SYMPOSIA PAPER Published: 26 November 2021

Evaluating the Potential for Limestone Discoloration Using Accelerated Weathering Testing and Petrography


As part of an evaluation of two types of limestone as candidates for the replacement of limestone tablets at a historic cemetery, we conducted accelerated weathering testing to determine whether the color of limestone samples would change perceptibly after cyclic exposure to moisture and ultraviolet (UV) light. Although there is no ASTM standard for accelerated weathering testing of stone specifically, we followed the general guidelines and operating procedures for accelerated weathering testers provided by ASTM G151, and ASTM G154, in developing our testing protocol. After every 10 cycles of testing, we documented the test specimens on a flatbed scanner with a photographic color reference in each scan to verify color accuracy and consistency in the images. After the completion of testing after 1,008 total hours, we used color sampling and measurement tools in photographic editing software to quantify differences in the L*a*b* color values of reference areas on images collected before the start of testing (zero cycles) and images collected at the end of testing (84 cycles). The accelerated weathering testing generally produced only slight changes in the color of the stones, but quantitative measurements of color differences and calculations of total color difference based on changes in L*a*b* values confirmed the color of one of the types of limestone changed more than that of the other. Although the results of laboratory-based accelerated testing cannot be extrapolated to weathering within defined time frames in outdoor environments, our findings show that perceptible and measurable changes in the overall color of the evaluated limestone types could occur as a result of exposure to high levels of solar UV radiation and moisture at elevated temperatures. Our petrographic examination of the accelerated weathering specimens suggested two potential causes for the observed color changes, both involving mobilization of iron-bearing compounds in the limestone samples.

Author Information

Carter, Sidney, W.
Simpson Gumpertz & Heger, Waltham, MA, US
Williams, Taryn, N.
Simpson Gumpertz & Heger, Washington, DC, US
Searls, Carolyn, L.
Simpson Gumpertz & Heger, Oakland, CA, US
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Pages: 159–184
DOI: 10.1520/STP162820190169
ISBN-EB: 978-0-8031-7703-1
ISBN-13: 978-0-8031-7702-4