Effect of the titanium-dioxide addition on the structural, dielectric, and mechanical properties of different cement-based mortars with corundum aggregate

The primary objective of this study was to look into the role of titanium dioxide in the production of corundum-based mortars, with a focus on finding the optimal mortar composition for achieving improved mechanical and dielectric performances. Changes in the mix design (different binders, different additive dosages), as well as their effects on the hydration pathway, chemical bonds, phase modifications, and microstructure, were examined. These findings were then correlated to the designed mortars' mechanical strengths and dielectric properties. Experimental mortars were produced with binders made from ordinary Portland cement, high alumina cement, and their mixtures, and corundum as aggregate. Titanium dioxide was employed as an additive (3 and 5 wt%). Nine different mortars were submitted for comprehensive mineralogical and microstructural characterization upon curing and solidification. The compressive and flexural strengths were monitored throughout the 28-day period. The dielectric constant (εr), dielectric loss tangent (tan δ), and electrical resistivity (ρ) were measured over a frequency range of 100 Hz to 1 MHz. XRD analysis highlighted the appearance of mayenite as a dielectric-prone phase in the samples doped with titanium dioxide. Differential thermal analysis and FTIR spectroscopy identified a higher amount of extra-low crystalline phase in OPC and HAC mortars with TiO2 addition, which accelerated hydration mechanisms, created a surplus of hydration products and made a more compact cement matrix. TiO2 added in 3 wt% amount led to higher mechanical strengths in OPC-based mortars, while it improved the dielectric properties of HAC mortars

The recycling of demolition roof tile waste as a resource in the manufacturing of fired bricks: A scale-up to the industry

This study illustrates the utilization of roof tile waste as a resource in the manufacturing of fired bricks. Although commonly referred to as demolition waste, it is technically classifed as construction and demolition waste (C&D). This demolition waste was used as a partial replacement of two soils (alluvial and laterite soil) at three firing temperatures that were considered economical (700, 850, and 900 ◦C). The waste considered was obtained from roof tiles previously fired at a low temperature below 800 ◦C, thus containing residual carbonates and clay minerals. The increased waste input resulted in higher firing shrinkage, bulk density, and water absorption while decreasing loss on ignition. An increase in firing temperature led to higher firing shrinkage, loss on ignition, and bulk density, but lower water absorption. The bricks met both Indian and ASTM standards for 2nd and 3rd class by adding 20–35 wt% of roof tile waste and firing at 850–900 ◦C in laboratory and industrial settings. The minimum acceptable quality for the produced bricks was achieved with an addition of 35 wt% waste, resulting in a water absorption of approximately 19% and a compressive strength ranging from 6 to 9 MPa. The study suggests that incorporating waste from demolished roof tiles into the production of burned bricks can be advantageous. It can partially replace the need for soils, reduce natural resource usage, lower energy consumption during production, and decrease the carbon footprint

Influence of Barite Sand on The Strength on Self-Compacting Concrete with Fly Ash

. This study compared the performance of self-compacting concrete (SCC) based on fly ash addition and limestone filler. A SCC prepared with Portland cement, river sand, and limestone filler was used as a reference sample. Additional experimental self-compacting concretes with different types of fine aggregates, fillers, and special additives for increasing freeze-thaw resistance were prepared and optimized. The correlation between mix design, i.e., percentage of barite sand and additives, on properties of hardened SCC (compressive and flexural strengths), were investigated and discussed

Reapplication Potential of Historic Pb–Zn Slag with Regard to Zero Waste Principles

Smelting used to be less efficient; therefore, wastes obtained from historical processing at smelter plants usually contain certain quantities of valuable metals. Upon the extraction of useful metal elements, metallurgical slag can be repurposed as an alternative mineral raw material in the building sector. A case study was conducted, which included an investigation of the physico-chemical, mineralogical, and microstructural properties of Pb–Zn slag found at the historic landfill near the Topilnica Veles smelter in North Macedonia. The slag was sampled using drill holes. The mineralogical and microstructural analysis revealed that Pb–Zn slag is a very complex and inhomogeneous alternative raw material with utilizable levels of metals, specifically Pb (2.3 wt.%), Zn (7.1 wt.%), and Ag (27.5 ppm). Crystalline mineral phases of wurtzite, sphalerite, galena, cerussite, akermanite, wüstite, monticellite, franklinite, and zincite were identified in the analyzed samples. The slag’s matrix consisted of alumino-silicates, amorphous silicates, and mixtures of spinel and silicates. Due to the economic potential of Pb, Zn, and Ag extraction, the first stage of reutilization will be to transform metal concentrates into their collective concentrate, from which the maximum amount of these crucial components can be extracted. This procedure will include combination of gravity concentration and separation techniques. The next step is to assess the Pb–Zn slag’s potential applications in civil engineering, based on its mineralogical and physico-mechanical properties. Alumino-silicates present in Pb–Zn slag, which contain high concentrations of SiO2, Al2O3, CaO, and Fe2O3, are suitable for use in cementitious building composites. The goal of this research is to suggest a solution by which to close the circle of slag’s reutilization in terms of zero waste principles. It is therefore critical to thoroughly investigate the material, the established methods and preparation processes, and the ways of concentrating useful components into commercial products

