Volume 3, Issue 1

    Measuring Freeze and Thaw Damage in Mortars Containing Deicing Salt Using a Low-Temperature Longitudinal Guarded Comparative Calorimeter and Acoustic Emission

    (Received 1 August 2013; accepted 16 January 2014)

    Published Online: 2014

    CODEN: ACEMOAD

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    Abstract

    Deicing salts are often applied to the surface of pavements and bridge decks in the winter to melt ice, thereby improving safety for the traveling public. In this paper, the influence of NaCl deicing salt on freezing and thawing temperatures of pore solution and corresponding damage of mortar specimens were investigated. A low-temperature longitudinal guarded comparative calorimeter (LGCC) was developed to cool down a mortar sample at a rate of 2°C/h and to re-heat the mortar at a rate of 4°C/h. Heat flux during freezing and thawing cycles was monitored, and the temperatures at which freezing and thawing events occurred were detected. During cooling and heating, acoustic emission (AE) activity was measured to quantify the damage (cracking) caused by aggregate/paste thermal mismatch and/or phase changes. The results show that NaCl solution in a mortar sample freezes at a lower temperature than the value expected from its bulk phase diagram because of under-cooling. Conversely, the frozen solution in mortar melts at the same melting temperature as the bulk frozen NaCl solution. As the salt concentration increases, the freezing temperature is lowered. For samples containing more highly concentrated solutions, an additional exothermic event is observed whose corresponding temperature is greater than the aqueous NaCl liquidus line in the phase diagram. Damage also begins to occur at this temperature. For mortar samples saturated by solutions with 5 % and 15 % NaCl by mass, greater freeze/thaw damage is observed. The AE calorimeter developed herein is applicable for investigating damage behavior during freezing and thawing of different phases in pore solution (in mortars).


    Author Information:

    Farnam, Yaghoob
    Research Assistant, Lyles School of Civil Engineering, Purdue Univ., West Lafayette, IN

    Bentz, Dale
    Chemical Engineer, Materials and Structural Systems Division, National Institute of Standards and Technology, Gaithersburg, MD

    Sakulich, Aaron
    Assistant Professor, Dept. of Civil and Environmental Engineering, Worcester Polytechnic Institute, Worcester, MA

    Flynn, Daniel
    Research Associate, Energy and Environment Division, National Institute of Standards and Technology, Gaithersburg, MD

    Weiss, Jason
    Jack and Kay Hockema Professor of Civil Engineering, Director, Pankow Materials Laboratory, Lyles School of Civil Engineering, Purdue Univ., West Lafayette, IN


    Stock #: ACEM20130095

    ISSN: 2165-3984

    DOI: 10.1520/ACEM20130095

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    Title Measuring Freeze and Thaw Damage in Mortars Containing Deicing Salt Using a Low-Temperature Longitudinal Guarded Comparative Calorimeter and Acoustic Emission
    Symposium , 0000-00-00
    Committee C09