A portable volumetric concrete mixer is a concrete batch plant on wheels.
A volumetric concrete mixer truck is a mobile concrete batch plant mounted on a transport vehicle. The mixer is loaded with component materials of coarse aggregates, cement, sand, and water to produce fresh concrete. These materials can be mixed in a consistent, regulated manner with admixtures to produce a specified concrete mix design on a continuous or intermittent basis, on-site, where the concrete mix is to be placed. All ingredients are held in their own separate bins or tanks.
The volumetric mobile batch plant is the key to allowing a well-trained crew to work with Rapid Set Concrete. Rapid Set concrete sets and gains strength fast – usually in about an hour – it can be driven on in about an hour! Therefore using ready-mix trucks to deliver Rapid Set concrete from a remote plant is not a practical option. The volumetric mobile batch plant truck produces the concrete seconds before placing, ensuring the freshest concrete possible. Throop’s crew can bring their experience and train crews in all of the aspects of the job therefore ensuring a smooth and successful operation that opens on time!!
Our concrete portable batch plants are chassis- or trailer- mounted and allow the mixing and blending of concrete materials on job sites. One of the biggest advantages of the mobile batch plant is the total control and ability to produce many types of specialty concrete mixes.
Individual machines are self-contained and can produce from one to 60 cubic yards per hour. If needed we can rent out our mobile batch plants on a temporary basis. We have produced concrete on mountain tops, as well as on vessels, barges, and on islands. When the concrete pour exceeds the capacity of the plant, additional materials are delivered to the site and fed into the machine therefore never having to stop work.
Concrete production from a volumetric mixer must meet the same standards as batch plants. ASTM C 685, AASHTO 241M, VMMB, and Caltrans C109. Volumetric mixer trucks produce the same quality concrete as a batch plant with the same accuracy. Throop’s volumetric mixers are calibrated and certified monthly by Caltrans authorities.
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. The concrete is mixed on site so the concrete is made fresh.
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.
“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, mixed on-site, 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.
The George L. Throop Company also coordinates material mix designs and any other services required to provide maximum service to our customers. Our equipment meets and continues to exceed all government regulations for accuracy and consistency.