Concretes, mortars and grouts have the potential to create significant amounts of dangerous dust when the water is first added. There is only 1 part water for every 4 parts concrete by weight, so much stirring is required before all the dry concrete will be wet. In fact, you can create a lot of dust just by pouring the water in too rapidly or from too high above the powder.
But it is possible to mix up concrete inside a workshop or studio without creating very much dust and collecting what dust you do create.
How To Stir In The Water
The water should be poured gently over the top of the powder. Pour the water from a low height and pour it gently against the wall of the container. Stir slowly, spreading the water over the top of the dry material instead of digging into it.. Keep the growing blob of mud over the top of the dry stuff. Gradually use your spoon or scoop to slowly scrape into the dry materials until the blob absorbs it all. Make sure you get all the pockets of dry stuff in the bottom corners.
Tips Useful for Batches Large and Small.
Always wear a dust mask when pouring and mixing dry powders, especially when mixing up concrete products.
Humidifiers and Spray Bottles
Use humidifiers and misting spray bottles to control dust generation, but keep them away from electric power tools to avoid electric shock.
- Locate the humidifier in the room, not where you are actually working.
- If your hand or glove gets wet while handling a spray bottle, dry it with a rag before using drills, mixers, etc.
HEPA Shop Vacuum
A dust mask isn’t going to protect you if you spread the dust all over your clothing or work space. A few days later you will move a box or a board and breath that same dust right in. Buy a HEPA shop vacuum and use it regularly. Use a vacuum bag to protect your HEPA filter, as always.
How To Get Concrete Out Of The Bag Without Pouring.
Pouring dry powders and chips from bags creates more dust than is necessary. Concrete should be scooped or shoveled from partial bags or whole bags should be lifted off similar to how a person takes off a shirt. Misting bottles or HEPA shop vacuums are still required.
For Small Batches
For small batches (and anything else under a full bag), scoop your material from a bag which is kept stored in a plastic bucket with snap-on lid. Use hand shovels, coffee mugs, ice scoops or whatever you have to scoop it out of the bag-in-bucket. Old coffee mugs and serving spoons from thrift stores can be left inside the bucket for next use.
For Whole-Bag Batches
- Sit the bag on one end of the bag in the tub or mixer. Make sure the bag is leaning against one wall of the tub.
- Slit the bottom seam or panel. Make an X-shaped cut on the bottom panels of concrete bags so that the hole opens evenly from the center of the X. Or cut 3 sides of the bottom panel so that it falls open like a door.
- Cut open the top seam or panel of the bag so that it can breath in air as the powder exists from the bottom.
- Lift remaining bag off like a sleeve off a column of powder.
Remember to cut the top open in step 3 so that the material slides right out.
Careful With Shop Vac
I usually keep my shop vac running while doing this, but I am careful where I place the nozzle.
Suck in the dusty air but avoid piles of dry concrete. The elephant will eat those as well, and
while that is happening, your vacuum is a machine for keeping the air saturated with very
fine dust, which is bad.
Tell your vacuum to use its powers for good not evil. If not, the first time you drop the nozzle to grab or lift something, it will go straight for the open bag of concrete. Or bucket of nails. The elephant is always hungry. He’ll eat anything he can suck up his nose: Tape measure. Keys to the truck.