1. So, first you need to slightly enlarge the crack using chisel and hammer, slowly and carefully cutting the edges for the formation of shallow hollows.
2. Before applying the cement mortar it is necessary to purify the resulting hollow with a stiff brush, for example, of steel wire.
3. Prepare solution (1 part cement to 2 parts sand), thoroughly moistened with water groove and fill it with a solution as tightly as possible.
4. Carefully smooth the solution and wetting the trowel with water, smooth out the seam. While the cement cures (3-7 days), the former crack better cover the Board that the work was not in vain.
5. If the crack time has not “healed” and a concrete strip crumbled, nothing to do, you will have to restore it. But first you need to cut with a chisel the damaged area.
6. To indicate the edge of the track, we need to sit to it wooden plank, a metal strip or Board and fasten it by two or three pegs, not to depart.
7. A shovel lay in the niche of sand-cement mortar (1 part cement to 2.5 parts gravel), compacted, for example, Poleshko, if necessary adding a solution.
8. Final step: carefully restored, smooth place grout from sheet metal or plywood. Now it is desirable to shield or cover a restored section of the track.
According to the magazine “Earmaster” (Hungary)
Recommend to read CAN BE ALONE Two-handed saw because so called that it requires the application of tractive effort of the two hands for which at each end there is inserted on top of the wooden handle. But experience... DESIGN SHADOW Undeservedly forgotten in the garden plots of the so-called architecture of small forms. For example, pergolas and trellis — light openwork structures, usually overgrown with plants... 
Wow, what a shame — cracked and crumbled concrete path on your country station! To talk about the fact that slim was a layer of mortar or the soil slipped, too late… But you shouldn’t be upset— your track is easily “cured”. But this must be done as quickly as possible, while the crack is small.