrement in strength as well as limited strength recovery. Therefore, this study was twofold, addressing the surface treatment of polystyrene (PS) capsules and the evaluation of the compatibility of the modified capsules for cement-based applications. Secondly, assessing the healing performance of modified PS capsules in cementitious composites. Furthermore, the study also evaluates the potential healing performance due to the synergic effect between the encapsulation method and the autogenous self-healing mechanism. The investigation was carried out by measuring the changes in the pH of pore solution, FTIR analysis, survival ratio, and bonding strength. For self-healing assessment, the compression cracks on the cement paste were created at an early age and the strength recovery was measured at the age of 28 and 56 days. To identify the chemical compounds responsible for the healing process, SEM-EDX tests were conducted. Moreover, the effect of silica fume (SF) on bonding strength and self-healing was also evaluated. Based on the results, the modified PS capsules by roughing approach showed promising performance in terms of survivability, bonding, and recovery. The modified PS capsule increased the strength recovery by about 12.5–15% for 100%OPC and 95%OPC + 5%SF, respectively. The finding observed that the combining of modified PS capsules and the inclusion of SF gave high strength recovery of about 20% compared to 100%OPC without capsules. Thus, the modified PS capsule has a good potential for self-healing of cementitious-based applications.

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6

Guo, Shannon, and Samir E. Chidiac. "Probability Characteristics of a Crack Hitting Spherical Healing Agent Particles: Application to a Self-Healing Cementitious System." Materials 15, no. 20 (October 20, 2022): 7355. http://dx.doi.org/10.3390/ma15207355.

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A geometric model is developed to statistically study the probability characteristics of crack intersecting self-healing capsules with a structured random distribution in a cement paste mix. To evaluate the probability of a crack intersecting encapsulated particles, the fill ratio of the crack, and the depth of the first-hit capsule, Monte Carlo simulations are performed. The variables are the crack geometry, i.e., width, length, depth, orientation, skewness, and so on; the size and mass fraction of healing capsules; and the agglomeration of capsules. Models based on statistical analyses for hit probability , crack fill ratio at 95% confidence level, and first hit depth at 95% confidence level are expressed as functions of capsule size and mass fraction, as well as crack geometry. The model assumptions and results are evaluated using data reported in the literature. The data include results from experimental and theoretical studies.

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7

Anglani, Giovanni, Jean-Marc Tulliani, and Paola Antonaci. "Behaviour of Pre-Cracked Self-Healing Cementitious Materials under Static and Cyclic Loading." Materials 13, no. 5 (March 5, 2020): 1149. http://dx.doi.org/10.3390/ma13051149.

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Capsule-based self-healing is increasingly being targeted as an effective way to improve the durability and sustainability of concrete infrastructures through the extension of their service life. Assessing the mechanical and durability behaviour of self-healing materials after damage and subsequent autonomous repair is essential to validate their possible use in real structures. In this study, self-healing mortars containing cementitious tubular capsules with a polyurethanic repairing agent were experimentally investigated. Their mechanical behaviour under both static and cyclic loading was analysed as a function of some factors related to the capsules themselves (production method, waterproof coating configuration, volume of repairing agent stored) or to the specimens (number, size and distribution of the capsules in the specimen). Their mechanical performances were quantified in terms of recovery of load-bearing capacity under static conditions and number of cycles to failure as a function of the peak force under cyclic conditions. Positive results were achieved, with a maximum load recovery index up to more than 40% and number of cycles to failure exceeding 10,000 in most cases, with peak force applied during cyclic loading at least corresponding to 70% of the estimated load-bearing capacity of the healed samples.

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8

Fang, Xurui, Zichao Pan, and Airong Chen. "Analytical models to estimate efficiency of capsule-based self-healing cementitious materials considering effect of capsule shell thickness." Construction and Building Materials 274 (March 2021): 121999. http://dx.doi.org/10.1016/j.conbuildmat.2020.121999.

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9

Kim, Dong-Min, In-Ho Song, Ju-Young Choi, Seung-Won Jin, Kyeong-Nam Nam, and Chan-Moon Chung. "Self-Healing Coatings Based on Linseed-Oil-Loaded Microcapsules for Protection of Cementitious Materials." Coatings 8, no. 11 (November 15, 2018): 404. http://dx.doi.org/10.3390/coatings8110404.

