Hi @sammyla,
When you say they don't use aggregate, is this in their concrete mix? Or as a base for the concrete slab?
Either way, aggregate in some form is necessary for the base and as part of the concrete mix.
Pouring a concrete slab starts with preparation. The site is marked out, soil is excavated to around 100–150 mm, and a compacted crushed rock base is laid, with compactible material such as drainage gravel or road base.
Formwork is then built around the slab area, followed by a vapour barrier and reinforcement mesh supported on reinforcing bar chairs.
Concrete is then poured, usually 100 mm thick for general use or 125–150 mm for driveways. A ready-mix of 20–25 MPa is standard. The surface is screeded, smoothed with a bull float, edges finished, and a broom finish applied for slip resistance.
If the quotes you have received do not include some allowance for base material, then I would suggest you ask them to include this in their quote, as it is an essential part of the process.
If they are not using aggregate in the concrete itself, I would not consider their quote. Without aggregate, it is not concrete; it is mortar, which is not suitable for a slab.
Check out How To Pour A Small Concrete Slab for some further guidance.
Let me know if you have further questions.
Jacob
