Porous materials are subjected to the corrosive effects of soluble salts. This corrosion, typically known as efflorescence, is primarily superficial. However, internal corrosion within the material is also frequently observed. This article presents a simulation of volumetric damage in sintered porous ceramic materials (made of clay (75 vol.%), quartz sand (10 vol.%), and sawdust (15 vol.%), fired at 950 °C), caused by the crystallization of double salts, specifically ploweite (6Na₂SO₄·7MgSO₄·15H₂O) and/or glauberite (CaSO₄·Na₂SO₄). The exact mechanism responsible for the formation and interaction of these salts has yet to be fully comprehended. It is established that this mechanism occurs in ceramic materials containing calcium compounds and in mixtures of Na₂SO₄ and MgSO₄ salts. Dissolved Na₂SO₄ acts as a substrate for the formation of glauberite, while dissolved MgSO₄ participates in intermediate reactions (which are necessary for the creation of glauberite).

A large group of industrial and municipal waste are glassy in nature. One of the main directions of their use is thermal treatment, which aims to melt them (solid waste) or sinter (powdered waste). Fine grained glass cullet as well as silica fly ash was the subject of our research. During heating of glassy powders, high sintering dynamics is observed along with the accompanying glass devitrification process. Our objective in this research was to partially or entirely decouple the simultaneous occurrence of glass crystallization reaction and the sintering process during the heat treatment of glassy wastes. We divided an experiment onto two parts, first we compared the effects of thermal treatment on glass in the form of: pressed powder and a bulk glass. In the second experiment the influence of the powder sample density on the progress of glass crystallization was analysed. Results of our study indicate that physical sintering of glassy powders can lower the devitrification temperature of this material. However, physical sintering is accompanied by shrinkage, which when high density is achieved can limit the expansive growth process of grains formed during devitrification. Graphical abstract

The amount of waste from washing dolomite aggregates increases continuously. Aggregates are washed to remove clayey pollutants.They consist of a large amount of clay minerals and carbonates. Their properties and amount depends on the type of raw material and type of washing technology. Utilization of waste from washing aggregates is common problem and has not been sought out yet. Their usage as the raw material in ceramics might be environmentally friendly way to utilize them. This paper presents technological properties, phase composition and microstructure analysis of materials made of waste sludge from washing dolomite aggregates. Research was divided into three parts: technological properties analysis, phase composition analysis and microstructure analysis. Samples made of waste dolomite sludge were formed in laboratory clay brick vacuum extruder and fired at 900, 1000 and 1100°C. For final materials, apparent density, open porosity, water absorption, compressive strength and durability were examined. Results of technological research suggest the possibility of the application of the waste sludge from washing aggregates in building ceramics technology as bricks materials. Waste sludge from washing dolomite aggregates can be used as the main raw material of building ceramics masses. Without any additional technological operations (e.g. drying or grinding), the material with satisfactory properties was obtained. According to durability results all obtained materials can be used for masonry protected against water penetration and without contact with soil and ground water and also for masonry subjected to passive exposure (F0 – according to the standard EN 771-1).

The main challenge for the European cement industry in the last decade is so-called decarbonisation, i.e. reducing CO2 emissions throughout the entire production cycle. In the case of the cement industry, this task is difficult because most CO2 emissions come from the thermal dissociation of calcite present in raw materials for the production of Portland clinker. The main way to reduce CO2 emissions from this source is to use calcium oxide sources in non-carbonate form. In practice, however, the availability of such raw materials in Europe is very limited, and their import from other continents is not only unprofitable, but also environmentally unfriendly due to emissions generated during transport. However, there are examples of the use of waste raw materials containing calcium oxide in the Portland clinker production. These include, among others, granulated blast furnace slag, converter slag, carbide lime, lime ash, as well as glass cullet which is the subject of analyses. The aim of the research is to analyse the burnability of clinkers with the addition of various glass wastes. The glass wastes selected were those that could not be reused in glass production due to contamination and fine-grained form. The use of glass cullet was quantitatively limited due to the high Na2O content [13 % –15 %]. Glass waste introduced into the raw material batch is mainly a source of SiO2 [67 % –- 69 %] and to a lesser extent CaO [9.0 % - 12.4 %]. The introduction of even small amounts of cullet increases the demand for high-lime raw material and also raw materials that are sources of Al2O3 and Fe2O3. Although glass waste introduces CaO in a non-carbonate form, the above changes in the raw material feed combined with the presence of carbonates in raw materials other than calcite [dolomite, siderite] mean that the addition of glass cullet does not necessarily reduce CO2 emissions from raw materials. The positive effect of the addition of glass waste on the burnability of raw material batches is noticeable at temperatures of 1200 °C – 1250 °C. It is probably related to the high Na2O content in the glassy waste and its amorphous form.

The production of building ceramics is an energy-intensive part of the industry, causing high CO₂ emission per production volume. In addition to the combustion of fossil fuels, CO₂ is emitted as a byproduct of calcium carbonate decomposition, a compound present in clay raw materials. In this paper, a method for reducing emissions by lowering the firing temperature of ceramics, thereby preventing the complete decarbonation of carbonate minerals, is presented. Thermal research has shown that lowering the firing temperature to 750 °C resulted in a 55% calcium carbonate decomposition and a reduction in CO₂ emissions by over 30 kg for every ton of clay used. At this temperature, sintering shrinkage mechanisms were not observed, which resulted in a reduction in the strength of the materials by almost 25% compared to samples fired at 900 °C. An attempt was made to compensate for the negative effects of lowering the firing temperature by adding ground glass cullet, which brought only partially positive results: an increase in flexural strength, but no change in compressive strength. Microscopic observations and phase composition studies indicate that lowering the firing temperature causes changes in the proportions of calcium compounds: increased amounts of calcite, and decreased amounts of silicates and calcium aluminosilicates.