Effect of Nanotechnology on Physical Properties of Concrete

2017 ◽  
Vol 733 ◽  
pp. 71-75
Author(s):  
Leila Remache ◽  
Nacerddine Djermane
Keyword(s):  
Fly Ash ◽  
Large Volume ◽  
Lower Cost ◽  
Material Behavior ◽  
The Self ◽  
Bridge Piers ◽  
Early Age ◽  
Self Healing ◽  
Positive Effects ◽  
Green Additive

The focus of this paper is the study of effect of nanotechnology on the concrete. It shows that:The control of moisture in buildings is key to their durability, functionality, health and efficiency. Concrete which is thoroughly soaked with water is less rigid in compression than concrete with is thoroughly dried out. Use of nano SiO2 could significantly increase the compressive for concrete, containing large volume fly ash, at early age and improve size distribution. The self-healing polymer could be especially applicable to fix the microcraking in bridge, piers and columns. With the hycrete waterproofing system, concrete is batched with hycrete liquid admixture to achieve hydrophobic performance. Concrete treated by hycrete shows less than 1% absorption. This product has positive effects on the environment. Green additive has lower cost than the materials they replace. Finally, two solutions are given to have appropriate material behavior: nanotechnology and green additive.

scholarly journals Effect of fly ash on the self-healing capability of cementitious materials with crystalline admixture under different conditions

AIP Advances ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 075018
Author(s):  
Xi Wang ◽  
Hao Qiao ◽  
Ziwei Zhang ◽  
Shiying Tang ◽  
Shengjun Liu ◽  
...  
Keyword(s):  
Fly Ash ◽  
Cementitious Materials ◽  
The Self ◽  
Self Healing

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.

Self-Healing Properties of Ultra-High Toughness Fly Ash Based Geopolymer under Air and Water Environments

2021 ◽  
Vol 1036 ◽  
pp. 214-222
Author(s):  
Jia Bao Huang ◽  
Gui Yan Xiong ◽  
Xiao Lu Guo
Keyword(s):  
Fly Ash ◽  
Tensile Stress ◽  
Water Absorption ◽  
Water Environment ◽  
The Self ◽  
Self Healing ◽  
Curing Conditions ◽  
High Toughness ◽  
The Matrix ◽  
Fiber Matrix Interface

The self-healing properties of ultra-high toughness fly ash based geopolymer curing in air and water were studied under 2% pre-tension strain. The experimental results show that under these two curing conditions the tensile stress and water absorption of FA-EGC have been recovered and the pore structure has also been improved, indicating that self-healing has taken place in the specimens. Compared to the air environment, the water environment is proved to be a better environment for the self-healing of FA-EGC. It was observed that there were unreacted fly ash particles at the cracks through SEM. And more N-A-S-H gels were found under the water environment, indicating that N-A-S-H gels may enhance the fiber/matrix interface and improve the density of the matrix, resulting in the higher recovery of tensile stress and water absorption.

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.

Influence of Slag and Fly Ash on the Self-Healing Ability of Concrete

2011 ◽  
Vol 306-307 ◽  
pp. 1020-1023 ◽  
Author(s):  
Zong Hui Zhou ◽  
Zhi Qiang Li ◽  
Dong Yu Xu ◽  
Jing Hua Yu
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Sem Analysis ◽  
The Self ◽  
Self Healing ◽  
Strength Measurement ◽  
Before And After ◽  
Optimal Mixing

The influence of slag and fly ash on the self-healing ability of concrete was researched by strength measurement and SEM analysis. The self-healing ratio was measured by the increase of compressive strength before and after self-healing. The optimal mixing amount of slag and fly ash were determined, and the reasonable sand ratio was obtained. Analyzing results show that the self-healing ability of concrete was the strongest when the mixing content of slag and fly ash were 30% and 40% respectively. The appropriate sand ratio was also obtained, when the sand ratio is 33%, the self-healing ability of concrete is the strongest.

scholarly journals Monitoring the Self-healing of Concrete from the Ultrasonic Pulse Velocity

2019 ◽  
Vol 3 (1) ◽  
pp. 16 ◽  
Author(s):  
Letícia Camara ◽  
Mayara Wons ◽  
Ian Esteves ◽  
Ronaldo Medeiros-Junior
Keyword(s):  
Fly Ash ◽  
Healing Process ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Ultrasonic Waves ◽  
The Self ◽  
Self Healing ◽  
Wetting And Drying ◽  
Rate Characteristic

Concrete has the ability to naturally heal its cracks, in a process called self-healing. This article aimed to analyze the self-healing of concretes, evaluating the influence of fly ash and the age of occurrence of cracks. Concrete specimens were submitted to cracking at 7 and 28 days. Subsequently, the samples were exposed to 12 wetting and drying cycles in order to favor the self-healing process. The phenomenon was evaluated through the ultrasonic pulse velocity testing, performed weekly on the specimens from the molding stage until the end of all cycles. The concretes showed a decrease in ultrasonic pulse velocity at the time they were cracked. This is due to the greater difficulty in the propagation of ultrasonic waves in the voids formed during cracking. This drop was higher for concrete with fly ash. Also, the results show that the fly ash concretes presented a more expressive self-healing process when cracked at 28 days, which may be related to the presence of pozzolanic reactions and the presence of more anhydrous particles. The concretes without fly ash had self-healing when they were cracked at 7 days. This is explained by the high hydration rate characteristic of ordinary Portland cement.

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