paving stone 
(British also paving slab)
noun
A large, flat piece of stone or similar material, used in paving: small plants grow between the paving stones...
- There are precast paving stones in a wide variety of sizes, shapes and colors that are perfect for borders.
- And it's the cheeky things, like setting up their little stepping stones, with my paving stones, that upset you as well.
- A local children's playground was ‘smashed to pieces’ and the paving stones from the playground were then hurled at his officers.