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Linseed oil undergoes an oxidative drying reaction upon exposure to air, resulting in a soft film. The reaction conversion after 48 h reached 88% and 59% when it reacted at room temperature and −20 °C, respectively. Linseed-oil-loaded microcapsules were prepared using a urea-formaldehyde polymer as the shell wall material. The microcapsules were integrated into a commercially available protective coating formulation to prepare self-healing coating formulations with different capsule loadings. The coating formulations were applied on mortar specimens to prepare self-healing coatings. The effect of capsule loading on adhesion strength of the self-healing coating was studied. The self-healing function of the coating was investigated by SEM, a water sorptivity test and an accelerated carbonation test. Successful self-healing was demonstrated for both scratch and crack damage in the coatings. Low-temperature self-healing was demonstrated with a saline solution sorptivity test conducted at −20 °C. The linseed-oil-based microcapsule-type self-healing coating system is a promising candidate as a protective coating for cementitious materials.

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10

Choi, Se-Jin, Sung-Ho Bae, Dong-Min Ji, and Sung-Hoon Kim. "Effects of Capsule Type on the Characteristics of Cement Mortars Containing Powder Compacted Capsules." Materials 15, no. 19 (September 29, 2022): 6773. http://dx.doi.org/10.3390/ma15196773.

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Several studies have been reported on self-healing concrete using bacteria, admixtures, and microcapsules. Among these self-healing techniques, encapsulating cement-based materials is advantageous in that large amounts of self-healing material can be contained in a capsule and released at the cracked site for a targeted reaction. This study produced a powder compacted capsule (PCC) using the droplet and blended manufacturing methods to encapsulate cementitious materials. This study refers to the PCCs as droplet-PCC (D-PCC) and blended-PCC (B-PCC) according to the manufacturing method used. The fluidity, compressive strength, carbonation, drying shrinkage, and water permeability of cement mortar with PCCs were evaluated. The test results show that the flow of the mortar sample using D-PCC was slightly higher than that of the mortar using B-PCC. The compressive strength of the mortar sample with B-PCC was generally higher than that of the mortar sample with D-PCC. The compressive strength of the B-PCC2 sample (with 0.2% of B-PCC) was the highest at all curing ages. This may be because the B-PCC fracture load was higher than that of the D-PCC. In addition, more hydrates were observed in the B-PCC sample than in the D-PCC sample. A crack healing effect was observed in the samples with PCC, regardless of the PCC type. The effect was the greatest in the B-PCC6 sample (with 0.6% of B-PCC). The results of this study provide a reference for the PCC type and mix ratio that would yield the best mechanical properties and crack healing effect.

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11

Lv, Zhong, Huisu Chen, and Haifeng Yuan. "Analytical solution on dosage of self-healing agents in cementitious materials: Long capsule model." Journal of Intelligent Material Systems and Structures 25, no. 1 (September 11, 2012): 47–57. http://dx.doi.org/10.1177/1045389x12457250.

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12

Lv, Le-Yang, Hongzhi Zhang, Erik Schlangen, Zhengxian Yang, and Feng Xing. "Experimental and numerical study of crack behaviour for capsule-based self-healing cementitious materials." Construction and Building Materials 156 (December 2017): 219–29. http://dx.doi.org/10.1016/j.conbuildmat.2017.08.157.

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13

Liang, Peng, Qian Jin Mao, Zi Ming Wang, and Su Ping Cui. "Mechanical Properties of Self-Healing System in Cementitious Material with Microcapsule." Materials Science Forum 913 (February 2018): 1090–96. http://dx.doi.org/10.4028/www.scientific.net/msf.913.1090.

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In this paper, several urea–formaldehyde/epoxy microcapsules with different particle sizes were synthesized by in-situ polymerization. The chemical structure and compressive rupture load of microcapsule were characterized. The effect of microcapsule dosage, particle size and preload pressure on compressive strength of cementitious materials was studied. The result shows: when the particle size of microcapsule is 2 mm~2.5 mm, the rupture load of microcapsule is highest, more than 3N; When the microcapsule dosage is less than 2.5%, the strength loss of the matrix is relatively small; With the increase of the particle size of the capsule, the strength of the matrix decrease greatly; When the dosage of microcapsule is 2.5%, the particle size is 1.5 mm and the preload pressure is 30%~45%fmax, the compressive strength of the self-healing specimen is 8% higher than that of the non-preloaded specimens, which shows a certain self-healing performance.

