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International Concrete Abstracts Portal

Showing 1-5 of 2573 Abstracts search results

Document: 

21-029

Date: 

September 1, 2021

Author(s):

Camila Simonetti, Bernardo Fonseca Tutikian, and Luiz Carlos Pinto da Silva Filho

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

The possibility of incorporating scrap tire residue into concrete has already been consolidated in previous studies, but there is a knowledge gap about how concrete made with recycled tire materials behaves when exposed to high temperatures. This study aims to investigate the performance of precast concrete panels made with scrap tire residues when exposed to fire when using recycled steel fiber and recycled rubber aggregates separately. The experimental design consisted of fire resistance tests. Real-scale panels were exposed to the standard fire curve based on ISO 834, measuring the temperatures on the panel surfaces. The recycled steel fiber-reinforced concrete and those containing 5% recycled rubber aggregate presented similar behavior when compared to the conventional concrete on thermal insulation, integrity, and structural stability. The concrete made with 10% recycled rubber aggregate registered the occurrence of explosive spalling and worse thermal insulation and integrity.

DOI:

10.14359/51732983


Document: 

20-266

Date: 

September 1, 2021

Author(s):

Davood Mostofinejad, Farzaneh Nosouhian, and Bahareh Tayebani

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

Microbial carbonate precipitation (or biodeposition) has been widely studied for use in characteristics improvement and selfhealing of concrete and mortar of cementitious materials. The presence of a calcium source contributes to the formation of calcite (CaCO3), which is a key component in the biode-position process. The current study is aimed at benefiting from the available calcium ion in seawater as a calcium source in the biode-position of marine structures. To this end, four different bacteria strains were cultured and added to the mortar mixture for making bacteria-containing mortar specimens. The specimens consisted of six groups of 50 x 50 x 50 mm mortar cubes, 40 x 40 x 160 mm (1.57 x 1.57 x 6.3 in.) mortar prisms, and conventional mortar briquettes, all of which were cured in seawater. The effects of the exposure to seawater were mechanically investigated at different mortar ages in terms of their compressive, flexural, and tensile strengths and compared with control specimens made with no bacteria and cured in water. The experimental results represented an increase of 97% and 101%, respectively, in compressive and flexural strengths of mortar specimens containing Bacillus subtilis and cured in seawater at 28 days. It was found that the specimens cast and treated with Bacillus sphaericus exhibit a rise of approximately 72% in tensile strength. Therefore, it was concluded that treated mortar with bacteria and cured in seawater may enhance the mechanical properties of mortar, which can be a beneficial development in marine structures. The use of such bacteria strains in concrete technology, specifically in inshore structures, can eliminate the destructive effects of the coastal environment.

DOI:

10.14359/51732978


Document: 

20-397

Date: 

September 1, 2021

Author(s):

Andrés A. Torres-Acosta and Paola Y. González-Calderón

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

Mortar cubes containing different addition levels (0, 1.5, 4, 8, 42, and 95%, by water mass replacement concentration) of Opuntia ficus-indica (OFI) mucilage were exposed for a 14-year (5110-day) period in a natural CO2-laden environment. Physical characterization tests were performed on the mortar cubes, such as saturated electrical resistivity (ρS), percent total void content (%TV), water capillary absorption (εEFF), and compressive strength (fc). Changes in pH due to carbonation were also determined, and carbonation rates (KCO2 ) were recorded. Findings suggest that the addition of OFI mucilage concentrations between 4 and 8% (by water mass replacement) may be suitable for durability-enhancing applications in cement-based mortar exposed to carbonation-induced environments.

DOI:

10.14359/51732796


Document: 

20-145

Date: 

September 1, 2021

Author(s):

Seung Hee Kwon, Kyong Pil Jang, and Jung Soo Lee

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

In this study, a new method was proposed to improve concrete pumpability. The friction between concrete and the internal surface of the pipe can be reduced by externally injecting a small amount of a chemical agent called a friction-reducing agent (FRA) into the pipe. The new idea was experimentally implemented with real-scale concrete pumping of 112, 137, and 518 m (367, 449, and 1700 ft) long pipelines. The experiments were performed with three different concrete mixtures and with the injection rate of the agent varying from 0.077 to 0.284% of concrete volume. It was found that the pumping pressure decreases from 26.6 to 60.2%. In addition, the rheological properties of concrete and the lubricating layer, and the viscosity of wet-screened mortar according to the dosage of FRA were measured. Based on analysis of these measurements, a method was proposed to quantitatively predict pressure reduction due to the external injection of the FRA.

DOI:

10.14359/51732977


Document: 

21-008

Date: 

September 1, 2021

Author(s):

Yifeng Ling and Peter Taylor

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

Although internal vibration has been widely implemented in concrete pavements, reports about concrete deterioration caused by improper vibration have been emerging. This study investigates the transmission of vibration energy, water movement, and air movement in concrete under vibration to provide the experimental basis for a better understanding of vibration in different concrete mixtures. An innovative experimental method was developed to measure energy transmission in concrete. The mixtures varied by air content, slump, and water-reducing admixture addition and were prepared to test the vibration energy, water absorption, and the air-void system for a range of vibrator frequencies. The vibration energy transferred through the mixture generally displayed a linear rise, then a slight drop, and, finally, stability, indicated by both measurements of transferred energy and voltage demand of the vibrator. The magnitude of vibration energy transferred through the mixtures increased with an increasing slump. For all samples tested, water appeared to move away from the vibrator, most markedly with an increasing frequency. There is a clear indication of air movement to the surface of the concrete in all tested samples.

DOI:

10.14359/51732981


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