The chemical reaction that binds concrete in a matrix takes place after you add the water and continues until you dry it out. Anything you put in the crack will be a temporary fix only. The material will work itself out over time, and you will additionally be trapping a certain amount of moisture in the crack with it. You will now have a concrete pad with a ‘pocket’ and a ‘plug’ made from different materials. Materials that are likely to expand and contract at different rates exposing an opening for moisture and debris at least once through the year.
You only get (1) chance to successfully pour concrete i’m afraid. Your pad is damaged for all time. The crack will certainly grow from thermal conditions alone. It’s incapable of healing itself. What you need to stave that off is good chemistry for binding and something that expands and contracts at approx. the same rate as the concrete. I’d call the company that poured it. They’ll know what repair product best matches their chemistry. If you put the wrong products in it, it’s going to accelerate the degradation.
I am a refractory designer, and the company I work for makes several ‘patch’ type products of different chemistries. They all have a use. Temperature, application, chemistry, elevation even. While these do work, they are again only temporary.
They come in different consistencies. One of those is what we call a plastic. It is very much like a putty until it dries. It does contain some moisture so it will shrink as it dries out. It does not contain as much moisture as a self flowing castable would.