Experimental Research on the Self-Healing Performance of Micro-Cracks in Concrete Bridge

2011 ◽  
Vol 250-253 ◽  
pp. 28-32 ◽  
Author(s):  
Ling Sun ◽  
Wen Yong Yu ◽  
Qi Ge
Keyword(s):  
Crack Width ◽  
Crack Surface ◽  
The Self ◽  
Strength Analysis ◽  
Self Healing ◽  
Healing Effect ◽  
Concrete Crack ◽  
Micro Cracks ◽  
Before And After ◽  
Capillary Tension

Hollow glass fiber with full of repair agent is embedded in concrete to repair components, and one - third point loading experiment is carried out to test the mechanical properties of it. Based on the strength analysis of specimens before and after self – healing, the self – healing effect of concrete is evaluated. By simulating the closed heal agent flowing and penetrating into the concrete crack surface under the capillary tension, the influence of crack width to the healing effect is analyzed.

Self-Healing Properties of Conventional and Fly Ash Cementitious Mortar, Exposed to High Temperature

2015 ◽  
pp. 1-11
Author(s):  
Shaswata Mukherjee ◽  
Saroj Mondal
Keyword(s):  
Fly Ash ◽  
Calcium Carbonate ◽  
Crack Surface ◽  
Physical Property ◽  
Pulse Velocity ◽  
The Self ◽  
External Loading ◽  
Self Healing ◽  
Micro Cracks ◽  
The Matrix

Direct stress and sub-stress caused by fire, temperature variation and external loading in a structure are most important for the development of cracks. The chemical reactions of natural healing in the matrix was not been established conclusively. The most significant factor that influences the self-healing is the precipitation of calcium carbonate crystals on the crack surface. The mechanism which contribute autogenic healing are: (a) Continued hydration of cement at cracked surface as well as continued hydration of already formed gel and also inter-crystallization of fractured crystals; (b) blocking of flow path by water impurities and concrete particles broken from the crack surface due to cracking; (c) expansion of concrete in the crack flank (swelling) and closing of cracks by spalling of loose concrete particle are also reported as the sealing mechanism by researchers. The recovery of mechanical as well as physical property was discussed by different researchers. An experimental investigation was carried out to study the autogenic healing of fire damaged fly ash and conventional cementitious mortar samples subjected to steam followed by water curing at normal atmospheric pressure. The micro cracks are generated artificially by heating the 28 days aged mortar samples at 800 Deg. C. The effect of fly-ash replacing ordinary Portland cement by 0 and 20% was studied. Recovery of compressive strength and physical properties i.e. apparent porosity, water absorption, ultrasonic pulse velocity and rapid chloride ion penetration test confirm the self-healing of micro cracks. Such healing is more prominent for fly ash mortar mix. Optical as well as scanning electron microscopy With EDAX analysis and X-ray diffraction study of the white crystalline material formed in the crack, confirms formation of calcium carbonate.

scholarly journals Application of GGBFS and Bentonite to Auto-Healing Cracks of Cement Paste

2018 ◽  
Vol 1 (1) ◽  
pp. 38 ◽  
Author(s):  
J J Ekaputri ◽  
M S Anam ◽  
Y Luan ◽  
C Fujiyama ◽  
N Chijiwa ◽  
...  
Keyword(s):  
Cement Paste ◽  
Surface Crack ◽  
Crack Width ◽  
Healing Process ◽  
Crack Depth ◽  
The Self ◽  
External Loading ◽  
Self Healing ◽  
Carbonation Reaction ◽  
Granulated Blast Furnace Slag

Cracks are caused by many factors. Shrinkage and external loading are the most common reason. It becomes a problem when the ingression of aggressive and harmful substance penetrates to the concrete gap. This problem reduces the durability of the structures. It is well known that self – healing of cracks significantly improves the durability of the concrete structure. This paper presents self-healing cracks of cement paste containing bentonite associated with ground granulated blast furnace slag. The self-healing properties were evaluated with four parameters: crack width on the surface, crack depth, tensile strength recovery, and flexural recovery. In combination with microscopic observation, a healing process over time is also performed. The results show that bentonite improves the healing properties, in terms of surface crack width and crack depth. On the other hand, GGBFS could also improve the healing process, in terms of crack depth, direst tensile recovery, and flexural stiffness recovery. Carbonation reaction is believed as the main mechanism, which contributes the self-healing process as well as the continuous hydration progress.

