Inside the Materials Engineering Unit: Putting Concrete to the Test

By Neal Buccino, Media Relations Staff

The lab near the Holland Tunnel opening in Jersey City resembles a kind of torture chamber, reminiscent of something a Bond villain might consider as a hideout. Inside, devices that could have come from a sci-fi movie pulverize concrete, electrify it, freeze it and thaw it – and then freeze it again to the point of destruction.

No, it’s not the set of a blockbuster Christmas movie release. It’s where the Port Authority keeps its Materials Engineering Unit lab, and the activity within is done all in the name of quality control and, more importantly, public safety.

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Concrete being poured for Goethals Bridge Replacement Program.  The thick, muddy liquid is poured over green steel rebar, then smoothed into shape to create an approach for the new bridge.  Photo by Mike Dombrowski, Port Authority

The MEU performs a vitally important job for the Port Authority. The agency requires safe, high-quality construction materials for products as varied as the Goethals Bridge replacement, the Bayonne Bridge “Raise the Roadway” initiative, a runway replacement at John F. Kennedy International Airport, and other investments in concrete, steel and asphalt.

Casimir Bognacki, the Port Authority’s materials chief, says the lab’s mission is to make sure all building materials used at agency facilities meet the high standards required in each contract and promised by the manufacturers.

For concrete used in transportation structures, the most important qualities are “durability first, and strength second,” Bognacki said.

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Casimir Bognacki, Chief of Materials in the Port Authority’s Engineering Department, examines a concrete puck, the size of a Big Mac, that’s about to undergo the electrical test.  Photo by Neal Buccino

Concrete doesn’t work alone. To create a roadway, tower or building, concrete that is uncured (or liquified) must be poured around steel rebar. If the cured concrete isn’t durable enough, water can infiltrate its pores and corrode the steel. Rusted steel will expand up to four times its original volume, breaking up concrete and setting up a cycle of further deterioration.

To get a sense of how the testing process works, let’s start with the Goethals Bridge replacement project. On a recent day in Elizabeth, N.J., workers poured 260 cubic yards for a segment of the roadway that will approach the new bridge. That’s the equivalent of filling four backyard swimming pools with concrete.

Engineers from the MEU scooped random samples of the thick, muddy liquid. Some they tested on site with a metal gallon jug connected to an air meter. This will ensure the proper distribution of tiny, pinpoint-size air bubbles needed to protect against weather-related damage.

The engineers took more concrete samples back to the lab. There they will cure and solidify for about a month, before undergoing intricate torture. There is the electrical test, which requires some prep work. Concrete pucks the size of Big Macs are placed in a vacuum that sucks the air out of every pore and crevice. Then they are fully saturated with water – and, finally, clamped between the poles of a battery.

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To prepare for the electrical test. chunks of concrete are first placed inside these pressure cooker-like contraptions.  After all traces of air have been sucked from every pore and crevice, they will be saturated with water.

Why such an involved process? Concrete resists the flow of electricity, but water is a natural conductor. The amount of current that flows through is a good measure for the amount of water that has permeated the concrete. And that’s a good measure of vulnerability to the cycle of water infiltration and corrosion.

There is also the crushing test. Concrete cylinders are placed in a compression chamber and subject to slow, pneumatic pressure until they break. Not an easy feat as some of these concrete samples, roughly the size of a junior league football, can withstand pressure of more than 16,000 pounds per square inch.

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Technician Jared Vassell prepares a concrete sample for testing in the compression chamber, which subjects concrete samples to pneumatic pressure until they break.  Some samples withstand a load of 200,000 pounds.  Photo by Neal Buccino

Then there is the freeze-thaw test, which subjects concrete samples to 300 freezing and thawing cycles – equivalent to 30 years of hard winters – over six weeks. Concrete that is not durable will break apart during this process.

“Concrete is a universal constant throughout just about every one of our facilities,” Bognacki said. “This lab exists to make sure the public is getting what it needs, and what the Port Authority demands, in terms of quality and safety.”

 

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