Weathering potential of wetting and drying of sandstone and basalt : a laboratory isolation study

• Main Author: Loubser, M.J. (Michael John)
• Other Authors: Sumner, P.D. (Paul)
• Format: Doctoral or Postdoctoral Thesis
• Language: unknown
• Published: University of Pretoria 2013
• Subjects: Sandstone and basalt; Cyclic wetting and drying of a rock; UCTD; Marion Island
• Online Access: http://hdl.handle.net/2263/29251; http://upetd.up.ac.za/thesis/available/etd-11052010-142738/

The cyclic wetting and drying of a rock is considered to be one of a number of physical weathering processes that have an effect on the weathering of rock. While the presence of moisture is known to be of critical importance for the activation and enhancement of a number of other known weathering processes, such as cryogenic weathering, salt weathering and slaking it is possible that the mere cyclic application and removal of moisture over time may also have an effect on the physical structure of a rock. The precise nature of the process is not well understood, however. This document begins by investigating the studies that have previously been undertaken to determine how the wetting and drying weathering process is defined and to ascertain the current state of knowledge regarding this process. After an establishment of background context, a physical experiment is carried out on Clarens Formation sandstone and Marion Island basalt to note the relationship between cyclic wetting and drying and the changing physical properties of the rocks. The rocks were subjected to 105 wetting and drying cycles over a period of 21 weeks. At the beginning of the experiment, physical rock properties were measured by way of the method laid out by Cooke (1979) and again at the end of the experiment. Since the experiment was carried out under static environmental conditions, the comparison of physical rock properties gives a good indication of how the rocks have altered their structure over the experimental time period. The results obtained in this experiment show that different rock types will change in different ways when exposed to a common weathering process. The basalt samples experienced no mass loss at, while the sandstones did. The sandstones, which are rocks that are of common lithology and of very similar physical and chemical structure reacted to the wetting and drying weathering process in ways that could not be predicted without experimentation. The data does show a clear causal link between the application of external ...