How is cement made so much more complicated than I thought

Strength of cement

The strength of cement is an important criterion for evaluating the quality of cement and an important basis for dividing the strength grade. The strength of cement refers to the maximum destructive force it can withstand per unit area after hardening, which is expressed by MPa (mpa).

We will see that the cement bag is marked with the words 52.5, which refers to the strength level of the cement, meaning that the standard specimen can withstand a maximum pressure of 52.5 mpa, and the words such as 52.5R, R means early strength, indicating that this cement can reach a higher strength in the early (short time).

Since the cement, the building is higher and higher, the road is longer and longer, the size of the city is also getting larger and larger, these have the credit of cement, it is one of the essential basic materials for the construction of modern society, cement has changed the face of the earth, known as one of the inventions to promote human civilization, is the cornerstone of human civilization.

However, some people have listed cement as one of the worst inventions in the history of mankind. Why?