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Title: Alteration of alkali reactive aggregates autoclaved in different alkali solutions and application to alkali-aggregate reaction in concrete (II) expansion and microstructure of concrete microbar

Abstract

The effect of the type of alkalis on the expansion behavior of concrete microbars containing typical aggregate with alkali-silica reactivity and alkali-carbonate reactivity was studied. The results verified that: (1) at the same molar concentration, sodium has the strongest contribution to expansion due to both ASR and ACR, followed by potassium and lithium; (2) sufficient LiOH can completely suppress expansion due to ASR whereas it can induce expansion due to ACR. It is possible to use the duplex effect of LiOH on ASR and ACR to clarify the ACR contribution when ASR and ACR may coexist. It has been shown that a small amount of dolomite in the fine-grained siliceous Spratt limestone, which has always been used as a reference aggregate for high alkali-silica reactivity, might dedolomitize in alkaline environment and contribute to the expansion. That is to say, Spratt limestone may exhibit both alkali-silica and alkali-carbonate reactivity, although alkali-silica reactivity is predominant. Microstructural study suggested that the mechanism in which lithium controls ASR expansion is mainly due to the favorable formation of lithium-containing less-expansive product around aggregate particles and the protection of the reactive aggregate from further attack by alkalis by the lithium-containing product layer.

Authors:
 [1];  [2];  [2];  [2];  [3];  [4]
  1. College of Materials Science and Engineering, Nanjing University of Technology, 5 New Model Road, Nanjing, 210009 (China). E-mail: duyoulu@njut.edu.cn
  2. College of Materials Science and Engineering, Nanjing University of Technology, 5 New Model Road, Nanjing, 210009 (China)
  3. Analysis and Test Central, Nanjing Normal University, 122 Ninghai Road, Nanjing, 210097 (China)
  4. ICON/CANMET, Natural Resources Canada, 405 Rochester Street, Ottawa, ON, K1A 0G1 (Canada)
Publication Date:
OSTI Identifier:
20871561
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cement and Concrete Research; Journal Volume: 36; Journal Issue: 6; Other Information: DOI: 10.1016/j.cemconres.2006.01.012; PII: S0008-8846(06)00012-3; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CARBONATES; CONCRETES; DOLOMITE; EXPANSION; LIMESTONE; LITHIUM; LITHIUM HYDROXIDES; MICROSTRUCTURE; POTASSIUM; REACTIVITY; SILICA; SODIUM; SOLUTIONS

