I have a slab of concrete over the front entrance of my house with some serious cracks in it. I don't actually know what the proper name for it is, which makes this difficult to Google - so I've uploaded two photos to illustrate:
How do I repair those cracks? Firstly, what's the best thing to fill them in with? Secondly, how do I get that filler to not fall out while it sets?
You may need to approach this with some caution. It looks like the reinforcing steel is corroding from the picture. When this happens the steel expands and causes the concrete cover over the steel to spall off. Once the reinforcing bar looses its cover the rate of corrosion will increase and the bond between the steel and the concrete is substantially reduced.
The problem is that just covering up the steel with a crack repair mortar may not fix the corrosion problem and either another section of the concrete could spall off or the repair mortar could spall off. I would suggest you get it looked at by a specialist. It doesn't look like it is in imminent risk of failure but just covering up the cracks may mean that you are hiding a long term problem.
I would use a product specifically designed for repairing cracks in concrete, something like:
Carefully follow all the instructions that come with the product, plus:
Thorough cleaning and preparation of the cracks is vital when using "crack repair" products. If you take shortcuts on the prep-work, the repair (patch) will never look that good, and will more than likely "fail" fairly quickly.
Personally, while I was doing the prep-work on the cracks, I would also take the time to prepare the complete concrete porch roof for repainting.
Then to finish the job properly, once you've repaired the cracks, waited at least a further 24 hours:
