A Durability Classification of Clay-Bearing Rocks Based on Particle Size Distribution of Slaked Material

Abstract

Clay-bearing rocks disintegrate at varying rates, due to slaking, when exposed to moisture. This research aims to develop a durability classification of clay-bearing rocks based on particle size distribution of slaked material, quantified in terms of disintegration ratio (D R ). D R is the ratio of the area under the particle size distribution curve of slaked material for a sample, upon completion of the standardized slake durability index test, to the total area encompassing all particle size distribution curves of the samples tested. Although second-cycle slake durability index (Id 2 ) is the most frequently used parameter for classifying the slaking behavior of clay-bearing rocks, it does not consider the range of particle sizes in the slaked material after the test. Compared to Id 2 , D R accounts for all particle sizes present in the slaked material and provides a better measure of the degree of slaking. The slake durability index test was used to investigate the slaking behavior of samples from 20 different clay-bearing rocks, and Id 2 and D R values were determined for all samples. Id 2 showed a nonlinear relationship with D R . The relationship was used to develop a durability classification, based on disintegration ratio, as follows: low durability: D R = 0 to 0.20; medium durability: D R = 0.20 to 0.65; medium-high durability: D R = 0.65 to 0.85; and high durability: D R = 0.85 to 1.00. In order to use this classification, one needs to perform a sieve analysis on material left after the slake durability test and determine D R .