Besides the answer of Game Freak made him like that he may carry the ("Concrete Pillars") because he can attack with them,Without using its physical strength?
Conkeldurr can create concrete, a technique it was believed to have taught humans 2000 years ago. It uses its concrete pillars to attack strongly, without using its physical strength. It also uses them to support its massive upper body.
I love Weird things ¯(°_o)/¯