An Assessment and Evaluation of Acidic Cleaning Methods on Unglazed Terracotta Using Accelerated Weathering Test Protocols

According to the published literature, there has been very little quantitative evaluation of the short or long-term effects of cleaning terra cotta, other than visual assessment where success is pronounced by the degree of soiling removed. Very little work (only 3% of our literature review) has attempted to measure the effects on terra cotta of various cleaning methods. Nevertheless, today, still 80% of terracotta cleaning relies on chemical products, the majority acid-based. This research evaluates the effects of acidic cleaners on unglazed terracotta to verify the potential for damage by accelerated weathering testing. This investigation continues previous studies (Matero et. al. 1996) where findings showed that by using hydrofluoric acid-based commercial cleaning system, an increased porosity of unglazed terra cotta resulted. The questions remains whether this physical alteration will lead to accelerated weathering and material damage. In the first phase of this research a Literature Review of past and current cleaning of terra cotta was completed, together with a survey of professionals involved in terra cotta restoration. In the second phase, two commercial chemical cleaners are being tested in two applications on new unglazed red and tan terracotta samples: Prosoco Heavy Duty Restoration cleaner based on HF (1:3), and Prosoco Enviro Klean based on Ammonium Bi-fluoride (generally applied as a concentrate). These are now undergoing accelerated weathering based on the Rilem salt test (V.1B) and a QUV weatherometer (ASTM G154-12) to access the effects of acid cleaning on performance. Several methods of assessment were used to evaluate the tiles before and after testing: optical microscopy, scanning electron microscopy, porosity by liquid nitrogen immersion, color change, and texture mapping imaging. By examining physical changes and their response to accelerated weathering across two typical terra cotta clay bodies, it is hoped that better cleaning methods will be considered in practice and parameters to measure potential damage as well as cleaning efficacy become established

Integrated 3D Mapping and Diagnosis for the Structural Assessment of Architectural Heritage: Morano’s Parabolic Arch

: The architectural heritage of the 20th century is affected by several conservation problems in terms of material preservation, structural analysis, and reuse. Among these, material degradation and durability issues are the ones that have the most effect on the health state and, consequently, the survival of the constructions of the period. In order to conduct a proper analysis for preservation purposes, an interdisciplinary approach is necessary. The parabolic arch in Morano sul Po (Italy) is a reinforced concrete landmark in the Casale Monferrato area and is related to the industrial vocation of the territory, which is indissolubly linked to the cement production chain. The present paper reports the results of a non-destructive test campaign by a Politecnico di Torino multidisciplinary group, which combined acquisitions using different methods. The paper highlights the importance of a structured procedure to integrate different information coming from different techniques. The aim was to assess the health state of the structure and define the best procedures for building an information system based on the as-built modeling strategy, which could serve as the basis to provide conservation guidelines

ASR: Practical investigative techniques and field monitoring systems used to assess ASR for service life modeling.

Alkali Silica Reaction (ASR) is a common deterioration mechanism affecting many concrete structures of any type and age. Initially identified more than 60 years ago (Stanton, 1930), this mechanism is based on the chemical reactions between certain siliceous minerals present in the aggregate and the alkalinity of the concrete in the presence of moisture (internal RH). While certain deterioration patterns are clearly associated with ASR, such as gel exudation, aggregate expansion, and characteristic cracking, the material degradation can often be misdiagnosed to the untrained eye. In addition, certain elements of a structure can be severely affected while neighboring elements of the same batch/ mix design do not bear signs of deterioration or impact. Thus far, in situ field monitoring of ASR affected structures is related to moisture measurements, electrical resistivity, expansion, service life models are based on fracture mechanics of the aggregate. The impact to the concrete is loss of integrity, decreased compressive strength, shear and tensile strength. Some observed structures have split, with such force, that the concrete structure had cracks greater than 25mm where steel retention bands have split. The authors of this paper were engaged in two instances to provide service life assessments for ‘corrosion related degradation’ on ASR affected structures. In all instances the elements which were assessed were structural, load bearing elements, which if failed could pose a significant risk to owner, user, or end recipient. The need to develop an assessment technique for monitoring and service life assessments which are practical and efficient is being developed. The paper will discuss the development of the approach, from visual indicators identifying condition hierarchies, to long term condition monitoring for various concrete parameters combined with laboratory testing (expansion and residual alkalis) and mathematical modeling. Three case studies will be presented to illustrate conditions and process

A novel approach to in-depth façade assessments: Improved corrosion test methods for embedded steel framing in historic masonry clad buildings

