Quality
How to read a GBFS certificate of analysis
A useful GBFS certificate names the lot and reports the oxides, glass, moisture, sulfur, and size the buyer actually checks. It does not set a universal spec.
3 min read
A certificate of analysis is a description of a lot, not a brochure. For raw granulated blast furnace slag, the useful sheet says which plant and which production window it covers, which laboratory ran it, and the results the receiver intends to police.
Oxide analysis is the first block buyers ask for. Calcium, silicon, aluminum, and magnesium oxides describe the glass. Other oxides and minor elements show up because a mill’s internal window includes them. There is no honest universal table of minimums to paste into a website. Windows differ by mill, by the finished standard that mill sells, and sometimes by season of the furnace. Ask the buyer for the window. Then put the certificate next to it.
Glass, or amorphous content, is the second block. It is evidence that granulation did what it was supposed to do. Methods differ. A number without a method is a weaker number. If two labs disagree, the contract should already say whose method governs.
Moisture is commercial, not only technical. It changes the tons of solid you think you bought and the energy a dryer will spend. Record whether the figure is as-shipped or dried for analysis. A laboratory moisture on a prepared sample can look calmer than the pile.
Sulfide sulfur and sulfate matter because slag-cement standards limit them in the finished powder. The raw lot does not have to recite the finished limit as if it were already ground. It does have to be capable of being processed into a powder that can meet the limit the buyer named. That is a conversation with the mill, not a slogan.
Particle size should show a granulated product. Lump, or a tail of oversize, is a handling and milling problem. Tramp metal and foreign matter deserve a line of their own. Bulk density is worth having when someone is calculating stowage or a stockpile footprint.
Mark the sheet as supplier-reported or independent. Both can be legitimate. They are not the same kind of evidence. GulfGran will pass through what we receive and will say which is which. We are not an accredited laboratory, and we will not average three lots into a prettier one.
Bring the certificate you buy against to the quote request, or read the document list on the quality page. The point of the paper is a decision: accept, test further, or decline.