Question: How does the partial replacement of aggregates by slag in self$-$compacting concrete $($SCC$)$ contribute to sustainability in civil engineering?

A$)$ It increases the cost of construction projects due to the higher price of slag.

B$)$ It decreases the durability of SCC$,$ leading to more frequent repairs and maintenance.

C$)$ It reduces the environmental impact of concrete production by utilizing a waste material.

D$)$ It has no significant effect on the sustainability of civil engineering projects.