Collaborative learning technology has been used across disciplines in support of argument development. These technologies allow multiple users to concurrently analyze and edit documents in the same online virtual space, and can offer richer cues for collaboration awareness. However, little is known about how such synchronization mechanisms work together to support small group collaborative argumentation. This exploratory study reports the experiences and reactions of 14 dyads that worked together using Critical Thinker, a web application that allows learners to collaboratively develop structured arguments in a synchronous workspace with collaboration affordances. Our qualitative data shows how the structural juxtaposition provided by the tool can scaffold dialectical construction of arguments, while the synchronization mechanisms can facilitate collaborative learning tasks. We use these findings to inform ongoing design efforts to deploy Critical Thinker as classroom technology. This paper reports how synchronization mechanisms can work together in Critical Thinker, a web application that allows learners to develop structured arguments collaboratively in a synchronous workspace with awareness support.