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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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Preparation procedure of microcapsules.
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pone-0081616-g001: Preparation procedure of microcapsules.

Mentions: The epoxy was firstly mixed with BA (14 wt%) in a 500-ml three-neck round-bottomed flask for dilution. The surfactant water solution of SDBS (4 wt%) and OP (4 wt%) with an amount of 2.8 times of the epoxy was added into the flask and mechanically stirred to form a well-dispersed solution. The solution was gradually heated up to 75°C and maintained at this temperature for 1h. While still under this temperature, the mixture of St, BPO and BP was then added into this solution. After that, air in the container was replaced by argon through an opening on the flask with the help of a vacuum pump. The temperature was maintained for 5h for synthesis. PP (1 wt%) was then added and allowed for 3 more hours for continuous reaction. An emulsion of microcapsules with 30% concentration by mass was obtained finally. The preparation procedure is shown in Figure 1.


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)

Preparation procedure of microcapsules.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0081616-g001: Preparation procedure of microcapsules.
Mentions: The epoxy was firstly mixed with BA (14 wt%) in a 500-ml three-neck round-bottomed flask for dilution. The surfactant water solution of SDBS (4 wt%) and OP (4 wt%) with an amount of 2.8 times of the epoxy was added into the flask and mechanically stirred to form a well-dispersed solution. The solution was gradually heated up to 75°C and maintained at this temperature for 1h. While still under this temperature, the mixture of St, BPO and BP was then added into this solution. After that, air in the container was replaced by argon through an opening on the flask with the help of a vacuum pump. The temperature was maintained for 5h for synthesis. PP (1 wt%) was then added and allowed for 3 more hours for continuous reaction. An emulsion of microcapsules with 30% concentration by mass was obtained finally. The preparation procedure is shown in Figure 1.

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