Browsing by Author "De la Varga, Igor"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Application of internal curing for mixtures containing high volumes of fly ash
    (ELSEVIER SCI LTD, 2012) De la Varga, Igor; Castro, Javier; Bentz, Dale; Weiss, Jason
    This paper focuses on testing performed on mixtures that would be consistent with the mortar portion of a concrete bridge deck mixture for many state departments of transportation. In this work a relatively large percentage of cement (40%, 60%, or 80% by volume) is replaced with Class C fly ash. To overcome concerns associated with slow set and early-age strength development that are often expressed with the high volume fly ash mixtures (HVFA), the water-to-cementitious materials ratio (w/cm) by mass has been reduced from a conventional value of 0.42 to 0.30. To overcome potential complications that the low w/cm may cause in terms of self-desiccation, internal curing (IC) with prewetted lightweight aggregate was used to reduce shrinkage and increase hydration. By adopting this approach (lowering the w/c and using IC) IC HVFA mixtures show additional benefits that should permit their broader application. (c) 2012 Elsevier Ltd. All rights reserved.
  • Thumbnail Image
    Item
    Using Isothermal Calorimetry to Assess the Water Absorbed by Fine LWA during Mixing
    (ASCE-AMER SOC CIVIL ENGINEERS, 2012) Castro, Javier; De la Varga, Igor; Weiss, Jason
    Fine lightweight aggregate (LWA) is being increasingly used for the manufacture of internally cured concrete. Internally cured concrete can be viewed as a concrete that contains fluid (water) in the pores of the LWA (or other porous inclusions) that can be released to the paste after setting. Most research performed on internally cured concrete assumes the LWA has been prewetted for some time before mixing (generally lab studies use 24-h soaking, whereas this value varies in practice). The research described in this paper investigated the potential for using aggregate that begins the mixing process from a different moisture state (i.e., not 24-h prewetting). Specifically, this paper considers oven-dry aggregate as a worst-case scenario to determine how much water would be absorbed by the LWA during the mixing and placement processes. To determine the amount of water absorbed by the LWA, isothermal calorimetry was used. Two different mixing scenarios were investigated, showing that 56-71% of the 24-h water absorption could be achieved using the worst-case scenario of oven-dry aggregates. Although the use of oven-dry aggregate would be extremely rare for a field application (except for possible application to bagged products), this approach could be extended to include fine LWA with other initial moisture conditions. DOI: 10.1061/(ASCE)MT.1943-5533.0000496. (C) 2012 American Society of Civil Engineers.