Kinetics of Moisture Expansion in Fired Clay Ceramics: A(Time)1/4Law

Abstract

We report the results of experiments to estimate the moisture expansion of several modern and ancient clay brick ceramics from the time of manufacture. From these data we propose a new expansion law, in which the expansive strain increases as (age)(1/4) approximately. Such time dependence is consistent with a mechanism in which expansion arises from a diffusion-controlled rehydration reaction on a linear or low-dimension structure. Our results provide new guidance for the engineering design of masonry and suggest a possible new method for archaeological dating of ceramics.

Dating fired-clay ceramics using long-term power law rehydroxylation kinetics

“…also indications (Wilson et al 2003) that this relation holds over much longer time scales. We now exploit this t 1/4 power law to provide a method of determining the age of ceramic artefacts.…”

“…Laboratory-based dating of any material depends on identifying and measuring a physico-chemical property, which changes in a predictable way with time, thus providing the material with an internal clock (as in radiometric dating). It is established (Cole 1962;Wilson et al 2003) that the fired-clay ceramics produced in the manufacture of bricks, tiles and pottery gain mass and expand continuously from the time of firing as a result of chemical recombination with environmental moisture (here described as rehydroxylation). Furthermore, these ceramics can be returned to their initial as-fired condition by heating to a suitable high temperature.…”

“…• C. It is now established that the rate of rehydroxylation of ceramics is described by a (time) 1/4 power law (Wilson et al 2003). Two distinct stages are seen (Savage et al 2008) when ceramics, both in the freshly fired state and after reheating, react with environmental moisture.…”

Composition, Microstructure and RHX Dating of Romanesque Relief Ceramic Tiles

“…The RHX method has been presented [22][23] as a suitable mathematical model describing the rehydroxylation process which can be used to date ceramic artefacts. This method relies on the ability of the ceramic body containing unstable non-crystalline residues of clay minerals to rebind water in a two-step process of rehydration (1 st stage) and rehydroxylation (2 nd stage).…”

“…1/4 power law [22]. The principle of the rehydroxylation dating method is the determination of the initial mass of a sample, which is the sum of the sample mass after firing and the mass of water bonded to the structure of a ceramic artefact during its deposition.…”