The Romans are thought to have been the fi rst to use the binding properties of volcanic ash in mass concrete structures. The art of making concrete was then lost until Portland Cement was discovered in 1824 by Joseph Aspedin from Leeds. His work was developed by two Frenchmen, Monier and Lambot, who began experimenting with reinforcement. Deformed bars were developed in America in the 1870s, and the use of reinforced concrete has developed worldwide since 1900 – 1910. Concrete consists of a paste of aggregate, cement and water which can be reinforced with steel bars, or occasionally fi bres, to enhance its fl exural strength. Concrete constituents are as follows:
Cement Limestone and clay fi red to temperatures of about 1400°C and ground to a powder. Grey is the standard colour but white can be used to change the mix appearance. The cement content of a mix affects the strength and fi nished surface appearance.