Performance of blended metakaolin/blastfurnace slag alkali-activated mortars

Borges, Paulo Henrique Ribeiro; Banthia, Nemkumar; Alcamand, Himad Ahmed; Vasconcelos, Wander L.; Nunes, Eduardo H.M.

doi:10.1016/j.cemconcomp.2016.04.008

Cited by 118 publications

(40 citation statements)

References 36 publications

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“…In these systems, both type of reaction products C-A-S-H from GGBS and N-A-S-H from the metakaolin are able to coexist and have only small interactions [47]. Borges et al [49] partly explained the compressive stress gain by a lower porosity.…”

Section: Introductionmentioning

confidence: 99%

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Formulation and characterization of blended alkali-activated materials based on flash-calcined metakaolin, fly ash and GGBS

Samson

Cyr

Gao

2017

Construction and Building Materials

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Highlights AAMs initial setting time, shrinkage, mass loss, compressive strength were studied. Low activation leads to high drying shrinkage because of important mass loss. Very low shrinkage values were found for MK-GGBS compared to the other AAMs. High early strength compressive strength was observed for MK-GGBS blends. Graphical abstract 2 AbstractStudies performed on alkali-activated materials (AAMs) in recent years reveal that they could be an alternative to ordinary Portland cement (OPC). The main precursors used are flash-calcined metakaolin (MK), fly ash (FA), and ground granulated blast furnace slag (GGBS). Usually, only one precursor is used to produce an AAM. The aims of this study were to measure and compare the performances of pure (one precursor) and blended AAMs (two precursors). Alkaline solution is added to activate the precursors and the influence of the activation rate was also investigated by changing the activator amount (15% and 25% of alkaline solution dry extract). Twenty-six different mixes were studied and are presented in a ternary representation. The mixtures were characterized in the fresh state (initial setting time) and the main properties useful for building applications (shrinkage, mass loss, and compressive strength) were recorded and analysed. In contrast to the situation in OPC systems, shrinkage and mass loss in AAMs were not directly correlated. The high shrinkage values observed for pure MK AAMs and pure GGBS AAMs were significantly reduced when they were associated in appropriate proportions. The association of MK and GGBS also proved very interesting regarding early age compressive strength.Keywords: Alkali-activated material (AAM), metakaolin (MK), fly ash (FA), ground granulated blast furnace slag (GGBS), compressive strength, shrinkage 3 IntroductionThe building sector is faced with the gradual exhaustion of natural resources and/or increasing difficulty in accessing them. 27°C, the reaction of alkali-activated GGBS-FA blend paste is dominated by the GGBS activation (dissolution and precipitation of C-A-S-H) while at 60°C the reaction is due to combined interaction of FA and GGBS, which indicates that FA has lower reactivity than GGBS under ambient conditions. There is only small interaction of fly ash and GGBS probably due to different kinetics of dissolution process and distribution of species. Puligulla et al.[39] studied GGBS-FA blend pastes. They found that the calcium that dissolves from slag significantly influences both early and late age properties. The availability of free Ca ions seems to prolong FA dissolution and enhance geopolymer gel formation. It is proposed that the hardening process is initiated by the precipitation of C-A-S-H and that rapid hardening continues due to accelerated geopolymerization. Liu et al. 5The studies mentioned above reveal that, under particular conditions, mixing two different precursors cangive very interesting results. However, these studies have usually focused on the identification of a particular property under particu...