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14

Fahimizadeh, Mohammad, Ayesha Diane Abeyratne, Lee Sui Mae, R. K. Raman Singh, and Pooria Pasbakhsh. "Biological Self-Healing of Cement Paste and Mortar by Non-Ureolytic Bacteria Encapsulated in Alginate Hydrogel Capsules." Materials 13, no. 17 (August 22, 2020): 3711. http://dx.doi.org/10.3390/ma13173711.

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Crack formation in concrete is one of the main reasons for concrete degradation. Calcium alginate capsules containing biological self-healing agents for cementitious materials were studied for the self-healing of cement paste and mortars through in vitro characterizations such as healing agent survivability and retention, material stability, and biomineralization, followed by in situ self-healing observation in pre-cracked cement paste and mortar specimens. Our results showed that bacterial spores fully survived the encapsulation process and would not leach out during cement mixing. Encapsulated bacteria precipitated CaCO3 when exposed to water, oxygen, and calcium under alkaline conditions by releasing CO32− ions into the cement environment. Capsule rupture is not required for the initiation of the healing process, but exposure to the right conditions are. After 56 days of wet–dry cycles, the capsules resulted in flexural strength regain as high as 39.6% for the cement mortar and 32.5% for the cement paste specimens. Full crack closure was observed at 28 days for cement mortars with the healing agents. The self-healing system acted as a biological CO32− pump that can keep the bio-agents retained, protected, and active for up to 56 days of wet-dry incubation. This promising self-healing strategy requires further research and optimization.

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15

He, Jialuo, and Xianming Shi. "Developing an abiotic capsule-based self-healing system for cementitious materials: The state of knowledge." Construction and Building Materials 156 (December 2017): 1096–113. http://dx.doi.org/10.1016/j.conbuildmat.2017.09.041.

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16

Shields, Yasmina, Tim Van Mullem, Nele De Belie, and Kim Van Tittelboom. "An Investigation of Suitable Healing Agents for Vascular-Based Self-Healing in Cementitious Materials." Sustainability 13, no. 23 (November 23, 2021): 12948. http://dx.doi.org/10.3390/su132312948.

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Self-healing cementitious materials can extend the service life of structures, improve safety during repair activities and reduce costs with minimal human intervention. Recent advances in self-healing research have shown promise for capsule-based and intrinsic healing systems. However, limited information is available regarding vascular-based self-healing mechanisms. The aim of this work is to compare different commercially available healing agents regarding their suitability in a self-healing vascular network system by examining a regain in durability and mechanical properties. The healing agents investigated include sodium silicate, two polyurethanes, two water repellent agents and an epoxy resin. Sealing efficiencies above 100% were achieved for most of the healing agents, and both polyurethanes and the epoxy resin showed high regain in strength. The results obtained from this study provide a framework for selecting a healing agent given a specific application, as a healing agent’s rheology and curing properties can affect the optimal geometry and design of a vascular network.

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17

Lv, Zhong, Huisu Chen, and Haifeng Yuan. "Quantitative solution on dosage of repair agent for healing of cracks in materials: short capsule model vs. two-dimensional crack pattern." Science and Engineering of Composite Materials 18, no. 1-2 (June 1, 2011): 13–19. http://dx.doi.org/10.1515/secm.2011.004.

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AbstractCracks are vitally detrimental to the load-bearing capacity of materials and further to the durability and service-life of various structures. Crack-repairing technology via embedded capsules with repair agent is becoming a promising approach to sustain the performance of structural materials. However, the appropriate dosage of capsulated repair agent for autonomic healing is not theoretically solved in the literature. In this study, taking cementitious materials as an example, the surface cracks in materials caused by various mechanisms are firstly simplified as linear cracks and zonal cracks in two-dimensional plane. Then, from the viewpoint of geometrical probability, the theoretical solutions on the exact dosage of capsules required are developed for different types of crack models via the knowledge of integral geometry and the concepts of probability distribution. Finally, reliability of these theoretical solutions is verified via computer modeling technology.

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18

Mu, Ru, Dogniman Landry Soro, Xiaowei Wang, Longbang Qing, Guorui Cao, Shaolin Mei, and Yongshuai Liu. "Performance of Self-Healing Cementitious Composites Using Aligned Tubular Healing Fiber." Materials 14, no. 20 (October 18, 2021): 6162. http://dx.doi.org/10.3390/ma14206162.

