We have two types of slag that I'm aware of in our area. One is a black glass type slag from Tyler Pipe. It's very attractive looking when on the ground, but it never locks together, so it's always moving and shifting around. Kind of like walking on sand. It also sticks to your shoes, so if you walk on it, you will carry some of it into the house with you. Over time, it breaks down and disapears. When it's there, it is a dry place to walk and drive on, but I don't know how much of a load it can handle. People use it for driveways and parking areas with fair results.
There is another type of slag that comes from down towards Austin that looks like limestone. It's grey in color and rough around the edges. You buy it by the size and they truck it up here. First you buy a load of the big stuff, which is several inches in size. Spread that and then have the fine stuff delivered. They don't mix the sizes on the trucks that deliver it. Spread the fines over the big stuff so that it locks together. When done, it's a very nice looking driveway that is solid. It's rather labor intensive since you have to do it twice. It's fairly new to the area, so I don't know how long it will last or hold up. The guy selling it says its as strong as limestone, but from looking at it, I don't believe him. A load of it costs just as much as limestone, which is a proven road building material.
That price is very cheap, which makes it very tempting. Of couse, if it doesn't do anything, you just wasted your time and money. Before buying it, I would ask to see where it's been used and then go take a look. Even better, check it out on a rainy day when it really matters.
Even more important then what you use is that you have sufficient drainage. If you don't have a place for the water to go, and for it to move away from your road quickly, nothing that you put down will last, or even perform very well.
Good luck,
Eddie
