RoadWorks is a mod focusing on adding the base connection infrastructure currently missing from Factorio. The mod expands on the car aspect of the game, adding features such as paved roads or speedometers.
RoadWorks also adds limestone, which is a new kind of ore used to make concrete. Once the Hydraulic Cement research is done, limestone can to be burned into quicklime, which is then mixed with water and stone in a chemical plant to make concrete. At the moment, concrete is only used in pavement crafting, but eventually it will also be used in bridge construction and possibly other recipes. Concrete pavement needs 4 concrete blocks for crafting and speeds up both cars and players by 30%. Note that you do not need the Oil Refining technology to build the chemical plants needed to create concrete.