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International Concrete Abstracts Portal

Showing 1-5 of 55 Abstracts search results

Document: 

20-250

Date: 

March 1, 2021

Author(s):

Philipp Riedel and Torsten Leutbecher

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

The structural behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) is mainly affected by the fiber volume fraction, the fiber distribution, and the fiber orientation. Fiber orientation especially may vary (locally) in structural members depending on their geometry, the consistency of the fresh concrete, and the way of placing and compacting the concrete. As a result, UHPFRC may behave anisotropically in both tension and compression. To quantify the effect of fiber orientation on the behavior of UHPFRC in compression, tests on cylinders and differently fabricated cubes made of fine- and coarse-grained UHPFRC mixtures were performed. Especially for high fiber volume fraction, specimens with predominantly unidirectional fiber orientation perpendicular to the loading direction showed significantly higher compressive strengths than specimens with predominantly unidirectional alignment of the fibers parallel to the loading direction. Unlike for ultra-high-performance concrete without fibers, a noticeable difference between cylinder and cube compressive strength could be observed in case of UHPFRC.

DOI:

10.14359/51730417


Document: 

20-080

Date: 

January 1, 2021

Author(s):

Ângela Costa Piccinini, Luiz Carlos Pinto da Silva Filho, and Américo Campos Filho

Publication:

Materials Journal

Volume:

118

Issue:

1

Abstract:

This research evaluated the bond behavior of reinforcement and the mechanical characteristics in a reactive powder concrete (RPC) replacing 35% cement with blast-furnace slag. Pullout tests were performed at the ages of 3, 7, 28, 56, 63, and 91 days on cylindrical samples. The embedded length used was double the diameter of the bar. At 3 days it presented compressive strength of 41% of the maximum obtained, which was 123.06 MPa at 91 days. There was an increase in strength until the age of 56 days and after stabilization of the curves. In pullout tests, it was noticed the considerable influence of the rib, because in tests with plain bars, the bond force was below 20% of the results with ribbed bar, which reached 54.38 MPa of strength. The compression curve was similar to the bond curve. Underestimated values were observed when the researchers’ equations were applied to calculate the maximum bond strength.

DOI:

10.14359/51725995


Document: 

19-374

Date: 

September 1, 2020

Author(s):

D. Marcon Neto, C. Effting, A. Schackow, I. R. Gomes, G. Aurélio Cifuentes, and D. Ganasini

Publication:

Materials Journal

Volume:

117

Issue:

5

Abstract:

In this work, concretes with high levels of fly ash replacing portland cement were elaborated. The concretes’ properties in the fresh state (consistency, workability, and heat of hydration) and in the hardened state (compressive strength, modulus of elasticity, conductivity, void index, water absorption, and density) were measured. Microstructural and thermal characterization were performed. Numerical simulations were performed to analyze the heat exchange during the cement hydration process. Statistical analysis was adequate, and a proposed regression model was validated for the high-volume fly ash concrete, with 60% replacing the portland cement. This concrete presented values of mechanical strength (33.38 ± 3.99 MPa) and modulus of elasticity (38.58 ± 0.81 GPa) which confirms its use as structural concrete. This concrete showed low heat of hydration, a reduction of 23% in relation to the reference concrete (without fly ash) during its curing process, and its microstructure presented a lower level of cracking.

DOI:

10.14359/51725783


Document: 

19-232

Date: 

May 1, 2020

Author(s):

Mohamed M. Sadek, Mohamed K. Ismail, and Assem A. A. Hassan

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

This study aimed to optimize the use of fine and coarse expanded slate lightweight aggregates in developing successful semi-lightweight self-consolidating concrete (SLWSCC) mixtures with densities ranging from 1850 to 2000 kg/m3 (115.5 to 124.9 lb/ft3) and strength of at least 50 MPa (7.25 ksi). All SLWSCC mixtures were developed by replacing either the fine or coarse normal-weight aggregates with expanded slate aggregates. Two additional normal-weight self-consolidating concrete mixtures were developed for comparison. The results indicated that due to the challenge in achieving acceptable self-consolidation, a minimum binder content of at least 500 kg/m3 (31.2 lb/ft3) and a minimum water-binder ratio (w/b) of 0.4 were required to develop successful SLWSCC with expanded slate. The use of metakaolin and fly ash were also found to be necessary to develop successful mixtures with optimized strength, flowability, and stability. The results also showed that SLWSCC mixtures made with expanded slate fine aggregate required more high-range water-reducing admixture than mixtures made with expanded slate coarse aggregate. However, at a given density, mixtures developed with expanded slate fine aggregate generally exhibited better fresh properties in terms of flowability and passing ability, as well as higher strength compared to mixtures developed with expanded slate coarse aggregate.

DOI:

10.14359/51722407


Document: 

19-088

Date: 

March 1, 2020

Author(s):

B. Cantero Chaparro, I. F. Sáez del Bosque, A. Matías Sánchez, M. I. Sánchez de Rojas, and C. Medina

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

A full understanding of the characteristics of the granular skeleton comprising different percentages of conventional and recycled aggregates is requisite to the reusability of construction and demolition waste. This study analyzed the effect of partially replacing natural aggregate with recycled concrete (RCA) and mixed (RMA) aggregates on the performance of granular mixtures. Each type of aggregate was characterized physically, chemically, mineralogically, and mechanically, and the physical and mechanical properties of the mixtures were assessed. Correlations were established to predict the optimal mixture proportions. The recycled aggregates analyzed met most requirements laid down in the national legislation and complied with international recommendations. The mixtures exhibited a close linear correlation between the properties analyzed and the recycled aggregate replacement ratios. For concrete, the upper limit was 75% for RCA and RMA, and for the base and intermediate layers in medium/low traffic roads, 75% for RCA and 35% for RMA.

DOI:

10.14359/51720299


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