Durability of Rock as Function of Grain Size, Pore Size, and Rate of Capillary Absorption of Water

Abstract

A series of experiments were performed to determine the relationship of grain and pore size to the capillary absorption of rock and the level to which water will naturally penetrate when the rock is exposed to it. As expected, the fine grained rocks showed the fastest rate and highest penetration of water and salt solution. Rates were found to be log-normally distributed—fast initial absorption, slower subsequent absorption. A correlation was found between rates of absorption and durability. High rate of absorption specimens were less durable during freezing and thawing than rocks with a low rate of absorption. All other conditions, such as mineralogy and environment, being constant, it is concluded that finer grained rocks, because of their more rapid water and salt solution intake, tend to deteriorate and weather faster than coarser grained equivalents. The results indicate the importance of grain size and pore size in assessment of the long term durability of rock when used as construction material.