Concrete: The world's most useful ugly material

Few materials are as loathed, or as unavoidable. Concrete built the Pantheon and the Opera House, then spent the back half of the twentieth century being blamed for everything ugly in the city — a reputation brutalism earned it, fairly or not. But raw concrete has also produced buildings people travel across the world to stand inside. So why is this environmentally disastrous material still so much a part of our building toolkit, and how has it evolved along the way?