Throop can produce Rapid Set or Type II concrete for airports, in remote mountain areas, on water and almost anywhere in the United States.

Concrete Projects

Within limited time-frames — and under the threat of strict liquidated damages in the event of failure to finish on time — the George L. Throop Company, a California-based ready-mix concrete producer, is doing projects from producing rapid-setting, high-strength specialty concrete to repair airport pavements to producing specialty concrete for footings and slabs on mountain tops for phone cell sites coast-to-coast — all using their volumetric mixers.

Multifaceted George L. Throop Co. is a Pasadena, California-based building materials supplier which makes conventional concrete mixes as well as specialty concretes. That's in addition to operating a popular building materials retail store in that city. But its specialty concrete supply practice is what sets it apart from its peers.

"Whether it's a highway or airport repair, mix design is always a 'race to strength'," said Jeff Throop, president, George L. Throop Co. "The sooner you can get strength, the more work you can do. Yet you also have to give the crews enough time to do their job. The cement we use, CTS Rapid Set®, is perfect in that regard, as there is no faster way for an airport authority or highway agency to repair their property. And the quality is there: there is no downside as far as shrinkage or durability. The quality is as good as it gets."

Various projects the George L. Throop Company has completed:

Keeping Mix Fresh with Volumetric Mixers

An essential element in Throop's success in the fast-set, high-strength concrete market is its use of its own custom-made concrete volumetric batch plant mixers.

Unlike a conventional barrel mixer, a volumetric mixer carries the raw materials for concrete within itself, and with the help of a water tank, mixes fresh concrete on-site. Throop's volumetric "mobile batch plants", as they call them, allow Throop to place both small or large jobs, using any kind of material or cement.

And Throop has found that a unique combination of volumetric mixers and high-performance, fast-setting, high-durability specialty concrete mixes is the perfect application for expressway, bridge deck, and airport runway, taxiway and apron repairs when done under time-restricted, liquidated-damages circumstances.

Throop's volumetric mixers vary in size, and can produce from five to 100 cubic yards of concrete per hour, or more. While Throop can produce standard concrete mix designs, it specializes in custom mixes such as rapid strength concrete achieving 3000 psi in an hour and a half, using its volumetric mixers to keep costs down by producing only the amount of mix required, on demand in real time at the job site.

Serving Custom Mix Niche

"We have heard stories of unnecessary waste and of loads of Rapid Set concrete having been sent back, because of the way the concrete had been produced and delivered — for decades by barrel mixers," said Jeff Throop. "With volumetric mixers we can't compete on a volume commodity basis, as with barrel mixers, but the conventional ready-mix industry doesn't appear willing or able to serve the custom mix niche."

And the volumetric mixers make it possible for Throop to serve that niche. "Anything 'fresh' is better than 'old'," Throop said. "It applies to mixed drinks as well as concrete. Research shows that fresh concrete is superior to concrete that is aged, or has been hydrating and mixing for a time. Also, when you get to a job, and the crew isn't ready, we can start mixing when they are. We also can stop and restart production at any time with no waste. And we also can use cements that conventional ready-mix producers can't use, like rapid-setting cements like Rapid Set from CTS Cement."

Rapid Set is a specialty cement which gains structural strength in 1.5 hours after placement, materially reduces drying shrinkage, and reduces porosity for enhanced durability. It results in a workable, 5-in. slump concrete that gains compressive strength of 2500 to 3000 psi in 1.5 hours. The shrinkage of Rapid Set concrete is about 25 percent of the shrinkage of same slump portland cement concrete (PCC).

This improved durability by reduced porosity is demonstrated by superior freeze-thaw resistance. When tested by the ASTM 666 method, PCC fails within 350 cycles of freezing and thawing, but the Rapid Set is good for 1,000 cycles. Also, the chloride ion penetration test shows the rapid-setting concrete to have very low permeability. When latex is added, the coulomb rating is in single digits, versus a rating of over 500 for conventional PCC.

These attributes make it ideal for placement where speed and durability is of the essence, for example on night patching on urban expressways, freeways, highways, bridge decks, or night runway repairs at major airports, where liquidated damages for failure to open can run into the tens of thousands of dollars.