A document from the manufacturer certifying the chemical composition and mechanical properties of a specific heat or batch of steel or other material.
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In the Field
Specs for structural steel, rebar, and pipe typically require certified mill test reports (CMTRs). Collect them at delivery, match to heat numbers on the material, and turn them in at closeout. Losing them delays final payment.
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Rule of Thumb
Every piece of structural steel has a heat number stamped on it. Match it to the CMTR — if you can't trace it, the material may be rejected by the inspector.