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From the perspective of improving the self-healing method in construction, a tubular healing fiber was adopted as a container to improve the encapsulation capacity, which was available using a micro-capsule as a container. Knowing the direction of the stresses to which structure members are subjected, this research investigated the influence of aligning tubular healing fibers parallel to intended stress into a cementitious composite to increase the self-healing capability. For that, a healing agent was encapsulated into a tubular healing fiber made with polyvinylidene of fluoride resin (PVDF). Then, the healing fiber was combined with steel fibers to align both fibers together parallel to the direction of an intended splitting tensile stress when subjected to a magnetic field in a cylindrical cementitious composite. The alignment method and the key point through which the alignment of the healing fibers could efficiently improve autonomic self-healing were investigated. Since the magnetic field is known to be able to drag steel to an expected direction, steel fibers were combined with the healing fibers to form a hybrid fiber that aligned both fibers together. The required mixture workability was investigated to avoid the sinking of the healing fibers into the mixture. The healing efficiency, according to the orientation of the healing fibers in the composite matrix, was evaluated through a permeability test and a repetitive splitting tensile test. The aligned healing fibers performed better than the randomly distributed healing fibers. However, according to the healing efficiency with aligned healing fibers, it was deduced that the observed decreasing effect of the container’s alignment on the specimen’s mechanical properties was low enough to be neglected.

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19

Adak, Dibyendu, Donkupar Francis Marbaniang, and Subhrajit Dutta. "Experimental studies on the development of a self-healing cementitious matrix for repair and retrofitting of concrete structures." International Journal of Structural Integrity 12, no. 5 (October 7, 2021): 799–814. http://dx.doi.org/10.1108/ijsi-07-2021-0082.

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PurposeSelf-healing concrete is a revolutionary building material that will generally reduce the maintenance cost of concrete constructions. Self-healing of cracks in concrete structure would contribute to a longer service life of the concrete and would make the material more durable and more sustainable. The cementitious mortar with/without incorporating encapsulates at different percentages of slag replacement with the cement mix improves autogenous healing at different ages. Therefore, this study’s aim is to develop a self-healing cementitious matrix for repair and retrofitting of concrete structures.Design/methodology/approachIn the present work, waste straw pipes are used as a capsule, filled with the solution of sodium hydroxide (NaOH), sodium silicate (Na2SiO3) and colloidal nano-silica as self-healing activators. An artificial micro-crack on the control and blended mortar specimens at different percentages of slag replacement with cement (with/without encapsulation) is developed by applying a compressive load of 50% of its ultimate load-carrying capacity. The mechanical strength and ultrasonic pulse velocity, water absorption and chloride ion penetration test are conducted on the concrete specimen before and after the healing period. Finally, the self-healing activity of mortar mixes with/without encapsulation is analysed at different ages.FindingsThe encapsulated mortar mix with 10% of slag content has better self-healing potential than all other mixes considering mechanical strength and durability. The enhancement of the self-healing potential of such mortar mix is mainly due to hydration of anhydrous slag on the crack surface and transformation of amorphous slag to the crystalline phase in presence of encapsulated fluid.Research limitations/implicationsThe self-healing activities of the slag-based cementitious composite are studied for a healing period of 90 days only. The strength and durability performance of the cracked specimen may be increased after a long healing period.Practical implicationsThe outcome of the work will help repair the cracks in the concrete structure and enhances the service life.Originality/valueThis study identifies the addition encapsulates with a self-healing activator fluid that can recover its strength after minor damage.

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Roy, Rahul, Emanuele Rossi, Johan Silfwerbrand, and Henk Jonkers. "Encapsulation Techniques and Test Methods of Evaluating the Bacteria-Based Self-Healing Efficiency of Concrete: A Literature Review." Nordic Concrete Research 62, no. 1 (June 1, 2020): 63–85. http://dx.doi.org/10.2478/ncr-2020-0006.