scholarly journals Curable Area Substantiation of Self-Healing in Concrete Using Neutral Axis

2019 ◽  
Vol 9 (8) ◽  
pp. 1537 ◽  
Author(s):  
Choonghyun Kang ◽  
Taewan Kim
Keyword(s):  
Neutral Axis ◽  
The Self ◽  
Strain Gauges ◽  
Self Healing ◽  
Distinct Area ◽  
Before And After ◽  
Strength And Stiffness ◽  
Underlying Mechanisms ◽  
Healing Assessment ◽  
Physical Recovery

The self-healing nature of concrete has been proved in many studies using various methods. However, the underlying mechanisms and the distinct area of self-healing have not been identified in detail. This study focuses on the limits of the area of self-healing. A bending specimen with a notch is used herein, and its flexural strength and stiffness before and after healing are compared and used for self-healing assessment. In addition, the neutral axis of the specimen was measured using successive strain gauges attached to the crack propagation part. Although the strength and stiffness of the concrete recovered after self-healing, the change in the location of the neutral axis before and after healing was insignificant, which indicates that physical recovery did not occur for once-opened crack areas.

Influence of Cement Coarse Particle on the Self-Healing Ability of Concrete Based on Ultrasonic Method

2010 ◽  
Vol 177 ◽  
pp. 526-529 ◽  
Author(s):  
Zhi Qiang Li ◽  
Zong Hui Zhou ◽  
Dong Yu Xu ◽  
Jing Hua Yu
Keyword(s):  
Particle Size ◽  
Wave Amplitude ◽  
Ultrasonic Method ◽  
The Self ◽  
Experimental Results ◽  
Coarse Particle ◽  
Head Wave ◽  
Self Healing ◽  
Before And After ◽  
The Relationship

The influences of particle size and mixing content of coarse cement on the self-healing ability of concrete were researched by ultrasonic method. Damaged degree was measured through the decrease of ultrasonic head wave amplitude (UHA) before and after loading. The relationship between damaged degree and self-healing ratio of concrete was built based on the experimental results as well as the relationship between cement diameter and self-healing ratio of concrete. Analyzing results show that UHA can evaluate the damaged degree of concrete clearly. There exists a damaged threshold of the concrete during loading. Under the same mixing content of coarse cement, when the damaged degree is higher than the threshold, the self-healing ratio of concrete decreases with the increase of damaged degree and increases with the increase of coarse cement diameter, however, while the damaged degree is less than the threshold, the self-healing ratio of concrete increases with both the increase of damaged degree and coarse cement diameter.

Self-Healing Effect Caused by Accelerated Carbonation of Thermally Damaged Cement Mortar: Changes in Microstructural and Macroscopic Properties

2014 ◽  
Vol 529 ◽  
pp. 36-40
Author(s):  
Son Tung Pham ◽  
William Prince
Keyword(s):  
Electrical Resistivity ◽  
High Temperature ◽  
Cement Mortar ◽  
Nitrogen Adsorption ◽  
The Self ◽  
Size Distributions ◽  
Self Healing ◽  
Accelerated Carbonation ◽  
Healing Effect ◽  
Macroscopic Properties

The objective of this work was to examine the influence of accelerated carbonation on the microstructural and macroscopic properties of thermally damage cement mortar. A normalised CEM II mortar was treated at 500°C then submitted to carbonation at 20°C, 65% relative humidity and 20% of CO2 concentration. The pores size distributions were determined from nitrogen adsorption. We also followed changes in electrical resistivity and ultrasonic velocity. The results showed that losses of macroscopic properties caused by cracks appeared at high temperature were restored due to carbonation. This highlighted the self-healing effect by accelerated carbonation which allowed the thermally damaged mortar to recover its initial properties.

scholarly journals Evaluation of Self-Healing Performance of PE and PVA Concrete Using Flexural Test

