Papers by Keyword: Weathering

Abstract: Roofing slate is a traditional natural material for roofing and other construction applications in various types of buildings. The paper deals with both traditional methods of mineralogical-petrographic analysis as well as completely new methods (X-ray CT) rendering fast and reliable determination of qualitative parameters and potential slate durability in building constructions. A mutual combination of the methods represents a rapid, effective and modern alternative to lengthy laboratory tests to determine physical-mechanical properties of newly used roofing, especially in historical buildings.

Abstract: A special software simulating changes to wood due to various processes (either treatment or degradation) has been developed within the SWORFISH (Superb Wood Surface Finishing) project. The definition of the material modifications due to processes is based on the expert knowledge and/or experimental data. The dedicated algorithm simulates material modifications (with a special focus on surface) taking into account original material characteristics (evaluated by means of NDT techniques) and setting of process parameters. In this way, it is possible to analyze the sequence of processes (i.e. material modifications) and to estimate properties of the resulting product. Two case studies are presented for illustration of the potential uses of the SWORFISH approach in the field of timber structures.

Abstract: Fracturing is the most limiting factor in the extraction of large blocks of granite for gang saw processing and should be carefully studied in the exploration stage. This paper presents the results of the fracturing evaluation of the granite from the quarries of Mondim de Basto, located in the north of Portugal. This very weathered granite has a high market demand and its commercial value is controlled by its yellowish brown colour. The fracturing was evaluated based on the mean/median joint spacing, as well as the volumetric joint count. The results stress the difficulty in obtaining large blocks since few places have the appropriate degree of jointing.

Abstract: Seven silicate rocks used as ornamental stones and having different surface finishing were submitted to salt fog atmospheres in order to compare different susceptibilities to alteration. Polished, honed, hammered and flamed finishing types were tested. Rocks come from Portugal, Brazil and Angola and are widely commercialized. Samples covered quartz rich rocks, silica saturated and undersaturated rocks, mono and plurimineralic rocks, coarse and fine grained rocks. Mineral composition, texture and open porosity showed to be important parameters which determine mass loss among samples, but the finishing type was very effective within samples. Mass loss and porosity increase are higher on hammered samples, contrasted with the lowest loss values on polished samples. The effect of surface hydrophobicity and roughness on the samples having polished finishing was also analysed by atomic force microscopy (AFM) and water contact angle (WCA), indicating that texture and mineral diversity influence the hydrophobic character of the rock surfaces.

Abstract: Longmen Grottoes is the world’s cultural heritage, now it is facing with serious weathering problems. The weathering problems of Longmen Grottoes are divided into three categories: physical weathering, chemical weathering and biological weathering. With the continuous deterioration of environmental and climatic conditions, the damage of chemical weathering to Longmen Grottoes becomes more and more obvious. The damage and damage mechanisms of three categories of weathering to Longmen Grottoes are discussed based on the previous studies.

Abstract: In this study, digital treatment method was developed in order to reconstruction of the 3D CAD of hemp fibre geometry. The influence of each aging condition (moisture, heat and UV aging) on the mechanical properties of hemp fiber is investigated by micro tensile tests. Different hemp fibre morphologies was presented and discussed. The results showed a high impact of the hemp fibre morphology on their mechanical properties (Young modulus, maximum stress and failure strain). The influence of aging conditions on the mechanical properties of hemp fibers is also investigated.

Abstract: Black strata is a wildly distributed and special rock, whose weathering tends to speed up the weathering and the worsening of all rocks and the construction materials. The paper, via the geochemical process of the sulphide oxidation in the black strata, is to make analysis of the weathering features of the black strata in the west of Hunan province, China; the stability of other minerals in the black strata under acid condition, as well as the effect on the weathering of the black strata by rock components, geologic formation and different movements and moving speeds of the underground water.

Abstract: Considering the long-term atmospheric weathering effects on expansive soil strength, geogrid reinforcement effects of expansive soil slope are analyzed with FLAC3D. The research in this paper shows that: (1) when the reinforcement is deeper than the weathered layer, the inhibition effect of soil stress and displacement increases with increasing length of geogrid, in this case a critical slip arc moves away from the slope surface, and the maximum safety factor of slope stability increases approximately 50 percent; the grid stress decreases with the increasing height of grid location; (2) when the reinforcement depth exceeds the weathered layer 1 m, the denser geogrid in the vertical direction, the smaller shear stress and horizontal deformation in reinforced region, so that the slope safety factor increase and the critical slip arc moves towards the slope back. However,if the geogrid length exceeds the weathered layer more than 3 m, the vertical grid distance change has no significant influence on the safety factor and the location of critical slip surface.

Abstract: Doing experiment about weathering of two kinds of stone cultural relics, through measuring some technology index, comparing weathering resistance and surface deterioration of these stone cultural relics, discussing the reason of arising weathering and surface deterioration from internal and external factors, so these may offer some contribution to protect this kind of stone cultural relics.

Abstract: Polyethylene (PE) film coated with polyurethane/nanosilica composite with varying composition were prepared and then exposed to ultraviolet radiation for accelerated weathering studies. The chemical and physical changes on nanocomposite coated PE film induced by UV exposure were studied by monitoring the changes in tensile strength, tensile modulus, elongation, carbonyl index, and visible light transmission. The effect of polyurethane/nanosilica composite coating on the durability and optical properties of polyethylene substrate was determined after 200 hrs and 500 hrs of ultraviolet exposure. There is no significant change was observed on visible light transmission for nanocomposite coated PE film after 500 hrs UV weathering. The mechanical properties of coated and uncoated PE were tremendously affected by UV exposure. PE coated with 4 µm of nanocomposite containing 6 wt% nanosilica showed less tensile properties deterioration compared to uncoated PE film after UV weathering. The surface protective coating of polyurethane/nanosilica composite with 6 wt% nanosilica content reduced the photodegradation rate of PE due to its excellent thermal stability compared to PE.