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International Concrete Abstracts Portal

Showing 1-5 of 361 Abstracts search results

Document: 

20-362

Date: 

July 1, 2021

Author(s):

Adeyemi Adesina and Sreekanta Das

Publication:

Materials Journal

Volume:

118

Issue:

4

Abstract:

Engineered cementitious composites (ECC) are special fiber-reinforced cementitious composites with outstanding performance. However, the high cost and unavailability of the special sand (that is, microsilica sand [MSS]) used as the aggregate for such composites have limited its use and even made it impractical in some geographical locations. Therefore, there is a dire need to find alternative materials that can be used to replace MSS in ECC. This study was carried out to investigate the feasibility of using recycled concrete (RC) as an alternative aggregate, which is a much cheaper and more sustainable option as opposed to the conventional MSS currently used in ECC. Fly ash—the coal-based, thermal, plant-generated waste material—was incorporated as an alternative binder to partially replace the traditional binder, portland cement (PC), which is a large greenhouse emitter. Thus, the use of fly ash to replace a high volume of ECC would result in a reduction in the carbon footprint of ECC. The RC was used to replace the MSS in proportions ranging from 0 to 100% at an increment of 25%. The mechanical performance of the ECC mixtures was assessed in terms of the compressive, tensile, and flexural properties. The results obtained from this study showed that the use of RC as a partial replacement of MSS in ECC mixtures resulted in a satisfactory ECC mixture. However, at a replacement ratio of 75% and above, the performance of ECC may not be acceptable. The sustainability index assessment of the mixtures indicates that the use of RC as a replacement of up to 50% of MSS is optimum.

DOI:

10.14359/51732794


Document: 

20-317

Date: 

July 1, 2021

Author(s):

Ankur Bhogayata, Sneh Kakadiya, and Rinkesh Makwana

Publication:

Materials Journal

Volume:

118

Issue:

4

Abstract:

The paper discusses the development and application of the artificial neural network (ANN) model for predicting the compressive and splitting tensile strength of the geopolymer-based concrete composites (GPC). The strength properties of GPC are influenced by the proportions of the constituents—namely, the alkaline solution, fly ash, aggregates, and sand and water—and require optimization for the desired quality of the composite. The optimum mixture may be obtained by using modern techniques; namely ANN modeling. The ANN models have been developed by training and validating the input data using the sigmoid function and the feed-forward backpropagation algorithm in the hidden layers. The ANN layer is the functional part of the model consisting of the operators to carry out the specific task largely based on mathematical calculations. A five-layered ANN model has been developed and used to predict the strength to optimize the mixture design. The predicted values have been compared with the experimental strength values, and the effects of the most significant constituents have been studied.

DOI:

10.14359/51732711


Document: 

20-217

Date: 

May 1, 2021

Author(s):

R. D. Kalina, S. Al-Shmaisani, S. Seraj, R. Cano, R. D. Ferron, and M. C. G. Juenger

Publication:

Materials Journal

Volume:

118

Issue:

3

Abstract:

Fly ashes with high alkali contents have been observed to be less effective in controlling expansion due to alkali-silica reaction (ASR) in concrete than low-alkali fly ashes, a problem that can be hard to predict using accelerated testing. Many natural pozzolans have high alkali contents, and there is concern that these alkalis may likewise reduce their effectiveness in ASR control and affect accelerated test results. This study examines the performance of natural pozzolans in ASR testing. The mineralogies of the natural pozzolans were determined using Rietveld quantitative X-ray diffraction (XRD), and the compositions of the natural pozzolans were determined using X-ray fluorescence spectroscopy (XRF) and available alkali testing. The results suggest that the available alkalis from fly ashes and natural pozzolans are different, and high-alkali natural pozzolans perform well in both the accelerated mortar bar and concrete prism tests for ASR.

DOI:

10.14359/51732598


Document: 

20-192

Date: 

March 1, 2021

Author(s):

A. M. Yasien, M. T. Bassuoni, A. Abayou, and A. Ghazy

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

With aging, concrete structures exhibit deterioration due to multiple reasons. Consequently, repair processes become overwhelmingly essential to extend the service life of structures. This experimental study investigated nano-modified concrete cast and cured under cyclic freezing/low temperatures, including its applicability to partial-depth repair. Seven mixtures, incorporating general-use cement, fly ash (0 to 25%), and nanosilica (0 to 4%) with a cold weather admixture system (antifreeze/accelerator) were tested. The mixtures were evaluated based on fresh, hardened, and durability properties as well as their compatibility with parent/substrate concrete. In addition, mercury intrusion porosimetry and thermogravimetric analysis were conducted to assess the evolution of microstructure under cold temperatures. The incorporation of 4% nanosilica in the cementitious binder, even with the presence of 15% fly ash, markedly enhanced the performance of concrete cast and cured under low temperatures without protection; thus, it may present a viable option for cold weather applications including repair.

DOI:

10.14359/51729331


Document: 

19-503

Date: 

March 1, 2021

Author(s):

Ablam Zidol, Monique T. Tognonvi, and Arezki Tagnit-Hamou

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

It has been demonstrated in recent studies that, unlike general-use cement (GU), glass powder (GP) performs better in concrete mixtures with high water-binder ratios (w/b) in terms of both mechanical properties and chloride ion permeability. This paper aims to deepen investigations on the behavior of concrete incorporating GP in aggressive outdoor environments such as chloride ion diffusion, carbonation, and sulfates as a function of w/b. For comparison purposes, concretes containing conventional supplementary cementitious materials (SCMs) such as Class F fly ash (FFA) and ground-granulated blast-furnace slag (GGBFS) along with control concrete were also studied. In general, GP-based concretes behaved as those containing SCM. Indeed, despite their high w/b, concrete incorporating GP better withstands sulfate attack than the reference. This was mainly attributed to the low chloride permeability of such concretes. Also, as commonly observed with SCM concretes, carbonation was higher with GP-based concrete and increased with w/b.

DOI:

10.14359/51729326


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