Thirdrail𝕏

Concrete is the most used man-made material in the world (second only to water). 25–30 billion tonnes of concrete produced every year. More than twice as much as all other construction materials combined. (Cement, the binder, is ~4 billion tonnes/year.) But concrete has a problem: It cracks. Almost always, eventually. Why: • Concrete expands and contracts with temperature and moisture • Steel reinforcement corrodes, expands, and splits the concrete from inside • Design life: typically 50 years for buildings, 100 years for major infrastructure Much of the world’s post-war infrastructure built in the 1950s–1970s is now at or past design life. 
In the US alone, the investment gap to bring infrastructure to a state of good repair is on the order of $2.5–3.7 trillion. We built a civilisation on a material that slowly fails.