Abstract: The ecotoxicological view is one of the least studied aspects of sustainability in the cement sector. Although some regulations starting to include it, since new products incorporating waste materials need to be environmentally safe throughout their circular life cycle. Chemically bonded phosphate cements are a more sustainable alternative to conventional cements due to their lower environmental impact and the promotion of the Circular Economy by incorporating industrial waste. This paper analyzes the potential ecotoxicity over marine biological life of two alternative magnesium phosphate cements obtained from secondary sources of MgO. MPC-LG using the by-product low-grade MgO (LG-MgO) from the air pollution control system of the magnesite calcination kiln, and MPC-TUN using the tundish deskulling waste (TUN) obtained at the end-life of refractory material employed in the last metallurgical vessel of the steel casting process. For this purpose, the ecotoxicity criteria proposed by the European Construction Products Regulation are used as a reference. The Compliance leaching test, as well as two different ecotoxicity tests, the marine bacteria Vibrio fischeri luminescence reduction and the sea urchin Paracentrotus lividus embryo-larval development success, were conducted. No significant effects were observed on the bioluminescent bacteria within the leachate concentration range (until 80 %). In the sea urchin embryo-larval development test it was observed that the MPC-TUN sample showed lower toxicity than the MPC-LG sample. In summary, the results obtained from both ecotoxicity tests show consistency with the leaching behavior of Sust-MPCs, and demonstrate that they are environmentally safe in a marine scenario.

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