In construction, a cement mixer is a device that is used for mixing and pouring cement. The first thing that usually comes to mind at the mention of a cement mixer is a cement truck, which is a vehicle that is large enough to carry a heavy-duty cement mixer on its back. Cement mixers can come in all sizes, though, and a typical lightweight portable cement mixer is about the size of a wheelbarrow.
Mixing cement is a process that can require a certain degree of precision, and the cement mixer is a crucial component of the process. The main thing required is the cement itself, which is a mixture of sand, water, and aggregate (crushed stone) and a place to mix it all together. The precision comes into the process in mixing the exact quantities of these items. The most common mixture of cement that is used in a cement mixer is known as Portland cement, a mixture that has specific properties that are easy to control, such as the time it takes to dry.
The most visible part of a cement mixer is a rotating drum, which allows all of the parts of the cement to be mixed simultaneously and keeps the mixture even. Inside this drum there are blades, which turn and mix all of the parts of the cement together, and these are usually propelled by a motor that is attached to the drum. Once the concrete is ready to pour, there is a hole in the drum from which the wet concrete easily comes out.
The direction that the blades turn can be reversed when pouring the wet cement, and they act to scoop it out rather than mixing it. Cement trucks can obviously be a little more complex, and a lot of the time the cement is mixed while the truck is on the way to a job. In the case of a delay, cement mixer trucks are designed add an agent to the cement mix to keep it from drying too fast.
The size of cement mixer that is necessary to complete a job is mainly dependent on the size of the job itself. Work that requires seven or eight cubic feet of cement or less can usually be completed with a portable cement mixer. Anything larger than that, however, will typically require the use of cement mixer truck, with some large jobs requiring many more.