Multiquip LS600P Manual De Usuario

Mix design is most important to achieve maximum 

pumpability. Pumpability is affected by, among other 

factors, the type and gradation of aggregate used. Natural 

aggregates make a more workable mix and pump more 

readily than crushed aggregates. A blend of natural and 

crushed aggregates will produce a workable mix. The 

type and gradation of aggregates is equally important 

for workability as the size and percentage of coarse 

aggregates in the mix.
The term “aggregates” describes all of the solid materials, 

from the largest rock to the smallest grain of sand, 

contained in the concrete mix.
Concrete mixes with a consistency as dry as one-inch 

slump and as wet as ten-inch slump have been pumped; 

but for maximum efficiency from the pump, a slump ranging 

from two to six inches will produce a more workable mix 

than one that contains more or less water.
The principle of concrete pumping is based on self-

lubrication. As it moves through the transfer line, the 

concrete takes the shape of a plastic cylinder. It is forced 

through the transfer line on a film of mortar that is self-

troweled to the service of the transfer line around its full 

periphery by the slug of concrete itself.
A slump rating should be used with discretion; it is not 

always a real indication of the pumpability of the mix. The 

concrete may be workable in the sense that it will readily 

flow into place, but the same mix may not respond to 

pressure. 
Overly wet mixes tend to separate. In addition to affecting 

the strength and quality of the concrete, the delivery 

system will not tolerate separation. Overly dry mixes are 

similarly unsatisfactory if they lack plasticity and tend to be 

crumbly. To be properly pumped, the mix must be able to 

continuously coat the inside of the line with a lubricating 

seal of mortar.
There are four ways in which this seal can be lost:
1.  By pumping excessively wet mixes which do not have 

enough cohesion to hold together.

2.  By pumping harsh undersanded concrete with poorly 

graded aggregates which can jam together when the 

pressure becomes too great for the insufficient amount 

of sand to hold the aggregates apart.

3.  By getting a rock pocket, such as mixer tailings, into the 

pump valve. This rock pocket will have an insufficient 

coating of mortar and the mix will not be plastic enough 

to allow the valve to operate or the mix to move in the 

line.

4.  Through excessive bleeding. If the mix is short or fines, 

but the sand is otherwise fairly well graded, bleeding 

will not normally create any problems as long as the 

pump continues operation. But, if the pump is shut 

down, bleeding can result in a loss of lubrication and 

blocked erratic flow.

The above are bad concrete practices, regardless of how 

the mix is to be placed. But, these points do show that 

special mixes are not always needed, within limits, for 

pumping concrete. Good aggregate gradation is most 

important to pump concrete the maximum distance.
The use of admixtures can have a beneficial effect on 

pumpability. Most of the dispersing agents will fatten, 

retard bleeding, and increase workability. Thus, the average 

concrete can be pumped for appreciably longer distances. 

Air entraining agents will also improve workability, although 

they cannot be used as a substitute for good gradation of 

the aggregate. 
Pumping will not appreciably affect the final air content of 

the mix. High-early cement tends to give a more readily 

pumpable mix with superior water retaining qualities. 

However, if delays are likely to occur, extra care must be 

exercised due to the faster setting time over regular cement.
The Mayco LS600P will pump a wide variety of concrete 

pump mixes. But, there are guidelines that must be followed. 

Use this information in conjunction with the Operation 

section of this manual.