Indirect Evaluation on Frost Susceptibility on Clay Roofing Tiles

Abstract

Thirty one kinds of clay roofing tiles were prepared under different fabrication conditions, such as deairing pressure in extrusion, grain size of clay particle aggregates, raw clay and firing temperature. Fundamental data set of frost damage for indirect evaluation of frost susceptibility were obtained by direct freezing-thawing method which has been developed by Hudec for natural aggregates in concrete. Water absorption, saturation coefficient, apparent porosity, water adsorption, bending strength, capillary water saturation and several characteristic values from pore size distribution were employed as indirect evaluation factors for frost susceptibility. Indirect evaluation procedures were undertaken as follows. First, the multi-regression equation to achieve the maximum value of a poly-nominal multi-correlation coefficient among weight loss after 130 cycles of freezing-thawing (FT130) and several characteristic variables is derived. Second, the indirect evaluation values, “Frost Index” (“FINDX”) calculated from the multi-regression equation were compared. Considering the analysed results from the time and cost saving point of view, the following reliable equation for indirect evaluation of frost susceptibility for clay roofing tiles was suggested.“FINDX”=0.762×Ln(ADS45)+21.387×Ln(WABSB)-24.154×Ln(APPRS)+27.575 Moreover, the critical range of pore radius for frost damage of a clay roofing tile was suggested as 100-400nm from the correlation analysis between FT130 value and specific pore volume within a respective range of pore size.