The lifting looks good, I wouldn't touch it anymore. The character has a ways to go, the walk is too choppy, a little bit of sliding at the feet that needs to be corrected, and while the slab is being lifted have his right arm go down to his side and have him take his hard hat with his left and scratch his head with his left pinky, or something... ya know? That's what I saw people do at the construction site where I work. It'll give your character something viewers can associate with - just my thoughts