ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
