Composite in which concrete carries compression and embedded steel rebar carries tension.
Core Principles & Analysis
Steel and concrete have nearly identical coefficients of thermal expansion, around 10-12 ppm/°C, so the bond survives temperature swings.
Concrete's pore water is highly alkaline (pH near 13) and passivates the rebar; carbonation or chloride ingress breaks this protection and triggers rust and spalling.
French gardener Joseph Monier patented steel-reinforced concrete in 1867, originally to make stronger flower tubs and basins.