Corrosion of structural steel frames and associated steel assemblies within ‘vintage’ buildings circa 1880s to 1930s pose a health and safety risk to the public in major urban centers. The projecting masonry elements pose a particular concern when the underlying steel assemblies and anchorage begin to corrode. Failed masonry has fallen from buildings, leading to death in worst case scenarios. While some signs of masonry cracking or displacement are usually visible prior to failure, the level of degradation of the embedded steel is not. With the equipment available to test these unforeseen conditions, methodologies need to be shifted to understand unobservable conditions to assist in condition state ratings of embedded steel. In many cities, building owners are being faced with large expenditures to strip and replace terra cotta or stone elements where the underlying steel is in fair condition. This paper will discuss the field-testing programs where a building elevations' masonry clad, steel assemblies (outriggers, anchorage and cross bracing) were evaluated for corrosion. The testing program assessed various steel components which either projected from the structure or were embedded at great depth with a bespoke, in-depth advanced testing program geared towards the development of condition state ratings for the façade elements

Petrology of Late Jurassic-Early Cretaceous Tusaquillas and Abra Laite-Aguilar plutonic complexes (Central Andes, 23°05’S - 66°05’W): A comparison with Rift related magmatism of NW Argentina and e Bolivia

The Late Jurassic-Early Cretaceous Tusaquillas and the Abra Laite-Aguilar Plutonic Complexes represent the most extensive intrusive bodies belonging to the rift-related magmatism developed in NW Argentina from Upper Jurassic to Lower Eocene. Both complexes are characterized by rocks of a wide compositional spectrum, ranging from gabbro and diorite to syenogranite and monzogranite. Geochemical and isotopic data obtained on from samples of the two complexes allowed to distinguish rocks with: 1) basic composition (SiO2=45-52 wt%), low HFSE and REE contents, low initial 87Sr/86Sr ratio (R0=0.703198-0.705868) and high ε t Nd (3.82 to 1.51); 2) felsic compositions (SiO2=70-77 wt%, low HFSE and REE, high R0 (0.708677-0.722668) and low ε t Nd (-3.85 to -1.77); 3) intermediate features, i.e. SiO2=53-69 wt%, R0=0.703303-0.713121, ε t Nd 2.10 to -4.97. On the whole, the data suggest that the basic rocks could have been derived from a mantle source with OIB-like signature, whereas the granitic rocks could have been generated by partial melting of a radiogenic crust. Geochemical and isotopic characteristics of intermediate rocks suggest complex interactions (FC, AFC and mixing processes) between mantle derived magmas and crustal materials. In order to have a more complete scenario of the magmatic events which affected the south-central part of South America in the Jurassic-Cretaceous times, the Tusaquillas and the Abra Laite-Aguilar Plutonic Complexes have been compared with coeval NW Argentina (Rangel and Hornillos) and E Bolivia (Velasco) magmatic provinces. In view of the comparative data, we tentatively propose that the E Bolivia and NW Argentina magmatic provinces could be related to the same regional petrogenetic event, probably linked with the extensional tectonics that affected the western Gondwana at pre-drift times.Fil: Cristiani, C.. Università degli Studi di Pisa. Dipartimento di Scienze della Terra; ItaliaFil: Matteini, Massimo. Universidad Nacional de Salta. Facultad de Ciencias Naturales; ArgentinaFil: Mazzuoli, R.. Università degli Studi di Pisa. Dipartimento di Scienze della Terra; ItaliaFil: Omarini, Ricardo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta; Argentina. Universidad Nacional de Salta. Facultad de Ciencias Naturales; ArgentinaFil: Villa, Irene María. Universität Earl; Suiz

Direct growth of nanotubes and graphene nanoflowers on electrochemical platinum electrodes

Multi-walled carbon nanotubes and graphene nanoflowers were grown by a catalytic chemical vapor deposition process on metal surfaces. Electrodeposition was used as a versatile technique to obtain three different iron catalyst coatings on platinum microelectrodes. The influence of growth parameters on carbon deposits was investigated. Characterization was carried out by scanning electron microscopy and Raman spectroscopy. A chemical treatment in sulphuric acid produced an increased voltammetric background current. In Raman spectra, the effect of the chemical treatment is seen as a more pronounced sp3 hybridisation mode of C resulting from surface functionalization of the C nanomaterials. Overall, the hybrid electrodes we produced exhibit a promising performance for oxidase-based array biosensors. Therefore, our study opens the possibility of integrating the hybrid electrodes in biochip applications

High-Performance Multipanel Biosensors Based on a Selective Integration of Nanographite Petals

We report the first selective growth of nanographite petals and various carbon nanomaterials onto a multipanel electrochemical platform. Different types of nanomaterials can be obtained by fine-tuning the growth parameters of the chemical vapor deposition (CVD) process. First, absolute novelty is the catalytic CVD selective growth of different carbon nanomaterials only on the working electrodes of the platform. A second novelty is the growth obtained at complementary metal–oxide–semiconductor compatible temperatures. These novel electrodes have been incorporated in sensors in which performance characteristics improve with the content of nanostructures. Unprecedented sensing parameters with respect to both direct and enzyme-mediated electrochemical biodetection have been obtained