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Choonghyun Kang ◽  
Jungwon Huh ◽  
Quang Huy Tran ◽  
Kiseok Kwak
Keyword(s):  
Water Environment ◽  
The Self ◽  
Bending Test ◽  
Self Healing ◽  
Recovery Effect ◽  
Three Point Bending ◽  
Strength Recovery ◽  
Before And After ◽  
Healing Environments ◽  
Pva Fiber

The self-healing performance of PE and PVA concrete was evaluated, by using the three-point bending test with a notch. Four different crack inducement days were applied (7, 28, 49, and 91 days), and the same 21 days of healing period were applied to each case. The self-healing environments were in 20°C water, and in the curing room with 20°C temperature and 60% humidity. The flexural strength and the initial flexural stiffness of before and after healing were compared. As a result, both the strength recovery effect and the stiffness recovery effect decreased with the delay of crack inducement, and specimens in the water environment showed higher healing effect than those in the air environment. PVA fiber showed a relatively greater recovery effect than PE fiber.

scholarly journals Investigating the Self-Healing of Dynamic Covalent Thermoset Polyimine and Its Nanocomposites

2019 ◽  
Vol 86 (10) ◽  
Author(s):  
Chuanqian Shi ◽  
Zhanan Zou ◽  
Zepeng Lei ◽  
Xingli Wu ◽  
Zhengwei Liu ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Shear Strength ◽  
Environmental Pollution ◽  
Interfacial Shear Strength ◽  
Interfacial Shear ◽  
The Self ◽  
Self Healing ◽  
Dynamic Covalent Chemistry ◽  
Healing Effect ◽  
Press Time

Self-healable and recyclable materials and electronics can improve the reliability and repairability and can reduce environmental pollution; therefore, they promise very broad applications. In this study, we investigated the self-healing performance of dynamic covalent thermoset polyimine and its nanocomposites based on the dynamic covalent chemistry. Heat press was applied to two laminating films of polyimine and its nanocomposites to induce self-healing. The effects of heat press time, temperature, and load on the interfacial shear strength of the rehealed films were investigated. The results showed that increasing the heat press time, temperature, and load can significantly improve the interfacial shear strength and thus the self-healing effect. For polyimine nanocomposites, increasing the heat press time, temperature, and load led to the improved electrical conductivity of the rehealed films.

scholarly journals Key Factors Determining the Self-Healing Ability of Cement-Based Composites with Mineral Additives

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4211
Author(s):  
Kamil Tomczak ◽  
Jacek Jakubowski ◽  
Łukasz Kotwica
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Crack Width ◽  
Defect Formation ◽  
Cementitious Materials ◽  
The Self ◽  
Supplementary Cementitious Materials ◽  
Self Healing ◽  
Key Factors ◽  
Important Indicator

This paper reveals the relationships between key factors that determine the ability of cementitious composites to self-heal autogenously and specific measures for quantifying the effects of this process. The following material factors: water-to-binder ratio (w/b), uniaxial compressive strength and age of the composite at the time of defect formation were considered, as well as the method and degree of damage to the tested material. The subjects of this study were mortars and concretes in which Portland cement was partially replaced, to varying degrees, with mechanically activated fluidized bed combustion fly ash (MAFBC fly ash) and siliceous fly ash. The samples were subjected to three-point bending or cyclic compression tests after 14 or 28 days of aging, in order to induce defects and then cured in water for 122 days. Microscopic (MO) and high-resolution scanning (HRS) observations along with computer image processing techniques were used to visualize and quantify the changes occurring in the macro-crack region near the outer surface of the material during the self-sealing process. Techniques based on the measurement of the ultrasonic pulse velocity (UPV) allowed the quantification of the changes occurring inside the damaged materials. Mechanical testing of the composites allowed quantification of the effects of the activity of the binder-supplementary cementitious materials (SCMs) systems. The analysis of the results indicates a significant influence of the initial crack width on the ability to completely close the cracks; however, there are repeated deviations from this rule and local variability of the self-sealing process. It has been shown that the compressive strength of a material is an important indicator of binder activity concerning crack width reduction due to self-sealing. Regardless of the crack induction method, the internal material changes caused by self-sealing are dependent on the degree of material damage.

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