What’s the Problem with On Site Concrete Washout Trays

The concrete washout tray is the most common concrete washout containment method used on sites. Most trays hold around .8 of a cubic metre.

Sites need to have plant equipment like a crane or manitou to move the tray around empty, and full, and to tip it into the onsite skip once used. Room for storage needs to be found and on some tight sites this could be a challenge.

Trays can be rented or more commonly supplied by the concreter so the builder can look after the waste. All washout trays need to be lined with plastic to prevent the concrete from sticking.

So, over a large project, the amount of plastic used will add up to a considerable volume.

The plastic will contaminate the concrete to be recycled, just like the concrete wrapped in plastic from the washout bags.

For builders looking at a sustainable method of handling the concrete washout waste, this may not be the preferred method.

Washout trays just like concrete washout bags have no alternate method to contain the water overflow when full, and so often spill over the sides to the surrounding area. Like the washout bags, it can create a slip hazard when the slurry dries.

I have had builders tell me that after a couple of trays have been tipped into the skip, the water runs out of the skip onto the road when transported and are concerned about the possibility of fines from the council.

Again, with this onsite tray some builders talk about the extra or “hidden” costs that go with the handling of the trays with their equipment and the cost of the waste when the turnover of the bins is increased because of the weight in the skips.

Some of the problems we have seen:

Storage Issues:


Plastic Contamination:

Has anybody seen my washout tray?

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The Trouble with Concrete Washout Bags

Concrete washout bags are easy to use and are cheap to buy. They are lined with an inner plastic bag to stop the leaching of the washout water. They have tie ropes to keep the bag up while being filled.

Concrete pump operators keep them on their pumps in case of emergencies when builders haven’t thought of organising a washout area. They have a holding capacity of .5 of a cubic metre. When used on site, the builder needs a crane or forklift to lift as the bag would weigh around a tonne or more when full.

We used to sell the bags around 2 years ago but stopped because of the amount of plastic we were taking to the concrete recyclers and our decision not to use plastic in our operation.

Concrete recyclers were also explaining that it was very difficult to remove all the plastic from the concrete, contaminating the

recycled concrete, and the bags outside weaved material getting caught in the crusher causing them to shut down to untangle the material.

The builder’s problems arise when the pump needs more than a volume of .5m3 to wash out and the water ends up all over the surrounding area. This can create slip hazards when the slurry dries or if used on a roadway, as well as time and labour to clean up after the pump has gone. When the bag is picked up full and wet, the slurry often pours out of the bag, as it has no rigidity until the concrete has cured.

These bags are usually dumped into the onsite skip and add to hidden costs as the skip bin will quickly get to its weight limit without even utilising the skips volume capacity. The builders who are adopting a more sustainable future would possibly not use these bags on their sites.

Enjoy the photos.  The next post is on concrete washout trays.

Is this set up really going to work?

Overweight issues:

Need a bigger bag:

Future land fill; there is a better way:


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