Pore Properties as Indicators of Breakdown Processes in
Experimentally Weathered Limestones

Dawn T. Nicholson

The results are reported of four experimental weathering tests: freeze-thaw, wetting and drying, slake durability and salt weathering, on five different types of limestone. Effective porosity, mercury intrusion porosimetry and SEM were used to evaluate changes in pore properties, while weight loss and fracture density were used to assess deterioration severity. A primary aim was to observe modifications in porosity due to weathering and to draw inferences about the internal rock deterioration mechanisms taking place.

It is concluded that the five limestones not only show a wide range of resistance to weathering in general but considerable difference in resistance to particular weathering processes. Consequently, when assessing durability it is essential to consider rock properties in the context of the weathering process to which the rock is subject. The type of deterioration indicator used is also important in interpretation of durability.

A variety of pore modification mechanisms operate, including changes in pore connectivity, pore infilling, and the introduction of additional void space. There are indications that changes to the internal pore structure of rocks due to weathering may be a pre-cursor to more substantial macro-deterioration.

Keywords: Porosity, limestone, weathering, breakdown mechanisms, durability