Effect of the green porous texture on porcelain tile properties

Porcelain tile is a product characterised by low water absorption (usually less than 0.1%) and excellent mechanical properties. To enhance tile aesthetic qualities, much of the porcelain tile production is polished to provide a high-gloss surface finish, in which certain closed pores in the tile body become visible. This apparent porosity of the polished tile, which had been closed porosity before polishing, sometimes lowers the product's stain resistance.Test pieces were formed from a porcelain tile composition prepared under different milling conditions, pressing variables being kept constant, and the pore size distribution of these pieces was determined. The effect of the porous texture of the green pieces on the evolution of porosity during sintering and on the residual porosity of the densified body was analysed. It was verified that the porous texture of the fired piece was conditioned by the porosity and size of the largest pores in the green piece. The effect of residual porosity on stain resistance was determined by two cleaning methods. The presence of large pores in the green body, stemming from insufficient milling of the raw materials mixture, led to tiles with greater residual porosity and worse stain resistance.     

Porcelain tile microstructure: Implications for polished tile properties

The present study was undertaken to determine the influence of sintered porcelain tile microstructure on mechanical properties (fracture strength, modulus of elasticity and fracture toughness) and surface properties (gloss and stain resistance). To obtain sintered specimens with different microstructures the peak firing temperature was varied for bodies made with industrial spray-dried powder, and sets of test compositions were also made in which quartz content and quartz particle size were varied.Liquid-phase sintering is the typical densification mechanism involved in the achievement of minimum porosity, which is characterised by isolated round pores. Bloating occurred above the firing temperature for minimum porosity. Increases in quartz content and quartz particle size in the starting composition led to reduced body sinterability, and thus gave rise to higher porosity in the fired tile.Mechanical properties were adversely affected by an increase in fired tile porosity. For the same variation in porosity, mechanical properties were more sensitive to the change in quartz content than to changes in particle size. No toughening effect was observed with a rise in quartz content or a decrease in particle size: mechanical properties depended primarily on sintered specimen porosity.Gloss and stain resistance (which characterise polished surface quality) varied with surface porosity, both showing the highest values for lowest porosity. The relationship between porosity and gloss was close to linear.     

Cleaner production of porcelain tile powders. Fired compact properties

A new ceramic powder preparation process, the droplet-powder granulation process (DPGP), was recently proposed for the cleaner production of ceramic tiles. The DPGP granules and resulting pressed compacts were characterized and compared with the granules and compacts obtained by spray-drying (SD) and dry granulation (G) processes in a previous paper. The results showed the feasibility of using the DPGP in the pre-firing stage of porcelain tile manufacture.This study compares the firing behaviour and fired properties of compacts pressed from three different types of granulated powders: DPGP, SD, and G and from a non-granulated powder (NG) obtained by dry milling. The evolution of compact microstructure (porosity and pore size distribution) with firing temperature was monitored and the fired compact properties (bulk density, water absorption, and stain resistance) were determined.The study shows that the DPGP improved the sintering behaviour and final properties of the resulting porcelain tiles with respect to those obtained by the G process. However, the fired compacts prepared from the DPGP powder exhibited a higher porosity and pore size compared with those of the compacts obtained from the SD granules at the same pressing pressure. The results obtained open up the possibility of manufacturing glazed porcelain tiles with a more eco-friendly process. However, the results also indicate that polished porcelain tile manufacture by the DPGP requires further research in order to improve granule characteristics, in particular green granule deformability, which is the critical factor in porcelain tile densification and vitrification during firing.     

Application of grits waste as a renewable carbonate material in manufacturing wall tiles

This work focuses on the reuse of grits waste, from cellulose industry, as a raw material to replace traditional carbonate material in ceramic wall tiles. Wall tile formulations bearing up to 15?wt% of the grits waste were prepared for replacement of calcareous. The tile manufacturing route consisted of dry powder granulation, uniaxial pressing, and firing at temperatures ranging from 1100?°C to 1180?°C by using a fast-firing cycle. The wall tile specimens were tested to determine their physical and mechanical properties (linear shrinkage, water absorption, apparent porosity, apparent density, breaking strength, and flexural strength). The firing behavior, phase transformations, and microstructure were evaluated by dilatometry, XRD, and SEM. The results showed that the fired wall tile specimens are composed of anorthite and quartz, as major mineral phases, and mullite as a minor phase. It was found that the grits waste had a positive influence on the properties and microstructure of the wall tile specimens. The results also revealed that the grits waste from cellulose industry could be used as a total replacement of traditional calcareous material in wall tile formulations.     

