Question

compound formed by natural self healing of concrete

Answer 1

Explanation:

Chemically, black carbon (BC) is a component of fine particulate matter (PM ≤ 2.5 µm in aerodynamic diameter). Black carbon consists of pure carbon in several linked forms. It is formed through the incomplete combustion of fossil fuels, biofuel, and biomass, and is emitted in both anthropogenic and naturally occurring soot.[1] Black carbon causes human morbidity and premature mortality.[1]