Repairing cracked concrete

During the warmer months I spend most of my 'leisure' time trying to keep the weeds from going in the cracks in the concrete in the backyard. It is a flat, rectangular area approximately 5 metres deep and 8 metres wide which connects the house to the backyard. It is old, there is holes and cracks and weeds and grass grow very quickly in the holes, cracks and grooves that are meant to be there.

I have tried weedkiller, boiling water, salt, vinegar, using the weedeater and weeding by hand. Each method has limited success. Handweeding is probably the most effective but is incredibly time consuming.

Today while I was crawling around on my hands and knees, breaking nails pulling up grass and dandelions again, I started wondering about filling in the cracks and gaps so there would be no where for the weeds to grow.

Would it work if I cleaned out the cracks, maybe with the hose, then filled it with a mix of sand and cement then damp it down with more water?

Or should I make up a wet mix of sand and cement and slap it in the cleaned out cracks and gaps?

I am concerned the new cement won't stick to the old concrete. Do I need to do something to make it happen?

I would be grateful for any advice. I would love to spend the Summer doing fun things like weeding the veggie garden and fighting the weedeater.

BTW - we rent this place so a major renovation is not an option, as much as I have dreamed about it.

hire a waterblaster for the day, absolutely blast those cracks and joints, until no more mud will come out of them, mix some cement with plastering sand and broom it in, wet it gently and wet it again in 20 minutes, again 20 minutes later, run the hose onto the pad beside the cracks not directly into them

or buy a pack of permasol or another pavement permanent weed killer, it will give at least 12 mnths of protection and you can redo it a few months later for longer - most of your weeds will be new seeds either blown in or carried in

a small bag of urea is often all thats needed, simply drop a spoonfull into the center of each weed, it will burn it right down the tap root and that wedd will never come back -an urea spill in a paddock often takes 3 yrs to grass over, should mean you'd only have to repeat every couple of years

Thanks Skin1235. I will give it a go. I think I'll just use the hose to clean the cracks though. The concrete is so old and crumbly the water blaster would blow it all away.

Most of the weeds that grow is grass, which will be coming from seeds. There is a lot of dandelions, would urea work on them?

http://www.cemix.co.nz/
have all kinds of concrete products that should stick very well. Cemix is available at some hardware shops.

http://www.cemix.co.nz/products/crack-fillers-products