Yes. In this sentence pavimentō is ablative, which is the normal case for the object of a preposition.
The preposition "in" is tricky, though. When it expresses motion, it takes the accusative; when it expresses static location it takes the ablative.
It's like there was a two-for-one sale on prepositions, and the Romans bought "in" ("into", taking an accusative object), expecting to then get a second preposition, but the clerk said "I just gave you the second one, 'in' ("within", taking an ablative object)."