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Section: Introductionmentioning

confidence: 99%

“…As the previous quoted references, FA has a negative impact on compressive but it reduces shrinkage. MK-GGBS AAMs (paste [23,[46][47][48], mortar [49]) have been investigated too. Bernal et al [23] showed the beneficial effects of GGBS addition on MK AAMs compressive strength.…”

Section: Introductionmentioning

confidence: 99%

Formulation and characterization of blended alkali-activated materials based on flash-calcined metakaolin, fly ash and GGBS

Samson

Cyr

Gao

2017

Construction and Building Materials

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“…The end products after the acid attack are calcium salts of the acid and/or decalcified residue of the hydrated cement products (Pavlík and Unčík, 1997). These reported negative effects of acids on alkali-activated binder awakens the need for more studies to ascertain the durability properties of alkaliactivated binder especially with different precursor materials (Borges et al 2016). Bakharev (2005) started an early work to establish the actual durability performance of alkali-activated mortar in acid using fly ash as a base material.…”

Section: Introductionmentioning

confidence: 99%

POFA-Engineered Alkali-activated Cementitious Composite Performance in Acid Environment

Salami

Johari

Ahmad

et al. 2017

ACT

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The durability performance of palm oil fuel ash engineered alkali-activated cementitious composite (POFA-EACC) mortar exposed to different acid solutions is assessed in this study. 50 mm cubic specimens used for the study were prepared from 100% POFA, alkali-activator (Na 2 SiO 3(aq) /NaOH (aq) ) ratios of 2.5, different molarities (10, 12 and 14 M) of NaOH (aq) and 2% volume fraction of polyvinyl alcohol (PVA) fibres. Specimens were exposed to 10% H 2 SO 4(aq) , 10% HNO 3(aq) and 10% HCl (aq) at pH of 0.56, 0.52 and 0.42 respectively for 3, 6 and 9 months, with unexposed specimens as control. Small changes in compressive strength were identified with POFA mortar specimens during exposure to H 2 SO 4(aq) , while exposure to HNO 3(aq) and HCl (aq) greatly reduced the strength of the POFA mortar specimens. The results were supported through microstructural examinations using SEM, while the characterization was done using XRD and FTIR. The high resistance of POFA-EACC mortar to H 2 SO 4(aq) is the contribution received through the formation of gypsum, which hinders the infiltration of more acids into the matrix microstructure.

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“…11H2O. The latter was stablished following the results obtained in previous studies [7,8]. Sodium silicate and hydroxide solutions were mixed in appropriate proportions, and the final blend was cooled in a water bath for 10 min, before being added to the aluminosilicate source.…”

Section: Materials and Processingmentioning

confidence: 99%

Mechanical response of geopolymer composites reinforced with distinct types of fibers

Trindade¹,

Borges²,

Silva³

2018

Proceedings of the 4th Brazilian Conference on Composite Materials

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Ceramic materials, such as geopolymers, have been increasingly used in civil construction as a compatible, green-friendly, and even more efficient alternative. They are obtained through the mixture of an aluminosilicate source, with an alkali solution, and its mechanical properties may vary according to its molar ratios, curing regimes and processing conditions. Geopolymers present compatible mechanical and durable responses, despite their characteristic brittle behaviour. Fiber reinforcement appear as an interesting solution to overcome this vulnerability. Particulate, discrete and textile forms of distinct fibers can be used as reinforcements, resulting in sustainable solutions (natural fibers) and even ultraductility performance (synthetic fibers). This study presents an experimental evaluation of distinct geopolymer composites reinforced with natural (sisal, jute and curauá) and synthetic fibers (PVA). The geopolymer mixture was produced with metakaolin in a sodium based solution. Compression, tensile and pull-out tests were performed. Scanning electron microscopy (SEM) was used to investigate the hardened geopolymer microstructure. Despite presenting distinct quantitative responses, all composites exhibited strain-hardening behaviour with multiple cracking formation.

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Performance of blended metakaolin/blastfurnace slag alkali-activated mortars

Cited by 118 publications

References 36 publications

Formulation and characterization of blended alkali-activated materials based on flash-calcined metakaolin, fly ash and GGBS

Formulation and characterization of blended alkali-activated materials based on flash-calcined metakaolin, fly ash and GGBS

POFA-Engineered Alkali-activated Cementitious Composite Performance in Acid Environment

Mechanical response of geopolymer composites reinforced with distinct types of fibers

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