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Timothy Wangler received a BS in Chemical Engineering with a minor in Waste Management, from the New Mexico Institute of Mining and Technology (Socorro, New Mexico, USA) in May 2001, graduating with highest honors. He worked for Intel Corporation (Rio Rancho, New Mexico, USA) for three years before deciding to pursue a Ph.D. In September 2004, he entered the Ph.D. program at Princeton University (Princeton, New Jersey, USA) in the Department of Chemical Engineering. He received his Ph.D. in Chemical Engineering in June 2009, working for Professor George W. Scherer with the research topic of "Conservation of Clay-Bearing Sandstone: Understanding the Swelling and Damage Mechanisms." He is currently working as a postdoctoral researcher at ETH Zurich.


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Research Interests

Biocide Leaching from Building Facades

Biocides are often incorporated into the protective coatings of building facades to prevent functional and aesthetic damage caused by algal and fungal growth. These biocides can leach from the protective coating when contacted with water, which reduces the effectiveness of the biocide in protecting the coating and also allows the biocides to enter the environment at potentially harmful levels. The purpose of this research is to develop a better understanding of how the biocides enter the environment by determining the effects of environmental factors such as wind-driven rain as well as developing an understanding of the leaching mechanism itself.

Swelling Clays

Clay minerals are layered aluminosilicates that are present in many engineering problems such as tunnelling, borehole drilling, and foundation engineering. They are also present in sedimentary stones that are often used in decorative building facades or monuments of interest for conservation. In these stones, certain types of clays will swell upon wetting, leading to differential strains and stresses that can exceed the strength of the stone. This leads to damage that resembles buckling and surface delamination, which is expected to occur during a wetting cycle.

Clays swell due to hydration of cations that exist between negatively charged aluminosilicate layers, and occurs over two distinct ranges: short range, discrete intracrystalline swelling, and longer-range, continuous osmotic swelling. Research has shown that a,w alkyldiamines can substitute for the cations and inhibit swelling. Through a novel experimental approach combining X-ray diffraction and dilatometric methods, it can be shown that clays in certain sandstones swell only by intracrystalline swelling, and that the a, w alkyldiamines inhibit intracrystalline swelling by reducing the water layers between the clays by half. Based on these results, a Cu-coordination complex can be shown to be a more effective inhibitor of swelling. Additionally, the damage mechanism can be described as crack propagation due to uneven wetting patterns leading to eventual buckling.


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Publications & Presentations

  • T. Wangler, A. Stratulat, P. Duffus, J.H. Prévost, and G.W. Scherer. “Flaw Propagation and Buckling in Clay-Bearing Sandstones”, Env. Geo., accepted 2010.
  • T. Wangler and G.W. Scherer. “Clay Swelling Inhibition Mechanism of a,w Alkyldiamines in Portland Brownstone”, J. Mat. Res., 24 (5) 2009.
  • T. Wangler and G.W. Scherer. “Clay swelling mechanism in clay-bearing sandstones”, Env. Geo., 56 (3-4) 529-534 (2008).
  • P. Duffus, T. Wangler, and G.W. Scherer. “Swelling damage mechanism for clay-bearing sandstones”, Proc. 11th International Congress on Deterioration and Conservation of Stone, Nicolaus Copernicus University Press, Torun, Poland, 2008.
  • T. Wangler and G.W. Scherer: “Controlling swelling of Portland Brownstone”, in Materials Issues in Art and Archaeology VIII, edited by Pamela B. Vandiver, Blythe McCarthy, Robert H. Tykot, Jose Luis Ruvalcaba-Sil, Francesca Casadio (Mater. Res. Soc. Symp. Proc. Volume 1047, Warrendale, PA, 2008), 1047-Y05-03.
  • T. Wangler, P. Duffus, and G.W. Scherer. “Hygric swelling of clays in sandstones”, Presented at 7th International Symposium on the Conservation of Monuments in the Mediterranean Basin, Orléans, France, 2007.
  • T. Wangler, A. Wylykanowitz, and G.W. Scherer. “Controlling stress from swelling clay”, pp. 703-708 in Measuring, Monitoring and Modeling Concrete Properties, ed. M.S. Konsta-Gdoutos (Springer, Dordrecht, The Netherlands, 2006).

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