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International Concrete Abstracts Portal

Showing 1-5 of 359 Abstracts search results

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: 

20-222

Date: 

March 1, 2021

Author(s):

M. R. Sakr and M. T. Bassuoni

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

The response surface method, a statistical modeling approach, was used to assess the influence of water-binder ratio (w/b), binder content, and dosages of supplementary cementitious materials on the performance of 52 mixtures under accelerated physical salt attack (PSA). The test protocol simulated partially embedded elements. Also, the PSA damage of concrete was mapped by regression analysis based on combination of performance-based parameters. Mineralogical, thermal, and microstructural analyses were conducted to elucidate the bulk trends obtained from the models. Multi-objective optimization was also performed to determine optimal combinations of parameters (w/b; binder content; and dosages of fly ash, slag, and silica fume) producing mixtures resistant to PSA. In addition, a classification for the resistance of concrete to PSA based on performance indicators (mechanical capacity and wicking factor) was proposed.

DOI:

10.14359/51730515


Document: 

19-406

Date: 

March 1, 2021

Author(s):

Anvit Gadkar and Kolluru V. L. Subramaniam

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

Self-leveling concrete is developed with low-calcium alkali-activated fly ash (AAF) binder paste. The rheological behavior of AAF pastes with different compositions is evaluated. AAF pastes are proportioned with alkali-silicate activating solutions to ensure specific reactive oxide ratios for comparable geopolymer strength. The yield stress and the viscosity of the AAF binder paste vary with the silica content and the silica modulus (SiO2/Na2O mass ratio) in the alkali-silicate activating solution. The slump and flow behaviors of concrete mixtures made with AAF paste are evaluated. The requirements of the AAF binder characteristics, paste content, and aggregate packing for achieving self-leveling flow characteristics under gravity-induced flow are assessed. The transition from a frictional to a flow-type behavior in concrete mixtures depends on the AAF binder paste content. Self-leveling is achieved without the use of admixtures with an AAF binder paste of low yield stress and at a paste content of 45%. Improving the aggregate packing using the Fuller-Thompson curve and reducing the yield stress of the AAF binder paste increase the flow achieved in concrete mixtures. The specifications for cement-based self-consolidating concrete (SCC) are closely applicable for self-leveling AAF-based concrete.

DOI:

10.14359/51729324


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


Document: 

20-221

Date: 

March 1, 2021

Author(s):

Xing Ming, Mingli Cao, Li Li, and Hong Yin

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

In this paper, a novel kind of cement blend with high temperature resistance and self-healing abilities is tailored by incorporating fly ash (FA) and calcium carbonated whisker (CW). The physiochemical changes after high temperature exposure and water re-curing were examined in this blended cement. Incorporation of FA and CW would be able to lower carbon dioxide footprint of cement manufacture and the resulting cementitious composite demonstrates high temperature resistance and self-healing performance. Due to pozzolanic effect of FA, formation of ceramic phases, rehydration process, and carbonation, the deterioration in residual strengths and microstructure after high temperature exposure can be partially recovered during the self-healing process.

DOI:

10.14359/51729332


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