Durcir belong to the 2nd
group. Durcir is a common french verb.
Durcir is conjugated the same way that verbs that end in : -ir
Durcir is conjugated with auxiliary avoir
Durcir verb is
direct transitive, intransitive.
French verb durcir can be conjugated in the reflexive form: Se durcir
verb is a direct transitive verb, so passive voice can be used.