Moisture impact on building rocks - the laboratory and in situ investigations FIDRÍKOVÁ D., KUBIČÁR Ľ. Institute of Physics SAS, Bratislava, Slovakia The work was supported by the project APVV LPP–0442–09 Principle of Hot-ball method: A heat source in the form of ball delivers constant heat flux for t > 0 to the medium and simultaneously the ball surface temperature is measured. Heat flux is in the form of a step-wise function. The stabilized value of temperature Tm is measure and from the parameters of the temperature response the thermophysical parameters can be calculated, according to the model used. Goal: Rocks are influenced by moisture that in combination with temperature, hydrological conditions, climatic conditions, etc. leads to changes of physical and chemical properties. These changes can be observed in the laboratory, where different conditions can be simulated in which the rocks can be found. This work is focused on water transport and moisture determination in various sandstones observed in laboratory conditions and also directly in environment. Porosity affects transport properties of rocks. Experiments are focused on the mechanism distributing the water in sandstones with different porosities. Measurements were carried out by thermal conductivity sensors (Hot-ball sensor) which measure local temperature and local thermal conductivity. The sensor in connection with the RTM device is used for monitoring of the moisture in various sandstones with different porosity. For in situ measurements a moisture sensor is constructed. The sensor is made of the original stone in a form of the cylinder (diameter and length around 20 mm) in which thermal conductivity sensor is placed. The moisture sensor must be calibrated for dry and water saturated state, and then it is inserted into the original site to start monitoring of the impact of surrounding weather conditions on the rock. Meteorological data are correlated to the measured data. Results from water transport and change of moisture in sandstones at various monitoring conditions are presented. Working relation: t → ∞, T = T m at r = r b Working regime: steady state The laboratory The laboratory monitoring of moisture In situ In situ monitoring of moisture in St. Jacob Church in Levoča, Slovakia Initial and boundary conditions: q = const, t > 0, r = r b rbrb R Thermal conductivity sensor (Hot-ball sensor) approximation Temperature function: Ground water Rain Frost water diffusion capillary transport CONCLUSIONS: Hot-ball sensor (thermal conductivity sensor) allows investigation of processes running in pores that depend on various conditions The structure of porous materials the most affects moisture transport in samples Moisture monitoring in porous stones gives a information about deterioration of building and other industrial objects Change of material stability in laboratory by cycles freezing-thawing, moisture-drying can be studied By cycles of temperature and humidity we are able to simulate behaviour of material in laboratory devices By means of above described cycles we are able to predict behavior in material during day-night, summer-winter and in dry-wet enviroment Hot-Ball method is advantageous for continuous monitoring changes of moisture in rock massive and in historical monuments and for other applications (monitoring of concrete setting, monitoring of polymerization, monitoring of structure transformation in pores, material ageing) gradually saturation integral moisture local moisture capillary transport Mechanism sustaining a constant water level Other monitoring by Hot-ball probe:  Spis Castle  St. Martin's Cathedral in Bratislava, Slovakia  Pravčicka gate in Czech republic Moisture impact to building rocks: Moisture affects the life of building materials and reduced the weathering resistance, so it´s very important to determine of water content in a material in dependence on surrounding conditions Moisture goes into the material: by capillary transport by water diffusion freezing the wall