A strange job

This past week contractors were on the Saint Joseph's College campus leveling concrete. The freeze-thaw cycles gradually break up the even surface of sidewalk, lifting some sections and lowering others, so that the danger of tripping and falling increases over time. For some sections of walks, the contractors were grinding down high points. Near Halleck Center they were doing a more complicated procedure, drilling holes in the slab and then forcing concrete underneath its low side to raise it and get rid of the slope.

I was told that it was expensive. But it must be cheaper than removing the old concrete and replacing it with new.

I had never seen this procedure before.