Modern society requires a large number of metal components manufactured by sand casting, which involves the generation of a waste product known as Used Foundry Sand (UFS), of which approximately 100 Mt are generated on an annual basis. Virtually all UFS is currently landfilled, despite the economic and environmental cost overruns that this entails. Here, the recovery of UFS as fine aggregates for the manufacture of concrete is proposed. Since the presence of UFS will mainly affect the mortar that binds the aggregates in the manufacture of concrete, it was decided to isolate this fraction and study only the effect of UFS in mortars. This study evaluated a total of 32 different mixes combining different W/C ratios varying between 0.5 and 0.7 with 5 replacement ratios of natural sand by UFS: 0, 25, 50, 75 and 100%, respectively. The combined effect was evaluated of the W/C ratio and the replacement ratio on the workability, physical properties, mechanical properties, mechanical durability, and microstructure of the mortars. The incorporation of UFS decreases the workability of the mortars due to the absorption of the residue. For the physical properties of the mortars, density decreased and porosity and absorption increased at all replacement percentages. Flexural and compressive strength decreased when the replacement percentage was higher than 25 wt.%. In terms of mechanical durability, the mortars with UFS showed abrasion marks within the limits of the EN-1338 standard. From the results obtained, it is possible to conclude that the mortars with UFS require a higher amount of water. Therefore, while small replacement levels lead to a slight improvement in the mechanical properties, this trend breaks down for high replacement levels due to the negative effect of the high W/C ratios required. The authors recommend that for replacements higher than 25 wt.% of UFS, the W/C ratio has to be taken into consideration to obtain the same workability as the control mortar, although this decreases the mechanical properties.

Chromium (Cr) is an element present in nature in mineral form. It has a dual effect, both as an essential micronutrient and a carcinogenic agent depending on its chemical form and concentration. It is present in various environmental matrices such as water, soil, and air, coming from natural and anthropogenic sources, and causes harmful effects on biota, ecosystems, and even human beings. This study's objective was to evaluate chromium toxicity and teratogenicity in zebrafish embryos of Danio rerio exposed to chromium through the D. rerio teratology assay (DarTA) test by evaluating spine malformations. To this end, the chromium toxicity curve was calculated from zebrafish embryos exposed to potassium dichromate (K2Cr2O7), and the probit test was used to establish the mean lethal concentration (LC50) and three subtoxic concentrations LC25, LC12.5, and LC6.25 to evaluate the teratogenicity. The results showed that potassium dichromate was statistically positive for the teratogenic effect at the three highest concentrations evaluated. Potassium dichromate exposure causes abnormal embryonic development and teratogenic effects, including severe heart defects in zebrafish embryos. Therefore, we conclude that potassium dichromate is toxic to the zebrafish developmental stages. The finding that potassium dichromate is teratogenic in zebrafish embryos suggests that this metal should be tested and evaluate potential risk in mammalian systems.

This review explores the potential of water hyacinth (WH) as a sustainable material in cement-based applications, focusing on its use as an addition, admixture, and fiber reinforcement. WH’s unique physical and chemical properties, such as high cellulose content and pozzolanic potential, make it suitable for bio-composites and eco-friendly concrete formulations. The present study highlights several promising findings, including the enhancement of the resulting mechanical properties and the reduction in their environmental impact when the WH is incorporated in controlled quantities. Challenges such as workability and durability issues at higher dosages are discussed. This review aims to bridge knowledge gaps and support WH’s adoption in sustainable construction practices.

In this work, the feasibility of partially and totally replacing natural sand with used foundry sand in self-compacting concrete was studied. Natural sand was replaced in 50% and 100% vol. by used foundry sand. The fresh state properties parameters analyzed in this study were slump flow, t₅₀₀, V-funnel, Japanese ring and L-box following EFNARC guidelines. Results indicated an improvement in the fresh state properties when used foundry sand was utilized for partial and total replacement. The mechanical properties compressive strength and splitting tensile strength were obtained and analyzed at 7 and 28 days. Regarding the compressive strength, used foundry sand enhanced compressive strength by up to 67% compared to control concrete. For splitting tensile strength, the self-compacting concrete with 50% vol. of used foundry sand displayed a slight decrease (2.8%) compared with the control concrete. SEM images showed that the concretes with used foundry sand had a less porous and more compacted matrix than the control concrete. It was concluded that the incorporation of used foundry sand in large volumes can be utilized as a sustainable alternative natural fine aggregate.

Se presenta un método de análisis rápido para la evaluación de potencial de riesgo genotóxico asociado a metales pesados presentes en agua potable. Este método se basa en el análisis de las principales características fisicoquímicas, cinética ambiental, biodisponibilidad, efectos biológicos reportados y/o potenciales que puedan incrementar la probabilidad de manifestar un efecto adverso. Se planteó un caso de estudio en Zimapán Hidalgo, debido a que existen evidencias de la presencia de metales pesados de interés toxicológico en el agua potable. Los resultados de la aplicación de la metodología ERPRG muestran que el cromo, cadmio, arsénico y plomo se encuentran en la categoría de potencial de riesgo alto; mientras que el mercurio en la categoría de riesgo intermedio. ERPRG, es una herramienta que permite identificar situaciones de potencial de riesgo biológico y ambiental, basada en el análisis sistemático de reportes bibliográficos y estudios previos que permiten determinar cualitativamente el impacto de variables ambientales, biológicas y situacionales de manera clara, rápida y resumida.