Investigation of the Freezing—Thawing Effect on the Slip Resistance of Natural Stones

The effect of freeze–thaw cycling on the slip resistance of dimension stones was investigated. Slip and frost resistance of limestones, granites and marbles were determined via pendulum tester in dry and wet conditions and controlled freeze–thaw cycles, respectively. Unpolished surfaces under dry conditions (mainly granites and marbles) were positively affected by freezing-thawing. In wet surfaces no significant change was observed. Polished surfaces were not affected even after 100 freeze–thaw cycles. Electron microscopy showed increased wear, hence roughness, of unpolished surfaces after freezing–thawing; homogeneity of polished surfaces prevented slip resistance from being significantly affected.

Correlations between the Physical Mechanical Properties of Greek Dimension Stones

This study focuses on the investigation of possible relations betweenthe physical mechanical properties of natural stones from various places in Greece, i.e., limestones, marbles, sandstones and schists. Specimens were prepared to perform laboratory tests according to the applicable EN. Overall and “by stone type” correlation equations were established between flexural strength under concentrated load valueswithout and either after freeze–thaw cycling or thermal shock, indicating a linear and a powerrelationship, respectively. A power function was establishedbetween flexural strength under a concentrated load and under a constant moment. Results have also shown that water absorption increases linearly with open porosity.

Nano-materials enhanced protectants for natural stone surfaces

Most heritage buildings and monuments are constructed out of natural stones which suffer irrevocable degradation when undergoing wet weathering, bowing, and dissolution in outdoor conditions. Self-cleaning treatments are effective for stone protecting. Herein, nano-materials which provide enhanced protectants for Marble, Qingshi and Hedishi were prepared. Inherent microscale interstices and holes exist on polished natural stone surfaces. When treated by a commercial protectant, 101S, the surfaces were hydrophobic but not self-cleaning. Colloidal protectants were prepared by dispersion of Al2O3 and SiO2 nano-powder in 101S, respectively. Self-cleaning stone surfaces were achieved after treated by the protectants, meanwhile, the interstices and holes were reserved as much as possible. The principle of the as- prepared protectants is penetrating and crosslinking on the stone surfaces as well as the inner surfaces of the interstices and holes. The reserving of the micro interstices and holes is important since the breathability of the stones is remained. The self-cleaning surfaces showed good thermal stability below 250 °C. Meanwhile, changes of color and gloss of the treated stone surfaces are in the acceptable range.

TEK KATLI DUVAR DEFORMASYONUNUN GÖRÜNTÜ İŞLEME TEKNİKLERİ KULLANILARAK BELİRLENMESİ

Image processing technique has been used frequently in the solution of engineering problems recently. In engineering studies, photographs are taken at certain intervals between the initial state of the material and the state after the change, and changes during the study are observed with the Image processing technique. Based on these photos, the change is transferred to numerical data and the change of the material is observed thanks to these data. Package program systems are used in Image processing technique applications. But these systems are quite expensive systems. In this study, a simpler and feasible system has been developed. The initial sliding test was carried out on 9 single-layer wall systems with natural stones in 20 * 30 * 10 cm dimensions. The displacement values formed on the walls under load during the experiments were measured with the help of potentiometric linear rulers. At the same time, photographs were taken at certain intervals from the baseline to the conclusion of the experiment. The photographs were digitized in the ArcGIS program and the changes on the wall were converted into numerical data. Experimental data and data obtained by photographs were compared. As a result of this comparison, 84% similarity is observed between experimental values and analytical values. It is observed that the image digitization application performed as a result of the study yielded very successful results. In this context, it is believed that the use of this system will be both fast and economically beneficial in larger scale experiments and the number of data.

Assessment of Stone Protective Coatings with a Novel Eco-Friendly Encapsulated Biocide

The conservation of stone monuments is a constant concern due to their continuous weathering, in which biofouling plays a relevant role. To enhance the effectiveness of biocidal treatments and to avoid environmental issues related to their possible toxicity, this research aims at formulating and characterizing a coating charged with an eco-friendly biocide and showing hydrophobic properties. For this purpose, zosteric sodium salt—a natural biocide product—has been encapsulated into two silica nanocontainers and dispersed into a tetraethoxysilane-based (TEOS) coating also containing TiO2 nanoparticles. The coatings were applied on four different types of stone: brick, mortar, travertine, and Carrara marble. The effectiveness of the coating formulations and their compatibility concerning the properties of coated stones were assessed. The results showed that all coatings conferred a hydrophobic character to the substrate, as demonstrated by the increase of the static contact angle and the reduction in the capillary water absorption coefficient. The transmission of water vapor of the natural stones was preserved as well as their natural aspect. Furthermore, the coatings were homogeneously distributed on the surface and crack-free. Therefore, the protective capability of the coatings was successfully demonstrated.

Diamond tool wear monitoring by sensory analysis in milling of absolute black granite

Diamond tools suitable for machining operations of natural stones can be divided into two groups: cutting tools, including blades, the circular blades and the wires, and the surface machining ones, involving mills and grinders, that can be of different shapes. For the stone sawing process, the most adopted tool type is the diamond mill, whose duration and performance are influenced by various elements such as: the mineralogical characteristics of the material to be machined; the working conditions such as the depth of cut, the feed rate and the spindle speed; the production process of the diamond segment and the characteristics of both the matrix and the diamond, such as the size, the type and the concentration of the diamonds and the metal bond formulation hardness. This work allows to indirectly assess the wear of sintered diamond tools by signal analysis (in time and frequency domain) of the cutting force components acquired in the process. The results obtained represent a fundamental step for the development of a sensory supervision system capable of assessing the tool wear and hence to modify the process parameters in process, in order to optimize cutting performance and tool life.