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AbstractCrack formation in concrete structures due to various load and non-load factors leading to degradation of service life is very common. Repair and maintenance operations are, therefore, necessary to prevent cracks propagating and reducing the service life of the structures. Accessibility to affected areas can, however, be difficult as the reconstruction and maintenance of concrete buildings are expensive in labour and capital. Autonomous healing by encapsulated bacteria-based self-healing agents is a possible solution. During this process, the bacteria are released from a broken capsule or triggered by water and oxygen access. However, its performance and reliability depend on continuous water supply, protection against the harsh environment, and densification of the cementitious matrix for the bacteria to act. There are vast methods of encapsulating bacteria and the most common carriers used are: encapsulation in polymeric materials, lightweight aggregates, cementitious materials, special minerals, nanomaterials, and waste-derived biomass. Self-healing efficiency of these encapsulated technologies can be assessed through many experimental methodologies according to the literature. These experimental evaluations are performed in terms of quantification of crackhealing, recovery of durability and mechanical properties (macro-level test) and characterization of precipitated crystals by healing agent (micro-level test). Until now, quantification of crack-healing by light microscopy revealed maximum crack width of 1.80mm healed. All research methods available for assesing self-healing efficiency of bacteria-based healing agents are worth reviewing in order to include a coherent, if not standardized framework testing system and a comparative evaluation for a novel incorporated bacteria-based healing agent.

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van den Heede, Philip, Bjorn van Belleghem, Maria Adelaide Araújo, João Feiteira, and Nele de Belie. "Screening of Different Encapsulated Polymer-Based Healing Agents for Chloride Exposed Self-Healing Concrete Using Chloride Migration Tests." Key Engineering Materials 761 (January 2018): 152–58. http://dx.doi.org/10.4028/www.scientific.net/kem.761.152.

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The service life of steel reinforced concrete in aggressive marine environments could be increased substantially by embedding a self-healing mechanism that ensures autonomous healing of cracks upon their occurrence. Previous proof-of-concept experiments have shown that the incorporation of encapsulated polymer-based healing agents (HAs) counts as a very appropriate way to achieve this goal. Over the years, several polymer-precursor-capsule systems have been developed in that perspective at our laboratory. Cementitious materials containing either commercial or in-house developed encapsulated HAs have been subjected to preliminary feasibility tests (water absorption, permeability tests, etc.). However, these experiments did not yet allow for a fast and straightforward assessment of the self-healing efficiency (SHE) in relation to the expected durability and service life performance of the material. This approach would have many advantages when having to select the most suitable polymer-precursor-capsule system for a particular concrete application. In this paper, a modified chloride migration test based on the one prescribed in NT Build 492 has been proposed to support the development of self-healing concrete for marine environments. Four polymer-based HAs have been screened that way, i.e. an in-house developed high-viscosity polyurethane (PU) precursor, a commercial low-viscosity PU precursor, the same commercial PU precursor with addition of accelerator and benzoyl peroxide (BPO), and an in-house developed 2-component acrylate-endcapped precursor + cross-linker. For now, a highly repeatable SHE value of 100% could only be obtained for the second option.

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Savija, Branko. "Use of 3D printing to create multifunctional cementitious composites: review, challenges and opportunities." RILEM Technical Letters 5 (September 3, 2020): 17–25. http://dx.doi.org/10.21809/rilemtechlett.2020.113.

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Additive manufacturing has been a topic of interest in the construction industry for the past decade. 3D printing of concrete structures promises great improvements in construction efficiency, waste reduction, and shape optimization. Another field where additive manufacturing offers opportunities is on the material level of cementitious composites. Techniques developed in other fields can be used to create multifunctional cementitious composites beyond what is possible with conventional technologies. This letter reviews recent developments in the field. Different applications are discussed: creating reinforcement for cementitious composites, creating capsules and vascular networks, and cementitious composites with superior mechanical behavior. Challenges for further research and practical applications of such materials are also discussed.

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Anglani, Giovanni, Tim Van Mullem, Xuejiao Zhu, Jianyun Wang, Paola Antonaci, Nele De Belie, Jean-Marc Tulliani, and Kim Van Tittelboom. "Sealing efficiency of cement-based materials containing extruded cementitious capsules." Construction and Building Materials 251 (August 2020): 119039. http://dx.doi.org/10.1016/j.conbuildmat.2020.119039.

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Taqa, Ala Abu, Ghassan Suleiman, Ahmed Senouci, and Mohamed O. Mohsen. "Using Aerosol OT in Hexane Solution to Synthesize Calcium Nitrate Self-Healing Refined Microcapsules for Construction Applications." Buildings 12, no. 6 (May 31, 2022): 751. http://dx.doi.org/10.3390/buildings12060751.

