Crucible will send automated reminder to reviewers before the due date, if such date was defined for review. Review author and moderator can also manually send reminder to reviewers who didn't complete review yet. You can find more information on this here: https://confluence.atlassian.com/display/CRUCIBLE/Using+Review+Reminders
There are no means to automatically send reminders on overdue reviews though. Those reviews would be displayed on all overdue reviewers' dashboards.
Hope that helps,