Post-Tension and GPR

Post-tensioning, or PT, has become increasingly popular over the past 30 years or so as the technology has been perfected. Post tensioning is a technique for reinforcing concrete. Post-tensioning tendons, which are prestressing steel cables inside plastic ducts or sleeves, are positioned in the forms before the concrete is placed. Afterwards, once the concrete has gained strength but before the service loads are applied, the cables are pulled tight, or tensioned, and anchored against the outer edges of the concrete.

Post-tensioning is a form of prestressing. Prestressing simply means that the steel is stressed (pulled or tensioned) before the concrete has to support the service loads. Most precast, prestressed concrete is actually pre-tensioned-the steel is pulled before the concrete is poured. Post-tensioned concrete means that the concrete is poured and then the tension is applied-but it is still stressed before the loads are applied so it is still prestressed.

We were recently contracted to locate and identify post-tensioned cables in a structural slab on the top floor of a parking garage. Our technician, shown above, is marking out the post-tensioned cables in red paint on the floor of the garage. Ground Penetrating Radar (GPR) is a useful tool in identifying many structural components that are embedded in concrete.

If you are an engineer or general contractor please give us a call at 617-799-9777  or send an email to contact@pro-scanning.com to discuss your project and see how we can help.

Utility Location & Field Drawings

Call Before You Dig is not only the law in most New England states, but is a really good idea before you begin your project. Many times, however, they can only identify public utilities and very often do not mark those utilities onto the property. Here at Pro-Scanning, we have years of experience and work with you to properly identify all underground utilities on the entire property of your project if needed. Using the the latest technology in utility tracing equipment and GPR, we can cover the project area or entire property to locate the utilities that you do not want to disturb. We can also provide field drawings of our findings, like the one above, that will aid in communicating with the project’s ownership team. Please contact us at 617-799-9777 or contact@pro-scanning.com with your projects needs.

Circular Rebar

We are often faced with challenging concrete slabs, and this particular job was no exception. This slab was on the third floor of a circular building that was in the process of being fit-out for a new tenant. Using the 1.6 GHz antenna, our technician was able to determine both the lower and upper mats of rebar, as well as a conduit, in the 12″ thick concrete slab. Accurately identifying the location of the rebar is paramount before coring or slab cutting, as you do not want to compromise the structural integrity of the slab.

Structural Detail of Footings using GPR

GPR is a very beneficial tool to the general contractor. GPR enables us to “see” underground and into concrete which is much less destructive than cutting or chipping open the concrete slab.  As you can see in the picture our technician was able to locate dimensions of the under slab footing as well as give a sample of the steel reinforcement grid in the slab and vertically up the structural concrete column. Give us a call at (781) 799-9777 to find out what we can do for you and your project.

Happy Holidays from the Pro-Scanning Family

 

Best wishes to you and your family for a happy holiday season. Looking forward to the warm association we share in the coming year. From everyone here at Pro-Scanning, Happy Holidays and a Happy New Year!

Roof Installation of HVAC Equipment

 

We were recently brought to a local university to layout the structural reinforcement of a roof before the contractor installed new HVAC equipment. In the picture you will find the layout of the structural “waffles”, or ribs of the slab, marked in red and the steel reinforcement grid marked in blue. The structural waffles and steel reinforcement layout was vital to this install as the contractor was not only cutting holes for duct work, but drilling dowels in for a concrete curb. “Waffle slabs” i.e. ribbed slabs have long been used in construction because they offer a lighter, stiffer, and more flexible option compared to the common flat design. They are often used in buildings, housing, laboratories, and other equipment that vibrates as they provide excellent vibration control.

Underground Chemical Storage Tanks

Recently, we were hired by an environmental service company to locate chemical storage tanks buried underneath a concrete slab at a former dry-cleaning facility prior to excavation and removal. Using the 400 MHz antennae we were able to accurately locate the UST’s and give a basic outline of their shape and size. In the pictures above you will notice that we correctly identified both circle and rectangular tanks with approximate depths of 18″ and marked the outlines in pink paint.

Beautiful Morning in Copley Square

We were called out to an early morning job near Copley Square. One of our technicians, who is a avid photographer, snapped this picture of Trinity Church and its reflection on the Hancock Building.

GPR Is Vital to Hospital Safety

 

Hospitals and medical centers rely heavily on electricity and other utilities as they are vital to keeping their patients healthy and alive. Pro-Scanning is a crucial part of hospital and medical center renovations as we understand the importance of keeping utilities and the hospital up and running. In the picture above, we scanned a structural slab that was 9 inches thick with conduit located in the slab. The steel reinforcement is marked in black, conduit and unknown anomalies are marked in red, and the profile of the capital (extra support) of the nearby column in blue.

Old-School Steel Pan Decking

 

Recently we came across a rather rare concrete slab in a very old hospital. The picture on the left is the bottom side of the slab and the picture on the right is a screenshot of the 1.6 GHz antennae scan on the GSSI Sir3000 system. The two foot wide steel panels were supported with a 6 in wide by 6 in deep concrete beam. This type of slab was most likely cutting edge at the time of installation, but has been phased out and replaced by Q-decking or corrugated steel decking.