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The micro-encapsulation procedure of calcium nitrate in urea-formaldehyde shell is well known. The most recent developed method for the synthesis of the calcium nitrate self-healing micro-capsules was based on the in-situ polymerization using water-in-oil emulsion. Although the microcapsules’ yield was significantly improved using this approach, incorporating the micro-capsules into concrete mixes has been found to reduce strength. One potential strength reduction cause might be the presence of sulfonic acid as a component in the continuous (oil) phase. As the anionic surfactant, Aerosol OT (AOT) has been widely used to prepare water-in-oil emulsions and to form aggregates in non-polar solvents; submicron calcium nitrate refined microcapsules were synthesized using AOT in hexane solution. While the aqueous phase in the original encapsulation procedure has not been altered, the continuous organic phase was prepared by dissolving AOT in hexane. The prepared microcapsules were characterized using Scanning Electron Microscopy (SEM). The preliminary assessment of the effect of incorporating of the refined microcapsules into cementitious materials has been carried out by preparing mortar mixes using 75% capsules’ concentration (by weight of cement). The reported yield values, average shell thickness, and average diameter of the prepared microcapsules were found satisfactory. Moreover, the mortar samples containing calcium nitrate refined microcapsules that were prepared using the proposed method did not experience significant reduction in their mechanical properties. Hence, such encapsulation procedure may be adopted for further investigation of the self-healing efficiency in cementitious materials of the microcapsules prepared using the proposed procedure. Future work shall be directed towards this end.

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Souza, Lívia Ribeiro de, Briony Whitfield, and Abir Al-Tabbaa. "Biobased Acrylate Shells for Microcapsules Used in Self-Healing of Cementitious Materials." Sustainability 14, no. 20 (October 20, 2022): 13556. http://dx.doi.org/10.3390/su142013556.

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To facilitate the ongoing transition towards carbon neutrality, the use of renewable materials for additive manufacturing has become increasingly important. Here, we report for the first time the fabrication of microcapsules from biobased acrylate shells using microfluidics. To select the shell, a wide range of biobased acrylates disclosed in the literature was considered according to their tensile strength, ductile transition temperature and global availability. Once acrylate epoxidised soybean oil (AESO) was selected, its viscosity was adjusted to valuables suitable for the microfluidic device using two different diluting agents. Double emulsions were successfully produced using microfluidics, followed by photopolymerisation of the shell and characterisation of the capsules. Microcapsules containing AESO and isobornyl acrylate (IBOA) were produced with an outer diameter ~490 μm, shell thickness ranging between 36 and 67 μm, and production rates around 2.4 g/h. The mechanical properties of the shell were characterised as tensile strength of 29.2 ± 7.7 MPa, Young’s modulus of 1.7 ± 0.4 GPa and the ductile transition temperature was estimated as 42 °C. To investigate physical triggering, microcapsules produced with a size of 481 ± 4 μm and with a measured shell thickness around 6 μm were embedded in the cementitious matrix. The triggered shells were observed with scanning electron microscopy (SEM) and the uniform distribution of the capsules in cement paste was confirmed using X-ray computed tomography (XCT). These advances can facilitate the wide application of biobased resins for the fabrication of microcapsules for self-healing in cementitious materials.

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26

Van Tittelboom, Kim, Nele De Belie, Denis Van Loo, and Patric Jacobs. "Self-healing efficiency of cementitious materials containing tubular capsules filled with healing agent." Cement and Concrete Composites 33, no. 4 (April 2011): 497–505. http://dx.doi.org/10.1016/j.cemconcomp.2011.01.004.

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27

Huang, Haoliang, Guang Ye, and Zhonghe Shui. "Feasibility of self-healing in cementitious materials – By using capsules or a vascular system?" Construction and Building Materials 63 (July 2014): 108–18. http://dx.doi.org/10.1016/j.conbuildmat.2014.04.028.

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28

Lv, Leyang, Peiyan Guo, Gang Liu, Ningxu Han, and Feng Xing. "Light induced self-healing in concrete using novel cementitious capsules containing UV curable adhesive." Cement and Concrete Composites 105 (January 2020): 103445. http://dx.doi.org/10.1016/j.cemconcomp.2019.103445.

