Ocmer North America

SELECTING A CONCRETE MIXER - what is the best type for you?

The best concrete mixer for your application can be selected by following a few simple steps and rules:

Size by batch or production per hour

Fixed batch size

Once the batch size is settled, how many batches do you need per hour? 

Example 1:

Example 2:

Two rules appear here:

Compare production requirements with mixer throughput.  If too great, increase batch and container size or stagger production over a greater time.

If still too much for a reasonable mixing cycle time, you need a second mixer.

Throughput per hour

First, you need to calculate the amount of concrete required per hour, then you need to determine the mixing cycle time.  To determine the hourly throughput, consider the process the batch plant is feeding. 

Example 1: 

Example 2: 

The rule here is simple:

Taking the combined, maximum throughput per hour, divided by the number of batches that can be made per hour, gives the required mixer output.

Multiple-batch containers

Where the bucket, hopper, skip or truck holds more than one batch from the mixer, first determine the time in which the container must be filled.  This will allow you to size the mixer to fill it with your required number of batches.

Example: 

What mixer is best for my application?

The effects of mixer charging methods

In order to get the fastest mixing cycle time from pan, planetary or twin-shaft batch mixers, the mixer has to be filled quickly.  Often overlooked, the system for getting aggregates and cement into the mixer is critical and can prevent a plant from ever living up to expectations if not considered up-front.  See Planetary or Twin Shaft mixing cycles for details.

If a mixer moisture correction system is used, expect to add from 20 to 40 seconds onto the complete cycle.  Also, if high rate plasticizers or SCC admixtures are added after the water, expect a further 20 to 40 seconds for full dispersal and action.  Note also that SCC will increase in slump as mixing continues;  a compromise must be reached between the amount of admixture and the acceptable mixing time.

Note that we consider only the mixing cycle time, from completion of one batch discharge to the next.  The batching (weighing up) time does not come into the equation because after the first batch of the day it always happens in parallel with the mixing - as mixing proceeds, the next batch is being weighed up.  Even the fastest mixer cannot outpace a batch weighing system, and most batch plants can keep two mixers supplied without missing a beat.

Call, Skype or email us - see Contact Us on menu, for fast, free advice and a full evaluation of your plant and mixer needs.  We refurbish older plants, supply mixers, hoppers and scales, fabricate on site and install the whole system if you wish.