Chemical acceleration of a neutral granulated blast-furnace slag activated by sodium carbonate

Kovtun, Maxim; Kearsley, Elsabé P.; Shekhovtsova, Julia

doi:10.1016/j.cemconres.2015.02.014

Cited by 125 publications

(54 citation statements)

References 37 publications

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“…Kovtun et al [29] found that the intensity of gaylussite decreased in all accelerated pastes using accelerators such as sodium hydroxide and cement. The formation of hydrotalcite is also observed at the early ages but with only weak reflections (Fig.…”

Section: Xrdmentioning

confidence: 99%

“…As reported by Bernal et al [4] and our previous study [26], CO 3 2-anions concentration in the pore solution and the initially precipitated calcium carbonate significantly control the sodium carbonate activation process. According to the previous researches [4,23,[28][29][30] The present research aims to study the effect of LP on the reaction kinetics, reaction products and strength development of sodium carbonate activated slag. The heat evolution of mixtures with different LP incorporation levels was measured, up to 7 days.…”

Section: Introductionmentioning

confidence: 99%

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Assessing the chemical involvement of limestone powder in sodium carbonate activated slag

Yuan

Brouwers

2017

Mater Struct

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This study aims to investigate the effect of limestone powder (LP) on the reaction of sodium carbonate activated slag. The results show that the incorporated LP up to 30% improves the strength development, especially at advanced curing ages. A slightly accelerated reaction is observed for samples containing low amount of LP (B5%), while mixture with 10% LP shows the optimized results with respect to the heat release and strength development. Chemical effect of incorporating LP is observed at high replacement levels (C15%), indicated by the formation of a new phase, natron (Na 2 CO 3 Á10H 2 O). Besides, relatively high contents of hydrotalcite-like phases are generated when increasing the dosage of limestone powder. The chemical changes, including the volume changes of generating natron and the transformation of natron to calcite, is potentially responsible for the enhanced mechanical properties.

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Section: Xrdmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Assessing the chemical involvement of limestone powder in sodium carbonate activated slag

Yuan

Brouwers

2017

Mater Struct

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“…There is a good consensus that, at early times of reaction, calcium and mixed sodium-calcium carbonates are the predominant crystalline reaction products forming in sodium carbonate-activated slag cements [11,29,30], instead of strength-giving phases such as calcium silicate hydrates (C-S-H). At advanced times of curing, formation of a highly cross-linked C-A-S-H type phase with a relatively low content of Ca in the outer product has been reported [28,31,32], providing strength to the hardened material.…”

Section: Sodium Carbonate Activated Slag Cementsmentioning

confidence: 99%

Advances in near-neutral salts activation of blast furnace slags

Bernal

2016

RILEM Tech Lett

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The utilisation of near-neutral salts as activators to produce alkali-activated slag cements offers several technical advantages, including reduced alkalinity of the binders, minimising the risk associated with handling of highly alkaline materials, and better workability of the fresh paste compared to that of sodium silicate-activated slag cements. Despite these evident advantages, the delayed setting and slow early-age mechanical strength development of these cements have limited their adoption and commercialisation. Recent studies have demonstrated that these limitations can be overcome by selecting slags with chemistry, which is more prone to react with near-neutral salts, or by adding mineral additives. A brief overview of the most recent advances in alkali-activation of slags using either sodium carbonate or sodium sulfate as activators is reported, highlighting the role of material design parameters in the kinetics of reaction and phase evolution of these cements, as well as the perspectives for research and development of these materials.Keywords: Alkali-activation; Blast furnace slag; Sodium Carbonate; Sodium sulfate; Characterisation Brief overview of alkali-activated slag materialsAlkali-activated cements are materials produced via the chemical reaction of a poorly crystalline aluminosilicate powder, and a highly alkaline solution, to form a hardened solid. These materials have been studied for more than a century, and in the past decades one of the main drivers for their development has been the potential environmental benefits associated with their production [1]. Alkali activated cements are usually produced from industrial wastes or byproducts such as blast furnace slag derived from the ironmaking industry, fly ashes from the coal combustion process, among others [2], and are now commercialised in several places around the world [3]. These materials can develop desirable properties including high mechanical strength [4], good retention of integrity when exposed to high temperatures [5] and acidic media [6], if properly formulated and cured. Significant advances have been made over the past decade in understanding alkali-activated slag materials at micro-and macroscopic scales, as discussed in recent reviews [7,8], particularly for those materials produced with sodium silicate solutions as alkali-activator. The influence of formulation parameters such as chemistry of the slag [9, 10], type of activator [11], addition of metakaolin [12] or fly ashes [13], on the microstructural development and therefore performance of these materials have been the main focus of study in recent years. The application of advanced analytical techniques, including synchrotron X-ray diffraction [14] and X-ray fluorescence microscopy [15], along with thermodynamic modelling [16], have revealed detailed information about the chemistry and phase assemblage of these cements, allowing the development of descriptive models for the activation processes of slags (Fig. 1). Figure 1. Simplified schematic diagram of the alk...

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“…Several aluminosilicate sources are being studied to produce alkali-activated binders such as fly ash from thermoelectric power plants [10,13], metakaolin [14], spent fluid catalytic cracking catalysts [9], blastfurnace slag [15] and others. In addition, residues from the agroindustry are being researched in alkaliactivated binders, such as rice husk ash [16].…”

Section: Introductionmentioning

confidence: 99%

Study of the binary system fly ash/sugarcane bagasse ash (FA/SCBA) in SiO2/K2O alkali-activated binders

Castaldelli

Moraes

Akasaki

et al. 2016

Fuel

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Due environmental problems related to Portland cement consumption, many studies have been performed to diminish its use. One solution is the development of alkali-activated binders, which can decrease CO 2 emissions and energy consumption by 70% when compared to Portland cement production. In addition, an alkali-activated binder presents mechanical properties similar to Portland cement mixtures, which turns into an interesting material in civil construction. Aluminosilicate-based materials are important raw materials to produce the alkali-activated binders. Therefore, two residues are presented as an aluminosilicate source in this study: fly ash (FA) and sugarcane bagasse ash (SCBA). Both residues were obtained from a combustion process to generate energy, the former from coal and the latter from the bagasse of the sugarcane industry. In addition, the alkaline activating solution is an important factor to achieve improved mechanical properties. In this context, this study investigated the influence of four different SiO 2 /K 2 O molar ratios (0, 0.36, 0.75 and 1.22) in the activating solution with a constant water content, and three FA/SCBA binder proportions (75/25, 50/50 and 25/75). Microstructural characterization was carried out by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, mercury intrusion porosimetry, pH and electrical conductivity measurements to study the evolution of the reaction process. The compressive strength of mortars was assessed in order to determine the optimum SiO 2 /K 2 O molar ratio and FA/SCBA ratio. The tests showed that a SiO 2 /K 2 O molar ratio of 0.75 and FA/SCBA proportion of 75/25 provided the best mechanical properties.

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Chemical acceleration of a neutral granulated blast-furnace slag activated by sodium carbonate

Cited by 125 publications

References 37 publications

Assessing the chemical involvement of limestone powder in sodium carbonate activated slag

Assessing the chemical involvement of limestone powder in sodium carbonate activated slag

Advances in near-neutral salts activation of blast furnace slags

Study of the binary system fly ash/sugarcane bagasse ash (FA/SCBA) in SiO2/K2O alkali-activated binders

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