Crack-Pac® Injection Epoxy | Simpson Strong-Tie- concrete slab crack repairs ,The Crack-Pac injection epoxy is designed to repair cracks in concrete ranging from 1/64" to 1/4" wide in concrete walls, floors, slabs, columns and beams.DIY Concrete Crack Repair | The Family HandymanConcrete cracks are caused by sideways expansion, poor drainage conditions or settling soil beneath the concrete. If your concrete is the same height on both sides of the crack, you can fix it yourself.