Comparative life cycle analysis between commercial porcelain stoneware and new ones designed by using volcanic scraps.

To achieve carbon neutrality by 2050, many companies have started implementing sustainability policies. The aim of this work, as result of collaboration between Universities and companies, is to assess the environmental impacts associated with the production of alternative formulations of porcelain stoneware. The proposed formulations contain extraction scraps and chamotte and have promising technological properties. A comparative analysis of the life cycle in three different scenarios was carried out to assess the environmental footprint of the final products. The analyzed scenarios were a glazed porcelain stoneware (which was taken as a reference and is commercially available), a porcelain stoneware containing pumice scraps, and one containing volcanic lapillus scraps. It was observed that the transportation of raw materials has the largest environmental impact, followed by the production and extraction of the raw materials themselves. From the performed analysis, it was possible to observe that by replacing the currently used materials by the ones hereby studied, environmental benefits can be obtained. In particular, depending on the considered pollutant, the environmental impact can be reduced between a minimum of about 8 % (Freshwater Aquatic Ecotoxicity category) to a maximum of 48 % (Acidification category). In a time when raw materials supply is difficult, the use of scraps, which would otherwise be disposed of, is particularly interesting and can lead to the production of an environmentally friendly product.

Analyzing the Role of Fe0 and Fe3+ in the Formation of Expanded Clay Aggregates.

The effect of the addition of Fe0 and Fe3+ on the formation of expanded clay aggregates was studied using iron-free kaolin as an aluminosilicates source. Likewise, the incorporation of cork powder as a source of organic carbon and Na2CO3 as a flux in the mixtures was investigated in order to assess its effect in combination with the iron phases. An experimental protocol, statistically supported by a mixture experiments/design of experiments approach, was applied to model and optimize the bloating index, density, absorption capacity, and mechanical strength. The process of expansion and pore generation and the associated decrease in density required the addition of iron, such that the optimum mixtures of these properties presented between 25 and 40 wt.% of Fe0 or Fe3+, as well as the incorporation of 3.5-5 wt.% of organic carbon. The addition of Fe3+ produced a greater volumetric expansion (max. 53%) than Fe0 (max. 8%), suggesting that the formation of the FeO leading to this phenomenon would require reducing and oxidizing conditions in the former and the latter, respectively. The experimental and model-estimated results are in good agreement, especially in the aggregates containing Fe0. This reinforces the application of statistical methods for future investigations.

Evaluation of the Environmental Benefits Associated with the Addition of Olive Pomace in the Manufacture of Lightweight Aggregates.

A Life Cycle Assessment (LCA) using SimaPro software has been carried out concerning the manufacture of artificial lightweight aggregates (LWAs). The study aims to evaluate the changes in the environmental impact when an additive of residual origin, specifically olive pomace (OP), is added following the principles of the Circular Economy. This residue (commonly known as alperujo) was used as a substitute for clay in 1.25, 2.5 and 5 wt%. The environmental impact related to the use of olive pomace in the mixture was estimated using the CML 2000 methodology, yielding improvements of 3.8%, 7.7% and 15.3% for 1.25, 2.5 and 5 wt% OP added, respectively. Optimum addition results are in the range of 1.25 and 2.5 wt% OP. In this way, the reduction of emissions associated with LWA manufacture would be favored without negatively affecting the technological properties of the resulting material.

Ternary diagrams as a tool for developing ceramic materials from waste: relationship between technological properties and microstructure.

The present work proposes the manufacture of ceramic construction materials using raw materials which are only industrial wastes from different production processes (electric arc furnace steel slag, coal bottom ash, carbon fly ash, and oil-filtering diatomaceous-earth). From them, the SiO2-Al2O3-CaO equilibrium phase diagram has been used to formulate two materials compositions with the objective of obtaining ceramics whose chemical composition is located in the same area as a traditional clay-based material, but with two different technological behaviors: refractoriness due to calcium phase's development and densification due to a greater melting capacity. The waste-based pieces have been sintered at three firing temperatures (1000 °C, 1050 °C, and 1100 °C) and the mineralogical composition has been quantified by Rietveld refinement-XRD in order to establish the agreement between the phases foreseen by the formulations in the diagrams and the mineralogical compositions actually developed after the sintering treatment. In addition, fired materials have been subjected to a complete microstructural characterization by means of SEM-EDX and the pore size distribution has been determined by means of mercury intrusion porosimetry and helium pycnometry. In general, all obtained materials display adequate technological properties for their use as building materials so this characterization has allowed to show the suitability of the ternary diagram SiO2-Al2O3-CaO for the design of ceramic compositions from industrial wastes. Therefore, extending the use of phase diagrams as a design tool is still little explored for waste-based ceramics, and those that have been mainly used for studying Mg-based phases can have an important contribution to a more sustainable construction sector.

Use of marble sludge waste in the manufacture of eco-friendly materials: applying the principles of the Circular Economy.

The marble industry generates enormous amounts of waste every year, whose incorrect management can lead to environmental problems. The Circular Economy model can provide an effective solution to this issue, an aspect that has been addressed in this research. The suitability of a marble sludge generated in the ornamental rock industry of Andalusia (Spain) has been assessed as raw material in ceramic bricks. Mixtures containing a clayey base and 0, 2.5, 5, 7.5, and 10 wt% of marble powder have been shaped into 60 × 30 × 10-mm3 prismatic specimens and sintered at 950 °C in a muffle. The main technological properties of the bricks related to color, shrinkage, porosity, water absorption, suction, and compressive strength have been determined. The addition of marble sludge has fostered the development of a lighter color, together with a significant increase of the open porosity. This aspect has implied, on the one hand, higher water absorption and suction results and, on the other hand, a decrease of the density and the mechanical strength. The correlations obtained after applying Shapiro-Wilk normality tests and r Pearson coefficients endorse the clear relationship between the addition of marble powder and the abovementioned effects on the technological properties of the sintered bricks. All the measured properties fully meet the brick standardized requirements, which would indicate that the recycling of marble wastes could be a promising alternative to obtain eco-friendly lightweight ceramic materials.