Choosing the Right Portable Cement Mixer for your Projects
Picking the right cement mixer is equivalent to to making a sound investment. The right equipment will see you through years of projects, influencing your productivity and your bottom line. Choosing the right cement mixer requires calculating your future cement projects and understanding a mixer’s capacity, design and power source.
Most cement companies require a minimum order of three cubic yards for delivery, as you may have discovered. If you require less cement for many of your upcoming projects, a cement mixer would be an ideal investment. The background information here can help you reach a decision about which type of cement mixer is right for your work.
Calculating the Amount of Cement Needed for a Project
To calculate the amount of cement you’ll need for your project, multiply its length by width by depth and divide by 27, the number of cu. ft. in a cu. yd., the most common metric used for cement work.
Let’s say you want to pour a 10ft. x 10ft. patio pad that’s 4in. (1/3ft.) thick. Calculate as follows: 10 x 10 x .33 = 33ft. 33/27 = 1.22 cu. yds., the amount of cement needed for your patio. This amount is less than half of a typical minimum required for delivery and pouring by a cement contractor. It’s also an ideal size for you to mix and pour yourself with the help of an assistant, who could ensure that you finish cement pouring and finishing within 90 minutes, before it starts to settle in.
Determining the Right Size of Portable Cement Mixer for Your Work
Cement mixers are measured and advertised by the total volume they hold when filled to the brim, but it’s important to remember that they can’t operate when filled to the brim and they need some of their capacity for water as well as cement.
A cement mixer needs roughly half of its capacity for mixing activity, so the output of one mixed load is typically one half the stated volume of the mixer. Let’s look at some standard sizes of portable cement mixers on the market. Remember, cubic feet are converted to cu. yds. by dividing by 27, the number of cu. ft. in a cu. yd.
- 3 Cu. Ft.
- 6. Cu. Ft.
- 9 Cu. Ft.
- 12 Cu. Ft.
At this point, you may be wondering if any of these sizes is big enough to create a 10ft. x 10ft. x .33ft. patio pad. The answer is yes, three of these mixer sizes are big enough: the 6-, 9- and 12-cu. ft. units, and the reason is that it doesn’t take long for any of these mixer sizes to mix a batch of concrete. In fact, most mixers can do so within 5 minutes, so you can mix up to 12 batches an hour or 18 batches within 90 minutes, the length of time cement remains workable.
However, this is where an assistant’s help is critical. One of you can be mixing and pouring while the other one is spreading. For example, for a 10ft. x 10ft. x .33ft. patio pad, here’s how many batches you’d need to mix for each of the mixer sizes noted above. As you can see by the math, the 3 cu. ft. mixer is not big enough to create a 10ft. x 10ft. x .33ft. patio pad. Remember, that pad requires 1.22 cu. yds., so more than 18 batches are needed, the mixer is not big enough for the job.
- 6 Cu. Ft. Mixer with 3 cu. ft. mixing capacity (0.11 cu. yd. capacity): between 11 and 12 batches
- 9 Cu. Ft. Mixer with 4.5 cu. ft. mixing capacity (0.16 cu. yd. capacity): between 7 and 8 batches
- 12 Cu. Ft. Mixer with 6 cu. ft. mixing capacity (0.22 cu. yd. capacity): between 5 and 6 batches
- 3 Cu. Ft. Mixer (0.055 cu. yd. capacity): with a capacity between 22 and 23 batches, is not big enough for pouring a 10ft. x 10ft. x .33ft. slab. The number of batches required could not be mixed in this mixer and applied within 90 minutes, the length of time cement remains malleable.
A rule of thumb is that it’s best to mix roughly 10% more cement than the minimum requirement for project, so you have some ready to make up for possible spillage. If you need an amount that requires a few or several batches and part of another batch, it’s probably fine to go ahead and make close to a full final batch, so you have extra.
Cement Mixer Drum Capacity Relative to Various Projects
These scenarios provide you with a sense of what size portable cement mixer you need. Although the 3 cu. ft. size isn’t big enough for a 10ft. x 10ft. x 0.33ft. patio pad, it’s plenty big enough for pouring footings for posts as you build a fence or deck or install a barbecue. You could also use a 3 cu. ft. mixer for a smaller concrete slab, one just large enough to provide a permanent perch for your garbage and recycling cans or for a small kennel foundation.
With the 12 cu. ft. mixer, you could pour a 15ft. x 15ft. x .33 patio slab if you wanted. (learn more about patio and shed pad sizes with this article: Constructing a Concrete Patio or Shed Pad) That would take 12 ½ batches of cement, which is possible to handle easily within 90 minutes when you have assistance spreading and finishing. However, this same 12 cu. ft. mixer would not be big enough for a 20ft. x 20ft. x .33ft. patio pad. That would require 4.88 cu. yds. of cement, 22+ batches, which you couldn’t mix and pour within 90 minutes.
The good news is that 4.88 cu. yds is well over the minimum order of 3 cu. yds. typically required for a contractor with a much larger mixer. The 9 cu. ft. mixer can be used for a wide range of projects from footings to cement pads and more.
As you are most likely aware, cement comes in bags and containers of various amounts and requires various amounts of water. You’ll need to check carefully to ensure you use the ratios of water and mix required, and to stay within the mixing capacity of the mixer. Remember, mixing capacity is roughly half of total capacity.
Cement Mixer Power Sources: Gas, Electricity or Manual
Gas is usually the power source for larger towable cement mixers with the capacity to complete your biggest projects. Without the need for an external power source, gas-powered units are not subject to jobsite conditions, so they can be used outdoors almost anywhere. Here are some issues: noise, heat and exhaust. Gas-powered mixers can never be used indoors due to toxic exhaust buildup.
Electricity is typically the power source for smaller portable cement mixers. The smallest mixers use 110 Volt outlets and deliver 1/3 –1 1/2 HP, so they can be used just about anywhere. Medium-sized electric mixers usually use 220 Volts and deliver 1 HP–5 HP. Not every jobsite will have 220 Volt outlets available, so consider whether this is a critical concern. Electric-powered cement mixers operate quietly and more efficiently than gas-powered units and can be used indoors as necessary. Note: Some larger cement mixers require you to special order an electric motor.
Manual mixers are typically very small, rocker-style units designed for use by one person on projects that use small amounts of concrete. The capacity of this type of mixer is usually less than a cu. ft., so it works well for mixing cement footings for post holes and for other projects requiring a small amount of cement.
Cement Mixer Drum Styles: Tilting, Non-tilting, Reversing and Rocking
The type of motion by which your portable cement mixer functions may not be as important as the other characteristics described above. Still, it’s good to be aware that you will find the following drum styles: tilting, non-tilting, reversing and rocking.
Cement Mixer Drum Material: Steel or Plastic
Steel and plastic (referred to as poly) drums are both widely available, with steel usually the most common. Although steel drums are initially finished with paint, epoxy or powder-coat, the finishing eventually wears down to bare metal. Once down to bare metal, a mixer can rust if stored wet. It can also cause “mixer burn,” which is what happens when stiff, light-colored concrete scrubs steel off the drum as it is mixing. If this happens, white concrete turns out gray.
Additional Considerations
Discuss your cement project needs with a knowledgeable sales associate. Ask questions as they arise. Chat online with the company you purchase the cement mixer from, visit the manufacturer’s website and ask questions there if possible and call the toll-free customer service number provided at the time of your purchase. Read other customers’ reviews of portable cement mixers of interest to you. Armed with basic background information, insight into your own projects and the knowledge and insight of others, you’ll be well on your way to a unit to suit your needs.
