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In its simplest form, concrete is a mixture of paste and aggregates (sand & rock). The paste, composed of cement and water, coats the surface of the fine (sand) and coarse aggregates (rocks) and binds them together into a rock-like mass known as concrete.
Within this process lies the key to a remarkable trait of concrete: it’s plastic and can be molded or formed into any shape when newly mixed, strong and durable when hardened. These qualities explain why one material, concrete, can build skyscrapers, bridges, sidewalks, and superhighways, houses and dams.
Concrete mixtures can be designed to provide a wide range of mechanical and durability properties to meet the design requirements of a structure. The compressive strength of concrete is the most common performance measure used by the engineer in designing buildings and other structures. The compressive strength is measured by breaking cylindrical concrete specimens in a compression testing machine. The compressive strength is calculated from the failure load divided by the cross-sectional area resisting the load and reported in units of pound-force per square inch (psi) in US customary units or megapascals (MPa) in SI units. Concrete compressive strength requirements can vary from 2500psi (17 MPa) for residential concrete to 4000 psi (28 MPa) and higher in commercial structures. Higher strengths up to and exceeding 10,000 psi (70 MPa) are specified for certain applications.
A volumetric concrete mixer (also known as volumetric mobile mixer) is a mixer on a truck or trailer that contains concrete ingredient materials and water to be mixed at the job site to produce the exact amount of concrete needed.
A volumetric concrete mixer produces concrete by proportioning the materials out over time by volume and relating that volume back to the materials specific weight. These materials are then dispensed into a mixing auger where they are completely mixed together and all the cement is able to come in contact with water to begin hydration as well as encapsulate the complete surfaces of any other material being added into the mix. The material is being added into the mix auger as if it were in handfuls at a time so the there is more than enough energy in the mix auger to ensure a complete and uniform mix by the time it comes out of the discharge end of the auger, which is typically only about 5-10 seconds.
When a volumetric mixer is delivered, part of the delivery process is training and calibration. The calibration process is vital and important part to ensure your mixer is producing what you want to produce. In essence, we are not so much calibrating the mixer as we are the materials. Every material has its own density or weight by volume. When a calibration is done this weight by volume is determined for each material and the info is inputted into the computer. Once this is complete it is then possible to get the volume settings needed to accurately produce the mix design specified.
The calibration process therefore should be down one to two times a year to see if there are any major variances as well as if a new supply of material has been selected as the density may be different.
The production rate can vary depending on the mix design but if you are producing at maximum speed a volumetric concrete mixer with a 24” wide conveyor belt and 12” mixing auger can produce concrete at a rate of 40m3 (52 yd3) to 60m3 (78yd3) per hour.
Both a concrete plant with ready-mix drum trucks and volumetric concrete mixer produce quality concrete however, there are some distinct advantages to choosing a volumetric mixer.
i. Customer only pays for exactly what they need: Because the VCM is in essence a mobile concrete batching plant if the customer needs a little more or a little less then what they originally thought it is not a problem because production stops when the job is done. With Ready-mix drum trucks the customer has to make an accurate estimate of what is needed because it is batched and water is added at the plant then delivered to the site.
ii. Concrete is ALWAYS Fresh: With a VCM the concrete is made fresh every second as it is being produced so the newest concrete is what is being laid. With concrete from a drum truck the concrete coming out last is the oldest and may already be stiff.
iii. Small quantities are not a problem: With a VCM you can produce as little as a quarter of a cubic meter or yard of concrete and then pack up and go to another job. With traditional drum trucks, this becomes almost impossible and very uneconomical. After a small load, the drum truck also has to return to the plant to reload for the next job.
iv. Multiple mixes in one stop: With a VCM the operator can do a variety of concrete mixes in one stop. For instance, perhaps a sidewalk had to be removed to get at some utilities. A VCM could then produce some fill concrete to cover the utilities and bring the grade to underside of sidewalk slab height. Then the slab could be formed up and the VCM could produce the correct concrete for the sidewalk slab as well without have to return to the job site.
v. Time is not a factor: With a VCM the problem of time does exisht. Concrete in a delivered in a drum truck is exposed to water at the plant and is now perishable and the time to get it delivered and into position is less than 2 hours. With a VCM you can deliver concrete an infinite distance away. With a VCM you can be stuck in traffic and still deliver fresh concrete to the customer. With a VCM delays on the job are much less stressful.
vi. Evenings and Weekends: To open a traditional batch plant after hours or on the weekends can cost thousands of dollars and require a minimum quantity of concrete to be ordered. With a VCM anytime and any day is just like any other.
The standard that govern the quality of concrete produced by a volumetric concrete mixer may differ depending on where you are located. There are however also international and national standards as well as state and/or provincial that you should be aware of. Here is a list of some:
i. ASTM C685 / C685M – 14
ii. ACI 304.6R-91
iii. VMMB 100-01
If you are looking at getting into the concrete production business, you do not need to know anything about concrete. However, you do need to be willing to learn…a lot. As manufacturers of volumetric concrete mixers, we want our customers to succeed. We will come alongside you and share as much knowledge as we can as well as help set you up with a team of other suppliers you will need to make your business a success.
The Titan mixer was introduced in 2020. The most notable difference of the Titan is the build design and build material. The Titan is constructed of Hardox® 450 steel which is some of the strongest steel in the world. However to maximize on the strength of the Hardox® 450 steel, certain design changes need to take place. This includes removing the aggregate bin supports to allow the bin to flex and retain its form. This prevents additional cracking and denting. Overall the Titan can offer an additional 1,350 lbs of payload with the weight savings as well as provide twice the lifespan.
The Titan also has some of the top technology features in the volumetric industry. This includes a fully automated mixer set-up and the BatchPro Connect software solution which offers easy calibration, mix design uploads and a daily assignments resource.
The Hardox® in my Body program represents a quality build as certified by the SSAB team. When you see this sticker on any piece of machinery, it certifies a thoroughly inspected design and build that the Hardox® team can stand by.
The Ultralite Plus is the worlds first all aluminum bodied volumetric mixer. The Ultralite Plus provides amazing automation with the autodosage system, BatchPro Connect and wireless radio remote controls all included. The aluminum build won’t rust, is stronger and offers 2200 lbs (1,000 kg) of weight savings.