Reinforced concrete is currently the most important building material in both structural and civil engineering. It is a relatively young material, not much older than 150 years, that gained its significance in construction based on engineering research. The title of the book refers to a small booklet by Max Hasak from 1925, "What the Builder Needs to Know About Mortar." This publication deals with the history of reinforced concrete construction, the materials used, and the causes of damage. Civil engineers, architectural historians, and architects also present methods for the careful restoration of historical reinforced concrete structures.