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Self-healing efficiency of cementitious materials containing microcapsules filled with healing adhesive: mechanical restoration and healing process monitored by water absorption.

Li W, Jiang Z, Yang Z, Zhao N, Yuan W - PLoS ONE (2013)

Bottom Line: The effects of some factors, including the content of microcapsules, the curing conditions and the degree of damage on the healing efficiency were investigated.The results demonstrated that the capsule-containing cement paste can achieve the various mechanical restorations depending on the curing condition and the degree of damage.Though no noticeable improved stiffness obtained, the increasing fracture energy was seen particularly for the specimen acquiring 60% pre-damage.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education, Department of Materials Science and Engineering, Tongji University, Shanghai, People's Republic of China.

ABSTRACT
Autonomous crack healing of cementitious composite, a construction material that is susceptible to cracking, is of great significance to improve the serviceability and to prolong the longevity of concrete structures. In this study, the St-DVB microcapsules enclosing epoxy resins as the adhesive agent were embedded in cement paste to achieve self-healing capability. The self-healing efficiency was firstly assessed by mechanical restoration of the damaging specimens after being matured. The flexural and compressive configurations were both used to stimulate the localized and distributed cracks respectively. The effects of some factors, including the content of microcapsules, the curing conditions and the degree of damage on the healing efficiency were investigated. Water absorption was innovatively proposed to monitor and characterize the evolution of crack networks during the healing process. The healing cracks were observed by SEM-EDS following. The results demonstrated that the capsule-containing cement paste can achieve the various mechanical restorations depending on the curing condition and the degree of damage. But the voids generated by the surfactants compromised the strength. Though no noticeable improved stiffness obtained, the increasing fracture energy was seen particularly for the specimen acquiring 60% pre-damage. The sorptivity and amount of water decreased with cracks healing by the adhesive, which contributed to cut off and block ingress of water. The micrographs by SEM-EDS also validated that the cracks were bridged by the hardened epoxy as the dominated elements of C and O accounted for 95% by mass in the nearby cracks.

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Load-displacement curves for blank cement paste during pre-damage: (a) standard curing (b) water curing.
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pone-0081616-g005: Load-displacement curves for blank cement paste during pre-damage: (a) standard curing (b) water curing.

Mentions: Figure 5 shows the load-displacement curve of the specimens without microcapsule when the cracks were fabricated by various levels of loads as 30%, 60% and 100% of the maximum resistance, aged in air (a) and water (b) respectively. The reason that these three levels were chosen can be illustrated by that the failure of cementitious material is a process of initiation of microcracks, stable growth and propagation until coalescence of cracks to fracture the material due to its complex microstructure, which normally corresponds to 30%, 50%~60% and 75%~100% of its strength respectively, according to a quasi-linear constitutive relationship of stress-strain for concrete in compression [54]. While for uniaxial tension, the stress-strain curve keeps straight for a longer time until 60% of the ultimate stress, because the tensile stress is not beneficial to render cracks than that of compression [54]. Unlike concrete, cement paste is more elastic and the stress-strain curve maintains linear related until 80~90% of its resistance. But the geometry and amount of cracks are assumed to be quite different for the three levels of pre-damage.


Self-healing efficiency of cementitious materials containing microcapsules filled with healing adhesive: mechanical restoration and healing process monitored by water absorption.

Li W, Jiang Z, Yang Z, Zhao N, Yuan W - PLoS ONE (2013)

Load-displacement curves for blank cement paste during pre-damage: (a) standard curing (b) water curing.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3842932&req=5

pone-0081616-g005: Load-displacement curves for blank cement paste during pre-damage: (a) standard curing (b) water curing.
Mentions: Figure 5 shows the load-displacement curve of the specimens without microcapsule when the cracks were fabricated by various levels of loads as 30%, 60% and 100% of the maximum resistance, aged in air (a) and water (b) respectively. The reason that these three levels were chosen can be illustrated by that the failure of cementitious material is a process of initiation of microcracks, stable growth and propagation until coalescence of cracks to fracture the material due to its complex microstructure, which normally corresponds to 30%, 50%~60% and 75%~100% of its strength respectively, according to a quasi-linear constitutive relationship of stress-strain for concrete in compression [54]. While for uniaxial tension, the stress-strain curve keeps straight for a longer time until 60% of the ultimate stress, because the tensile stress is not beneficial to render cracks than that of compression [54]. Unlike concrete, cement paste is more elastic and the stress-strain curve maintains linear related until 80~90% of its resistance. But the geometry and amount of cracks are assumed to be quite different for the three levels of pre-damage.

Bottom Line: The effects of some factors, including the content of microcapsules, the curing conditions and the degree of damage on the healing efficiency were investigated.The results demonstrated that the capsule-containing cement paste can achieve the various mechanical restorations depending on the curing condition and the degree of damage.Though no noticeable improved stiffness obtained, the increasing fracture energy was seen particularly for the specimen acquiring 60% pre-damage.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education, Department of Materials Science and Engineering, Tongji University, Shanghai, People's Republic of China.

ABSTRACT
Autonomous crack healing of cementitious composite, a construction material that is susceptible to cracking, is of great significance to improve the serviceability and to prolong the longevity of concrete structures. In this study, the St-DVB microcapsules enclosing epoxy resins as the adhesive agent were embedded in cement paste to achieve self-healing capability. The self-healing efficiency was firstly assessed by mechanical restoration of the damaging specimens after being matured. The flexural and compressive configurations were both used to stimulate the localized and distributed cracks respectively. The effects of some factors, including the content of microcapsules, the curing conditions and the degree of damage on the healing efficiency were investigated. Water absorption was innovatively proposed to monitor and characterize the evolution of crack networks during the healing process. The healing cracks were observed by SEM-EDS following. The results demonstrated that the capsule-containing cement paste can achieve the various mechanical restorations depending on the curing condition and the degree of damage. But the voids generated by the surfactants compromised the strength. Though no noticeable improved stiffness obtained, the increasing fracture energy was seen particularly for the specimen acquiring 60% pre-damage. The sorptivity and amount of water decreased with cracks healing by the adhesive, which contributed to cut off and block ingress of water. The micrographs by SEM-EDS also validated that the cracks were bridged by the hardened epoxy as the dominated elements of C and O accounted for 95% by mass in the nearby cracks.

Show MeSH
Related in: MedlinePlus