For some DIY projects you need thin concrete or cement walls. They are prone to brake under tension or fall impact.
Instructables user "ucn" from Singapore wanted to make strong thing concrete molded business cards and successfully reinforced them with 3d printed mesh frame. It looks that this technique works great and could be applied to other concrete projects where you need internal reinforcement structure.
Here is a detailed buold guide with prototypes that led to final sucess and strenght testing: