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International Concrete Abstracts Portal

Showing 1-5 of 139 Abstracts search results

Document: 

20-528

Date: 

September 1, 2021

Author(s):

M. C. de Moraes, I. S. Buth, C. Angulski da Luz, E. A. Langaro, and M. H. F. Medeiros

Publication:

Materials Journal

Volume:

118

Issue:

5

Abstract:

Recently, alkali-activated cement (AAC) has been studied to partially replace portland cement (PC) to reduce the environmental impact caused by civil construction and the cement industry. However, with regard to durability, few studies have addressed the behavior of AAC. This study aimed to evaluate the performance of AAC made from blast-furnace slag with contents of 4 and 5% sodium hydroxide as an activator (Na2Oeq of 3.72% and 4.42%, respectively) when subjected to alkali-aggregate reaction (AAR). Length variation tests were carried out on mortar bars immersed in NaOH solution (1 N of NaOH, T = 80°C [176°F]) and on concrete bars (T = 60°C [140°F], RH = 95%); compressive strengths tests and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analyses were also made. Two types of PC were used as a comparison. The results showed good behavior of the AAC in relation to the AAR, with expansions lower than those established by the norm (34% of the limit) and without the finding of losses of mechanical resistance or structural integrity. The alkaline activator content had a small influence on the behavior of the AACs, in which the lowest amount of NaOH (4%) showed fewer expansions (only 15% of the limit established by the norm). Even for the highest activator content (5%), the results were good and comparable to those of PC with pozzolans, which is recommended for the inhibition of AAR.

DOI:

10.14359/51732937


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: 

20-221

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


Document: 

19-454

Date: 

November 1, 2020

Author(s):

Deborah Glosser, O. Burkan Isgor, and W. Jason Weiss

Publication:

Materials Journal

Volume:

117

Issue:

6

Abstract:

Thermodynamic modeling is an established tool that can use binder composition to predict reaction products and pore solution chemistry in hydrating cementitious systems. Thermodynamic simulations rely on the assumption that all reactions reach equilibrium; however, reacting systems are inherently dynamic. An established kinetic model exists and is used in conjunction with thermodynamic Gibbs free energy minimization software (GEMS) to provide quasi-equilibrium inputs for modeling hydrating cement clinkers. However, no similar model has existed to explicitly model the non-equilibrium reactions of cement with supplementary materials. Here, a framework to compute kinetic inputs for use in time-dependent thermodynamic calculations of cement/amorphous silica systems is demonstrated. Reaction products, pore solution composition, and pH are modeled and compared with experimental measurements for multiple ordinary portland cement (OPC)/SiO2 binders at varying replacement levels and water contents. The results show that when time-dependent clinker and SiO2 reactions are modeled together, the hydraulic reactions and the pozzolanicity of SiO2 can be accurately predicted.

DOI:

10.14359/51728127


Document: 

19-434

Date: 

September 1, 2020

Author(s):

T. Hemalatha, Arjun S, and B. S. Sindu

Publication:

Materials Journal

Volume:

117

Issue:

5

Abstract:

This study investigates the feasibility of using induction furnace slag as a substitute for river sand/manufactured sand (M-sand) in the production of concrete. The properties of concrete made with slag fine aggregate is compared with concrete made of river sand and M-sand. Experimental studies have been carried out on concretes made of three types of aggregates and two types of cement (ordinary portland cement [OPC] and portland pozzolana cement [PPC]). Mechanical and durability property tests performed according to standards showed that the characteristics obtained for the concrete made with slag aggregate is comparable with that of the concrete made with river sand and M-sand. This study suggests the 100% replacement of conventional fine aggregate with slag fine aggregate for the production of concrete without compromising the strength and durability characteristics. Further, the study demonstrates that with the suitable measures, the high water absorption of slag aggregate can be compensated.

DOI:

10.14359/51725981


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