Citation Formats

Lu Duyou, Mei Laibao, Xu Zhongzi, Tang Mingshu, Mo Xiangyin, and Fournier, Benoit. Alteration of alkali reactive aggregates autoclaved in different alkali solutions and application to alkali-aggregate reaction in concrete (II) expansion and microstructure of concrete microbar. United States: N. p., 2006. Web.
Lu Duyou, Mei Laibao, Xu Zhongzi, Tang Mingshu, Mo Xiangyin, & Fournier, Benoit. Alteration of alkali reactive aggregates autoclaved in different alkali solutions and application to alkali-aggregate reaction in concrete (II) expansion and microstructure of concrete microbar. United States.
Lu Duyou, Mei Laibao, Xu Zhongzi, Tang Mingshu, Mo Xiangyin, and Fournier, Benoit. Thu . "Alteration of alkali reactive aggregates autoclaved in different alkali solutions and application to alkali-aggregate reaction in concrete (II) expansion and microstructure of concrete microbar". United States. doi:.
@article{osti_20871561,
title = {Alteration of alkali reactive aggregates autoclaved in different alkali solutions and application to alkali-aggregate reaction in concrete (II) expansion and microstructure of concrete microbar},
author = {Lu Duyou and Mei Laibao and Xu Zhongzi and Tang Mingshu and Mo Xiangyin and Fournier, Benoit},
abstractNote = {The effect of the type of alkalis on the expansion behavior of concrete microbars containing typical aggregate with alkali-silica reactivity and alkali-carbonate reactivity was studied. The results verified that: (1) at the same molar concentration, sodium has the strongest contribution to expansion due to both ASR and ACR, followed by potassium and lithium; (2) sufficient LiOH can completely suppress expansion due to ASR whereas it can induce expansion due to ACR. It is possible to use the duplex effect of LiOH on ASR and ACR to clarify the ACR contribution when ASR and ACR may coexist. It has been shown that a small amount of dolomite in the fine-grained siliceous Spratt limestone, which has always been used as a reference aggregate for high alkali-silica reactivity, might dedolomitize in alkaline environment and contribute to the expansion. That is to say, Spratt limestone may exhibit both alkali-silica and alkali-carbonate reactivity, although alkali-silica reactivity is predominant. Microstructural study suggested that the mechanism in which lithium controls ASR expansion is mainly due to the favorable formation of lithium-containing less-expansive product around aggregate particles and the protection of the reactive aggregate from further attack by alkalis by the lithium-containing product layer.},
doi = {},
journal = {Cement and Concrete Research},
number = 6,
volume = 36,
place = {United States},
year = {Thu Jun 15 00:00:00 EDT 2006},
month = {Thu Jun 15 00:00:00 EDT 2006}
}
  • Surface alteration of typical aggregates with alkali-silica reactivity and alkali-carbonate reactivity, i.e. Spratt limestone (SL) and Pittsburg dolomitic limestone (PL), were studied by XRD and SEM/EDS after autoclaving in KOH, NaOH and LiOH solutions at 150 deg. C for 150 h. The results indicate that: (1) NaOH shows the strongest attack on both ASR and ACR aggregates, the weakest attack is with LiOH. For both aggregates autoclaved in different alkali media, the crystalline degree, morphology and distribution of products are quite different. More crystalline products are formed on rock surfaces in KOH than that in NaOH solution, while almost nomore » amorphous product is formed in LiOH solution; (2) in addition to dedolomitization of PL in KOH, NaOH and LiOH solutions, cryptocrystalline quartz in PL involves in reaction with alkaline solution and forms typical alkali-silica product in NaOH and KOH solutions, but forms lithium silicate (Li{sub 2}SiO{sub 3}) in LiOH solution; (3) in addition to massive alkali-silica product formed in SL autoclaved in different alkaline solutions, a small amount of dolomite existing in SL may simultaneously dedolomitize and possibly contribute to expansion; (4) it is promising to use the duplex effect of LiOH on ASR and ACR to distinguish the alkali-silica reactivity and alkali-carbonate reactivity of aggregate when both ASR and ACR might coexist.« less
  • Stereoscopic microscope observation and EDAX graph showed that reactive aggregate, quartz glass grain, was corroded differently in blended cement pastes containing different amounts of granulated blast furnace slag or fly ash. The higher the slag and fly ash content, the less the quartz glass was corroded and the lower the expansion of mortar. The authors also adopted the difference between electric resistance change with curing age of mortar with reactive quartz sand and that of mortar with nonreactive sand to express the degree of chemical reaction and expansion value of alkali-silica reaction. According to the above research, the authors concludedmore » that the key of slag and fly ash suppressing alkali-silica reaction damage is their alleviating or prohibiting the chemical reaction between reactive aggregate and alkalines, which indicates that the amount of ions reaching the reactive aggregate surface is reduced.« less
  • A non-reactive and several reactive aggregates were used in concrete specimens with and without two fly ashes (varying in total alkali content) at binder (cement + fly ash) alkali levels ranging from 0.46 to 2.5% and a binder content of 500 kg/m{sup 3} and fly ash/binder ratio of 0.25. Some specimens were steam cured at 75 C for eight hours, and then transferred to 40 C, 100% RH. The expansion behavior of the specimens was monitored over nearly six years, and showed that the effectiveness of the fly ash in preventing deleterious AAR expansion depended on the alkali content ofmore » the concrete. At the highest alkali content of 12.5 kg Na{sub 2}O equiv./m{sup 3}, the fly ashes only had a delaying effect (one to several years), whereas at 6.9 kg Na{sub 2}O equiv./m{sup 3} they eliminated deleterious AAR expansions. Generally, for more highly reactive aggregates, and at the 2.5% alkali level, fly ash was less effective at 40 C than 23 C because the rate of AAR expansion was much higher at 40 C. A measurable amount of chemical shrinkage occurred in the first few months in concretes containing fly ash and with high alkali contents, although some of these concretes later expanded and cracked as a result of aggregate reactivity. Fly ash was used in mortar specimens prepared for the expression and analysis of the pore solution and was found to be very effective in reducing the alkalinity of the pore solution a factor contributing to its preventive effects on AAR. It is concluded that the two fly ashes can be used to prevent deleterious AAR expansions in practical situations.« less
  • The paper discusses results of the research into the influence of high-alkali Portland cement on granite aggregate. The deformation of the concrete structure occurred after 18 months. The research was carried out by means of a scanning electron microscope equipped with a high-energy dispersive X-ray analyzer that allowed observation of unpolished sections of concrete bars exhibiting the cracking pattern typical of the alkali-silica reaction. Both the microscopic observation and the X-ray elemental analysis confirm the presence of alkali-silica gel and secondary ettringite in the cracks.
  • Fifty-year-old concrete from a large dam was examined in the scope of an investigation program concerning the properties of granite as aggregate material for concrete. Site inspection, which was developed in order to detect possible signs of deterioration of the concrete, revealed the existence of efflorescence and exudations. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) analyses were attempted to identify the composition of these materials and their morphology. From the analyses, it was concluded that some of the exudations were composed by alkali-silica gel. In these samples, an interesting behavior was observed in different moments after a 3-monthmore » interval. It was noticed that the initially noncrystalline alkali-silica gel transformed into sodium-rich needles and tablets after a few months kept in a desiccator in the laboratory. Therefore, it was concluded that the materials identified corresponded to different stages of evolution of an alkali-aggregate reaction product.« less