Final answer:
Concrete gains most of its strength within the first 28 days of placement, during which curing takes place, and it has historically been used by civilizations like the Romans for its durable properties.
Step-by-step explanation:
Concrete gains most of its strength in the first 28 days after it's been placed. During this time, the process of curing occurs, which is essential for the development of strength and durability. The initial phase of curing is most critical, during which concrete should be kept moist to allow the cement to hydrate properly. This process gradually transforms the fluid mixture into a hard, stone-like material. The strength of concrete continues to increase over time; however, a significant portion of its strength is achieved during the early stages of curing.
Historically, the Romans utilized concrete's strength and versatility in their architecture and infrastructure. They were able to create structures that could withstand earthquakes and even construct underwater, using concrete to build harbors and breakers in their ports. An example of Roman concrete can be seen in the ruins along the Via Appia. In contrast, the ancient Egyptians erected the pyramids using large stone blocks, utilizing a completely different set of architectural and engineering principles where the potential energy from lifting stones contributes to the stability of the structure.