Cementing small areas around drains and sewer covers etc

I have lots of small areas in the garden that need to be filled with sand / cement.
Thew are small areas around the likes of drains and sewer covers.
I have used aout a 3:1 sand:cement mixture and it never seems to stay for long.
Of course, it hardens ok, but it just seems to break away in chunks ater a very short time.
Any suggestions?
Should I change the ratio of sand . cement?
Should I tyy to break out more of the existing concrete so that the it I am filling in is larger, so will get a better hold?

Hi Conshine,

For small jobs like that, I have just used "ready made" bag of concrete from B&Q/Woodies. Just add water, mix it up & has done the job ok. Still ok after 12 months or so...

Thanks - Its just that these small areas tend to break up after some time with people walking over them etc. I have repeated this exercise at least once a year in recent years. I am talking very small areas, maybe an inch or two wide, the length of the drain.

I have done similar work on a sewer cover (not much activity on it), an extension of a raised floor /step (2 inches deep, around 12 inches long, 3 or 4 inches high) into an outhouse for the boiler (again not much activity) - also something similar (step wise) into a shed - that does get activity... and is holding it's own.

You could try drilling into the surrounding concrete & putting thin steel spikes in, over hanging the area you are to concrete over... even some long nails /screws (drill the holes though, don't hammer as the force will just crack the surround) - just to give the new concrete something to hold onto.

Could be water eroding it, on top of general wear & tear...

Is the cement part you are making very shallow?

I am just about to do something similar, but the pieces I took out are about 3inches deep.