scholarly journals Evaluation of Methodologies for Assessing Self-Healing Performance of Concrete with Mineral Expansive Agents: An Interlaboratory Study

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2024
Author(s):  
Chrysoula Litina ◽  
Girts Bumanis ◽  
Giovanni Anglani ◽  
Marta Dudek ◽  
Riccardo Maddalena ◽  
...  
Keyword(s):  
Water Absorption ◽  
Water Flow ◽  
Crack Width ◽  
Self Healing ◽  
Practical Applications ◽  
Traditional Design ◽  
Mineral Additions ◽  
Repeatability And Reproducibility ◽  
Width Reduction ◽  
Crack Widths

Self-healing concrete has the potential to optimise traditional design approaches; however, commercial uptake requires the ability to harmonize against standardized frameworks. Within EU SARCOS COST Action, different interlaboratory tests were executed on different self-healing techniques. This paper reports on the evaluation of the effectiveness of proposed experimental methodologies suited for self-healing concrete with expansive mineral additions. Concrete prisms and discs with MgO-based healing agents were produced and precracked. Water absorption and water flow tests were executed over a healing period spanning 6 months to assess the sealing efficiency, and the crack width reduction with time was monitored. High variability was reported for both reference (REF) and healing-addition (ADD) series affecting the reproducibility of cracking. However, within each lab, the crack width creation was repeatable. ADD reported larger crack widths. The latter influenced the observed healing making direct comparisons across labs prone to errors. Water absorption tests highlighted were susceptible to application errors. Concurrently, the potential of water flow tests as a facile method for assessment of healing performance was shown across all labs. Overall, the importance of repeatability and reproducibility of testing methods is highlighted in providing a sound basis for incorporation of self-healing concepts in practical applications.

scholarly journals Crack-healing in cementitious material to improve the durability of structures: Review

2018 ◽  
Vol 250 ◽  
pp. 03005 ◽  
Author(s):  
Hassan Amer Ali Algaifi ◽  
Suhaimi Abu Bakar ◽  
Abdul Rahman Mohd Sam ◽  
Ahmad Razin Zainal Abidin
Keyword(s):  
Crack Width ◽  
Cementitious Materials ◽  
Cementitious Material ◽  
Self Healing ◽  
Crack Healing ◽  
Harmful Substances ◽  
Crack Faces ◽  
Crack Widths ◽  
Long Term Studies

One of the most commonly used materials in the field of construction is concrete. Nevertheless, there are strong inclinations for concrete to form cracks, which would then allow the penetration of both aggressive and harmful substances into the concrete. Subsequently, this will decrease the durability of the affected structures. Thus, the ability for cracks to heal themselves in the affected cementitious materials is in demand to prolong the life of any structure. Autogenous self-healing is one approach to overcome smaller crack widths (macrocracks). Nowadays, crack width-healing is of great importance. Having said that, both polymers and bacteria are the most common approach to enhance autogenous self-healing and bond crack faces. Crack width-healing of up to 0.97 mm was achieved via bacteria-based self-healing. In this paper, the mechanisms of these approaches and their efficiency to heal crack were highlighted. Both bacteria-and polymers-based self-healing are promising techniques for the future. However, long term studies are still required before real applications can be made.

Self healing properties with various crack widths under continuous water leakage

2008 ◽  
pp. 121-122 ◽  
Author(s):  
T Kishi ◽  
K Kobayashi ◽  
S Komatsu ◽  
A Hosoda ◽  
S Ikeno ◽  
...  
Keyword(s):  
Self Healing ◽  
Water Leakage ◽  
Crack Widths

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 Self-Healing Biogeopolymers Using Biochar-Immobilized Spores of Pure- and Co-Cultures of Bacteria

2020 ◽  
Author(s):  
Jadin Zam S. Doctolero ◽  
Arnel B. Beltran ◽  
Marigold O. Uba ◽  
April Anne S. Tigue ◽  
Michael Angelo B. Promentilla
Keyword(s):  
Image Analysis ◽  
Crack Width ◽  
Ultrasonic Pulse ◽  
Self Healing ◽  
Weak Effect ◽  
Bacterial Cultures ◽  
Healing Agent ◽  
Optimum Response ◽  
Maximum Crack ◽  
Cultured Bacteria

