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The Ph. D. Thesis is devoted to the obtaining of porous ceramics from Latvian clay and household waste ‒ glass cullet. Using modern technological approaches porous and highly porous clay-glass ceramics were obtained, their properties and practical application possibilities were studied. The Doctoral Thesis consists of an introduction, literature review, methodical part, evaluation of the results of the experimental part, conclusions, and bibliography.
Influence of Boric Acid Additive on Physical Properties of Utilizing Wastes for Producing Eco-Friendly Fired Clay Tiles
This paper aimed at studying the influence of additive material boric acid in eco-friendly fired clay tiles. It is used as additive material by mixing with rice husk ash (RHA), brown glass cullet (BGC), local clay (LC), and sediment soil (SS). Effects of boric acid on the physical properties of ceramic bodies were investigated. The texture of specimen by utilizing waste materials was also studied. Mixture formulations consisted of 60% BGC, 10% RHA, 0-30% LC, and 0-30% SS with varying boric acid addition of 0-2%. Specimens were formed by uniaxial pressing with 100 bars, fired at 850 and 900°C, heating rate 100°C/h, and soaked for 1 h. The results showed that adding boric acid up to 2% had increased the flexural strength and decreased the water absorption of these specimens when fired at 850°C. On the contrary, the effects of adding boric acid fired at 900°C had decreased flexural strength and increased water absorption that showed the phenomenon of expanding specimens. However, the optimal formula of these clay tiles both fired at 850 and 900°C have passed the Thai Industrial Standards (TIS 2508-2555); Type BIII. Scanning electron microscope should they that microstructure characterization was in the glassy crystalline phase was found in high flexural strength specimens. In summary, exploiting boric acid can improve the physical properties of specimens with a low firing temperature, and fired clay wall tiles can be developed in this study. They can be identified as an environmentally eco-friendly building product.
The paper presents an experimental study on the production of non-fired ceramic tiles from rice husk ash (RHA) and green glass cullet (GGC) composites as a novel eco-friendly material. Eighteen mixture formulations were constructed as compared to control formula, specimens were uniaxially pressed at 10 MPa and then cured at room temperature for 7 and 28 days. Non-fired tiles (formula A4, B11, and C17) containing 20% GGC were mixed with 0%, 5%, and 10% RHA. The modulus of rupture can be increased by 87.23%, 48.8%, and 19.4%, respectively, at 28 days of curing as compared to control formula. These results were also coherent with microstructure characterization by scanning electron microscopy (SEM). Furthermore, formula A4 and C17 were selected to compare energy costs with wall tiles fired at 950°C. They were the same amount of energy-saving costs by 5.19 USD/m2. From these results, the new eco-friendly products can produce with a combination of RHA and GGC wastes which can enhance the physical properties due to the pozzolanic reaction. Moreover, the proposed non-fired ceramic tiles can conserve energy and reduce manufacturing costs.
The article investigated the possibility of reusing heat resistant glass cullet to improve the mechanical properties of high-temperature composites. This is an excellent recycled aggregate that may be used as a substitute for alumina cement, and for fine natural aggregate in the production of concrete based on hydraulic binder. The experimental programme comprised of strength testing conducted on 40 × 40 × 160 mm cuboidal samples. The model mixture was modified by filler that comprised glass recyclate, amounting to 5%, 10%, and 15% of the mass of gravel and cement. Given the degree of glass grounding, use was made of two fractions, 0/4 and 0/0.125 mm. Six modified mixtures were produced. Tests were then carried out on their selected physical and mechanical properties as well as the impact of temperature, topography, and chemical composition exerted on the composite. Next, the progress and development of compressive strength and flexural strength after 14 and 28 days of curing were studied. Results showed that concrete with a 5% content of glass dust had a maximum compressive strength at the level of 85.1 MPa. Results also showed that concrete (Zk.I.5) heated at a temperature of 500 °C had a 46% higher compressive strength when compared to basic concrete (Z.I.0). The results show that it is possible to use the described components to obtain a composite that meets requirements imposed on structural materials used in construction engineering.
