Consistency of Fly Ash and Metakaolin Concrete

Bai, Jiping; Gailius, Albinas

doi:10.3846/1392-3730.2009.15.131-135

Cited by 33 publications

(16 citation statements)

References 12 publications

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“…2a). More water is required for the wetting of the MK surface than for that of the PFA or PC because of its much larger surface areas, this is supported by earlier work of Bai and Gailius (2009). However although at 0% MK content the w/b ratio at standard consistence remains relatively unchanged with increasing PFA content, at increasingly fixed MK levels (Fig.…”

Section: Standard Consistence Of Binary Mk-pc and Pfa-pc Pastessupporting

confidence: 60%

Setting Times of Portland Cement–metakaolin–fly Ash Blends / Portlandcemenčio, Metakaolino Ir Lakiųjų Pelenų Mišinių Rišimosi Terminai

Snelson

Wild

O’Farrell

2011

Journal of Civil Engineering and Management

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In the present study two pozzolanic materials are used, Metakaolin (MK) and Fly Ash (PFA), as binary and ternary partial replacement binders with Portland cement (PC) to investigate their effect on standard consistence and setting times of paste. To maintain standard consistency for MK–PC pastes increasing w/b ratios are required with increasing MK levels, whereas PFA has little influence on consistency. For binary MK–PC pastes there are substantial increases in initial and final setting times at 5% MK followed by decreases at 10 and 15% MK before further increases at 20% MK. For binary PFA–PC pastes however setting times increase at approximately the same rate up to 30% PFA and then increase more sharply between 30% PFA and 40% PFA. In general the effects of both PFA and MK on consistency and setting times in binary pastes are reflected in the behaviour of the ternary pastes although the two pozzolans do not behave completely independently of each other. The different ways in which the two pozzolans influence setting times is explained in terms of differences in their pozzolanic activities and in the manner in which they influence the availability of water for hydration. Santrauka Šiame tyrime naudojamos dvi pucolaninės medžiagos—metakaolinas (MK) ir lakieji pelenai (PFA), kaip dviejų ir trijų komponentų dalinio pakeitimo rišikliai su portlandcemenčiu (PC), siekiant ištirti jų poveikį standartinėms konsistencijoms ir reguliuoti mišinio kietėjimo laiką. Siekiant išlaikyti standartinę MK–PC mišinio konsistenciją, didinant vandens ir rišamųjų medžiagų santykius, reikia didinti MK lygį, nes PFA turi mažai įtakos konsistencijai. Dviejų komponentų MK–PC mišiniams svarbu padidinti pradinius ir galutinius kietėjimo laikus 5% MK, po sumažėjimo 10 ir 15% MK, prieš tolesnį padidinimą 20% MK. Dviejų komponentų PFA–PC mišinių kietėjimo laikui padidinti maždaug tokiomis pačiomis normomis iki 30% PFA ir tuomet didinti atsargiau tarp 30% PFA ir 40% PFA. Apskritai PFA ir MK poveikis konsistencijai ir kietėjimo laikui abiejuose mišiniuose matomas iš trijų mišinio komponentų elgsenos, nors du pucolanai nėra visiškai nepriklausomi vienas nuo kito. Kiti būdai, kuriais du pucolanai daro įtaką kietėjimo laikui, yra pristatyti kalbant apie jų pucolaninės veiklos skirtumus ir jų elgseną, kurios metu jie daro įtaką vandens galimybei hidratuotis.

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Section: Standard Consistence Of Binary Mk-pc and Pfa-pc Pastessupporting

confidence: 60%

Setting Times of Portland Cement–metakaolin–fly Ash Blends / Portlandcemenčio, Metakaolino Ir Lakiųjų Pelenų Mišinių Rišimosi Terminai

Snelson

Wild

O’Farrell

2011

Journal of Civil Engineering and Management

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“…R7). Besides, concrete made according to formulation R3 contains an admixture of 30% of ground blastfurnace slag of the mass of cement, R4 contains 30% of fly ash (Bai, Gailius 2009), R5 10% of industrial microsilica (Antonovič et al 2010) and R6 a mixed admixture of 30% of fly ash and 10% of microsilica. Each of the concrete mixtures marked R1-R7 was prepared in two variants, without adding dispersion, and with 12% waterbased epoxy dispersion added into the original concrete mixture (Schulze et al 1990).…”

Section: Methodsmentioning

confidence: 99%

Testing the Strength of Concrete Made From Raw and Dispersion-Treated Concrete Recyclate by Addition of Additives and Admixtures

Stehlík

2013

Journal of Civil Engineering and Management

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Today, concrete comprises more than 65% of the total volume of building constructions. As it undergoes degradation and buildings require refurbishment, the volume of concrete increases at disposal sites. Due to a lack of non-renewable resources and due to high prices of energies, the reuse of concrete seems to be more than desirable. It is common knowledge that in concretes made from recycled concrete, the strengths of the original concretes can hardly be achieved. The addition of dispersion additives and mineral admixtures into the freshly mixed concrete can contribute to improving the mechanical properties of concretes made from recycled concrete. Potential composite action of the recyclate, mineral admixtures and dispersion additives in increasing the compressive strength of concretes made from recycled concrete remains to be a question.

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“…Calcium Hydroxide (CH) itself does not contribute significantly to the strength development, but its presence can compromise the durability of concrete (Siddique and Klaus, 2009). The removal of CH coarsens the pore structure and influences the transport mechanisms of moisture and aggressive substances as well as deterioration mechanisms of concrete (Sabir et al, 2001;Bai and Gailius, 2009). Metakaolin in the concrete mix reacts with cement hydrates, CH, resulting in calcium silica hydrates which are more stable.…”

Section: Introductionmentioning

confidence: 99%

Effect of metakaolin on the chloride ingress properties of concrete

2015

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Research and practical experience have shown that partial replacement of cement by metakaolin improves concrete durability as a result of the refinement of the pore structure. While much research has been presented on concrete performance with metakaolin, it is scarce concerning the transport properties of chlorides in concrete with metakaolin, in natural conditions (i.e., un-accelerated). This study determines the chloride diffusion coefficients for several concretes with vary levels of cement replacement with metakaolin, and compares these results with chloride migration coefficients obtained from accelerated laboratory testing. In this study, two cement types (CEM I 42,5R and CEM IV/A 42,5) and two cement contents levels where used with metakaolin replacement levels varying from 10-20%. Concretes where tested for fresh properties, compressive strength, electrical resistivity, chloride ingress characteristics (natural diffusion and migration), and mercury intrusion porosimetry. The results show improved strength, durability properties and chloride penetration resistance of concretes with metakaolin. Furthermore, the use of metakaolin in fly ash concrete improves the early age performance of the concrete (<90 days), counteracting the delay in strength and durability gain typically associated with fly ash concrete. The results obtained from this study fulfil the lack of critical input for service life design models of reinforced concrete structures in chloride environments, with emphasis on concretes with metakaolin replacement.

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Consistency of Fly Ash and Metakaolin Concrete

Cited by 33 publications

References 12 publications

Setting Times of Portland Cement–metakaolin–fly Ash Blends / Portlandcemenčio, Metakaolino Ir Lakiųjų Pelenų Mišinių Rišimosi Terminai

Setting Times of Portland Cement–metakaolin–fly Ash Blends / Portlandcemenčio, Metakaolino Ir Lakiųjų Pelenų Mišinių Rišimosi Terminai

Testing the Strength of Concrete Made From Raw and Dispersion-Treated Concrete Recyclate by Addition of Additives and Admixtures

Effect of metakaolin on the chloride ingress properties of concrete

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