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Abstract
A mathematical model upon the theory of total cumulative damage has been developed to describe the kinetics of thermal aging in roofing material subjected to changing temperatures and durations. The new model employs a degradation rate function that is derived from a chemical model using a diffusion theory coupled with Arrhenius rate function to desribe the temperature dependency of asphalt chemical composition under transiet conditions. Such a model enable the construction of master curves in asphalt composition as aged as various temperatures, and may be used to predict the change in property due to heat aging using known roof temperature profile and materials parameters obtained from lab accelerated testing. Examples of the model are demonstrated bu using the real-time roof temperature data collected from test houses located in a cold climate of Minnesota and in a hot climate of Florida. The calculations suggest that the high thermal history in a hot climate has a strong effect has a strong effect in accelerating aging of asphalt, particularly during the winter months. Furthermore, the effect of attic ventilation is found to reduce the uneven distribution of total cumulative damage across the roof deck due to unbalanced thermal history found in an unventilated deck. The potential applciation of the model and its advantage in predicting field properties by simulation are also discussed.
A mathematical model upon the theory of total cumulative damage has been developed to describe the kinetics of thermal aging in roofing material subjected to changing temperatures and durations. The new model employs a degradation rate function that is derived from a chemical model using a diffusion theory coupled with Arrhenius rate function to desribe the temperature dependency of asphalt chemical composition under transiet conditions. Such a model enable the construction of master curves in asphalt composition as aged as various temperatures, and may be used to predict the change in property due to heat aging using known roof temperature profile and materials parameters obtained from lab accelerated testing. Examples of the model are demonstrated bu using the real-time roof temperature data collected from test houses located in a cold climate of Minnesota and in a hot climate of Florida. The calculations suggest that the high thermal history in a hot climate has a strong effect has a strong effect in accelerating aging of asphalt, particularly during the winter months. Furthermore, the effect of attic ventilation is found to reduce the uneven distribution of total cumulative damage across the roof deck due to unbalanced thermal history found in an unventilated deck. The potential applciation of the model and its advantage in predicting field properties by simulation are also discussed.
Date
8/2003
8/2003
Author(s)
M Shiao; D Nester; L Terrenzio
M Shiao; D Nester; L Terrenzio
Page(s)
119-136
119-136
Keyword(s)
aging; kenetics; asphalt shingle; cumulative damage; thermal load; ventilation; accelerated test; temperature effect
aging; kenetics; asphalt shingle; cumulative damage; thermal load; ventilation; accelerated test; temperature effect