Post-Tension cables are stretched within the first week of concrete being poured and contain thousands of pounds of pressure. This pressure is held within the foundation by small metal wedges holding onto the metal cables just a few inches from the end. If gone unchecked these metal components could rust out releasing the tension and no longer reinforce the foundation! If this were to happen to one it can be fixed, the cables can be replaced and reset. To help avoid paying that price, try to keep the rust from developing.
If you have a foundation reinforced with post-tension cables you should see properly sealed port locations along two adjacent sides of your home. The opposite sides of the foundation should look normal because anchor plates would be within the concrete if correctly installed. The picture at the right shows a port with an exposed cable end beginning to rust, I see these all the time and I hope the recommended repairs are performed.
Walk around all four sides of your home and look for rust anywhere on the foundation, all rusting metal that is exposed should be cleaned off and protected from further damage. Some problems I've found with these port locations are:
Incorrect material used to cover and protect, the materials could be seen crumbling off and out of the port.
Poorly applied material may look okay but has a hollow sound when tapped on therefore it's loose, moisture will get in there causing rust to pop the cover off.
Incomplete coverage like the image above, it's just a matter of time for the rust to develop further and cause damage to the system.
Failed materials due to the rust development like the image below. If it gets to this point or beyond, I recommend a professional to come in and evaluate each location before covering and sealing these off.
If you find rusting foundation components exposed and you want to give it a shot, here are some tips; Wire brush the rust, clean with white vinegar and water, paint the metal and re-pack the port with an appropriate material. Also if you can see the anchor point at the opposite end, rebar or any another exposed metal component exposed, follow the same instructions and protect any metal with a waterproofing sealant. Be sure to monitor these locations over time because concrete is porous and will absorb some moisture, even the best repair may need maintenance.