Answer:
During the second industrial revolution which building material became one of the most important in the world
The answer is Steel
Step-by-step explanation:
The second industrial revolution covers the period from 1870 to 1914. During this revolution brought the Bessemer process in 1856 invented by Henry Bessemer's this process was the first inexpensive industrial process for the mass production of steel from molten pig iron. (please see image attach)