Monitoring moisture levels in stone masonry using Duff gauge sensors

Monitoring the moisture and temperature levels inside building envelopes of masonry structures is important to ensure their safe and long lasting performance. The presence of moisture within cavities can lead to frost damage and mould growth. Eventually, moisture in the envelope degrades the strength and integrity of a masonry structure. Monitoring moisture and temperature in masonry structures is greatly hampered by the lack of a simple and cost effective technique. Moreover, preservation guidelines for heritage masonry structures do not permit alteration of the original exterior appearance and texture. Thus, monitoring such structures is a complex task. One option for monitoring moisture and temperature is to use Duff gauge sensors with incorporated thermistors. Duff gauge sensors have been found to be reliable in monitoring moisture and temperature levels in brick masonry. These sensors were installed in masonry stones and moisture and temperature monitored while the stones were exposed to freeze-thaw cycles in both dry and wet conditions. Various types of anchors and anchor systems were installed in the stones in order to study their impact on the properties of the stones. Conventional Canadian masonry stones (e.g. St. Canut and Ohio sandstone, and limestone) were included in this study. A wireless data acquisition system facilitated real-time remote health monitoring of the test specimens. The data obtained will enhance our understanding of the impact of the various anchors on the performance of stone masonry.