Chile approves use of copper slag approved for use as artificial aggregate
Chile’s Ministry of Health’s this month officially authorised the use of copper slag in infrastructure including as artificial aggregates in construction such as for road surfaces, bringing a value add and important circularity benefit to what is a major significant waste product in the country’s copper industry.
Copper slag is defined in the decree “as that waste that is produced as a result of high-temperature smelting processes. This residue is mainly composed of iron oxides and silica, which is why it is also called iron silicate, along with small amounts of other elements such as aluminum (Al), titanium (Ti), calcium (Ca) and magnesium (Mg).”
Promulgated on October 23 and made legal when it was published on February 12, 2026, Supreme Decree 46’s Article 3 further states: “Copper slag may only be used as an artificial aggregate for construction and manufacture, with prior sanitary authorisation from the respective Regional Ministerial Secretariat of Health, which shall be granted exclusively for the uses specified in the application and provided that they meet the requirements and conditions established in these regulations.”
Joaquín Villarino Herrera, Executive President of Consejo Minero described it as a concrete advance to promote the circular economy in mining, “transforming a historical environmental liability into a valuable resource for road paving, prefabrication and infrastructure works, with demanding sanitary, traceability and leaching control standards.”
But he added that this regulation has not come out of nowhere – in fact it is the result of years of articulated work between the public sector, led by the Ministry of Health together with the portfolios of Mining, Public Works and Environment, and partner companies of Consejo Minero, such as Codelco and Anglo American, which have promoted successful pilots such as the Loncura road in Ventanas or paving at the Chagres Smelter and Las Tórtolas plant.
Miner Anglo American has been a major proponent of copper slag reuse for some years, and has done a lot of detailed background and technical work leading up to this development. “The approval of this regulation represents a key step in moving towards more modern and responsible mining. At Anglo American, for more than a decade we have gathered technical information and conducted studies with various universities to then demonstrate through concrete pilot projects that it is possible to use copper slag safely, with scientific backing and with real benefits, analyses that laid the foundation for the regulation recently published,” says Juan Pablo Schaeffer, Anglo American Vice President of Corporate Affairs and Sustainability.
As an example, in the city of Catemu, Anglo American reclaimed a public space for the community by using a mixture of copper slag and aggregates for the construction of a new plaza. This was a pilot project with scientific backing from the Pontifical Catholic University of Valparaiso.
At Anglo’s Chagres smelter in 2025 it paved 1,630 m² of internal roads, where more than 95% of the materials were slag from the smelter. And at its Las Tórtolas plant it constructed a 500 m road incorporating mixtures of chemically stabilised slag and tailings. These projects were part of a collaboration agreement with the Chilean Ministry of Public Works.
Katherine Ferrada Environmental Manager at Anglo “For us, this announcement is very relevant, because at Anglo American we have always believed that mining should be part of the solution and not part of the problem. Slag is a massive waste product of the smelter, and, being located – through our Chagres Smelter – in the Aconcagua River basin, we have seen for years the impact of aggregate extraction, especially in a context of prolonged drought. Reusing slag not only allows us to take responsibility for a liability, but also to contribute to reducing that environmental pressure, incorporating a circular economy approach into the smelter, and generating a concrete benefit for the region.”
Codelco has also been a supporter of the circularity benefits of the reuse of copper slag use for many years. In its case, the closure of the Ventanas Smelter presented an opportunity to materialise the efforts of more than a decade to make viable the reuse of the material accumulated in its slag deposit, located on the side of Route F 30, in Puchuncavi. Also working with the Pontifical Catholic University of Valparaiso, Codelco restored public spaces in a historic neighbourhood of Quintero, using copper slag from the former Ventanas Smelter as a base input in the manufacture of tiles, paving stones and urban furniture.
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