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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 241 Abstracts search results
January 1, 2022
Walid E. Elemam, Ahmed H. Abdelraheem, Mohamed G. Mahdy, and Ahmed M. Tahwia
This investigation aims to predict and optimize self-consolidating concrete (SCC) characteristics containing fly ash (FA), silica fume (SF), and limestone powder (LP) as part of the cement by mass in the total powder content. Total powder content (P), proportion of FA, proportion of SF, proportion of LP, water-powder ratio (w/p), and proportion of high-range water-reducing admixture (HRWRA) were the input parameters of the mixtures, and the desirable responses were slump flow, 7- and 56-day compressive strength, and flexural strength. A total of 90 concrete mixtures were designed using the central composite design (CCD) concept in Minitab 18 statistical software under response surface methodology (RSM) to simulate and optimize the variables and responses of models. Results showed that high relation can be developed between the responses and the constituent materials in predicting characteristics of SCC, removing the drudgery of repetitive laboratory testing and enabling rapid decision-making for building applications. The slump flow increased with the increase in total powder content, FA content, w/p, and HRWRA dosage and decrease in SF content, while LP has insignificant effect on slump flow results. The increase in partial replacement of cement by FA decreased the compressive strength of mixtures at early ages. The higher values of compressive strength were observed when SF incorporated in higher levels, and flexural strength also enhanced with the increase in SF content.
Süleyman Özen, Muhammet Gökhan Altun, Ali Mardani-Aghabaglou, and Kambiz Ramyar
The effect of the length of main and side chains of high-range water-reducing admixture (HRWRA) on some fresh and hardened properties of self-consolidating concretes (SCCs) was researched. For this purpose, three polycarboxylate ether-based HRWRA admixtures with different side and main chain lengths were synthesized. For a given SCC slump-flow value, the admixture requirement was the least when the admixture having a medium side chain length (2400 g/mol) was used. Moreover, decreasing the main chain length of the admixture improved the fresh properties’ retention of SCC. The fact was attributed to the increase in free polymer in the mixture by increasing the side chain length of the admixture. The main and side chain lengths of the HRWRA admixture were significantly influential on the early compressive strength of SCC mixtures but had a negligible effect on their 7- and 28-day compressive strength and 28-day water absorption.
Osama Al-Qassag, Ryan Brettmann, David Darwin, Matthew O’Reilly, and Rouzbeh Khajehdehi
A test procedure was developed to evaluate the effect of different techniques to limit settlement cracking over reinforcing steel with low concrete cover. Various specimen configurations and methods of finishing and curing were investigated. It was found that a clear cover of 1-1/8 in. (29 mm) over a No. 6 (No. 19) bar and covering the specimens after placement with sloped hard plastic enclosed in plastic sheeting provided a suitable method for obtaining clearly visible settlement cracks for concrete with slumps ranging from under 2 in. (50 mm) to over 8 in. (205 mm). The test specimen was then used to evaluate the effectiveness of a rheology-modifying admixture and four types of synthetic fibers on settlement cracking. Eighty-eight concrete batches were tested for mixtures with a cement paste (cement and water) content of 27 percent by volume and a water-cement ratio (w/c) of 0.45. The results show that the addition of the rheology-modifying admixture or fibers greatly reduces settlement cracking over reinforcing steel with low concrete cover.
November 1, 2021
Yannick Vanhove, Chafika Djelal, and Albert Magnin
Workability after concrete placement is important in continuous flight auger (CFA) piles construction because the reinforcement cage needs to be placed within the concrete at the end of casting. During the rest phase, which can last 30 minutes, the restructuring of the concrete affects the penetration capacity of the reinforcement cage.
An experimental investigation was carried out over a period of 30 minutes to compare the static and dynamic yield stress, measured using a rotational rheometer, with the shear stress interaction between the reinforcement cage and the concrete. Tests were performed using 10 mixtures in the laboratory. A viscosity-modifying admixture was used to promote the thixotropy effect. The
study was completed with four mixtures on site. The results showed a good correlation between the concrete rheological properties and the capacity to sink the reinforcement cage into the concrete. A simple model is proposed to estimate the shear stress applied to the reinforcement cage. The time needed to reach the final depth was correlated with the plastic viscosity, while the shear stress of the cage and the final depth were connected to the concrete yield stress. The penetration cage test is an effective tool to optimize concrete mixture proportions for the construction of CFA piles.
Jason Straka, Stephen P. Klaus, Junfeng Zhu, Pete A. Gentile, and Nathan A. Tregger
Tens of millions of cubic meters of concrete have now been delivered through in-transit measurement systems across the world. These sensor and control systems exist as true IoT (Internet of Things) systems, providing millions of data points describing the impact that process and materials changes have on concrete delivery and performance. Through advanced analytics, many insights can be garnered, leading to improvements in both concrete quality and the economic and environmental impact of concrete production. This paper discusses the current and future consequences of having an in-transit measurement system, including slump management, increased admixture efficiencies, and reduced environmental impact.
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