Long-term evaluation of building envelope materials

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Sin, Dat M.

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The building envelope is arguably the most important aspect of a building besides its structure. It is the first line of defense against the environment and maintains comfortable humidity and air conditions. However, in contrast to structural components, the material specification and testing standards of the building envelope are less well defined, which leads to premature failure and costly maintenance. This thesis summarizes the research performed, the developed test, and the findings from ongoing research at the Durability Lab to evaluate the long-term performance of various building envelope materials.

Code requirements for tapes and self-adhered flashings are tabulated and compared with test results. It is determined that the adhesion requirements of these products are not well developed. In addition, the performance of tape products is also evaluated using shear adhesion testing. The study emphasizes the compatibility of the adhesives at a variety of temperature ranges.

Furthermore, materials testing of exterior plaster mixtures specified in ASTM C926 and common manufacturer's pre-blended mixtures is conducted. The study aims to determine the physical and mechanical properties of exterior plasters. The variability of the coefficient of thermal expansion is found to correspond to different moisture conditions. Several ACI (American Concrete Institute) models are also introduced to predict the tensile strength and modulus of elasticity of plaster mixtures using their compressive strength. An additional model is developed to better characterize the plaster modulus. Strong agreement between the test results and models is observed.

Finally, the report summarizes the results from large-scale tests performed on 32 clear penetrating water repellents, for which data were collected over three years. Prolonged exposure to UV radiation is found to have a significant impact on evaluation of the long-term durability of water repellents. The general behavior of "good" and "bad" products is also noted.

This research is part of an ongoing project at the University of Texas at Austin's Durability Lab. The Durability Lab was formed by Building Diagnostics, Inc. to study the durability of building components. It is located at the University of Texas at Austin on the J.J. Pickle Research Campus. Other ongoing testing, including water-resistive barrier mockups, stucco panels, and elastomeric sealants, is not included in this thesis.


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