Steel Slag, GBFS & Mill Scale

GBFS for cement grinders, steel slag and mill scale in Supramax lots

Three steelworks by-products move in bulk under HS 2618.00 and 2619.00, and each is bought on a different number. Granulated blast furnace slag (HS 2618.00) is molten iron-furnace slag quenched in water into a glassy sand; the buyer is a cement grinder, and the number that matters is glass content (≥ 95% by microscopy or XRD), because only the glassy fraction reacts with lime in cement. Chemistry sets its grade: (CaO + MgO)/SiO₂ ≥ 1.0 and (CaO + MgO + Al₂O₃)/SiO₂ ≥ 1.6–1.9 to EN 15167 and BS 6699, with Al₂O₃ around 12–16%, MgO ≤ 12–14%, sulphide sulphur ≤ 2%, chloride ≤ 0.1% and loss on ignition ≤ 3%. As delivered it is 0–5 mm sand at 8–15% moisture; once ground to a Blaine of 4,000–4,500 cm²/g it is GGBS with a 7-day activity index of ≥ 45–55% and 28-day of ≥ 70–95% against reference cement. Steel slag (HS 2619.00, from BOF and EAF converters) is denser and does not vitrify, so it goes to road aggregate, railway ballast and cement raw feed rather than cement replacement; its risk is free lime (≤ 3–5% after weathering), which hydrates and expands, and free MgO, so it is sold aged and tested for volume stability. Mill scale (also HS 2619.00) is the dark flaky iron oxide (Fe₃O₄, FeO, Fe₂O₃) knocked off hot-rolled steel, 68–72% Fe with oil ≤ 0.5–1% and SiO₂, Al₂O₃ and P held low, and it is bought by sinter plants and cement kilns as an iron unit. Under the IMSBC Code mill scale ships as a Group A cargo when it is fine and wet, that is when a significant share is below 7 mm and moisture is near the transportable moisture limit, so a flow-moisture and TML certificate within six months and a moisture test within seven days of loading are required before a ship will take it; coarse, dry material can be declared Group C.

Japan is the reference exporter of GBFS to Asia. UN Comtrade, 2025 export declarations: Japan shipped 10.65 million MT of HS 2618 to 28 partners, led by Other Asia, nes (2.86 million MT, 26.8%, USD 8/MT), the USA (2.30 million MT at USD 12), Australia (1.46 million MT at USD 6), Malaysia (544k MT at USD 1), the United Kingdom (495k MT at USD 19), Singapore (331k MT at USD 11), Viet Nam (255k MT at USD 3), the UAE (234k MT at USD 3) and Qatar (116k MT at USD 2). China's own 2025 export declarations for HS 2619 are not available on UN Comtrade, so we do not quote a figure for them. Those unit values say what the trade is: the slag is worth USD 1–12/MT on the quay and the ship is the cost, so a Bangladeshi, West African or Gulf cement grinder buying GBFS is really buying a Supramax voyage with a slag cargo in it. The same holds for steel slag out of Chinese ports into the Bay of Bengal and for mill scale moving from Bangladeshi and Indian rolling mills to Vietnamese and Chinese sinter plants; steel-slag and mill-scale stems on those lanes are on our chartering desk now. CBIL is a commodity brokerage company with a chartering desk (LaycanDesk), so we quote cargo and vessel together, on FOB, CFR and CIF terms, against SGS, Intertek or Bureau Veritas certificates for glass content, chemistry, moisture and (for mill scale) Fe, oil and TML. Send your activity-index or Fe requirement, moisture ceiling, discharge port and whether you have a hopper or need geared tonnage, and we work the source and the ship to it.

Need the ship as well? Our chartering desk prices bulk limestone, gypsum and aggregates freight on LaycanDesk.