Porcelain tile microstructure: implications for polishability

The present study examines the influence of porcelain tile microstructure on tile polishability and polishing efficiency. A range of different fired porcelain tile microstructures was obtained by varying the quartz particle size and content in the starting composition, and the peak firing temperature.The polishability of these porcelain tile specimens was evaluated with a tribometer designed to simulate the industrial polishing operation, using cement-matrix silicon carbide abrasive tools. The wear rates of both the tile samples and the abrasive tools were measured. A new parameter, termed ‘polishing efficiency’, was defined as the ratio of tile specific wear rate to pin specific wear rate.Quartz particle size and content in the starting composition, as well as peak firing temperature, strongly affected the fired tile microstructure, and hence the polishability. When the firing temperature lies below the optimum value (at which porosity is minimised) the polishing efficiency increases, while the polished surface quality decreases (i.e. porosity rises). Quartz particle size and content should be minimised in the starting composition to achieve maximum polished surface quality and polishing efficiency.     

Relationship between certain ceramic roofing tile characteristics and biodeterioration

This paper examines the relationship of certain red ceramic roofing tile properties to roofing tile biodeterioration. The following properties were studied: apparent porosity, roughness, and the presence or absence of two types of coatings.The effect of apparent porosity was studied by varying the peak firing temperature of a standard industrial red ceramic roofing tile composition and by preparing several clay mixtures, of different chemical and mineralogical composition, that were fired at various peak temperatures. The effect of roofing tile roughness was determined by either polishing or sanding fired standard red roofing tiles. A waterproof ceramic glaze coating and a photocatalytic coating were formulated to analyse the effect of the presence of different types of coatings. Roofing tile bioreceptivity was evaluated with a method developed in a previous study using the cyanobacteria Oscillatoria sp, which enabled roofing tile resistance to microbial colonization to be determined.As expected, bioreceptivity rose as apparent porosity (measured as water absorption) increased, enabling possible water retention, which favours biological growth. Similarly, greater roughness encouraged micro-organism adhesion and raised bioreceptivity. It was found that, after prolonged exposure periods (several months) under very favourable conditions for biological colonization, roofing tiles coated with the waterproof ceramic glaze were colonized. However, glazed standard red roofing tiles covered with a TiO₂ photocatalytic coating exhibited practically no biological growth under the test conditions used, even after long exposure times, owing to the chemical-physical effect of the TiO₂-based coating.     

Development of a multipurpose tile body: Phase and microstructural development

In this study, an attempt was made in order to develop a multipurpose tile body using a single formulation. In order to achieve this, several body recipes were prepared using mainly local raw materials with clearly defined physical and chemical properties at different sieve residues and single fast fired under industrial conditions in the first part of the study. In the second part, the most suitable formulations with the corresponding sieve residues were determined and further fired at different peak temperatures under laboratory conditions in order to establish their vitrification ranges and optimum firing temperatures. The tested peak firing temperatures were varied at 20 °C intervals from 1120 to 1200 °C for multipurpose wall tile body and from 1140 to 1220 °C for multipurpose floor tile body. The physical and thermal properties of the fired bodies such as water absorption, linear firing shrinkage, bulk density and linear thermal expansion coefficient were measured. The vitrification behaviour of the multipurpose bodies was also evaluated using a double-beam optical non-contact dilatometer. Furthermore, the fired bodies were subjected to colour measurements. Particular consideration was given to the phase and microstructural evolution of the developed tile bodies. X-ray diffraction (XRD) was used to analyse the phases formed before and after firing. Scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDS) was further employed in order to observe the microstructural and microchemical characteristics of the fired bodies with respect to peak firing temperature. The preliminary experimental results showed that it was possible to obtain a multipurpose body with the properties in accordance with ISO-EN 10545.     

