Tracing the Salt Crystallization Front in Limestone Using the DRMS

Abstract

Salt crystallization is widely recognised as one of the most damaging factors affecting stone monuments and buildings. The conservation of stone heritage suffering from weathering due to the presence of salts can be very expensive and laborious. Furthermore, the assessment of salt-laden buildings alone is often challenging and costly in its own right. This paper focuses on the use of a micro-destructive technique, the Drilling Resistance Measurement System (DRMS), to trace the salt crystallization front in natural building stone subjected to continuous partial immersion in a salt solution. The results provide strong evidence of the efficacy of micro-drilling to “map” the crystallization front. This is facilitated by increased resistances recorded during drilling in areas where pore clogging due to salt crystallization occurs. The experimental results are important for future research aiming to validate models relating rising damp to salt crystallization. The combination of DRMS and continuous partial immersion in salt solution laboratory tests may also be used to investigate the effect of water repellents and coatings/finishes on salt transport and crystallization in porous materials. Last but not least, the potential of the portable DRMS to trace the salt crystallization front in limestone may be used to detect cryptoflorescence in situ, on stone monuments, before it becomes damaging.