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International Concrete Abstracts Portal

Showing 1-5 of 93 Abstracts search results

Document: 

SP-347_12

Date: 

March 1, 2021

Author(s):

Assem A. A. Hassan

Publication:

Symposium Papers

Volume:

347

Abstract:

The inclusion of rubber in concrete mixtures improved the impact resistance but negatively affected the strength and fresh properties of self-consolidating concrete (SCC). The objective of this investigation was to optimize the balance between the improved impact resistance and the reductions in the strength and fresh properties of rubberized SCC mixtures. This investigation evaluated and assessed the type/size and percentage of rubber needed to develop successful SCC mixtures with maximized impact strength and minimized reductions in strength. The studied variables were the type/size of rubber used (crumb rubber (CR) and two sizes of powder rubbers), percentage of rubber (0%, 15%, 25%, 30%, 35%, and 40%), type of concrete (SCC and vibrated concrete), and the use of fibers in the mixture. Because of the fresh properties restrictions of SCC, it was only possible to develop rubberized SCC with up to 25%, 30%, and 35% CR, powder rubber 40/80, and powder rubber 140, respectively. With the absence of fresh properties restrictions of SCC, it was possible to develop vibrated rubberized concrete with up to 40% of any type of rubber. Using higher percentages of rubber in vibrated rubberized concrete dropped the compressive strength to less than 25 MPa (3.63 ksi). The results also indicated that despite the slight improvement in the fresh properties and strength of mixtures with powder rubbers compared to mixtures with CR, mixtures with CR showed significantly higher improvements in the impact resistance.


Document: 

SP-343_07

Date: 

October 1, 2020

Author(s):

Javadian, A.; Mahdavi, A.; Benamrane, O. ;Majeed, M.; Aoude, H.

Publication:

Symposium Papers

Volume:

343

Abstract:

This study examines the effect of fiber properties, single fiber type and hybrid fibers on the fresh-state and hardened-state properties of self-consolidating fiber-reinforced concrete (SCFRC). As part of the study, 16 mixtures are examined with variables including the effect of fiber type, length, aspect ratio, and hybrid use of fibers (short and long fibers). Properties in the fresh state are studied using standard SCC tests including: slump flow, V-funnel and visual stability index (VSI) tests. Mechanical properties are studied by testing prisms under four-point flexural loading in accordance with the ASTM C1609 standard. The results demonstrate that self-consolidating FRC mixtures are possible at moderate fiber contents, however, once the limiting fiber contents are exceeded workability and mix uniformity are lost. The results also show the effects of fiber content, fiber type, fiber properties and hybrid fibers on the flexural toughness of SCFRC.


Document: 

SP-340-06

Date: 

April 1, 2020

Author(s):

Maria Kaszynska and Adam Zielinski

Publication:

Symposium Papers

Volume:

340

Abstract:

The research paper presents an analysis of autogenous shrinkage development in self-consolidating concrete (SCC). The first stage of the study involved an evaluation of concrete susceptibility to cracking caused by shrinkage of SCC with natural and lightweight aggregate. The shrinkage was tested on concrete rings according to ASTM C 1581/C 1581M- 09a. The influence of aggregate composition, the water content in lightweight aggregate, and SRA admixture on the reduction of concrete susceptibility to cracking, due to the early-age shrinkage deformation was determined. In the second stage of the research, the innovative method measurement of autogenous shrinkage was developed and implemented. The tests were performed on concrete block samples, dimensions 35x150x1150 mm, that had the same concrete volume as ring specimen in the ASTM method. Linear deformation of the concrete samples was measured in constant periods of 500 s using dial gauges with digital data loggers. The investigation allowed evaluating of the influence of water/cement (w/c) ratio of 0.28, 0.34, 0.42, and of aggregate composition on the development of autogenous shrinkage in different stages of curing SCC. The results were compared to existing material models proposed by other researchers. The conducted study indicated a significant influence of the w/c ratio and composition of aggregate on the concrete susceptibility to crack caused by the autogenous shrinkage deformation.


Document: 

SP-333_02

Date: 

October 1, 2019

Author(s):

Junwon Seo and Jharna Pokhrel

Publication:

Symposium Papers

Volume:

333

Abstract:

This paper investigates the effects of material constituents on fresh and hardened properties of Self-Consolidating Concrete (SCC) mixture necessary for efficient prestressed bridge girder fabrication using a surrogate modeling technique. Response surface methodology (RSM)-based surrogate models consisting of input parameterssuch as density of coarse and fine aggregate were created based upon the past laboratory testing results for differentSCC mixture trials. These models were used to estimate various SCC material characteristics, including slump flow, J-ring flow, passing ability, filling capacity, Visual Stability Index (VSI), T50 (concrete spread time to reach the 50.8 cm [20 in] mark), column segregation, 16-hour compressive strength, and 28-days compressive strength, while examining the correlation between the input parameters on each material characteristic. To observe the effect of core input parameters in an efficient manner, 2D contour plot and 3D surface plot for material characteristics were also created. Then, statistical analyses with the testing results were performed to determine the accuracy of the surrogate models in terms of coefficient of regression (R2). Most of the R2 values are higher than 90%, indicating a higher degree of correlation among the testing and surrogate data. Average predicted-to-measure ratios of the surrogate models were almost equal to or slightly greater than 1.00, showing good agreement with the testing results, and specifically, the surrogate and testing values for J-ring flow and 28-days compressive strength were nearly identical. Key findings indicate that the coarse aggregate content significantly affected the characteristics of the SCC mixtures.


Document: 

SP-334-08

Date: 

September 30, 2019

Author(s):

Yasser Khodair, Arif Iqbal, and Mohammed Hussaini

Publication:

Symposium Papers

Volume:

334

Abstract:

This study discusses the results of an experimental program conducted to study the fresh, hardened and unrestrained shrinkage characteristics of self-consolidating concrete (SCC) using fine recycled asphalt pavement (FRAP) and high volume of supplementary cementitious materials (SCMs) including class C fly-ash (FA) and slag (S). Sixteen mixtures were prepared with different percentages of FA, S, and FRAP. SCC mixtures were divided into four groups where each group had a different percentage of FRAP replacing fine aggregate (10%, 20%, 30%, 40%) and Portland cement being replaced by different percentages of SCMs. The water to cementitious material (w/cm) ratio of 0.4 was used for SCC mixtures with a target slump flow higher than 500 mm. The flowability, deformability, filling capacity and resistance to segregation were measured to determine the fresh properties of the mixtures. Moreover, the compressive strength at 14, 28, and 90 days and split tensile strength at 28 days were determined and durability characteristics including unrestrained shrinkage up to 90 days were tested. Analysis of experimental data showed that most of the mixtures satisfied the SCC fresh properties requirements. The addition of FRAP had an adverse effect on the compressive, tensile strength and unrestrained free shrinkage of SCC mixtures.


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