Page 41 - QR CIMAR LASER SCREED

SCREEDING OPERATIONS

Before you start actual screeding operations, make sure you have a screeding pattern in mind and
share that plan with the entire crew. That way they can work with you to achieve the best results.

In terms of good planning, a good, daily average speed to set for yourself when working with the screed
is 3,000-4,000 square feet per hour. But don’t expect to hit that target consistently throughout the job. A
number of factors on the site could reduce your speed, including cold weather, low slump concrete, or a
requirement for high-tolerance floors.

As the concrete is delivered to the placement area, it should be raked out in front of the screed head so
that is tops off at between one-eighth to one-quarter of an inch above finish floor height. By having the
crew provide this steady, slight oversupply, you’ll have enough concrete to fill any unexpected low spots.
This is important because if they consistently place the concrete too high, you’ll expend a lot of time and
energy dealing with excess concrete.

As soon as the first concrete comes in, the finishers can start troweling the edges of the placement.
This will eliminate the need to rescreed the edges by hand if they are not accessible after the screed
has completed its pass. However, if the edges of the placement are accessible after the screed has
screeded, they should be re-screeded by hand to blend the edges into the perimeter form or existing
floor edges.

After you make the first complete pass, and regularly thereafter, you should check the newly screeded
concrete for proper elevation. Remember, whenever you’re checking the grade, keep the screed Grade
Rod plumb and lower it into the laser beam.

When you’re ready to screed the next section, drive straight up to the point you’ll begin screeding with
the screed head overlapping the previous pass by one or two feet. The exact amount of overlap will be
determined by the slump of the concrete. The wetter the concrete, the more you’ll need to overlap.
Remember, the screed head will be coming down over screeded concrete, so it’s especially critical that
you bring it in for a smooth landing.

The screed comes equipped with six (6) counterweights. Start screeding with four (4) counterweights
on the back of the screed. When not needed, these counterweights are stored in front of the hydraulic
tank directly over the axle, where they will not affect the machine’s balance. However, depending on the
slump of the concrete you’re screeding, counterweights may need to be mounted at the rear of the
machine. If the concrete is relatively wet, counterweights can be hung at the rear of the machine to
reduce down-pressure on the screed head. This will help prevent the screed head from sinking into the
concrete.

As you continued to screed, you’ll no doubt encounter some shadow areas where one of the receivers
is blocked from seeing the laser transmitter. In cases where a receiver is blocked from the laser
transmitter, you’ll have to switch over to manual mode to continue screeding. In the manual mode you’ll
have to pay very careful attention to make sure that the screed head does not drop too low. Watch the
ridge on the overlapping section as an indication of your progress.

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