Resurfacing the Edges of a Post Tension Slab
Resurfacing the Edges of a Post Tension Slab
As we learned in Engineering 101 class, concrete is far stronger in compression than it is in tension. To counter this, builders use reinforcing steel bars within conventional slabs to help prevent the concrete from cracking when it experiences stretching forces such as that from vehicles or people walking on a foundation slab. Rather than placing reinforcement bars inside the concrete during construction, post tension slabs utilize high-strength steel cables (also known as tendons) that are placed when the slab is poured and then tensioned later. This allows the foundation to withstand shifting and expansive soil conditions such as those found in our Phoenix area.
While the benefits of this type of foundation slab are significant, they do come with a few distinct issues that can be difficult to detect. One of the most important is that the tendons must be positioned properly to avoid uplifting of the slab. This is caused when the tendons are not precisely aligned with the locations shown on the blueprints. Typically, this happens during the curing process of the slab when the tendons move from their original position. It can also happen if the tendons are tensioned too early.
Another issue is that the tendons have been stretched to extremely high tensile strengths and it is essential that no drilling or cutting of any kind occurs in a post tension slab to prevent tendon failure or rupture. If the tendons are exposed, it will cause premature cracking and eventually lead to failure of the entire slab. For this reason, most post tension slabs have a warning stamped in them to ensure that workers and future homeowners do not cut, drill or chisel into the foundation.
Lastly, the tendons are anchored in pockets embedded into the edges of the concrete and are subject to corrosion when the voids surrounding them are not filled. This is can be a result of a lack of quality installation when the slab was constructed or it may deteriorate over time due to improper maintenance.
To avoid this issue, it is highly recommended that the voids around the tendons and anchors are filled with a high-quality grout after stressing has been completed. This will provide a seal to protect the tendons and anchors from corrosive materials.
Resurfacing the Edges
A simple and inexpensive way to maintain your post tension foundation is to have us resurface your slab edge with our high-quality water resistant material. Not only does this improve the look of your home, but it will also help to extend the life of your foundation and slab.
In addition to resurfacing the slab, you can also help to correct drainage problems by grading your property for proper slope, ensuring that water and debris run off the foundation into a storm drain instead of pooling around the foundation.