Concrete
Concrete has relatively high compressive Strength, but significantly lower tensile strength, and as such is usually reinforced with materials that are strong in tension (often steel).
Concrete has a very low coefficient of thermal expansion, and as it matures concrete shrinks. All concrete structures will crack to some extent, due to shrinkage and tension.
Further training may be required for personnel, this can be undertaken by issuing a safety alert in relation to the incident, carrying out a toolbox talk, and training in Safe Operating Procedures.