The History of Cement and Concrete Part 4
Cements and concrete have a long and illustrious history. From the Ancient Egyptians to modern buildings, both have served as materials for the most astonishing of construction projects. This five-part series tracks how the materials have developed over time.
Part 4: Making modern cement and concrete
Both cements and concrete are made from limestone. Cement is made by heating powdered limestone with clay. Concrete can then be made by mixing the cement with sand, water and aggregate. The combinations cause chemical reactions to occur so that they both set hard. Different combinations can be created to produce concrete with specific characteristics, strength and durability – so that it works for each specific job.
Reinforced concrete takes the concrete and introduces another steel making it a composite material. Each substance reacts differently to forces; as steel has tensile strength and concrete has compressive strength. In other words, concrete is strong when pushed together and steel is strong when stretched. The addition of steel to the concrete makes the entire substance stronger.
Because different combinations of minerals and rocks can be used to create both concrete and cements, standard tests have been developed to ensure that they are being mixed and used appropriately. Bodies like the American Concrete Institute ensure these standards are maintained.