The influence of the pore structure on the moisture transport in lime plaster-brick systems as studied by NMR

This paper presents an experimental analysis of the porous structure and drying kinetics of lime-based plasters and plaster-brick systems using different methods. The effect of adding a water-repellent admixture (linseed oil) to the plasters was also evaluated. Nuclear Magnetic Resonance (NMR) was used to measure moisture profiles during drying of mono-material plaster specimens and of specimens constituted by the same plasters applied on fired-clay brick. NMR transverse relaxation time was used to examine the pore water distribution. The NMR moisture profiles showed that the drying behaviour of the water-repellent mono-plasters differs slightly from the reference, but when applied on brick, it significantly hinders the drying of the substrate. The results indicated that the addition of linseed oil to the lime plaster has negatively influenced the bonding process and created an hydraulic resistivity for the moisture to flow from the brick to the plaster during drying. This phenomena was mainly atributed to three factors: i) hydrophobization of part of the mortar pores; ii) the development of air bubbles related to entrained air during the mixing process; and iii) the mismatch between the physical-chemical properties of both systems, namely the different pore network and surface energy, which seems to affect the interpenetration of both porous layers.</p

Effectiveness and Compatibility of a Novel Sustainable Method for Stone Consolidation Based on Di-Ammonium Phosphate and Calcium-Based Nanomaterials

External surfaces of stones used in historic buildings often carry high artistic value and need to be preserved from the damages of time, especially from the detrimental effects of the weathering. This study aimed to test the effectiveness and compatibility of some new environmentally-friendly materials for stone consolidation, as the use thereof has been so far poorly investigated. The treatments were based on combinations of an aqueous solution of di-ammonium phosphate (DAP) and two calcium-based nanomaterials, namely a commercial nanosuspension of Ca(OH)2 and a novel nanosuspension of calcite. The treatments were applied to samples of two porous stones: a limestone and a sandstone. The effectiveness of the treatments was assessed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, ultrasound pulse velocity test, colour measurements, and capillary water absorption test. The results suggest that the combined use of DAP and Ca-based nanosuspensions can be advantageous over other commonly used consolidants in terms of retreatability and physical-chemical compatibility with the stone. Some limitations are also highlighted, such as the uneven distribution and low penetration of the consolidants

Sources of salts, their transport and action in masonry

Článek shrnuje základní informace o zdrojích solí a jejich chování ve zdivu s cílem posunout znalosti účastníků semináře o chování solí ve zdivu i o možnostech snižování vyvolaných škod

Microscopic analyses of sgraffito sampled from house façade in Brno, Venhudova street, CR

Report presents results of microscopic characterization of sgraffito from the the fifties of the twentieth century sampled from house façade in Brno, Venhudova street, CR. Light (optical) microscopy and electron microscopy SEM-EDS were used for characterization of the aggregate and the binder of two layers of sgraffito

Survey of salinity of masonry under III. courtyard at Prague Castle

Archaeological architectural monuments in the area under III. in the courtyard of Prague Castle were monitored in 2021 in terms of the extent of salt efflorescences and their chemical composition. Salt efflorescence on the marlstone walls of the church of St. Bartholomew contain sodium carbonate and bicarbonate, sodium sulfate and calcium sulfate. Sodium nitrate and potassium nitrate were also present in some samples. The aim of the research is to propose measures to mitigate the effect of salts on the degradation of historic masonry

Characterization of historical plasters sampled from town house in Cheb, CR

Report presents results of material characterization of historic plasters from townhouse in Cheb, CR. Thermal and SEM-EDS analyses were used to characterize the aggregate, the binder and painting layers on two samples of plasters

Chemical and mineralogical analyses of stone sampled from Troja Castle, baroque staircase, Prague 7

Chemical and mineralogical analyses of stone sampled from Troja Castle, baroque staircase, Prague 7

Design of a new mortar based on lime modified with pozzolanic materials for the repair of an historical exterior plaster floor at Karlštejn castle

The result of the report is an assessment of key characteristics (mechanical properties, absorbtion, porosity, resistance to frost) of samples taken from a mortar applied on exterior plaster floor at Karlštejn Castle as a trial test performed in 2006. The results of performed tests and a recommendation for a next conservation strategy is presented

Report of characteristics of the brick sample from the façade of the apartment building

The report brings characteristics of the brick sampled from the brick façade of the apartment building in Prague 4. Porosity, saturated water content, water absorption behaviour, water soluble salts content were determined to characterize the brick and then the effectivity of the surface protective treatment applied on the brick façade was assessed