Post-Tensioning
Many of the buildings you see today could not have been constructed if it weren't for the strength and durability of the foundation they stand on. Yet when you come right down to it, not all concrete foundations are the same. In fact, the kind of slab that's installed can make a big difference in terms of how long it takes and how much it costs to build a structure. As well as how much repair and maintenance will be needed in the long run.
Since the mid 1960's - and even before - most building and construction professionals have known that post-tensioned concrete slabs make superior foundations. They are the slab of choice for construction over marginal soils. And for a long time, they were installed almost exclusively for this purpose. Considering the poor quality of the soils, the performance of post-tensioned slabs has proved to be nothing less than extraordinary. Advantages like faster and easier installation, cost savings, and long-term performance make them ideal for all soil conditions.
What is Post - Tensioning?
Post - Tensioning uses high-strength steel strands or "tendons" to reinforce concrete. For example, imagine a set of wood blocks with holes drilled through them. If you insert a strand of rubber band through the holes and then hold it by the ends, the blocks suspended in the middle would sag. Now, if you attached wing nuts at each end of the rubber band and twisted them, the band would become tighter and the blocks would line up straight. Post-tensioning tendons act in much the same way. They're placed in the foundation before the concrete is poured. Once it hardens, the tendons are stretched by hydraulic jacks and held in place by wedge-type anchoring devices, thus strengthening the concrete and securing it in place.
Why Post - Tensioning vs. Conventional Concrete Reinforcement?
One of the great advantages of post-tensioning over conventionally reinforced concrete is the way it minimizes cracking and settling. Strong as concrete is, it can deflect and crack under the weight of heavy loads. A post-tensioned slab "bridges" over marginal and expansive soil. It works actively against cracking, using tendons that create pressure to hold the concrete together. In conventional foundations, steel reinforcement bars are embedded to limit crack widths. This method of reinforcement works passively. So in conventional foundations, the very thing that needs to be avoided-cracking-must occur before the reinforcing steel is activated.
with post-tensioning, tendons go to work right from the start to prevent cracking-even under a full load. That means you get a better slab. Installing a Coast Concrete Services post-tensioned foundation up-front can save you from complicated and expensive repairs over the long haul.
What is the Tendon Made Up Of ?
The above illustration shows the component parts that make up the tendon used by Coast Concrete Services. The monostrand tendon is a seven-wire strand coated with corrision-inhibiting grease and encased in an extruded plastic protective sheathing. The anchorage is made up of an iron casting and a conical, two-piece wedge that grips the strand. The anchorages keep the tendons permanently stressed or elongated. This, in turn, causes a compressive force to act on the concrete. The compression works to offset the tensile forces created when heavy loads from construction materials and equipment are added to the structure, and significantly increases the load-carrying capacity of the concrete.
What Coast Concrete Services, Inc Can Provide
Coast Concrete Services, Inc. provides complete insurance coverage. In fact, we assume structural liability for project utilizing our post-tension design and installation. Our post-tensioned systems provide a simple and economical foundation that is superior to other reinforcing systems. The following are some of the many services we offer:
- Feasibility Studies
- Post-tensioned design and stressing calculations
- Installation and stressing of cables
- Technical assistance at job sites
- Local sales staff to service your needs
- Radio dispatched service crews
