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International Concrete Abstracts Portal

Showing 1-5 of 96 Abstracts search results

Document: 

20-438

Date: 

July 1, 2021

Author(s):

Yao Luan, Takumi Arasawa, Hiroshi Mutsuyoshi, and Rikako Kawana

Publication:

Materials Journal

Volume:

118

Issue:

4

Abstract:

Cracks in concrete structures increase the penetration of water and deleterious ions, leading to accelerated deterioration. An innovative repair method using bacteria is currently gaining attention. In this method, CO2 is released by bacteria and reacts with calcium ions (Ca2+) to form CaCO3, which heals cracks by deposition. In this study, alkali-silica reaction (ASR)-induced cracks were repaired using two types of bacterial material, containing yeast and Bacillus, respectively. Microbial grouts containing these bacteria were prepared and used to impregnate mortar surfaces with ASR-induced cracks. The cracks were observed to be healed over time, and water absorption and gas permeability were reduced after repair. Thermogravimetric analysis (TGA) revealed that the main precipitate was CaCO3, while mercury intrusion porosimetry (MIP) indicated that the CaCO3 also densified the surface layer of the mortar by refining the pore structure. After repair, the specimens were immersed in water and NaOH solutions to test whether re-expansion occurred. The results showed that when immersed in 0.1 mol/L NaOH or water, the repaired specimens exhibited less expansion than the unrepaired ones.

DOI:

10.14359/51732798


Document: 

20-192

Date: 

March 1, 2021

Author(s):

A. M. Yasien, M. T. Bassuoni, A. Abayou, and A. Ghazy

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

With aging, concrete structures exhibit deterioration due to multiple reasons. Consequently, repair processes become overwhelmingly essential to extend the service life of structures. This experimental study investigated nano-modified concrete cast and cured under cyclic freezing/low temperatures, including its applicability to partial-depth repair. Seven mixtures, incorporating general-use cement, fly ash (0 to 25%), and nanosilica (0 to 4%) with a cold weather admixture system (antifreeze/accelerator) were tested. The mixtures were evaluated based on fresh, hardened, and durability properties as well as their compatibility with parent/substrate concrete. In addition, mercury intrusion porosimetry and thermogravimetric analysis were conducted to assess the evolution of microstructure under cold temperatures. The incorporation of 4% nanosilica in the cementitious binder, even with the presence of 15% fly ash, markedly enhanced the performance of concrete cast and cured under low temperatures without protection; thus, it may present a viable option for cold weather applications including repair.

DOI:

10.14359/51729331


Document: 

16-410

Date: 

January 1, 2021

Author(s):

M. A. Raden Maizatul Aimi, M. S. Hamidah, K. Kartini, H. Noor Hana, A. K. Khalilah, and E. Schlangen

Publication:

Materials Journal

Volume:

118

Issue:

1

Abstract:

Autonomous healing by the microbially induced calcite precipitation (MICP) mechanism has garnered significant interest in the sustainable approach to concrete repair and maintenance. Previous research works have reported that Bacillus pasteurii and Bacillus sphaericus are the most commonly used in concrete associated with bacteria. However, there is limited information on other types of bacteria species. In this study, the vegetative cells of Geobacillus stearothermophilus were introduced and encapsulated into alginate-hydrogel before incorporation into the mortar. The urease activity, viability, swelling, and water retention properties of the bacterial Geobacillus stearothermophilus cell encapsulated in alginate-hydrogel were measured. The performance of alginate-encapsulated Geobacillus stearothermophilus (AE-GS) in the mortar mixture as a self-healing agent was measured by compressive strength, water absorption, and crack-healing efficiency. The precipitation of calcium carbonate of the AE-GS mortar was measured using thermogravimetric analysis (TGA). The highest level of crack healing was 63% (by the initial crack width) which was achieved by incorporating 15% AE-GS (replacement by total weight of the mortar). However, the lower result of compressive strength and the highest absorption rate were portrayed by the mortar specimens that contained 15% of AE-GS replacement compared with the control mortar (AE-R) and with those of AE-GS replacement level at 3 and 9%.

DOI:

10.14359/51700895


Document: 

20-052

Date: 

January 1, 2021

Author(s):

Adeyemi Adesina and Sreekanta Das

Publication:

Materials Journal

Volume:

118

Issue:

1

Abstract:

The use of cementitious composites reinforced with fibers as repair materials for concrete pavements is gaining huge attention recently due to their enhanced mechanical and durability properties. However, the use of portland cement as the main binder of these composites still poses a serious sustainability issue. The production of portland cement has been associated with the high use of raw materials and the emission of carbon dioxide into the environment. On the other hand, alkali-activated binders exist that are capable of eliminating portland cement totally. However, the activators currently used to activate these types of materials are expensive and extremely corrosive. Therefore, this study used hydrated lime, which is a less expensive, less corrosive, and eco-friendly alternative activator to produced fiber-reinforced alkali-activated composites for repair applications. The mechanical performance of the developed composites was evaluated in terms of its compressive and flexural properties, as these properties are critical to the performance of repair materials. Results from this study showed that fiber-reinforced composites produced with an eco-friendly binder exhibited excellent mechanical performance suited for various repair applications. Microstructural investigations were also carried out on the evaluated mixtures to determine the microstructural properties of the developed mixtures.

DOI:

10.14359/51725993


Document: 

19-324

Date: 

July 1, 2020

Author(s):

Dhanushika Gunatilake Mapa, Manjriker Gunaratne, Kyle A. Riding, and A. Zayed

Publication:

Materials Journal

Volume:

117

Issue:

4

Abstract:

Jointed plain concrete pavement (JPCP) repair slabs experience high incidences of early-age cracking due to high temperature rise and increased autogenous shrinkage of high-early-strength (HES) concrete mixtures. This paper presents an investigation to evaluate early-age cracking mitigation strategies of JPCP repair slabs. Finite element analyses were performed to understand the effects of physical phenomena leading to early-age cracking in JPCP repair slabs. While the analyses indicate the importance of concrete hydration kinetics and viscoelastic behavior on the early-age stress development in slabs, concrete moisture loss to the base was found to be the most significant phenomenon. Numerical modeling of concrete slabs was found to be useful in predicting the stress development in advance of costly field trials. Therefore, the proposed modeling approach can be applied to evaluate the performance of concrete mixtures prior to slab placement and thus improve and economize the current rigid pavement maintenance practices.

DOI:

10.14359/51725780


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