Use of TDR to Compare Rising Damp in Three Tuff Walls Made with Different Mortars

Abstract

Capillary rise is a serious phenomenon that may have potentially devastating consequences within buildings (biological corrosion, worsening of indoor comfort parameters, worsening of thermal resistance, etc.). Therefore, measuring moisture in building structures is still a current research issue and time domain reflectometry (TDR) is considered one of the most-effective nondestructive methods for moisture estimation in porous media. This paper reports a research examining the effects of different kinds of mortar on the capillary rise in yellow volcanic tuff walls. To this aim, three model walls were built with tuff and three different kinds of mortar (a traditional cement lime mortar and two premixed mortars, one of which was specifically designed to prevent capillary rise), and then instrumented with TDR probes, to carry out continuous monitoring of volumetric water content without the need of sampling or material destruction. Preliminarily, the calibration relationship linking relative dielectric permittivity, provided by TDR measurement, with volumetric water content, measured gravimetrically, has been experimentally determined in laboratory with yellow tuff specimens. The obtained results suggest that TDR can be suitable to reliable in situ monitoring of moisture dynamics in tuff walls in a nondestructive way. The velocity and height of capillary rise resulted strongly affected by the adopted type of mortar. In particular, the wall made with simple premixed mortar was characterized by the highest water absorptivity, whereas the one made with the specific antirise mortar showed the lowest moisture increase. The obtained results also allowed a physical interpretation of the behavior of water uptake related to the different types of mortars.