Correct option is C
Ash :- Fly ash is a by-product of burning pulverized coal in electric power generating plants.
During combustion, the mineral impurities in the coal (such as clay, feldspar, quartz, and shale) fuse in suspension and are carried away from the combustion chamber by the exhaust gases. Fly ash is typically captured by electrostatic precipitators or filter bags before the flue gases reach the chimneys of coal-fired power plants.
Surkhi :- Surkhi is a type of pozzolana, which is an artificial material used in construction. It is made by grinding burnt clay bricks or burnt clay lumps. Surkhi is used in lime mortar to improve its strength and water-resistant properties.
Blast Furnace Slag:- Blast furnace slag is a by-product of the iron-making process. During the smelting of iron ore in a blast furnace, impurities such as silica, alumina, and other minerals are separated from the molten iron. These impurities combine with fluxes like limestone to form a molten slag. When this slag is cooled and solidified, it can be used in variousapplications, such as in the production of cement and concrete.
Silica Fume :- Silica fume is a by-product of producing silicon metal or ferrosilicon alloys. It is an ultrafine powder consisting of spherical particles of silicon
dioxide. Silica fume is used as a pozzolanic material in concrete, improving its strength and durability.
