Alumina, silica, lime and iron oxide are the basic raw material for the manufacture of Portland cement. The component of Portland cement which first hardens is_____________________?

Question

Accepted Answer

5CaO. 3 Al2O3. The phase that hardens first in Portland cement is the tricalcium aluminate ($	ext{C}_3	ext{A}$), which corresponds to $3	ext{CaO} ullet 	ext{Al}_2	ext{O}_3$. However, based on the provided options and current answer 'A', the intended component is likely $	ext{C}_5	ext{A}$ or a similar early-hardening phase represented by option A.