Microstructure, hydration and nanomechanical properties of concrete containing metakaolin

Barbhuiya, Salim; Chow, PengLoy; Memon, Shazim Ali

doi:10.1016/j.conbuildmat.2015.07.101

Cited by 115 publications

(38 citation statements)

References 35 publications

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“…The replacement levels presented are chosen such that they contain the optimums for mechanical strengths that are prevalent in the literature (10-20%). In addition, the range was chosen to include higher replacements because durability tends to increase systematically with replacement level [12,[23][24][25][26][27]. This concept of an 'optimum' replacement level is evoked because of the need to maximize performance and minimize cost.…”

Section: Objectivementioning

confidence: 99%

Sustainable Materials for Transportation Infrastructures: Comparison of Three Commercially-Available Metakaolin Products in Binary Cementitious Systems

et al. 2018

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Abstract:Metakaolin is the only major natural pozzolan to be specified for use as a supplementary cementitious material in the United States. As a result, the metakaolin market for concrete has grown dramatically in the past 20 years. As of now, the specifications of up to 16 state departments of transportation allow for the use of commercially-available and high-reactivity metakaolin products. However, to the best of the authors' knowledge, no study has been performed to evaluate whether these products are comparable in their performance. Three commercially-available (U.S.) metakaolin products, each replacing 10%, 15%, and 20% of the cement content in concrete and mortar mixtures are studied. Concrete mixtures contained a cementitious content of 422 kg/m 3 , a coarse aggregate fraction of 985 kg/m 3 , and a water-to-cementitious ratio equal to 0.43. Varying levels of a superplasticizer were used to maintain a uniform workability between mixtures. Each mixture was subjected to the following tests: compression, split-cylinder tension, modulus of rupture, dynamic elastic modulus, rapid chloride-ion penetrability, alkali-silica reactivity, sulfate resistance, the coefficient of thermal expansion, and drying shrinkage. Benefits from the inclusion of metakaolin were highly product-dependent and include increases in mechanical strength. All metakaolin supplemented concrete mixtures benefitted from decreased permeability and increased resistance to chemical attacks, with the exception of the sulfate resistance of mortars including a metakaolin product with high fineness. The inclusion of any metakaolin at any replacement level increased the coefficient of thermal expansion of concrete specimens. Reasons for difference in performance between products are discussed, and predictors of quality are recommended.

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Section: Objectivementioning

confidence: 99%

Sustainable Materials for Transportation Infrastructures: Comparison of Three Commercially-Available Metakaolin Products in Binary Cementitious Systems

et al. 2018

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“…Table 3 reveals that at the same curing time, MK2 group shows the smallest porosity values compared with other three groups. Moreover, the porosity decreases with increasing curing time at the same MK content, which is attributed to the pozzolanic reaction between geopolymer, cement, and water [41]. Figure 6 illuminates that both UCS and E 50 of MK-based geopolymer cemented silty clay decrease with the increase of porosity and exhibit a linear correlation.…”

Section: Nmr Resultsmentioning

confidence: 88%

Effects of Curing Time on the Mechanical Property and Microstructure Characteristics of Metakaolin‐Based Geopolymer Cement‐Stabilized Silty Clay

Zhang

2020

Advances in Materials Science and Engineering

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Metakaolin (MK), which has a fine particle size and higher activity in high alkaline environments, has been widely used in the fields of soil treatment engineering to stabilize soils. MK is used to replace part of ordinary Portland cement (OPC) with 0 : 15, 2 :13, 4 : 11 and 6 : 9 mass ratios of MK to OPC in this study. The mechanical property (e.g. stress-strain relationship, strength, and deformation performance) and microstructure characteristics of MK-based geopolymer cemented silty clay are investigated using unconfined compressive strength (UCS), nuclear magnetic resonance (NMR), and scanning electronic microscopy (SEM) tests. In addition, strength increase coefficient (ζs) and elasticity modulus increase coefficient (ζe) are defined to evaluate the effects of curing time on the mechanical property of MK-based geopolymer cemented silty clay. Moreover, the relationships among porosity, UCS, and E50 of MK-cemented silty clay are studied. By incorporating 2% MK, the UCS and E50 of MK-cemented silty clay at 28 d are 1.32 and 1.30 times compared with MK0 group, respectively. The increase rate of UCS and E50 from 1 d to 7 d is faster compared with that from 7 d to 28 d. Furthermore, the microstructure of the sample modified by 2% MK is most homogeneous and dense. Finally, the optimistic mass ratio between MK and cement is 2 : 13 for silty clay in this test condition.

