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International Concrete Abstracts Portal

Showing 1-5 of 478 Abstracts search results

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: 

20-528

Date: 

September 1, 2021

Author(s):

M. C. de Moraes, I. S. Buth, C. Angulski da Luz, E. A. Langaro, and M. H. F. Medeiros

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

Recently, alkali-activated cement (AAC) has been studied to partially replace portland cement (PC) to reduce the environmental impact caused by civil construction and the cement industry. However, with regard to durability, few studies have addressed the behavior of AAC. This study aimed to evaluate the performance of AAC made from blast-furnace slag with contents of 4 and 5% sodium hydroxide as an activator (Na2Oeq of 3.72% and 4.42%, respectively) when subjected to alkali-aggregate reaction (AAR). Length variation tests were carried out on mortar bars immersed in NaOH solution (1 N of NaOH, T = 80°C [176°F]) and on concrete bars (T = 60°C [140°F], RH = 95%); compressive strengths tests and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analyses were also made. Two types of PC were used as a comparison. The results showed good behavior of the AAC in relation to the AAR, with expansions lower than those established by the norm (34% of the limit) and without the finding of losses of mechanical resistance or structural integrity. The alkaline activator content had a small influence on the behavior of the AACs, in which the lowest amount of NaOH (4%) showed fewer expansions (only 15% of the limit established by the norm). Even for the highest activator content (5%), the results were good and comparable to those of PC with pozzolans, which is recommended for the inhibition of AAR.

DOI:

10.14359/51732937


Document: 

20-533

Date: 

September 1, 2021

Author(s):

Ahmed G. Bediwy and Ehab F. El-Salakawy

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

This study aims at assessing the long-term bond behavior of headed-end glass fiber-reinforced polymer (GFRP) bars to basalt fiber-reinforced cementitious composite (BFRCC) exposed to 300 consecutive freezing-and-thawing cycles, followed by 75 cycles of wetting and drying, mimicking successive winter and summer seasons. A total of 85 pullout specimens reinforced with recently developed basalt fiber pellets and steel fibers were tested. The durability of the specimens was quantified in terms of visual analysis, residual compressive strength, relative dynamic modulus of elasticity, as well as the residual pullout capacity. The addition of fibers was capable of retaining approximately 90% of the pullout capacity for specimens exposed to harsh conditions owing to the restriction of cracks in the fiber-reinforced cementitious composites. Therefore, the results confirmed the suitability of steel-free reinforcement systems for long-term application under severe freezing-and-thawing and wetting-and-drying environments.

DOI:

10.14359/51732980


Document: 

20-219

Date: 

July 1, 2021

Author(s):

R. V. M. Toffolo, T. K. Moro, D. H. Santos, L. C. B. Costa, J. C. Mendes, and R. A. F. Peixoto

Publication:

Materials Journal

Volume:

118

Issue:

4

Abstract:

This work evaluates the technical feasibility of a roller-compacted concrete (RCC) pavement with complete replacement of natural aggregates by electric arc furnace slag (EAFS) or basic oxygen furnace slag (BOFS). The methodology includes, initially, the processing of the slags, and physical, chemical, and environmental characterization of the natural and slag aggregates. Subsequently, concrete mixtures were designed, and the compaction at optimum moisture was performed. Finally, the behavior of specimens under service and their mechanical performance were evaluated. Results show that both EAFS and BOFS enhance the RCC’s compressive strength and modulus of elasticity. The RCC produced with BOFS aggregates presented some expansibility due to its high contents of chemically active finer-than-75-µm materials and higher porosity. The EAFS aggregate was stable in durability analysis. In conclusion, through optimal mixture proportions and using compatible energy compression, it is viable to produce pavements with EAFS steelmaking slag in efficient, economical, and environmentally friendly manners. BOFS also showed promising results but requires further investigation.

DOI:

10.14359/51732791


Document: 

20-172

Date: 

July 1, 2021

Author(s):

S. E. S. Mendes, R. L. N. Oliveira, C. Cremonez, E. Pereira, E. Pereira, P. O. Trentin, and R. A. Medeiros-Junior

Publication:

Materials Journal

Volume:

118

Issue:

4

Abstract:

Blast-furnace slag (BFS) has been increasingly used in cement production and has shown great influence on the electrical resistivity of concrete. The objective of this paper is to compare the theoretical values of electrical resistivity obtained through a mathematical model with experimental values for concrete with BFS. Reference concrete mixtures with ordinary portland cement were also studied. Results indicate higher electrical resistivity and smaller porosity for concretes with CEM III/A. The electrical resistivity of the CEM III/A concrete does not have a well-defined correlation with the water-binder ratio (w/b) or with the compressive strength, unlike CEM I concretes. The correlation between calculated and experimental resistivity requires a correction factor for the CEM III/A concretes. In this study, the correction factor was obtained empirically by reducing the theoretical tortuosity of concrete by 15%. Therefore, the model should be used in cements with BFS with the application of a correction factor.

DOI:

10.14359/51732597


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