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John L Provis – One of the best experts on this subject based on the ideXlab platform.

Susan A Bernal – One of the best experts on this subject based on the ideXlab platform.

  • Chloride binding and mobility in sodium carbonate-Activated Slag pastes and mortars
    Materials and Structures, 2017
    Co-Authors: Susan A Bernal, Oday H. Hussein, John L Provis
    Abstract:

    This study evaluates the chloride binding capacity and the migration of chloride in sodium carbonate-Activated Slag cements and mortars. The effect on chloride mobility and binding of adding a calcined layered double hydroxide (CLDH) to the binder mix was also assessed. Significantly improved durability characteristics can be achieved for sodium carbonate-Activated Slag mortars by the addition of small fractions of CLDH, as a consequence of a higher degree of reaction, higher chloride binding capacity, and the refined pore structures present in these modified materials, in comparison with alkali-Activated cements produced without CLDH. The addition of CLDH enables the production of sodium carbonate-Activated Slag cements with notably reduced chloride ingress compared to silicate Activated Slag cements.

  • Water content modifies the structural development of sodium metasilicate-Activated Slag binders
    , 2015
    Co-Authors: Susan A Bernal, Rackel San Nicolas, J.s.j. Van Deventer, John L Provis
    Abstract:

    The effect of modifying the water content of an alkali – Activated Slag binder was assessed, in terms of the kinetics of reaction and the structural development of the material. There is not a s ystematic correlation between the water content of the mix and the rate of reaction, indicating that there is an optimal value that favours dissolution of the Slag and precipitation of reaction products. A h igher water content reduce d the crystallinity and density of the reaction products, especially at advanced age. Small changes in the water content can have a significant impact on the compressive strength development of alkali – silicate Activated Slag mortars, suggesting that when producing materials base d on alkali – Activated binders , it is essential to carefully control the water content.

  • Thermodynamic modelling of alkali-Activated Slag cements
    Applied Geochemistry, 2015
    Co-Authors: Rupert J. Myers, Susan A Bernal, Barbara Lothenbach, John L Provis
    Abstract:

    This paper presents a thermodynamic modelling analysis of alkaliActivated Slag-based cements, which are high performance and potentially low-CO2 binders relative to Portland cement. The thermodynamic database used here contains a calcium (alkali) aluminosilicate hydrate ideal solid solution model (CNASH_ss), alkali carbonate and zeolite phases, and an ideal solid solution model for a hydrotalcite-like Mg–Al layered double hydroxide phase. Simulated phase diagrams for NaOH- and Na2SiO3-Activated Slag-based cements demonstrate the high stability of zeolites and other solid phases in these materials. Thermodynamic modelling provides a good description of the chemical compositions and types of phases formed in Na2SiO3-Activated Slag cements over the most relevant bulk chemical composition range for these cements, and the simulated volumetric properties of the cement paste are consistent with previously measured and estimated values. Experimentally determined and simulated solid phase assemblages for Na2CO3-Activated Slag cements were also found to be in good agreement. These results can be used to design the chemistry of alkaliActivated Slag-based cements, to further promote the uptake of this technology and valorisation of metallurgical Slags.

Pavel Rovnaník – One of the best experts on this subject based on the ideXlab platform.

Francisca Puertas – One of the best experts on this subject based on the ideXlab platform.

  • Alkali-Activated Slag concrete: Fresh and hardened behaviour
    Cement and Concrete Composites, 2018
    Co-Authors: Francisca Puertas, B. González-fonteboa, I. González-taboada, M.m. Alonso, Manuel Torres-carrasco, G. Rojo, F. Martínez-abella
    Abstract:

    The behaviour of fresh and hardened alkaliActivated Slag (AAS) and OPC concretes was compared and the effect of mixing time assessed. OPC and AAS concrete slump and rheological results proved to differ, particularly when the Slag was Activated with waterglass (WG). The nature of the alkaline activator was the key determinant in AAS concrete rheorheology. Bingham models afforded a good fit to all the OPC and AAS concretes. In OPC and NaOH-Activated AAS concretes, longer mixing had an adverse effect on rheology while improving hardened performance only slightly. In WG-AAS concrete, longer mixing times, improved mechanical properties and also rheological behaviour was enhanced, in which those conditions were required to break down the microstructure. Longer mixing raised thixotropy in OPC and NaOH-Activated AAS concretes, but lowered the value of this parameter in waterglass-Activated Slag concrete.

  • Rheology and Setting of Alkali-Activated Slag Pastes and Mortars: Effect of Organic Admixture
    ACI Materials Journal, 2008
    Co-Authors: Marta Palacios, Phillip Frank Gower Banfill, Francisca Puertas
    Abstract:

    The rheology of waterglass-(Na 2 O·nSiO 2 ·mH 2 O) and NaOH-Activated Slag pastes and mortars depends on the nature of the alkaline activator used: in waterglass-Activated Slag pastes and mortars, the extensive structural breakdown under shear makes the Herschel-Bulkley model a better fit to the down ramp of the flow curve, whereas NaOH-Activated pastes and mortars, such as portland-cement pastes and mortars, behaved like Bingham fluids. Admixtures were unable to reduce the yield stress of waterglass-Activated Slag pastes, but the inclusion of a naphthalene derivative admixture in NaOH-Activated Slag pastes reduced the yield stress by 80%. The problem of undesirably short setting times for waterglass-Activated Slag mortars and concretes could be overcome by an extended mixing time, giving an initial set of nearly 3 hours.

  • Effect of Carbonation on Alkali‐Activated Slag Paste
    Journal of the American Ceramic Society, 2006
    Co-Authors: Marta Palacios, Francisca Puertas
    Abstract:

    Carbonation on waterglass- and NaOH-Activated Slag pastes was analyzed and compared with carbonation in Portland cement pastes to determine possible differences. Thermogravimetry-differential thermal analysis (TG/DTA), Fourier-transform infrared spectrometry, and nuclear magnetic resoresonance were used to determine the effects on the main reaction products. According to the TG/DTA results, carbonate precipitation following carbonation is much more intense in Portland cement pastes than in alkaliActivated Slag pastes. This may be attributed to the fact that in Portland cement paste both the portlandite and the C–S–H gel can be carbonated, whereas in alkaliActivated Slag pastes, only the C–S–H gel is carbonated directly. In both systems, carbonation leads to the formation of CaCO3, Si-rich C–S–H gel, silica gel, and alumina. The carbonation of waterglass-Activated Slag pastes is not altered by the presence of either of the organic additives used in the study.

Zuhua Zhang – One of the best experts on this subject based on the ideXlab platform.