Interactions between Organic Chelation Agents and Ions in Seawater for Accelerating Self-Healing of Cracks in Cement Paste

2021 ◽  
Vol 33 (4) ◽  
pp. 04021036
Author(s):  
Hao Liu ◽  
Haoliang Huang ◽  
Xintong Wu ◽  
Kai Wu ◽  
Jie Hu ◽  
...  
Keyword(s):  
Author(s):  
Dawei Sun ◽  
Ma Wenxu ◽  
Ma Jikun ◽  
Jianhua Yan ◽  
Mao Qianjin ◽  
...  

2018 ◽  
Vol 1 (1) ◽  
pp. 38 ◽  
Author(s):  
J J Ekaputri ◽  
M S Anam ◽  
Y Luan ◽  
C Fujiyama ◽  
N Chijiwa ◽  
...  

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.


Author(s):  
S. Christopher Gnanaraj ◽  
Ramesh Babu Chokkalingam ◽  
G. Lizia Thankam ◽  
S.K.M. Pothinathan

AbstractFor the past few decades innovation in construction material has grown a lot. This leads to special concrete such as self-compacting concrete, geopolymer concrete, self-healing concrete, etc. To prepare a special concrete apart from regular concreting material some sort of special materials was also needed, like mineral and chemical admixtures. Hence it is necessary to study the effect of these admixtures in cement paste and mortar before studying the same in concrete. Hence an attempt is made to study the effect of mineral and chemical admixtures in the fresh and hardened properties of cement paste and mortar. For this study ultrafine natural steatite powder is taken as mineral admixture and polycarboxylic based superplasticizer and glenium stream 2 were taken as chemical admixtures. Ultrafine natural steatite powder was used as additive to cement in various percentages like 0%, 5%, 10%, 15%, 20% and 25%. Superplasticizer and viscosity modifying admixture were taken as 1.5% and 0.5%, respectively. Then various combinations were worked out. To study the fresh property of cement paste consistency, initial setting time and miniature slump cone test were done based on the results yield stress of cement paste also calculated empirically. To study the hardened property compression test on cement mortar was done. Based on the test results it is clear that the addition of ultrafine natural steatite powder increases the water demand hence reduces the workability. On the other hand, it increases the compressive strength up to a certain limit. Adding superplasticizer increases the workability and reduces the water demand and viscosity modifying admixture reduces the bleeding and segregation effects hence increases the compressive strength.


2018 ◽  
Vol 195 ◽  
pp. 01012
Author(s):  
Kiki Dwi Wulandari ◽  
Januarti Jaya Ekaputri ◽  
Triwulan ◽  
Chikako Fujiyama ◽  
Davin H. E. Setiamarga

Specific microbial agents such as bacteria are often used in concrete to improve its performance. Some microbes act as self-healing agents to close cracks in concrete, and to increase concrete strength. This paper presents a study to observe the effects of microbe addition to two types of concrete mixtures the fly ash-based, as geopolymer paste, and portland cement paste containing fly ash. Furthermore, the investigation was conducted to compare the properties of each paste, such as its compressive strengths, specific gravities, porosity, microstructures, and XRay diffracting properties. The results indicate that microbial activities positively affected the properties of both, portland cement paste and geopolymer paste. The result reported here strongly suggests that fly ash can be used to produce a high quality, but environmental friendly construction material when it’s mixed together with useful microbes.


2019 ◽  
Vol 104 ◽  
pp. 103357 ◽  
Author(s):  
Qiu Li ◽  
Zhilin Liu ◽  
Wanyu Chen ◽  
Bo Yuan ◽  
Xiang Liu ◽  
...  

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3711
Author(s):  
Mohammad Fahimizadeh ◽  
Ayesha Diane Abeyratne ◽  
Lee Sui Mae ◽  
R. K. Raman Singh ◽  
Pooria Pasbakhsh

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.


2020 ◽  
Vol 249 ◽  
pp. 118556 ◽  
Author(s):  
Mohammadhossein Zamani ◽  
Saeid Nikafshar ◽  
Ahmad Mousa ◽  
Arash Behnia
Keyword(s):  

2020 ◽  
Vol 995 ◽  
pp. 161-167
Author(s):  
Hana Schreiberova ◽  
Josef Fládr ◽  
Karel Šeps ◽  
Alena Kohoutkova

The application of self-healing concrete for durability enhancement has become a widely studied topic in recent decades. This paper focuses on addition of a superabsorbent polymer (SAP) to bio-based self-healing concrete – a material in which cracks are autonomously sealed by incorporated microorganisms. As previously proposed, the SAP could serve as protection of the microorganisms against the harsh concrete environment and possibly to further enhance the materials autogenous sealing capacity. However, determining the applicable bio-based concrete mix design is not without obstacles as the immense absorption capacity of the SAP is, inter alia, closely related to ions present in the solution. This current study compares different mix designs of cement paste with the nutrients applied in the bio-based concrete and the addition of the SAP in dry and partially saturated states. The paste consistencies are determined, and a number of cement paste specimens is prepared to measure flexural and compressive strengths at 7 and 28 days from casting. The flowability results indicate that the SAP in a dry state absorbs slightly less than 25 g/g SAP of extra mixing water as the final consistency was similar to the reference paste. Further, the results showed that the partially saturated SAP is able to retain a great amount of the liquid throughout the mixing process. In this study, the strengths generally drop by still admissible 20% in the case of the dry SAP and extra water addition, whereas the replacement of mixing water by the partially saturated SAP results in a significant strength increase. These findings indicate that the dosage 0.5% SAP by cement weight in both of the states, dry and saturated, is applicable in the nutrient enriched cement paste from the mechanical perspective, although further work which would describe the absorption and retention mechanisms in depth is needed.


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