Experimental definition of microclimatic conditions based on water transfer and porous media properties for the conservation of prehistoric constructions: Cueva Pintada at Galdar, Gran Canaria, Spain

Abstract

Microclimatic parameters and natural materials were studied in order to assess conservation of the cave complex at Galdar, Gran Canaria. Based on the microclimatic data, experimental simulations were carried out to quantify water retention capacity and water vapour transport kinetics under continuously changing extreme temperatures and relative humidity values. The behaviour of natural construction materials is greatly influenced by changes in thermo-hygrometric conditions and is linked to pore structure. The host rock has a complex porous media: high porosity and polymodal pore size distribution, where the smallest pores contribute to water condensation, whilst large pores lead to high water absorption rates. The axial compressive strength of the host-rock decreases between 30 and 70% at water saturation. Stuccos covering cave wall paintings are formed by clay minerals, mainly smectites. These clay minerals cover a large specific surface area, which leads to a high capacity for water condensation and retention. It is also shown that neither water condensation nor vapour transport are noticeably modified by the presence of stucco on the host-rock when rapid, highly variable changes occur in environmental conditions if large shrinkage cracks are present. Results show that safe threshold microclimatic conditions can be found below 75% RH in the natural temperature range and that slight variations in temperature and relative humidity do not modify durability properties.

The Influence of the Type of Lime on the Hygric Behaviour and Bio-Receptivity of Hemp Lime Composites Used for Rendering Applications in Sustainable New Construction and Repair Works

“…This might indicate that the presence of hemp does not significantly improve the transpirability of the material, as expected. However, the mortars studied in Arizzi and Cultrone’s work [ 22 ] developed shrinkage fissures that are known to increase the water vapour diffusion within the mortar [ 27 ]. This suggests that the K v values of the same mortars without shrinkage fissures should be lower than those of the lightweight hemp lime composites studied here, which did not suffer shrinkage.…”

The imprint of thermally induced devolatilization phenomena on radon signal: implications for the geochemical survey in volcanic areas

“…This is also qualitatively evidenced by the onset of H 2 O condensation in the Teflon tube and gas-drying unit of the experimental setup. Notably, the mean vapour-adsorption curve obtained for tuff rocks indicates that the amount of adsorbed H 2 O increases significantly at a relative humidity of about 70-75% (Benavente et al 2009). The exponential growth rate of vapour adsorption is related to an increase in H 2 O film on the surface layer of rock pores and the beginning of capillarity H 2 O condensation (Papachristodoulou et al 2007;Prasad et al 2012;Fernandez-Cortes et al 2013).…”

Characterization of trace gases' fluctuations on a ‘low energy’ cave (Castañar de Íbor, Spain) using techniques of entropy of curves

“…In order to characterise the porous media of the host rock, mercury intrusion porosimetry (MIP) and helium picknometry techniques were carried out using the Applied Petrology Lab facilities (University of Alicante). A detailed description of these analytical techniques and procedures has been provided by Benavente et al (2009). From MIP, the connected porosity and pore size distribution were all obtained using an Autopore IV 9500 Micrometrics mercury porosimeter.…”