, I renovated my house, plaster cracks, cement cracks, brick cracks. Even I cried. After a long search on the Internet I found out that ordinary PVA glue is an excellent additive for the grout mix and the concrete, making them stronger, more stable and "stickier" (well, it's still glue). Make a solution of water mixed with this glue, about 10% glue. I paint the area I am correcting with this solution. I then mix powdered mortar or concrete into this solution. I apply modified joint compound or concrete and proceed as usual. In fact, I mixed concrete with undiluted glue and pigment to make concrete almost clay-colored and used it to "fix" or "brick" some broken bricks. You can't tell where I made the repairs. It's been two months since the repair and it's holding up great! Just make sure you remove any rotten or chipped bricks and coat them with grout a few times to stabilize them first. I used modified stucco on a curved stucco wall under the stairs that constantly cracks from the vibration of the footsteps. My repair seems solid and crack free even months later. I will never again just use water to mix grout or concrete. Now it's a staple of the weird but effective things that make repairs easier and more efficient!