If the spawl is because the brick was soft or because of freezing it probably isn't worth the trouble to glue back. More spawls will occurr as time passes. Just do your best to prevent moisture from getting into the brick by applying several coats of masonry sealer each year.

If the brick is solid and was chipped from an isolated impact it can be glued back with a two part epoxy glue such as JB Weld. In this case I don't recommend mortar because it doesn't adhere well in thin joints. Most epoxy glues are available in quick setup (5 minutes) or standard setup (1hour). I prefer the 5 minute type but it requires that you work quickly. Full strength is reached in 24 hours. Mix more than enough for the job, but don't apply so much that it squeezes out of the joint when compressed. The brick must be dry. Clean away all loose material and apply a thin layer to each surface. Then press the pieces together and hold in place by hand or with masking tape. Be very careful, most epoxies are dark in color and cannot be removed from rough surfaces such as brick.

Regards

What is JB Weld glue and where do you buy it?

JB Weld is a 2-part epoxy adhesive that comes in two tubes. You squeeze out a strip from each tube onto a 3x5 card and mix them with a stout toothpick. You can usually find it at auto supply stores and at some Walmarts. On the web, go to "jbweld.net" and click on "products" to see what the package looks like. It is a really good adhesive for repairing most large items whereas its dark color doesn't lend itself to china repair. It sticks to just about anything. When first mixed, it has the consistancy of cold molasses and tends to "run". However, with a thin joint like your brick it's not much of a problem. The 5-minute version begins to stiffen in about 2 minutes and is fairly hard in 5 minutes. The full cure time is 24 hours. It takes a little practice to learn how to handle it, but after a few repairs, you won't use anything else. Be sure to work over newspapers to prevent getting it on anything. Epoxy glues are somewhat messy to work with but the material you are repairing will break before the epoxy does.

Regards