Onsite testing of ammonium oxalate treatment applied to historical salt-infested limestone

Abstract

Ammonium oxalate treatment, previously extensively studied on limestone in the laboratory, was applied to powdering historical stonework (limestone) situated on the shoreline in the Mediterranean Island of Malta. This paper presents the results obtained from onsite testing that aimed at evaluating the treatment in terms of its aesthetic performance, the depth of treatment, the mechanical properties of the consolidated stone and the influence on water transport. To this end, the testing program included colorimetry, DRMS (drilling resistance measurement system) and water absorption through the contact sponge method. This study is Part One of the final phase of a wider research program which included two previous phases progressing from treating this same very porous stone type in a laboratory-based controlled environment to uncontrolled site conditions, seeking to quantify this treatment’s effectiveness in the field. Results showed that onsite consolidation was achieved and that although some changes in colour and water absorption were brought about by the treatment, these were within acceptable tolerance limits. Besides carrying out these treatments and evaluations directly on the coast, this study anticipates further studies which will look at rural and urban sites where the types and concentrations of salts are expected to be different.