escórias

Escórias are byproducts of metal smelting and metalworking, produced when molten metals react with oxides and silicates to form a solid that cools into a glassy or porous material. They vary by process and feedstock; in Portuguese they mainly refer to metallurgical slag, but geologically similar material known as scoria exists in volcanic rocks.

Most common forms include blast-furnace slag from ironmaking, steelmaking slag, and non-ferrous slag (copper, lead, zinc). Their composition is largely calcium, silicon, and aluminum oxides, with varying levels of magnesium, iron, and trace elements depending on the process. Some slag products are rapidly quenched to produce granulated slag; others are air-cooled to form coarse aggregates.

Uses of escórias are widespread in construction. Ground granulated blast-furnace slag is used as a cement supplementary cementitious material; slag aggregates are employed in concrete, asphalt, and road bases; and certain slag products are used as soil amendments where appropriate. Other applications include producing glass-ceramics or mineral wool insulation, depending on the properties and contaminants of the slag.

Environmental and regulatory aspects are important in slag management. Slag can contain hazardous elements, so leaching tests and stabilization processes are used to improve safety. Regulatory frameworks may classify slag as hazardous or non-hazardous waste, and recycling and reuse are encouraged to reduce mining demand and disposal.

Geological note: in geology, escória may refer to scoria, a vesicular volcanic rock formed by eruptive processes. It is mined and used as a natural material for lightweight aggregate and decorative stones, distinct from metallurgical slag.