Roman concrete was made of limestone, water and pozzolana, which was volcanic dust and gave it great resistance and durability against the elements. The concrete was used in most of Rome's greatest designs, like the Pantheon, the Colosseum and the aqueducts, It was also used for every day buildings.
Building the Pantheon in rome
Today's Concrete
The most used product in concrete is Portland cement which gives the concrete the same resistance and durability against the elements of roman concrete. unlike roman concrete, today most buildings that are made of concrete use steel rebar to help enforce it.