Granite as flux in stoneware tile manufacturing

Natural granite was used to completely replace both feldspathic and inert components of a traditional ceramic body. Raw material from Sinai (Egypt) was added (in the range 20-35 wt%) to a commercial Egyptian ball clays (from Aswan, Egypt) in order to obtain laboratory tiles sintered at 1220 °C.Densification was studied according to ISO rules, while sinterability was estimated by optical dilatometry. Chemical, physical and microstructural analyses were accomplished to find the relationship between both the phase composition and microstructure of the fired bodies properties. The fired samples show moderate thermal expansion as well as reasonable bending strength. Therefore, as a nonconventional raw material in the modern ceramic production, the studied batches are recommended for the production of industrial fast firing tiles showing properties similar to commercial ceramic floor and/or wall tiles.     

Reusing sanitaryware waste products in glazed porcelain tile production

Reusing the waste products generated in ceramic manufacturing is an environmentally responsible and sustainable approach. This study aims to protect natural resources, minimise raw material costs and manage waste-generated pollution by reusing the vitrified sanitaryware waste (VSW) products from Canakkale Kalebodur Seramik San. A. S. Six sample formulations were prepared under industrial conditions and compared with a standard tile body. The results indicated that using VSW in place of feldspar results in an increased firing shrinkage and decreased bending strength, whereas using VSW in place of pegmatite results in an increased bending strength and reduced thermal expansion coefficients. The reduction in the thermal expansion coefficients is an important finding that aids in meeting the dimensional and deformation requirements of porcelain tiles and also results in a slight lightening of the tile colour. This study shows that the fired VSW products can be used in glazed porcelain tile production as a sustainable and technologically, economically and environmentally suitable approach.     

Effect of spray-dried powder granulometry on the porous microstructure of polished porcelain tile

The low porosity of porcelain tile is the result of strict control of the material's processing conditions (milling of raw materials, compaction and sintering) and the characteristics of the raw materials used in its formulation (formation of liquid phases). Sealed pores remaining after the manufacturing process are revealed at the surface after polishing and are the main factor responsible for staining the product. The porous microstructure of the sintered material depends on the characteristics of the porous microstructure of the green compact and on how the densification process evolves during sintering. The present work evaluated how the size distribution of spray-dried granules acts upon the porous microstructure of green compacts and of polished porcelain tile. The results revealed that minor adjustments in the granulometric distribution curve can reduce the visibility of stains on the polished surface, thus improving this property.     

Effect of quartz particle size on the mechanical behaviour of porcelain tile subjected to different cooling rates

Porcelain tile is a high-performance ceramic tile, in which quartz is a major compositional component. After the firing cycle, macroscopic residual stresses develop in the product as a result of rapid cooling. Further, during cooling, the presence of quartz particles also increases natural flaw size. Both phenomena significantly affect the product's mechanical behaviour. This study examines the effect of quartz particle size on the mechanical behaviour of porcelain tile subjected to two very different cooling rates: a rapid or a slow cooling rate. A series of porcelain tile compositions were designed for this purpose, in which quartz particle size was varied. The mechanical behaviour of the sintered pieces was evaluated on the basis of linear elastic fracture mechanics. It was verified that, in the slowly cooled material, the modulus of elasticity and fracture energy increased, and natural flaw size decreased as quartz particle size decreased. However, fracture energy also diminished in pieces that contained excessively small particles, with an advanced state of dissolution. For the rapidly cooled material, though the larger sized quartz particles debonded at higher temperatures owing to thermal stress, their presence, even in small quantities, contributed to natural flaw growth. The lower fracture energy associated with this last type of piece also favours this phenomenon.     