State and perspectives of sustainable production of traditional silicate ceramics

The traditional ceramics industry uses large amounts of primary mineral raw materials. Improvements in the production of building materials based on non-metallic minerals can contribute to sustainable development in many ways, such as saving natural resources, using waste materials, reducing energy consumption, decreasing emissions hazardous to the health and the environment, particularly carbon dioxide, and reclamation of mines after exploitation of raw materials, etc. This paper describes the state of application of mineral raw materials and waste in the traditional ceramics industry with a perspective on future challenges. Intensified research is needed to complement the laboratory data and re-scale to the industrial-sized products while improving communication between both sectors

Life Assessment of Corroded Wire for Prestressing

The repair of structural elements for the prestressing of reinforced concrete is necessary when existing prestressing wires are damaged or after a certain period of time. The objective of this paper is to describe the methodology for the life assessment of corroded prestressing wires, sampled from prestressed concrete elements after a few decades of use. The aim of the presented research was to determine the real properties of corroded wire in terms of the evaluation of remaining load capacity using the Theory of Critical Distances (TCD). The methodology also includes spatial 3D characterization of corroded surfaces, determination of mechanical properties, and Finite Element Analysis (FEA) of a model of wire with corrosion pits. The final goal of the presented methodology is to enable more efficient evaluation of repair range and options for the elements of mechanical prestressing systems within various structures. The results and conclusions indicate that the developed methodology, based on the interdisciplinary approach and implementation of state-of-the-art methods, has a high applicability potential for both static and fatigue fracture prediction in the case of prestressed wires. The proposed method has a huge potential for simple and fast prediction of the life assessment of engineering structures, particularly for damaged elements with arbitrary geometry feature

Proračun ugiba grednih struktura na osnovu izmerenih vrednosti dilatacija

Ponašanje struktura pod delovanjem različitih vrsta opterećenja određene su njenim deformacionim karakteristikama, globalnim deformacionim karakteristikama – pomeranjima i rotacijama i lokalnim deformacionim karakteristikama - dilatacijama u materijalu strukture. Poznavanjem globalnih i lokalnih deformacionih karakteristika strukture ostvarujemo mogućnost da pratimo ponašanje strukture u celini ili nekog njenog segmenta. Osnovni cilj ovog istraživanja je provera algoritma proračuna za dobijanje vertikalnih pomeranja - ugiba strukture, na osnovu poznatih vrednosti dilatacija u materijalu strukture, pri delovanju opterećenja. Provera algoritma sprovodi se poređenjem numeričkih i eksperimentalnih rezultata

Influence of Aggregate Type on the Properties on SCC with Fly Ash

This study compared the performance of self-compacting concrete (SCC) based on fly ash addition and limestone filler. A SCC prepared with Portland cement, river sand, and limestone filler was used as a reference sample. Additional experimental self-compacting concretes with different types of fine aggregates, fillers, and special additives for increasing freeze-thaw resistance were prepared and optimized. The correlation between mix design, i.e., percentage of barite sand and additives, and properties of fresh SCC (slump-flow test, V-funnel test, and L-box test), as well as properties of hardened SCC (compressive strengths), were investigated and discussed

Parameter programs for 3D modeling in the function of nondestructive testing and determination of the lifetime of pressure vessels

Preparation for non-destructive testing (NDT), preparation of test reports, as well as control calculation of a pressure vessel (PV) using the finite element method (FEM), with or without identified irregularities, requires the use of commercial programs for parametric modeling, which allow the rapid creation of three-dimensional (3D) model of the test object. 3D modeling programs enable the determination of one or more rappers in order to orient the test object, accurately define the established irregularity or error after NDT, as well as the most critical part of the PV construction after FEM calculation with the possibility of optimization. Programs for 3D modeling also enable modeling of determined irregularities after performed tests that occurred during the construction, calculation, production or exploitation of the PV construction itself. Irregularities are reflected in the form of improperly performed welded joints, cracks, corrosion, erosion or cavitation of materials, and are used for the preparation of test reports and control calculations of the PV structure with and/or without established irregularities and errors, with the aim of making the correct decision on the continuation of exploitation construction of PV or about its degree of rehabilitatio