Yards of concrete is an industry-standard measure for transportation and project planning, but how many yards of concrete are in a truck, and what can you expect from different situations?
A standard truck can carry about nine yards, give or take one a yard depending on its size. Smaller vehicles may only hold four yards, while large trucks can hold fourteen or more. Let’s take a closer look at what all the measurements mean.
Definition of a Yard of Concrete
A yard of concrete is a 3 x 3 x 3-foot square, or 27 cubic feet of concrete. Most projects don’t use an actual cube of concrete unless it’s major construction. Instead, it’s far more common to pour or mold the concrete into a desired shape.
For example, a typical sidewalk is five inches of concrete. When you know the length, width, and depth of your proposed sidewalk, you can convert that to cubic feet and then yards of concrete to determine how much you need for your project.
Most companies and buyers deal in yards of concrete because it’s the smallest practical volume for measuring projects. It’s easier to write and say than dozens or hundreds of cubic feet, and it doesn’t imply more precision than most trucks can deliver.
Other countries typically use meters of concrete instead, as they use a different measuring system. A meter of concrete is approximately 0.764555 cubic yards or a little more than three-quarters the volume of a yard. As such, trucks that carry meters may have slightly higher numbers on their high-capacity trucks.
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Types of Concrete Trucks
There are three primary types of concrete trucks available today. You may also see specialty trucks, possibly designed for unique needs or projects, but most people do fine with one of the three standard options.
Some people call typical concrete truck mixers. This name comes from the fact that companies can load the raw materials and water into the truck, then keep it spinning and stop it from drying out until it reaches its destination. However, there is a limit to how long a drum can spin.
Rear Discharge Mixer
Rear discharge mixers are easily one of the most iconic types of concrete trucks. They feature a large spinning drum attached behind the engine, angled upward so the opening points into the air. This design stops the concrete from sliding out while the drum turns.
Rear discharge trucks are easy to load from the top, and hydraulic systems can raise the drum to pour out the concrete. Drivers of rear discharge mixers can’t easily see where they’re pouring without cameras, so they usually have crew support to help them back into the correct position.
Rear discharge vehicles are usually shorter and have an easier time on narrow roads, so they can access some job sites that are challenging for other vehicles. However, the driver has to exit the truck to dump the concrete.
Front Discharge Mixer
Front discharge trucks are somewhat rarer than rear discharge trucks. While they feature a similar design, the loading and discharge go over the front, so the driver can navigate to the right spot for pouring easier. The hydraulic dump systems are otherwise similar.
Front trucks are usually larger than rear trucks and aren’t as good on narrower roads. However, drivers can dump the contents without getting out, which is far more comfortable for the driver in bad weather (including not just rain but heat and cold).
Front-loading trucks are larger and take longer to wash out after each load, which is essential for avoiding concrete buildup on the inside. However, thanks to the time savings from driving up and positioning the vehicle, front-discharge vehicles can often take less time for each run than a rear-discharge machine.
A volumetric mixer truck is a large vehicle with separate compartments for cement, stone, sand, and water, which are the basic ingredients for concrete. Rather than loading the materials at a plant and mixing it on the way to a job site, a volumetric mixer creates the concrete just before pouring it.
These trucks allow for more precise measurements on projects, as you can stop mixing concrete at any point. If you need an extra yard of concrete, a volumetric truck can usually provide it without needing to dump an entire load on the project.
Volumetric trucks are usually better for small projects or the final load on a project. If you know you’re going to need forty-two yards of concrete and may need up to three more, a volumetric truck can come in for the final pour to mix the exact amount you need.
Volumetric mixers are not as relevant when you know you’re going to use a truck’s entire load. They’re somewhat slower than a front or rear discharge mixer, so most project managers prefer to avoid using them for too many yards.
The Capacity of Concrete Trucks
As you’d expect, every concrete truck has a capacity that indicates the maximum amount of concrete you can get in a single load. Most trucks can carry less than their rated capacity but may have a minimum amount to ensure they mix the concrete correctly.
The primary factor that determines capacity is a vehicle’s size. Larger vehicles can hold more concrete. However, some specialty designs can reduce the mixing drum’s size or ingredient areas. Limits are more common when a truck needs to do something like carry an extra-long chute to ensure the concrete reaches the project site.
Concrete companies usually sell by the yard and will pick whichever truck(s) they have available that best meets the needs of the project.
Standard Truck Capacities
Most companies build cement trucks in intervals of one yard of concrete. The smallest typical truck can hold three yards, while the biggest standard options can hold up to sixteen. Odd numbers in the double digits are rare, though. It’s not hard to find a truck with ten or twelve cubic yards of capacity, but eleven cubic yards is far less common.
