A preliminary study on the alkali activation of ground granulated blast-furnace slag

Douglas, E; Brandštetr, Jiří

doi:10.1016/0008-8846(90)90008-l

Cited by 131 publications

(37 citation statements)

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“…While other studies indicated that there is an optimum ratio between slag and fly ash, for instance Chi and Huang reported the critical fly ash content is 50% [29], a 20% fly ash content by Yang et al and a 65% fly ash content by Zhang et al [30][31]. Differences in critical raw materials' relative content and activator parameters were also reported [15,[32][33][34][35]. Different used activators and curing conditions make it difficult to make valid comparison between those studies.…”

Section: Introductionmentioning

confidence: 97%

Reaction kinetics, gel character and strength of ambient temperature cured alkali activated slag–fly ash blends

Gao

Brouwers

2015

Construction and Building Materials

302

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h i g h l i g h t sSlag/fly ash ratio and activator modulus show synergetic effects on reaction. Activator modulus has a more significant influence on early age reaction. Gel structures remain stable regardless of activator modulus and slag/fly ash ratio. Slag content shows a dominating effect on compressive strength. a r t i c l e i n f o t r a c tRoom temperature cured alkali activated slag/fly ash blends have shown their advantages in field applications. Given that alkali activated materials are extraordinarily sensitive to the composition of the starting materials, identifying their influences is essential for their application. This paper focuses on the effects of two compositional factors: activator modulus (SiO 2 /Na 2 O from 1.0 to 1.8) and slag/fly ash mass ratios (between 90/10 and 50/50) on reaction kinetics, gel characters and compressive strength. The results show that when lowering the activator modulus, the early age reaction is significantly accelerated with a higher reaction intensity, and increasing the slag content also leads to an increased reaction rate, especially at low activator modulus. Regardless of the two influential factors, the main reaction products are chain structured C-A-S-H gels with similar water contents and thermal properties, and no typical N-A-S-H type gels are formed in the system. Slight differences in terminal SiAO bonds and crystallization temperature are caused by the activator modulus and slag/fly ash mass ratios, respectively. The compressive strength results show that the optimum activator modulus changes with the slag/fly ash mass ratio, and higher slag/fly ash mass ratios prefer higher activator moduli in general, while either too high or too low activator modulus has detrimental effect on strength. Understanding the reaction, gel structure and strength changes are fundamental for determining key manufacturing parameters and tailoring the properties.

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Section: Introductionmentioning

confidence: 97%

Reaction kinetics, gel character and strength of ambient temperature cured alkali activated slag–fly ash blends

Gao

Brouwers

2015

Construction and Building Materials

302

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“…Some of the technical challenges associated with the use of near-neutral salt activators have been overcome by incorporating into the activated slag cements minor fractions of clinker or Ca(OH) 2 [26], limestone [27], or utilising blended activating solutions of sodium carbonate or sulfates with sodium hydroxide or silicate solutions [28], or adopting high temperature curing [1]. All these different approaches make the material harden; however, in order to move towards a more standardised way of developing alkali-activated slag binders, it is required to consider the role of the chemical and mineralogical characteristics of slags from different sources, to select the most suitable activator for a given slag.…”

Section: Brief Overview Of Alkali-activated Slag Materialsmentioning

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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“…It is produced by pulverizing clinkers consisting essentially of hydraulic calcium silicates and contains one or more forms of calcium sulfate. Portland cement is usually added as a binder to stabilize/solidify heavy metals (Douglas & Brandstetr, 1990). After a short hydration period, the slurry mixture of heavy-metal wastes and Portland cement can be solidified.…”

mentioning

confidence: 99%

Metal Stabilization Mechanisms in Recycling Metal-Bearing Waste Materials for Ceramic Products

Shih¹,

Lü²

2011

Advances in Ceramics - Electric and Magnetic Ceramics, Bioceramics, Ceramics and Environment

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A preliminary study on the alkali activation of ground granulated blast-furnace slag

Cited by 131 publications

References 0 publications

Reaction kinetics, gel character and strength of ambient temperature cured alkali activated slag–fly ash blends

Reaction kinetics, gel character and strength of ambient temperature cured alkali activated slag–fly ash blends

Advances in near-neutral salts activation of blast furnace slags

Metal Stabilization Mechanisms in Recycling Metal-Bearing Waste Materials for Ceramic Products

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