What’s So Advanced About Rebar?
While exiting our building the other evening, I was stopped by a passer by who looked at the door than looked at me. “What is Advanced Rebar Applications?” he inquired, alluding to our company name. “We are an independent outside resource that creates rebar placing drawings and material lists,” I answered. His eyebrow furled. “Rebar? Is that those metal rods?” he asked. “Why yes, yes it is,” I replied. He turned as if to leave. But turned back and asked, “What is so advanced about rebar?”
It is a good question. What is advanced about rebar? To those outside of the industry, most would still assume that rebar or reinforcing steel, is the same as it has always been. It is simply a bunch of steel bars of various sizes that you place within concrete. It is a combination that takes the strength of one material and marries it to the weakness of the other. In doing so, a stronger, better building material is created, reinforced concrete. It is a system that has been used for decades. So what has changed?
The first “advanced in rebar” is the material itself. There are new grades of steel. 90 ksi and 100 ksi rebar is making its way onto jobsites. This added strength allows for less material to be used in a project. This is achieved due to the reduction in the quantity of steel required compared to the typical 60 ksi rebar and the decrease in the spacing of the bars, due to higher tensile strength of the grade. Less material can mean a reduction in cost of a project. While the material initial costs may be more expensive at the start, these costs are offset in less labor required for their installation and the reduction in quantities of material used. Rebar has also seen the availability of mechanical splices. These can eliminate lap splices or can be applied to existing rebar in structures to extend or expand the structure. There are now anchors or terminators that can develop acceptable anchorage in smaller spaces thus reducing the congestion of reinforcing and the labor required to manipulate the bars around that congestion.
Rebar is now available in materials Rebar splicing other than carbon steel. Stainless steel allows a change to a less corrosive material. This means that the life cycle of a structure increases and the maintenance costs can decrease. We are starting to see the use of fiber reinforced polymers or FRP reinforcing. This material is not metallic thus there is no corrosion and it is non-magnetic. Both stainless and FRP are seeing use in certain applications like magnetic sensitive structures or corrosive environments like bridges, a structure that are in great numbers that need repair or replacement.
Likewise, its complementary material, concrete, has developed over the past few years. Currently, there are new coatings and add mixtures that can be applied or added to a mix. This can allow the mix to be poured instead of placed. It can allow the concrete can drop greater distances and flow into forms without vibration. It can be caused not to set, so it can be washed and the aggregate exposed as an architectural finish. The equipment used to manipulate and move it has also changed. Trump Tower in Chicago was constructed of cast in place concrete. This can be attributed to the newer concrete pumps that allowed the material to travel hundreds of feet in the air. A task that until a few years ago was impractical if not impossible.