A single large truck usually costs less to operate than multiple small trucks, so most buyers try to get deliveries with the fewest number of trucks possible. Small projects may only require one, while large projects can require dozens of trucks over weeks or months.
A truck’s rated capacity is different from its maximum capacity. A truck rated for twelve yards can probably hold at least fourteen at most. However, over-filling can cause many problems for the vehicle.
Too much weight can slow the mixing, damage truck components, and lower the final quality of the concrete. Trucks need some space to blend. If you have to depart from the rated capacity, it’s better to put a little less into the drum instead of too much.
Trucks also tend to leave some material in the drums after each pour. If you order eight yards, you’re likely to get a little less than eight. This residue is one of the many reasons that companies often get volumetric mixers to finish a job by dispensing the exact amount of material they need for the final stretch, reducing waste.
The buildup is the leftover residue in a concrete truck that doesn’t get poured out. A quick wash after pouring helps minimize buildup, but there’s always going to be some after each pour. The more buildup in a truck, the fewer room companies have to add and mix cement.
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Buildup ultimately reduces the capacity of a truck below its rated capacity. To solve this, companies occasionally hire concrete chippers to clean out the inside and remove as much buildup as possible.
Buyers don’t have to worry too much about this because concrete companies will still mix and deliver the right amount of concrete, which is usually a little more than a project requires. A well-managed company will space out chipping to ensure it has enough vehicles available at all times.
Factors That Affect the Amount of Concrete a Truck Can Carry
So, how many yards of concrete are in a truck? The answer depends on a few factors.
Truck size is the most obvious factor. As a general rule, larger trucks can hold more concrete unless they have a special design. However, a truck that’s too large may not be able to navigate certain roads. If so, buyers may need to get concrete in multiple loads on smaller trucks.
Weight has a direct correlation to truck size. Bigger vehicles weigh more, and fuller trucks add that weight on top.
Weight is an issue because some routes have a weight limit on the vehicles that can travel over them. Limits are particularly common for bridges, which have defined size and weight limits, but even regular roads can have a cap on the amount of weight they can hold.
Some projects may require reducing the amount of concrete in a truck to ensure the entire vehicle is comfortably below the route’s weight limit. However, this doesn’t necessarily mean using a smaller truck.
Large vehicles spread their weight over a wider area, which is better for avoiding damage to roads and bridges. A small, heavy truck may be more dangerous to a bridge than a larger, heavier truck that spreads its weight out better. This is why some trucks may carry significantly less than their theoretical capacity.
For reference, a typical yard of concrete weighs roughly 4000 pounds (or two tons), give or take a little depending on the exact mix of materials. Some types of concrete are a little heavier than others, but most don’t depart too significantly from the standard weight.
Most places in the United States follow ASTM C94, a specification standard that applies to ready-mixed concrete. It mainly affects the front and rear discharge mixers. Volumetric mixers don’t carry ready-mixed concrete, instead mixing on-site, so they’re outside the scope of ASTM C94.
The specification standard includes multiple things for companies to pay attention to, including the maximum number of revolutions for a mixing drum (300), what goes on a delivery ticket, and when to take a quality-control sample.
The actual travel distance doesn’t matter as much as the time it takes to cover that distance. Mixers can travel quite a distance on a rural highway, but if they’re in a city with slow traffic, the realistic travel distance is much lower.
All this matters because most concrete should be poured within 90 minutes from the start of mixing, although some modern formulas can go beyond this. If the concrete sits and mixes for too long, its quality will go down significantly.
Smaller or lighter trucks can travel faster than a fully-loaded one, which in turn affects how fast they can reach their destination. Companies may decide to load less cement into a truck to ensure it has enough time to reach the destination and pour its load.
Calculating the Number of Yards of Concrete in a Truck
The easiest way to calculate the number of yards of concrete in a truck is to look at how much you’re putting in. Concrete’s volume doesn’t vary much throughout the mixing process. If you put seven yards in, you’re going to get seven yards out.
Most trucks have clearly-listed guidelines for the minimum and maximum amount of ingredients to load, which tells you how much you can expect to get out. Measuring how much is in a truck while it’s mixing is quite difficult even for experienced personnel, which is one of the many reasons why concrete deliveries include receipts detailing this information.
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So, how many yards of concrete are in a truck? That depends on a few factors, including the size of the truck, how full the drum is, and any weight limits on the road. The best way to measure the amount of concrete in a truck is by keeping track of how much goes into it.
With this knowledge, you can estimate the number of trucks you need for any project. If in doubt, talk to your concrete supplier and ask for help verifying the routes. They can let you know if any problems will require shrinking the vehicles or providing less concrete at a time.