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International Concrete Abstracts Portal

Showing 1-5 of 1007 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: 

20-509

Date: 

September 1, 2021

Author(s):

M. A. R. Manzano, Y. S. B. Fraga, E. F. da Silva, R. B. de Oliveira, B. Caicedo Hormaza, and R. D. Toledo Filho

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

This study investigates the influence of internal curing water on the compressive strength and microstructure of high-performance cementitious materials. For this, three high-performance fine-grained concrete (HPFC) and cement pastes were prepared. Two reference mixtures were investigated with total water-cement ratios (w/c) of 0.30 and 0.35. The third mixture was prepared with a basic w/c of 0.30 and the addition of 0.3% of superabsorbent polymer (SAP), resulting in a total w/c of 0.35. X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and compressive strength tests were performed. The incorporation of SAP resulted in a refinement of the porous structure of the paste, despite increasing the total porosity. In addition, the paste containing 0.3% SAP resulted in an intermediate calcium hydroxide content compared with the reference pastes. Thus, it was concluded that SAP internal curing water participates in the hydration reactions of the cementitious material.

DOI:

10.14359/51732979


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: 

20-443

Date: 

September 1, 2021

Author(s):

Julian Carrillo, José A. Ortiz-Lozano, and Juan G. Rueda-Bayona

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

The evaluation of the mechanical properties of steel fiber-reinforced concrete (SFRC) with different types of fibers and dosages endorses new design recommendations for using several types of construction materials for structural elements. The double-punch test (DPT) offers procedural and economic advantages for evaluating the indirect tensile strength of the SFRC. The objective of this paper is to show and discuss the results of the mechanical characterization obtained experimentally for SFRC using the DPT, with different types of anchorage and fiber dosages. The variables of the study were the dosage of steel fibers (20, 40, and 60 kg/m3) and the number of hooks at the ends of the fiber (1, 1.5, and 2 hooks). The paper develops empirical models for predicting the tensile strength, residual strength, and toughness of SFRC subjected to the DPT without resorting to experimental tests. The models were developed considering the trends of 385 results: 108 from 40 DPTs measured in this study, and 277 from 23 DPTs available in the literature.

DOI:

10.14359/51732932


Document: 

20-205

Date: 

September 1, 2021

Author(s):

Xu Luo, Jianming Gao, Chuanbei Liu, and Zhizhang He

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

In this study, the effects of carboxylated styrene butadiene rubber (SBR) and polyvinyl alcohol (PVA) on fluidity and setting time of gypsum-based material (GM) pastes were investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses were applied to study the early hydration and microstructure of GM pastes, further revealing the working mechanism of two polymers. The results show that the hydrophobic SBR is mainly absorbed on gypsum particles, breaking up the flocculation structures and simultaneously hindering the hydration, therefore increasing the fluidity and prolonging the setting time of GM pastes; the hydrophilic PVA can adsorb free water and therefore reduce the effective water-gypsum ratio (W/G), which promotes the formation of flocculent structures and accelerates the hydration. However, PVA could be also absorbed on gypsum particles and hinder the hydration. As a result, PVA decreases the fluidity and has little influence on setting time of GM pastes.

DOI:

10.14359/51732929


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