What is a Mobile Concrete Mixer?
A mobile concrete mixer, or mobile concrete dispenser, is an on-demand concrete production solution. A mobile concrete mixer is a batch plant mounted on a chassis–usually a truck or trailer–and carries unmixed material (sand, cement, coarse aggregates, water and any other materials or chemicals needed for more specialty applications) to a job site and mixed on a continuous or intermittent basis as required for fresh maximum strength concrete.
Any amount of concrete can be produced from a yard to 400 yards or greater per day for continuous pouring as long as the unit is re-loaded with materials at the job site. Volumetric proportioning is based on volume not weight so through an easy calibration process it is possible to produce concrete that will consistently meet or exceed the tolerances set in ASTM C685 and AASHTO M-241 standards as well as DOT requirements. You will have the exact amount needed every time.
The continuous blending process of the aggregates, sand, cement, water and admixtures allows for the exact mixture of fresh concrete every time. The operator can stop the mixing and delivery of the concrete and start again at any time, allowing production to balance the demands of finishing and placing crews or other job requirements.
Mix designs can be changed or altered without moving the machine; the operator can make adjustments at any time as required for the job site. When the job is finished cleanup is an easy process by only washing out the mixer area.
Mobile Concrete Mixers Have Separate Material Compartments
Mobile mixers carry materials such as sand, cement, and coarse aggregates in divided bins mounted on the unit; all the bins are loaded from the top and the cement bin has a water tight cover. Water is also carried on the mixer unit in tanks, the size of the tank may vary based on model.
Sand and stone are carried in a side by side divided, open-topped bin with the sand holding 45% of the bin’s volume and stone side holding 55%. Aggregates can be carried separately or mixed as needed according to the design mix; the versatility of mobile mixers allows for virtually unlimited concrete mixes.
Cement is carried in a water tight bin with automatic vibrators and mechanical devices to assure accurate cement proportioning and constant cement flow to the feeder. Water is carried in the tanks and pumped into the mixer; water flow controls and flowmeters accurately monitor the flow, stopping and starting automatically whenever the conveyor belt is stopped or started.
For other concrete output requirements or specialty jobs, liquid admixtures such as accelerators, retarders, air entraining agents, modified latex and such can be carried in a separate system which introduces the ingredient as needed via flow controls and flowmeters.
What Kind of Proportioning System do Mobile Concrete Mixers Use?
Measuring (or proportioning) by volume not weight is at the heart of the volumetric mobile mixer and the final product is capable of an accuracy of better than +/- 1%. Materials are stored in separate bins and based on the mix design are proportioned into the mix; this enables the operator to mix on-site exactly what is needed eliminating overages and shortages. Proportioning gives the operator control over the mix design and how much is mixed.
Mixing
A differentiator for mobile concrete mixers is that materials are mixed on site so the mix is fresh and hasn’t begun setting up or rejected because of being late to a job site. Materials are thoroughly mixed through the volumetric process to produce quality concrete in the exact amount needed.
The concrete is fresh and maximum strength every time, check out this white paper comparing the output of a volumetric concrete mixer with a traditional ready mix. Concrete produced by mobile concrete mixers meets standards established by ASTM 685 and AASHTO M-241 standards as well as DOT requirements.