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“…Szakirodalmi adatok alapján a portlandcement tömegének 8-20 tömeg%-a helyettesíthető metakaolinnal [7][8][9][12][13][14][15][16][17][18][19][20][21][22]. …”

Section: A Metakaolinunclassified

Analysis of metakaolin as supplementary cementing material by the k-value concept

Borosnyói¹,

Szijártó²

2016

Epitoanyag - JSBCM

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Analysis of metakaolin as supplementary cementing material by the k-value concept Present paper studies metakaolin as a supplementary cementing material (scm) for concrete in terms of compressive strength development and k-value concept of cen/tr 16639:2014. sixteen different concrete compositions are studied in the range of water-to-cement ratio of w/c = 0.50-0.65. results indicate that the effectiveness of metakaolin depends on the applied w/c-ratio and the applied cement substitution ratio; the smaller the w/c-ratio, the more effective the metakaolin; the higher the cement substitution ratio, the less effective the metakaolin. the k-value decreases by the increase of w/c-ratio, independently of the age of concrete. the higher the cement substitution ratio, the smaller the k-value. the k-value tends to reach a final value in time. keywords: concrete, metakaolin, supplementary cementing material, strength, k-value concept kulcsszavak: beton, metakaolin, cement kiegészítő anyag, szilárdság, k-érték elve betontechnológia, cement kiegészítő anyagok (scm). BevezetésAz egyik leggyakrabban alkalmazott és legszélesebb körben felhasznált építőanyagunk a beton. A betonipar évente több mint 4 milliárd tonna cement előállítását igényli a világon. A cementgyártás környezetterhelése viszonylag nagy, amelynek oka a nagy nyersanyag-és energiaigény, illetve a szén-dioxid kibocsátás [1]. Egy tonna portlandcement előállítása átlagosan 830 kg szén-dioxid (CO 2 ) kibocsátással jár, amely a globális felmelegedésre hatást gyakorol. A cementgyártás az antropogén eredetű CO 2 kibocsátás mintegy 4-7%-áért felelős. Napjainkban a betontechnológiai kutatások egyik kiemelt célja olyan építőanyagok előállítása, amelyekkel csökkenthető a cementgyártás által kialakuló környezetszennyezés. A CO 2 kibocsátás csökkentésére alkalmazott egyik módszer (az újrahasznosított adalékanyagok alkalmazásán [2-6] túlmenően), hogy a cement egy részét helyettesítik más, reakcióképes anyagokkal, ún. cement kiegészítő anyagokkal. Ezek az anyagok többnyire ipari melléktermékek, gyártásuk a cementipar számára nem jár többlet CO 2 kibocsátással.A beton egyes tulajdonságainak javítása vagy különleges tulajdonságok elérése céljából a betonban felhasznált, a portlandcement részleges helyettesítésére szolgáló, finom szemű szervetlen alkotóanyagokat nevezzük általánosságban cement kiegészítő anyagnak. A cement kiegészítő anyagoknak két csoportját különböztetjük meg: I. típusú kiegészítő anyagok a kö-zel inert kiegészítő anyagok, míg II. típusú kiegészítő anyagok a puccolános vagy latens hidraulikus tulajdonságú kiegészítő anyagok. Ez utóbbi csoportba tartozik az erőműi pernye, a szilikapor, az őrölt kohósalak és a metakaolin. A metakaolinA metakaolin az aluminoszilikátok csoportjába tartozó agyagásvány. Szilikátkémiai jele: AS 2 (sztöchiometriai képlete: Al 2 Si 2 O 7 vagy Al 2 O 3 ·2SiO 2 ). A kaolin agyagásvány termikus aktiválásával állítják elő. A metakaolin puccolános tulajdonságokkal rendelkező anyag, szemcsemérete általában kisebb, mint a cementé. A metakaolin á...

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Microstructure, hydration and nanomechanical properties of concrete containing metakaolin

Cited by 115 publications

References 35 publications

Sustainable Materials for Transportation Infrastructures: Comparison of Three Commercially-Available Metakaolin Products in Binary Cementitious Systems

Sustainable Materials for Transportation Infrastructures: Comparison of Three Commercially-Available Metakaolin Products in Binary Cementitious Systems

Effects of Curing Time on the Mechanical Property and Microstructure Characteristics of Metakaolin‐Based Geopolymer Cement‐Stabilized Silty Clay

Analysis of metakaolin as supplementary cementing material by the k-value concept

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