scholarly journals Understanding fracture mechanisms via validated virtual tests of encapsulation-based self-healing concrete beams

2022 ◽  
Vol 213 ◽  
pp. 110299
Author(s):  
Z. Dai ◽  
E. Tsangouri ◽  
K. Van Tittelboom ◽  
X. Zhu ◽  
F.A. Gilabert
Author(s):  
Luis Bonilla ◽  
Marwa Hassan ◽  
Hassan Noorvand ◽  
Tyson Rupnow ◽  
Ayman Okeil

The self-healing efficiency of cementitious materials was improved by developing several strategies to provide and deliver the products (healing agents) needed for cracks to self-repair. This study evaluated the self-healing efficiency of microcapsules filled with calcium nitrate in reinforced and unreinforced concrete beams. The structural behavior and healing efficiency were evaluated by measuring and then comparing the initial stiffness, peak strength, and deformation with posthealing measurements. Furthermore, as part of this study, crack monitoring was conducted to evaluate crack healing over time. Then characterization analysis was carried out with energy dispersive X-ray spectroscopy to quantify the healing components in the cracked areas. Results showed that the air content in samples containing microcapsules was two times higher than that in the control samples. Furthermore, addition of microcapsules lowered the flexural strength of concrete beams compared with that of the control samples. A positive stiffness recovery was recorded for all groups, with and without microcapsules or steel. Control samples showed the lowest stiffness recovery; however, the use of steel with microcapsules presented a superior healing efficiency and improved stiffness recovery significantly by 38%. Results from image analysis showed that crack widths did not completely heal for the control samples, while using microcapsules allowed the cracked widths to heal more efficiently. The best observed performance was for the microcapsules–steel group, which yielded 100% healing of the cracks.


Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5265
Author(s):  
Sha Yang ◽  
Fadi Aldakheel ◽  
Antonio Caggiano ◽  
Peter Wriggers ◽  
Eddie Koenders

Improving the durability and sustainability of concrete structures has been driving the enormous number of research papers on self-healing mechanisms that have been published in the past decades. The vast developments of computer science significantly contributed to this and enhanced the various possibilities numerical simulations can offer to predict the entire service life, with emphasis on crack development and cementitious self-healing. The aim of this paper is to review the currently available literature on numerical methods for cementitious self-healing and fracture development using Phase-Field (PF) methods. The PF method is a computational method that has been frequently used for modeling and predicting the evolution of meso- and microstructural morphology of cementitious materials. It uses a set of conservative and non-conservative field variables to describe the phase evolutions. Unlike traditional sharp interface models, these field variables are continuous in the interfacial region, which is typical for PF methods. The present study first summarizes the various principles of self-healing mechanisms for cementitious materials, followed by the application of PF methods for simulating microscopic phase transformations. Then, a review on the various PF approaches for precipitation reaction and fracture mechanisms is reported, where the final section addresses potential key issues that may be considered in future developments of self-healing models. This also includes unified, combined and coupled multi-field models, which allow a comprehensive simulation of self-healing processes in cementitious materials.


2020 ◽  
Vol 996 ◽  
pp. 91-96
Author(s):  
Guan Xi Liang ◽  
Xian Feng Wang ◽  
Zhiwei Qian ◽  
Ning Xu Han ◽  
Feng Xing

A cementitious system embedded in microcapsules can achieve self-healing, and the fracture and triggering behavior of microcapsules is with great importance. In this study, the crack behavior of the concrete-microcapsule system was simulated by a three-dimensional lattice model. Based on the results of the fracture energy test on concrete beams and the nanoindentation test on microcapsules, the local mechanical properties of the lattice elements were determined. The aim of this paper is to set up a three-dimensional lattice model to study the trigger mechanism of the microcapsule-interface-concrete zone.


Minerals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 284 ◽  
Author(s):  
Tobias Danner ◽  
Ulla Hjorth Jakobsen ◽  
Mette Rica Geiker

Self-healing of cracked concrete beams after 25 years of marine exposure was investigated. The extent of self-healing and the chemical and mineralogical composition of the self-healing products were characterized, and mechanisms proposed. There was no effect of varying silica fume (4%, 12%) and fly ash content (0%, 20%) on the mineralogy and chemistry of the self-healing products and the extent of self-healing. Crack widths smaller than 0.2 mm appeared closed. With increasing crack depth, a sequence of changing mineralogy of self-healing products was found. In the outer part of the crack (0–5 mm depth from the exterior surface) only calcite was precipitated followed by brucite layers from 5–30 mm depth. The brucite was occasionally intermixed with calcite. At crack depths >30 mm only ettringite was observed. It is hypothesized that the mineralogical sequence observed with increasing crack depth occurs due to an increasing pH of the solution inside the crack with increased crack depth. Self-healing of cracks in marine exposed concrete is proposed to happen through precipitation of ions from seawater partly in reaction with ions from the cement paste in the outer part of the crack and through dissolution and reprecipitation of ettringite at larger crack depths.


2002 ◽  
Vol 735 ◽  
Author(s):  
Eric N. Brown ◽  
Jeffrey S. Moore ◽  
Scott R. White ◽  
Nancy R. Sottos

ABSTRACTInspired by biological systems, in which damage triggers an autonomous healing response, a polymer composite material that can heal itself when cracked has been developed. The material consists of an epoxy matrix composite, which utilizes embedded microcapsules to store a healing agent and an embedded catalyst. This paper investigates issues of fracture and fatigue consequential to the development and optimization of this new class of materials. When damage occurs, the propagating crack ruptures the microcapsules, which releases healing agent into the crack plane. Polymerization of the healing agent is triggered by contact with exposed catalyst, which bonds the crack faces closed. The efficiency of crack healing is defined as the ability of a healed sample to recover fracture toughness. Healing efficiencies of over 90% have been achieved. Embedded microcapsules significantly increase the fracture toughness and reduce the fatigue crack propagation rate of epoxy. Fracture mechanisms for neat epoxy and epoxy with embedded microcapsules are presented.


2015 ◽  
Vol 744-746 ◽  
pp. 38-45
Author(s):  
Zi Jian Liu ◽  
Bo Diao ◽  
Xiao Ning Zheng

The durability of coastal reinforced concrete bridge structures will be deteriorated during service due to fatigue loads and Chloride erosion. Through the microscopic tests of reinforced concrete beams after fatigue and seawater corrosion, 10 reinforced concrete beams divided into 5 groups subjected to different fatigue loads were investigated under the alternative action of seawater corrosion, where the deterioration of concrete was degraded. From the experiment, it can be concluded that there was significant self-healing phenomenon on the cracked beams by fatigue loading; And there was regular and clear microcracks in the beams when the maximum fatigue load between 0.16~0.24Pu; the cracks of the beams became obvious,micro cracks increased and crystals can be significantly seen in cracks and low lying location when the maximum fatigue load exceeds 0.24Pu.


2020 ◽  
Vol 11 (41) ◽  
pp. 6549-6558
Author(s):  
Yohei Miwa ◽  
Mayu Yamada ◽  
Yu Shinke ◽  
Shoichi Kutsumizu

We designed a novel polyisoprene elastomer with high mechanical properties and autonomous self-healing capability at room temperature facilitated by the coexistence of dynamic ionic crosslinks and crystalline components that slowly reassembled.


1982 ◽  
Vol 118 (4) ◽  
pp. 267-272 ◽  
Author(s):  
E. Bonifazi
Keyword(s):  

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