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.

scholarly journals Self Compacting Concrete – an Analysis of Properties using Fly Ash

2018 ◽  
Vol 7 (2.24) ◽  
pp. 135
Author(s):  
Dasarathy A K ◽  
M Tamil Selvi ◽  
D Leela ◽  
S Kumar
Keyword(s):  
Fly Ash ◽  
Low Cost ◽  
Cementitious Materials ◽  
The Self ◽  
Experimental Program ◽  
Reinforcing Bars ◽  
Self Compacting Concrete ◽  
Construction Market ◽  
Class F Fly Ash ◽  
Class F

Self  compacting concrete has ability involves not only high deformability of paste or mortar, but also resistance to segregation between coarse aggregate and  mortar  when the concrete flows  through the confined zone of reinforcing bars. Several researchers have employed the different methods to achieve self- compactability. In recent years, self-compacting concrete (SCC) has gained wide use for placement in congested reinforced  concrete structures with difficult casting conditions. For such applications, the fresh concrete must possess high fluidity and good cohesiveness. The initial results of an experimental program aimed at producing and evaluating SCC made with high volumes of fly ash are presented and discussed. Nine SCC mixtures and one control concrete were investigated in this study. The content of the cementitious materials was maintained constant (400 kg/m3), while the water / cementitious material ratios ranged from 0.35 to 0.45. The self-compacting mixtures had a cement replacement of 40,50 and 60% by Class F fly ash. Tests were carried out on all  mechanical properties of hardened concretes such as compressive strength were also determined. The self-compacting concretes developed a 28- day compressive strengths ranging from 26 to 48 MPa. The results show that an economical self-compacting concrete could be successfully developed by incorporating high-volumes of Class F fly ash. The present project investigates the making of self-compacting concrete more affordable for the construction market by replacing high volumes of Portland cement by fly ash. The study focuses on comparison of fresh properties of SCC containing varying amounts of fly ash with that containing commercially available admixture. Test result substantiate the feasibility to develop low cost SCC using Class F fly ash.  

scholarly journals Biological Self-Healing of Cement Paste and Mortar by Non-Ureolytic Bacteria Encapsulated in Alginate Hydrogel Capsules

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3711
Author(s):  
Mohammad Fahimizadeh ◽  
Ayesha Diane Abeyratne ◽  
Lee Sui Mae ◽  
R. K. Raman Singh ◽  
Pooria Pasbakhsh
Keyword(s):  
Cement Paste ◽  
Healing Process ◽  
Cementitious Materials ◽  
The Self ◽  
Self Healing ◽  
Alkaline Conditions ◽  
Healing Agent ◽  
Encapsulated Bacteria ◽  
The Right

Crack formation in concrete is one of the main reasons for concrete degradation. Calcium alginate capsules containing biological self-healing agents for cementitious materials were studied for the self-healing of cement paste and mortars through in vitro characterizations such as healing agent survivability and retention, material stability, and biomineralization, followed by in situ self-healing observation in pre-cracked cement paste and mortar specimens. Our results showed that bacterial spores fully survived the encapsulation process and would not leach out during cement mixing. Encapsulated bacteria precipitated CaCO3 when exposed to water, oxygen, and calcium under alkaline conditions by releasing CO32− ions into the cement environment. Capsule rupture is not required for the initiation of the healing process, but exposure to the right conditions are. After 56 days of wet–dry cycles, the capsules resulted in flexural strength regain as high as 39.6% for the cement mortar and 32.5% for the cement paste specimens. Full crack closure was observed at 28 days for cement mortars with the healing agents. The self-healing system acted as a biological CO32− pump that can keep the bio-agents retained, protected, and active for up to 56 days of wet-dry incubation. This promising self-healing strategy requires further research and optimization.

Evaluation of Self-Healing Efficiency of Reinforced Concrete Beams with Calcium Nitrate Microcapsules

2017 ◽  
Vol 2629 (1) ◽  
pp. 63-72 ◽  
Author(s):  
Luis Bonilla ◽  
Marwa Hassan ◽  
Hassan Noorvand ◽  
Tyson Rupnow ◽  
Ayman Okeil
Keyword(s):  
Concrete Beams ◽  
Calcium Nitrate ◽  
Cementitious Materials ◽  
The Self ◽  
Reinforced Concrete Beams ◽  
Self Healing ◽  
Initial Stiffness ◽  
Air Content ◽  
Healing Efficiency ◽  
Control Samples

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.

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 Assessment of the self‐healing capacity of cementitious materials through active thin sections

2021 ◽  
Author(s):  
Emanuele Rossi ◽  
Claudia Romero Rodriguez ◽  
Henk Jonkers ◽  
Oğuzhan Çopuroğlu
Keyword(s):  
Cementitious Materials ◽  
The Self ◽  
Self Healing ◽  
Thin Sections

scholarly journals Self-Healing Products of Cement Pastes with Supplementary Cementitious Materials, Calcium Sulfoaluminate and Crystalline Admixtures

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7201
Author(s):  
Byoungsun Park ◽  
Young-Cheol Choi
Keyword(s):  
Phase Composition ◽  
Cementitious Materials ◽  
The Self ◽  
Ion Concentration ◽  
Supplementary Cementitious Materials ◽  
Self Healing ◽  
Cement Pastes ◽  
Main Compound ◽  
Calcium Sulfoaluminate ◽  
Granulated Blast Furnace Slag

The phase composition of self-healing products generated in cracks affects self-healing performance. This study investigated the self-healing products of cementitious materials using supplementary cementitious materials (SCMs), a calcium sulfoaluminate (CSA) expansion agent, and crystalline additives (CAs). Ground-granulated blast-furnace slag (GGBFS), fly ash (FA), and silica fume (SF) were used as SCMs, and anhydrite, Na2SO4, Na2CO3, and MgCO3 were used as crystalline additives (CAs). An artificial crack method was used to collect the self-healing products in the crack of the paste. The phase composition of the self-healing products was analyzed through X-ray diffraction (XRD)/Rietveld refinements and thermogravimetry/differential thermogravimetry (TG/DTG) analysis, and their morphology and ion concentration were examined through scanning electron microscopy with energy dispersive spectroscopy (SEM–EDS). From the results, the main compound of self-healing products was found to be calcite. GGBFS and FA decreased the content of portlandite, and the use of CAs led to the formation of alkali sulfate and alkali carbonate. The SEM–EDS analysis results showed that when GGBFS and FA were used, a large proportion of the self-healing products contained C-S-H and C-A-H, and the use of CSA led to the formation of monosulfate and ettringite.

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