瓷质抛光砖表面显微结构与防污性能的关系探讨

采用光学显微镜、扫描电镜等对抛光砖的表面显微结构进行了研究。结果表明：气孔率对抛光砖的防污性能有明显影响，但抛光砖中石英晶体在冷却过程中与玻璃体膨胀系数的差异产生的热应力，促使玻璃体沿石英周边形成了微裂纹，抛光时机械力的作用使晶粒剥落造成表面孔洞，是造成瓷质抛光砖容易吸污的主要原因之一。     

Properties of Triaxial Porcelain Bodies: Interpretation of Statistical Modeling

The effect of raw materials type and content on the properties of clay–feldspar–quartz compositions was studied using the statistical design of mixture experiments. Based on wall and floor tile industrial practice, 10 mixtures of three raw materials were selected and processed. Characterization results were used to calculate statistically significant and valid regression equations, relating fired body properties with clay, feldspar, and quartz contents in the unfired mixture. Such statistical modeling is discussed against quantitative X-ray diffraction and scanning electron microscopy results. The glassy phase present was found to control the microstructure and the mechanical strength of the fired ceramic body.     

Effect of feldspar particle size on the porous microstructure and stain resistance of polished porcelain tiles

The final porosity of porcelain tiles results from the incomplete densification of the material during the stages of processing. The use of raw materials such as feldspar, with a high potential for forming liquid phase during sintering, contributes to eliminate porosity when a suitable heating cycle is employed. This paper presents the results of a study that investigated the effect of the particle size distribution (PSD) of feldspar on the formation of pores in the green compact and the final product, using stain resistance as an evaluation parameter of surface porosity. To this end, the feldspar used in a standard paste of technical porcelain was milled under different conditions to produce the desired changes in its PSD. The groundbreaking results indicate that slight changes in the milling conditions of feldspar can significantly alter the porous microstructure of the material and the stain resistance of the polished tile surface.     

Hydro deformation in ceramic tiles at the pre-firing stage

The production of ceramic tiles with larger sizes and reduced thickness has increased the challenge of producing high-quality ceramic tiles in short single-firing cycles. For porcelain tiles, the pressing step is of upmost importance for the microstructure of the green bodies. The particle size distribution, mineral composition of the pastes and porosity before firing define the water flow during the decoration process. Hydro deformation is the curvature of unfired ceramic tiles caused by water absorption during the decoration step before firing. In this work, the hydro deformation is studied in function of tile thickness, compaction, and clay composition according to a 2^K factorial design. Two compositions of porcelain tiles (glazed and polished) were pressed at two thicknesses (3–6 mm) and pressing pressures (35.5–49.8 MPa) forming ceramic tiles with 55 × 110 mm² of surface area. Chemical (XRF), mineralogical (XRD), thermogravimetric (TG), specific surface area (BET), granulometric, bulk density, and porosity analyses were performed for the green tiles of both compositions. To simulate the hydro deformation during the decoration step, the curvature (mm) of the tiles was studied within a 0–180 min interval. The water absorption rate through the surface (g.m⁻²·s⁻¹) of the tiles in an interval of 0–180 s was studied as a function of thickness, pressure and porcelain tile composition. As a result, the thickness of the tiles can change the curvatures from concave to convex. Pressing conditions and composition of the tiles can change the water absorption rates. Porcelain tiles with higher content of clay minerals develop convex curvatures. For tiles with lower content of clay minerals, concave curvatures were developed.     

Evolution with Temperature of Crystalline and Amorphous Phases in Porcelain Stoneware

Porcelain stoneware tile is a ceramic building material characterized by high technological properties, especially regarding water absorption, chemical and frost resistance, bending strength and abrasion resistance. Because mineralogy is one of the main factors affecting the mechanical properties of porcelain stoneware, a complete determination and quantification of the mineral and amorphous phases is of special importance in the study of porcelain stoneware tiles. In the present work, a reference industrial composition (50% kaolinitic clay, 40% feldspar, and 10% quartz) of porcelain stoneware tiles fired at different temperatures (400°–1400°C) was characterized by X-ray powder diffraction combined with quantitative full-phase analysis using the Rietveld method, including amorphous content. The green composition contained albite, microcline, and muscovite as fluxing agents, which start to decompose at low temperatures (400°–800°C range) and are completely dissolved above 1200°C. The mullite phase is formed from 1100° to 1230°C and at the latter temperature, quartz particles start to dissolve. Studies of mineralogical evolution have revealed that the high heating rate (45°–50°C/min) required in ceramic tile manufacture leads to significant differences in comparisons with whiteware ceramics fired at a lower heating rate (10°C/min). Thus, the formation of mullite in porcelain stoneware occurs at higher temperatures (1100°C) whereas the transformation of β-quartz to β-cristobalite does not take place. The experimental results of this study show that qualitative mineralogical analysis, based on the intensity of a particular diffraction peak for each crystalline phase, is a suitable methodology to obtain preliminary knowledge of mineralogical changes with temperature.     

