Green concrete (coloured) may be made by adding:
Try it first: pick an option, then read the explanation.
Correct answer: A. Chromium oxide
Making Green-Coloured Concrete
Chromium oxide (Cr&sub2;O&sub3;) is a stable, alkali-resistant inorganic pigment that produces a green colour in concrete. It is compatible with the alkaline environment of cement paste and does not affect setting, strength, or durability when used at typical dosages (2–5% by cement weight).
Iron oxide gives red/yellow/brown; iron hydroxide gives yellow/tan; barium permanganate is not a standard concrete pigment and would not give stable green. Note: in this question “green concrete” refers to the colour, not eco-friendly concrete.
Chromium oxide — option A.
Key takeaway
Green concrete (colour) → chromium oxide. Iron oxides give warm colours (red, yellow, brown). Always check whether “green” means colour or sustainability.