Effect of moisture on tuff stone degradation

Tuff stone elements with a large length/width ratio often suffer damage in the form of cracks parallel to the surface and spalling of the outer layer. The response of tuff to moisture might be a reason for this behaviour. This research aimed at verifying if differential dilation between parts with different moisture content (as outer and inner part of partially encased mullion) can lead to damage. The effect of moisture on the degradation of Ettringen and Weibern tuff from the Eifel, Germany, has been investigated. A purpose-made weathering test was carried out to simulate the wetting-drying process. Despite no cracks developed during the test, existing cracks widened up and the flexural tensile strength of both materials decreased. The moisture transport properties their porosity and pore size of the stones were determined. Ettringen tuff has a considerable amount of very fine porosity, resulting in slow moisture transport and significant hygroscopic adsorption. Both tuff stones have an extreme hydric dilation. Environmental X-ray diffraction analyses showed that Ettringen tuff undergoes (reversible) mineralogic changes when subjected to RH cycles, whereas this does not occur for Weibern. The results support the hypothesis that moisture gradients in tuff elements may enhance decay in this stone.Heritage & Technolog

The volcanic foundation of Dutch architecture: Use of Rhenish tuff and trass in the Netherlands in the past two millennia

Occasionally, a profound but distant connection between volcano and culture exists. This is the case between the volcanic Eifel region in Germany and historic construction in the Netherlands, with the river Rhine as physical and enabling connection. Volcanic tuff from the Eifel comprises a significant amount of the building mass in Dutch built heritage. Tuffs from the Laacher See volcano have been imported and used during Roman occupation (hence called Römer tuff). It was the dominant dimension stone when construction in stone revived from the 10th century onwards, becoming the visual mark of Romanesque architecture in the Netherlands. Römer tuff gradually disappeared from the market from the 12th century onwards. Early 15th century, Weiberner tuff from the Riedener caldera, was introduced for fine sculptures and cladding; it disappears from use in about a century. Late 19th century, this tuff is reintroduced, both for restoration and for new buildings. In this period, Ettringer tuff, also from the Riedener caldera, is introduced for the first time. Ground Römer tuff (Rhenish trass) was used as a pozzolanic addition to lime mortars, enabling the hydraulic engineering works in masonry that facilitated life and economics in the Dutch delta for centuries.Heritage & Technolog

Historische mortels van de oude tijden tot de helft van de 19de eeuw

Heritage & Technolog

Oppervlaktebehandelingen: werkingsprincipe, afwegingen, voordelen en risico's

Heritage & Technolog

Preliminary results on corrosion products characterization in reinforced concrete subject to chloride-induced corrosion over more than 20 years

For reinforced concrete structures subject to chloride-induced corrosion, the assessment of service life at the design stage is often limited to the corrosion initiation phase, whereas in practice many structures are in the corrosion propagation phase. In these cases, for a proper assessment of the residual service life, it is necessary to better understand the processes leading to the detachment of the concrete cover, usually associated with the end of the service life, by studying the development of corrosion at the microscopic level over time. This note reports some preliminary results obtained during a research program aimed at characterising corrosion in reinforced concrete specimens cast in 1998, subjected to accelerated penetration of chlorides, and subjected to natural corrosion propagation over more than 20 years. Corrosion products and the steel-concrete interface were characterised through a combination of optical microscopy, SEM, Raman spectroscopy and computed tomography

Sloterhof, Amsterdam: Bouwhistorie, bouwtechnologie, bouwfysica en algehele bouwkundige staat

Old - Section Restoration, Re-use and RenovationOLD Heritage & Architectur

Oral, Nasal and Pharyngeal Exposure to Lipopolysaccharide Causes a Fetal Inflammatory Response in Sheep

BackgroundA fetal inflammatory response (FIR) in sheep can be induced by intraamniotic or selective exposure of the fetal lung or gut to lipopolysaccharide (LPS). The oral, nasal, and pharyngeal cavities (ONP) contain lymphoid tissue and epithelium that are in contact with the amniotic fluid. The ability of the ONP epithelium and lymphoid tissue to initiate a FIR is unknown.ObjectiveTo determine if FIR occurs after selective ONP exposure to LPS in fetal sheep.MethodsUsing fetal recovery surgery, we isolated ONP from the fetal lung, GI tract, and amniotic fluid by tracheal and esophageal ligation and with an occlusive glove fitted over the snout. LPS (5 mg) or saline was infused with 24 h Alzet pumps secured in the oral cavity (n = 7-8/group). Animals were delivered 1 or 6 days after initiation of the LPS or saline infusions.ResultsThe ONP exposure to LPS had time-dependent systemic inflammatory effects with changes in WBC in cord blood, an increase in posterior mediastinal lymph node weight at 6 days, and pro-inflammatory mRNA responses in the fetal plasma, lung, and liver. Compared to controls, the expression of surfactant protein A mRNA increased 1 and 6 days after ONP exposure to LPS.ConclusionONP exposure to LPS alone can induce a mild FIR with time-dependent inflammatory responses in remote fetal tissues not directly exposed to LPS