A sustainable solution for crack maintenance in geopolymers is necessary if they are to be the future of modern green construction. This study thus aimed to develop self-healing biogeopolymers that could potentially rival bioconcrete. First, a suitable healing agent was selected from Bacillus subtilis, B. sphaericus, and B. megaterium by directly adding their spores in the geopolymers and subsequently exposing them to a large amount of nutrients for 14 days. SEM-EDX analysis revealed the formation of biominerals for B. subtilis and B. sphaericus. Next, the effect of biochar-immobilization and co-culturing (B. sphaericus and B. thuringiensis) on the healing efficiencies of the geopolymers were tested and optimized by measuring their ultrasonic pulse velocities weekly over a 28-day healing period. The results show that using co-cultured bacteria significantly improved the observed efficiencies, while biochar-immobilization had a weak effect but yielded an optimum response between 0.3-0.4 g/mL. The maximum crack width sealed was 0.65 mm. Through SEM-EDX and FTIR analyses, the biominerals precipitated in the cracks were identified to be mainly CaCO3. Furthermore, image analysis of the XCT scans of some of the healed geopolymers confirmed that their pulse velocities were indeed improving due to the filling of their internal spaces with biominerals. With that, there is potential in developing self-healing biogeopolymers using biochar-immobilized spores of bacterial cultures.

scholarly journals Self-Healing of SiC-Al2O3-B4C Ceramic Composites at Low Temperatures

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 652
Author(s):  
Baoguo Wang ◽  
Rong Tu ◽  
Yinglong Wei ◽  
Haopeng Cai
Keyword(s):  
Flexural Strength ◽  
Low Temperatures ◽  
Ceramic Composite ◽  
Ceramic Composites ◽  
Self Healing ◽  
Vickers Indentation ◽  
Crack Healing ◽  
Practical Applications ◽  
Plasma Sintering ◽  
Spark Plasma

Self-healing ceramics have been researched at high temperatures, but few have been considered at lower temperatures. In this study, SiC-Al2O3-B4C ceramic composite was compacted by spark plasma sintering (SPS). A Vickers indentation was introduced, and the cracks were healed between 600 °C and 800 °C in air. Cracks could be healed completely in air above 700 °C. The ceramic composite had the best healing performance at 700 °C for 30 min, recovering flexural strength of up to 94.2% of the original. Good crack-healing ability would make this composite highly useful as it could heal defects and flaws autonomously in practical applications. The healing mechanism was also proposed to be the result of the oxidation of B4C.

Flow along the Gut and Intestinal Absorption of Salt and Water in Euryhaline Teleosts: A Theoretical Analysis

1974 ◽  
Vol 60 (2) ◽  
pp. 557-566
Author(s):  
K. KRISTENSEN ◽  
E. SKADHAUGE
Keyword(s):  
Water Absorption ◽  
Water Flow ◽  
Permeability Coefficient ◽  
Absorption Rate ◽  
Plasma Osmolality ◽  
European Eel ◽  
Drinking Rate ◽  
Osmotic Permeability ◽  
Nacl Absorption ◽  
Concentration Changes

1. In euryhaline teleosts the transmural salt and water flow and the flow and concentration changes along the gut were simulated by analogue computation. The purpose was to elucidate the interaction of and sensitivity to the parameters of the system particularly with respect to intestinal water absorption. The simulations were based on data obtained from the yellow European eel, the rainbow trout and the cyprinodont Aphanius dispar. 2. When the experimental values for drinking rate, maximal NaCl absorption rate and concentration at half-maximal absorption rate, osmotic permeability coefficient, solute-linked water flow, and concentrations in the gut were used in the model, good consistency was achieved, and predictions could be made. 3. The simulations demonstrated a close linkage between drinking rate and maximal NaCl absorption rate. A large water absorption was only possible close to an optimal drinking rate for each value of maximal NaCl transport rate. The water absorption was little sensitive to the osmotic permeability coefficient of the intestinal wall. 4. As a means of adaptation to waters of high salinity an increase in maximal NaCl absorption rate was shown to be very costly for energetic reasons. This supports indirectly the concept that the osmotic permeability of the gills must go down. The increase in plasma osmolality was a useful part of the adaptation.

