The natural weathering of an artificially induced calcium oxalate patina on soft limestone

Abstract

This paper focuses on the effects of natural weathering on Globigerina Limestone (Malta) which was treated with ammonium oxalate to produce a calcium oxalate surface layer. This study includes the first two phases of a larger research programme. Laboratory samples were considered first. These were treated and tested in a controlled environment (Phase 1). Identical samples sets were prepared for Phase 2. These were treated in situ and exposed to site conditions for the period of one year. In an attempt to simulate site conditions, for both Phase 1 and Phase 2 samples, the limestone was contaminated with soluble salts before treatment took place. These included three separate types; sodium chloride, sodium sulfate and sodium nitrate. Desalinated samples were also included in the study. Scanning Electron Microscopy (SEM) was carried out on the Phase 1 samples while Drilling Resistance Measurement System (DRMS) was carried out on the samples of both phases. This paper focuses on the results from the SEM and correlates these with those results from the DRMS in light of the influence of natural weathering on an artificial calcium oxalate layer, induced in the presence of soluble salts.