Expansion gaps

[cwr]

Hi folks,

 

There's one last bit of concrete floor to pour for my garage /outbuilding. 8 x 6m, 150mm thick C30 with A252 mesh. It is however bounded on 3 sides (the two 6m wides ends and one 8m long side) by existing concrete slabs.

Should I put in foam expansion strips along these edges? 

 

Concrete shrinks when it sets doesn't it, so presumably gaps will open up anyway. So just fill them with suitable flexible sealant afterwards?