Concrete is one of the cornerstone materials that has allowed for the development of our urban built environment. From roads to skyscrapers and stadiums, we rely on concrete to support our modern world. Concrete, first mastered by the Romans to develop their architectural and engineering marvels, is composed of some of the most bountiful materials on earth: sand, gravel, lime, and water. And unlike other building materials, concrete can be poured into whatever form is needed. Concrete’s strength is in its compressive force, but one of its drawbacks is that it can be brittle and weak against tension forces that bend it. One of the innovations in the 19th century that set the stage for our modern cities was reinforcing concrete with steel to increase its tensile strength. In order to provide their customers a single source for both concrete and reinforcement services, The Conco Companies has two rebar facilities in the West Coast to meet the needs of their customers, including concrete rebar in the Portland area.
Rebar is non-stressed steel placed inside a concrete block. It is set before the concrete is poured by shaping steel rebar within the formwork. The steel rebar is generally tied together to keep shape during placement and is placed several inches inside the concrete to prevent the rebar from impacting the sides of the form. Rebar effectively improves the tensile strength of concrete and is standard in concrete construction.
Tensioned concrete incorporates steel cables within a slab that are placed in tension to add internal compression to the concrete. This increases the concrete’s tensile strength with minimal material. Pre-tensioned concrete is a technique where the steel cables, called tendons, are tensioned before the concrete is poured. The concrete develops bonds with the tendons as it cures. When the tension in the tendons is released after curing, the tension forces are transferred to the concrete via friction. In post-tensioning, the tendons are in protective sheaths that allow them to be tensioned after curing. The tendons are put in tension by hydraulically tightening bolts at the end of the concrete slab after curing. Post-tensioning is effective in long spans of concrete, generally over 20 feet, where it can reduce the concrete needed up to 25 percent and reduce rebar more than 50 percent. These benefits make it a particularly popular choice for bridges and other projects with long spans of concrete.
At The Conco Companies, we are one of the leading concrete contractors in the Western U.S. and offer a wide range of quality services and products. Our experience includes providing services for commercial, educational, parking and other construction development as well as public works projects. Please contact us for more information about our full range of premium Portland area concrete services including shotcrete.