scholarly journals Noncovalent π-stacked robust topological organic framework

2020 ◽  
Vol 117 (34) ◽  
pp. 20397-20403
Author(s):  
Dong Meng ◽  
Jonathan Lee Yang ◽  
Chengyi Xiao ◽  
Rui Wang ◽  
Xiaofei Xing ◽  
...  
Keyword(s):  
Porous Structure ◽  
Organic Semiconductors ◽  
Organic Electronics ◽  
High Performance ◽  
Three Dimensional ◽  
Self Healing ◽  
Direct Construction ◽  
Covalent Bonds ◽  
Practical Applications ◽  
Organic Framework

Organic frameworks (OFs) offer a novel strategy for assembling organic semiconductors into robust networks that facilitate transport, especially the covalent organic frameworks (COFs). However, poor electrical conductivity through covalent bonds and insolubility of COFs limit their practical applications in organic electronics. It is known that the two-dimensional intralayer π∙∙∙π transfer dominates transport in organic semiconductors. However, because of extremely labile inherent features of noncovalent π∙∙∙π interaction, direct construction of robust frameworks via noncovalent π∙∙∙π interaction is a difficult task. Toward this goal, we report a robust noncovalent π∙∙∙π interaction-stacked organic framework, namely πOF, consisting of a permanent three-dimensional porous structure that is held together by pure intralayer noncovalent π∙∙∙π interactions. The elaborate porous structure, with a 1.69-nm supramaximal micropore, is composed of fully conjugated rigid aromatic tetragonal-disphenoid-shaped molecules with four identical platforms. πOF shows excellent thermostability and high recyclability and exhibits self-healing properties by which the parent porosity is recovered upon solvent annealing at room temperature. Taking advantage of the long-range π∙∙∙π interaction, we demonstrate remarkable transport properties of πOF in an organic-field-effect transistor, and the mobility displays relative superiority over the traditional COFs. These promising results position πOF in a direction toward porous and yet conductive materials for high-performance organic electronics.

A self-healing interface on lithium metal with lithium difluoro (bisoxalato) phosphate for enhanced lithium electrochemistry

2019 ◽  
Vol 7 (45) ◽  
pp. 26002-26010 ◽  
Author(s):  
Jingchun Zhuang ◽  
Xianshu Wang ◽  
Mengqing Xu ◽  
Zhi Chen ◽  
Mingzhu Liu ◽  
...  
Keyword(s):  
Energy Storage ◽  
Interfacial Instability ◽  
Self Healing ◽  
Lithium Metal ◽  
Practical Applications ◽  
Metal Anodes

The practical applications of lithium (Li) metal anodes are suppressed by one of the most serious obstacles to energy storage: the high interfacial instability during deposition and dissolution.

scholarly journals Method for Assessment of Changes in the Width of Cracks in Cement Composites with Use of Computer Image Processing and Analysis

2017 ◽  
Vol 39 (2) ◽  
pp. 73-80 ◽  
Author(s):  
Kamil Tomczak ◽  
Jacek Jakubowski ◽  
Przemysław Fiołek
Keyword(s):  
Image Processing ◽  
Crack Width ◽  
Healing Process ◽  
Cement Composites ◽  
Self Healing ◽  
Initial Image ◽  
Scale Invariant ◽  
Line Segments ◽  
Changes Over Time ◽  
Over Time

Abstract Crack width measurement is an important element of research on the progress of self-healing cement composites. Due to the nature of this research, the method of measuring the width of cracks and their changes over time must meet specific requirements. The article presents a novel method of measuring crack width based on images from a scanner with an optical resolution of 6400 dpi, subject to initial image processing in the ImageJ development environment and further processing and analysis of results. After registering a series of images of the cracks at different times using SIFT conversion (Scale-Invariant Feature Transform), a dense network of line segments is created in all images, intersecting the cracks perpendicular to the local axes. Along these line segments, brightness profiles are extracted, which are the basis for determination of crack width. The distribution and rotation of the line of intersection in a regular layout, automation of transformations, management of images and profiles of brightness, and data analysis to determine the width of cracks and their changes over time are made automatically by own code in the ImageJ and VBA environment. The article describes the method, tests on its properties, sources of measurement uncertainty. It also presents an example of application of the method in research on autogenous self-healing of concrete, specifically the ability to reduce a sample crack width and its full closure within 28 days of the self-healing process.

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