Glass-Ceramic Materials Obtained by Sintering of Vitreous Powders from Industrial Waste: Production and Properties
Glass-ceramics are advanced inorganic silicate materials that can be obtained by sintering glass powders using a careful temperature control to result in the densification, nucleation, and crystallization of the material. In the current work, three different samples were obtained starting from amorphous silicate materials derived from mixtures of metallurgical slag, coal fly ash, and glass cullet, mixed in different proportions. The as-received waste samples were heat-treated to high temperatures to achieve complete melting at 1200, 1300, and 1400 °C for two hours, performing a rapid cooling in order to yield an amorphous material (glass). The obtained frit was ball-milled to a powder, which was then cold pressed to obtain compact pellets. The thermal treatment of pellets was carried out at 800–1100 °C for 2 h followed by a cooling rate of 10 °C/min to obtain the final glass-ceramics. The microstructure of samples was evaluated with scanning electron microscopy (SEM), which showed heterogeneous conglomerates and clusters of ~20 microns. The formation of crystalline phases was corroborated by means of X-ray diffraction (XRD) analysis, showing the presence of anorthite in all samples. Depending on the sample composition, other crystalline phases such as augite, enstatite, and diopside were detected. Using the Debye–Scherrer equation, it was possible to find the average size of the nano-crystalline domains. The quantification of the non-crystalline or amorphous fraction was also performed. Additionally, the density and porosity of the materials were calculated using the procedures defined in the ASTM C373 and ASTM C20 standards, measuring density values in the range 2.2–3.1 g·cm−3. The apparent porosity was approx. 33% in the three materials. Raman spectroscopy analysis showed characteristic signals associated with crystalline phases containing alumina, silica, iron, and calcium. Overall, the study confirmed the possibility of obtaining glass-ceramics with fine (nanometric) crystal sizes from a combination of silicate waste and the capability of modifying the crystalline composition by changing the proportions of the different wastes in the initial formulations.
Ceramic Tiles Production from Cullet and Agricultural Wastes Obtained from Wheat and Sugarcane Cultivation
Agricultural wastes are a big source for environmental pollution so it’s a good choice to recycle them so as to get an environmental and economic benefit. The purpose of this research is to determine the possibility of recycling two types of agriculture wastes obtained from wheat and sugarcane cultivation in addition to broken glass (cullet) as raw materials for ceramic wall tiles production. The used agriculture wastes are the agricultural residue obtained from wheat and sugarcane cultivation. The experimental work starts with performing XRF and sieve analysis for all raw materials. Ceramic wall tiles specimens were made with dimensions 110.4 × 55.4 × 8 mm3 using 27 MPa dry pressing then dried at 120 oC overnight, then fired using firing temperatures equal to 1100 oC or 1150 oC during 15 min soaking time. Water absorption, apparent porosity, and mechanical properties were done to compare them with ISO standards. According to the previous experimental work, it was found that the samples with the composition (10% Cullet, 15% Wheat ash straw, 20% sugarcane) for samples that fired at 1150 oC or (10% Cullet, 13% Wheat ash straw, 18% sugarcane) for samples that fired at 1100 oC has the optimum properties.
This study was aimed at producing a porous layered glass ceramic material with a decorative-protective coating via one-stage firing. Waste products were used as gas-forming agents to fabricate a glass ceramic material, which partially solves a problem of their utilization; available natural raw materials were also used as gas-forming agents. A decorative-protective coating was applied simultaneously with the formation of the main layers of the material. It consisted of glass cullet and various amounts of coloring oxide. Firing of the samples was carried out at the temperature of 7500С. The coating containing 99.9 wt.% of glass cullet and 0.1 wt.% of Cr2O3 with the thickness of 425 m and having a greenish color was stated to be the coating of the highest quality. As a result of the research, a three-layer porous glass ceramic material was obtained with a low coefficient of thermal conductivity (0.056 W m–1 K–1). The presence of a fourth front decorative-protective layer will allow using this material in construction as a heat-insulating and structural material without additional cladding.