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29

Yuan, Haifeng, and Huisu Chen. "Quantitative solution of size and dosage of capsules for self-healing of cracks in cementitious composites." Computers & concrete 11, no. 3 (March 25, 2013): 223–36. http://dx.doi.org/10.12989/cac.2013.11.3.223.

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30

Dudek, Marta. "Self-healing cement materials – microscopic techniques." Budownictwo i Architektura 19, no. 2 (June 30, 2020): 033–40. http://dx.doi.org/10.35784/bud-arch.1494.

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The article presents a general classification of intelligent materials with self-healing (self-repairing) properties, focusing on self-healing cementitious materials. The purpose of the paper is to describe the prospects of two of the most popular micro-observation techniques, i.e. with the use of an optical and scanning electron microscope. In addition, it describes the advantages of using a tensile stage mounted in the microscope chamber for testing self-healing materials. The advantages and disadvantages of these devices have been characterized, and the results of preliminary research have been provided. The tests include the optical microscopy and scanning electron microscopy observations of the microstructure of cracks before and after the process of healing. They were carried out using ZEISS Discovery V20 optical microscope and ZEISS EVO-MA 10 scanning electron microscope on mortar samples modified with macro capsules filled with polymer. In addition to observations, chemical analysis was performed with the use of an EDS detector. The microscopic observations and chemical analyses provide the basis for assessing the effectiveness of the self-healing process, showing that the crack has been healed. Moreover, the preliminary results of the tests of micro-mechanical properties, carried out with the use of a tensile stage, have been described. The problems of using this research technique are also listed. This study shows the usefulness of this kind of tests for microcapsules for self-healing materials.

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31

Anglani, Giovanni, Tim Van Mullem, Jean-Marc Tulliani, Kim Van Tittelboom, Nele De Belie, and Paola Antonaci. "Durability of self-healing cementitious systems with encapsulated polyurethane evaluated with a new pre-standard test method." Materials and Structures 55, no. 5 (June 2022). http://dx.doi.org/10.1617/s11527-021-01818-3.

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AbstractThis work reports on the self-healing capabilities of mortar specimens with polyurethane encapsulated in two types of cementitious macro-capsules, by comparison with the performance of mortar specimens using the same healing agent encapsulated in glass capsules, as tested in an inter-laboratory testing campaign following a pre-standard procedure. This comparison was performed with a twofold objective of checking the robustness of such pre-standard procedure for varying types of capsules and testing the effectiveness of a new type of cementitious capsule that has never been used before in durability tests. The testing procedure was developed in the framework of the EU COST Action SARCOS. First, the specimens were pre-cracked via three-point bending followed by an active crack width control technique. Then, the self-healing effect was characterised in terms of water permeability reduction. The cementitious capsules offered equivalent or better performance compared to the glass capsules used in the inter-laboratory testing. The average sealing efficiency for the specimens containing cementitious capsules ranged from 54 to 74%, while for glass macro-capsules it was equal to 56%. It was also observed that when applying the pre-standard procedure to test specimens containing capsules with comparable size and geometric arrangement, the same results were obtained in different repetitions of the test. The results obtained confirmed the possibility to use the cementitious capsules as a valid macro-encapsulation system, offering additional advantages compared to glass capsules. The repeatability of the results corroborated the robustness of the adopted testing procedure, highlighting its potential for further standardisation.

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32

Alghamri, Rami, Mahmoud Jahjouh, Khalil Alastal, and Abir Al-Tabbaa. "A geometric study for determining the optimum volume fraction of pre-embedded capsules for self-healing of cracks in a cementitious matrix." Engineering Research Express, August 23, 2022. http://dx.doi.org/10.1088/2631-8695/ac8c1d.

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Abstract Autonomous healing of cracks using capsule-based systems is emerging as a promising solution to restore the durability and strength of damaged structures. For satisfactory self-healing efficiency, both capsule geometry and dosage are to be determined for the concrete mix proportion. With previous research being performed on self-healing efficiency using different capsule shapes and crack patterns, his paper introduces quantitative numerical solutions on the optimal dosage of the capsules required to completely repair cracks in a three-dimensional model of a cementitious matrix. Four different sizes of spherical capsules ranging between 0.6mm to 4.75mm embedded within a mortar matrix were tested in the model and the model results were validated using previous experimental findings. As the capsules could carry powder or liquid self-healing agents, three different scenarios were considered in this work to calculate the volume of the healing agent in the crack. It was found that the smaller the capsules the more homogenous and uniform the distribution of capsules is. However, the bigger sizes of the capsules are much preferable in terms of the amount of self-healing materials supplied to the cracked vicinity. For instance, capsules of 2-4mm size could fill 80% of the crack volume but were localised and unevenly distributed on the planes of the crack. Overall, the developed model in this study provides a robust and efficient tool to quantitively design the proportions of cement-based self-healing systems. Based on the results of the geometric model, an ANN model was also developed to calculate healing volume in terms of the volume fraction of the healing agents and the size of capsules. Results showed very close values to those obtained by the numerical model.

