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Provis J.L.,University of Sheffield | Provis J.L.,University of Melbourne | Duxson P.,Zeobond Pty Ltd. | Kavalerova E.,National University of Civil Engineering | And 5 more authors.
RILEM State-of-the-Art Reports | Year: 2014

Cement and concrete are critical to the world economic system; the construction sector as a whole contributed US$3.3 trillion to the global economy in 2008 [1]. The fraction of this figure which is directly attributable to materials costs varies markedly from country to country - particularly between developing and developed countries. Worldwide production of cement in 2008 was around 2.9 billion tonnes [2], making it one of the highest-volume commodities produced worldwide. Concrete is thus the second-most used commodity in the world, behind only water [3]. It is noted that there are certainly applications for cement-like binders beyond concrete production, including tiling grouts, adhesives, sealants, waste immobilisation matrices, ceramics, and other related areas; these will be discussed in more detail in Chaps. 12 and 13, while the main focus of this chapter will be large-scale concrete production. © RILEM 2014.

Provis J.L.,University of Sheffield | Provis J.L.,University of Melbourne | Brice D.G.,University of Melbourne | Brice D.G.,Zeobond Group | And 8 more authors.
RILEM State-of-the-Art Reports | Year: 2014

In the context of a Report such as this, it is of immense value to be able to provide tangible examples of structures and applications in which alkali-activated concretes have been utilised throughout the past decades. A detailed outline of the utilisation of AAM concretes in the former Soviet Union and in China is given in Chap. 12 of the book by Shi, Krivenko and Roy [1], and this chapter will briefly describe some of the applications mentioned in that (more extensive) document, along with applications elsewhere in the world where AAMs have been utilised on a significant scale in the construction of buildings and other civil infrastructure components. An overview of developments and applications in the former USSR has also been presented by Brodko [2] and by Krivenko [3]. Each project reported in this chapter involves at least pilot-scale, and in some cases full commercial-scale, production of alkali-activated concretes utilising largely standard concrete mixing and placement equipment and labour, indicating that these materials are both accessible and useful on this length scale, given sufficient expertise in mix design based on locally available precursors. In the former USSR in particular, slags obtained from local iron production facilities were used in each of the different locations in which the concretes were produced, and activators were sourced in large part from locally available alkaline industrial waste streams. © RILEM 2014.

Ismail I.,University of Melbourne | Ismail I.,University Malaysia Sarawak | Bernal S.A.,University of Melbourne | Bernal S.A.,University of Sheffield | And 5 more authors.
Journal of Materials Science | Year: 2013

Drying of cement paste, mortar, or concrete specimens is usually required as a pre-conditioning step prior to the determination of permeability-related properties according to standard testing methods. The reaction process, and consequently the structure, of an alkali-activated slag or slag/fly ash blend geopolymer binder differs from that of Portland cement, and therefore there is little understanding of the effects of conventional drying methods (as applied to Portland cements) on the structure of the geopolymer binders. Here, oven drying (60 C), acetone treatment, and desiccator/vacuum drying are applied to sodium silicate-activated slag and slag/fly ash geopolymer pastes after 40 days of curing. Structural characterization via X-ray diffraction, infrared spectroscopy, thermogravimetry, and nitrogen sorption shows that the acetone treatment best preserves the microstructure of the samples, while oven drying modifies the structure of the binding gels, especially in alkali-activated slag paste where it notably changes the pore structure of the binder. This suggests that the pre-conditioned drying of alkali activation-based materials strongly affects their microstructural properties, providing potentially misleading permeability and durability parameters for these materials when pre-conditioned specimens are used during standardized testing. © 2013 Springer Science+Business Media New York.

Ismail I.,University of Melbourne | Ismail I.,University Malaysia Sarawak | Bernal S.A.,University of Melbourne | Bernal S.A.,University of Sheffield | And 10 more authors.
Construction and Building Materials | Year: 2013

Mechanical strength, water and chloride permeability of alkali activated slag mortar and concretes with partial fly ash substitution are investigated. Volume of permeable voids (VPV) and sorptivity testing show that alkali-activated materials exhibit higher water absorption than OPC-based samples, and increasing fly ash addition leads to reduced mechanical strength and increased water absorption. Conversely, chloride permeability testing by the NordTest NT Build 492 standard accelerated method, and by chloride ponding (ASTM C1543), shows that the diffusion of chloride in alkali-activated binders is much less than in OPC binders. This divergence between measured water uptake and chloride permeability in alkali-activated specimens is attributed largely due to the specified standard preconditioning (drying) of the samples prior to water absorption testing due to the difference in water environments as a function of slag/fly ash ratio. Drying is likely to be inducing desiccation and consequent microcracking of slag-based binding gels, while less disturbance occurs in a fly ash geopolymer gel. The chemistry of the binding gels in these alkali-activated systems significantly controls the mass and ionic transport in chloride-containing environments. Although higher porosity was measured by these standards, a denser Al-substituted calcium silicate hydrate (C-A-S-H) gel contributes to a higher mechanical strength, and durability under chloride exposure. The inclusion of fly ash promotes the formation of more porous sodium aluminosilicate (N-A-S-H) type gels, reducing the resistance to transport. © 2013 Elsevier Ltd. All rights reserved.

Brice D.G.,Zeobond Group | Brice D.G.,University of Melbourne | Ko L.S.-C.,Holcim | Provis J.L.,University of Melbourne | And 3 more authors.
RILEM State-of-the-Art Reports | Year: 2014

The key outcome of RILEM TC 224-AAM has been the development of a conceptual framework from which the discussion of standardisation of alkali-activated binders and concretes can proceed. There has been agreement from the members of the TC that a performance-based approach to both materials formulation (as described in Chap. 7 of this report) and testing (as outlined in Chaps. 8,9, and 10) is essential in enabling the scale-up of alkali-activation as a method of concrete production in the global context. However, it is essential to proceed with a degree of conservatism, to avoid becoming ‘the next high-alumina cement problem’ through use of a material in environments and/or systems where it is not fit for purpose. So, it is critical that standards development is conservative to ensure that due care is taken, and to make sure that poor-quality AAM products, and/or products used in unsuitable applications, do not ruin the global reputation of the technology. A key discussion which occupied much of the time of the TC was the issue of how to achieve this - and the conclusion reached was that the use of strict performance criteria (and maybe even criteria which seem excessively strict until a higher degree of certainty regarding performance levels can be reached), and with good scientific foundations, must underpin any testing method applied to these materials. © RILEM 2014.

Provis J.L.,University of Melbourne | Rose V.,Argonne National Laboratory | Winarski R.P.,Argonne National Laboratory | Van Deventer J.S.J.,University of Melbourne | Van Deventer J.S.J.,Zeobond Group
Scripta Materialia | Year: 2011

Nanotomographic reconstruction of a sample of low-CO2 "geopolymer" cement provides the first three-dimensional view of the pore structure of the aluminosilicate geopolymer gel, as well as evidence for direct binding of geopolymer gel onto unreacted fly ash precursor particles. This is central to understanding and optimizing the durability of concretes made using this new class of binder, and demonstrates the value of nanotomography in providing a three-dimensional view of nanoporous inorganic materials. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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