Bricks, Masonry, Asphalt and Concrete - Concrete problems

My house was built 7 1/2 years ago and the cement in the garage keeps turning white, turning to powder and then just falls off (or we can use a broom and a lot of it will come off). Pretty soon the threshhold for the backdoor will no longer be....I really need to know what to do for this.

We also have very hard water and when the sprinklers spray the brick of the house it turns it white - I have tried washing the brick with vinegar but it really does not come off. Any suggestions? I hate to think my house is just desinegrating before my eyes....

Please let me know if you can think of any reason for all of this....
Thanks, J

Your concrete is dusting. There are a couple of possible causes. First, it's possible that the concrete finishers trowelled it while there was still a lot of bleed water on top. This re-integrates the water into the surface and makes for a high water to cement ratio resulting in a weak surface which can dust off.
Another possible cause, especially if your concrete was poured in the winter, is damage by carbon monoxide. Many times concrete finishers will use kerosene or diesel fuel "salamanders" to heat an enclosed space while they are finishing it. The fumes from the fossil fuel can greatly effect the surface and cause dusting as well.
The stuff on your outside brick could be hard water deposits from your sprinklers, or it could be efflorescence coming from inside the brick mortar and leeching out.
As to the cures: Google search for "concrete dusting" and "efflorescence" and I'm sure you'll find any info you need, including product advertisements. Good luck.

Pecos