FACTORS INVOLVED IN PRODUCTION OF THIN WALL TILE*

A study was made relative to the dry pressing of wall tile having a thickness of ³/₁₆ in. Three bodies, a high talc, a high pyrophyllite, and a regular body were studied. The water content was kept constant and the forming pressures were varied from 1000 to 3000 lb. per sq. in. The bodies were fired to cones 4, 6, and 8. The bisque tile were tested for thermal expansion, warpage, absorption, shrinkage, impact strength, transverse strength, and moisture expansion. The glazed tile were tested for warpage, impact resistance, and moisture expansion. The results showed that satisfactory thin wall tile could be made from all bodies, the high-pyrophyllite body indicating the greatest promise. It was found that pressing pressures had definite effects on impact strength, warpage, shrinkage, and thermal expansion.     

White sintered glass-ceramic tiles with improved thermal insulation properties for building applications

In order to provide a thermal barrier in an arid environment, highly reflective coatings were deposited on porous substrates made of natural raw materials from Saudi Arabia. Although highly reflective coatings inhibit heat absorption from the incoming sunlight, the body of conventional ceramic tiles warms up to environmental temperature through conduction, convection and radiation. A strategy to reduce the penetration of this heat into the building is to use a highly porous substrate, which reduces the thermal conductivity of the tile, coupled with a highly reflective glaze. The approach leads to the concept of “cool” tiles, aimed at improving the thermal efficiency of buildings. The present paper provides a first example, based on layered wollastonite-hardystonite glass-ceramics developed by double pressing of glass powders and additives followed by sinter-crystallization.     

Optimizing raw material composition to increase sustainability in porcelain tile production: A simulation-based approach

Reducing the environmental impact of porcelain tile production while maintaining cost-effectiveness is challenging. This work introduced a novel modeling approach for optimizing a standard composition range comprising kaolinite (15–38 wt.%), illite (0–20 wt.%), quartz (20–40 wt.%), and feldspar (20–45 wt.%) to establish a robust composition interval for porcelain stoneware tiles. The proposed study considers several factors, such as composition impact on the manufacturing sequence, production costs, and CO₂ emission. A flowsheet simulation database was generated by coupling the Dyssol framework with MATLAB. This study investigated the influence of raw material composition within the process sequence, the total CO₂ emissions, and production costs within the contexts of Spain and Brazil, two of the top five global producers. Granules with a higher proportion of talc and illite exhibit reduced moisture content after spray drying, and these combinations have lower green body porosity after compaction. The addition of talc allowed for decreased porosity content after compaction reduced firing temperature, and lowered costs and CO₂ emissions despite the higher prices associated with talc. The proposed simulation methodology offers a powerful decision-making tool for optimizing raw material composition to minimize cost and CO₂ emissions in the porcelain tile production. This methodology represents an early stride toward integrating digital twin methodologies within the ceramic tile sector, facilitating improved process regulation, and promoting the adoption of digital technologies.     

Preparation of hardened tiles from waste phosphogypsum by a new intermittent pressing hydration

The solid waste phosphogypsum (PG), as the sole-raw material, was processed into hardened tiles with favorable mechanical strength by a novel intermittent pressing hydration process. First, the raw PG with dihydrate gypsum was dehydrated into semi-hydrate gypsum. The dehydrated PG was granulated with water, press-formed, and then immersed in water under intermittent pressing. Using the optimal granulation humidity of 35%, pressing pressure of 20 MPa, pressing frequency of once per 2 min and total times of 24, PG hardened tiles with bending strength of 18.9 MPa was obtained. It was revealed that the dehydrated PG was hydrated into the dense dihydrate gypsum crystals under the action of intermittent pressing, which contributed to the high mechanical strength of the tiles. The hardened tile has the potential to be a new-type wall material and its application may help to solve PG׳s environmental risk.