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33

LV, Zhong, Songpeng LI, and Huisu CHEN. "Analytical Model for the Probability Characteristics of a Crack Penetrating Capsules in Capsule-Based Self-Healing Cementitious Materials." Materials Science 23, no. 3 (August 4, 2017). http://dx.doi.org/10.5755/j01.ms.23.3.16888.

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34

Muller, Vinicius, Fernanda Pacheco, Caroline Macedo Carvalho, Franciele Fernandes, Victor Hugo Valiati, Regina Celia Espinosa Modolo, Hinoel Zamis Ehrenbring, and Bernardo Fonseca Tutikian. "Analysis of cementitious matrices self-healing with bacillus bacteria." Revista IBRACON de Estruturas e Materiais 15, no. 4 (2022). http://dx.doi.org/10.1590/s1983-41952022000400004.

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Abstract Bacterial solutions have been studied to promote self-healing of cementitious matrices, however, the concentration of this solutions varied between studies. Consequently, the objective of this study was to evaluate the self-healing potential of different concentrations of Bacillus subtilis AP91 encapsulated in expanded perlite (EP). Visual examination and capillary absorption of water was measured over time. Test samples were also subjected to strength resistance tests. The physiochemical properties of EP and his distribution on the matrix was evaluated. There was no observable trend in the effect of solution concentration on the width of crack healed. However, concentration affected the quantity and length of the fissures healed. Capillary absorption decreased as fissures were healed while no significant changes were measured in strength resistance regardless of the concentration. Results indicated that EP provided suitable encapsulation to the bacterial solution and there is an adequate distribution of the capsules in the cementitious matrix.

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35

Ying, Yujie, Miaomiao Hu, Jingmin Han, Wenming Liu, Ben Qi, and Jintang Guo. "Self-healing in cementitious system using interface enhanced capsules prepared at room temperature." Journal of Cleaner Production, February 2023, 136465. http://dx.doi.org/10.1016/j.jclepro.2023.136465.

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36

Pacheco, Fernanda, Cláudio Henrique Boscaini, Thaize Nascimento Gauto, Vinicius Müller, Hinoel Zamis Ehrenbring, Regina Célia Espinosa Modolo, and Bernardo Fonseca Tutikian. "Evaluation of concrete self-healing by encapsulated sodium metasilicate in perlite and expanded clay." Revista IBRACON de Estruturas e Materiais 16, no. 2 (2023). http://dx.doi.org/10.1590/s1983-41952023000200001.

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abstract: Investigating the behavior of self-healing cementitious composites is necessary to know alternatives that can be applied in structures increasing their life service. Therefore, this study evaluated concrete self-he aling from the use of expanded perlite (EP) and expanded clay (EC) capsules impregnated with a sodium metasilicate solution. These materials were used to substitute natural aggregates in concrete in proportions of 0 wt·%, 15 wt·% and 30 wt·% which were cured in humid or submerged environments. Cracking was induced with a flexural test and a closing with cicatrization product. was evaluated and measured visually with a software. Capillary absorption tests indicated a reduction in the porosity of samples which incorporated self-healing materials, considering it as an important property related to durability. Samples with EP achieved 100% self-healing with 15% substitution. Crack filling was achieved in cracks up to 0.43 mm wide. Samples with EC achieved 50% crack recovery under humid curing and 90% under submerged curing. It was concluded that incorporating the sodium silicate allowed improvements to fissure sealing and it is an alternative to produce self-healing concrete in Brazil. EP was more effective than EC as encapsulating material. Despite that, the EP did not impact the compressive strength due to its small size and better packing of the mixture, Also, EP presented higher healing percentage when comparing with samples containing EC.

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