A typical mix is 1 part water, 2 parts cement and 3 parts sand/gravel by volume. A dry mix should be mixed first with the water added slowly. If a slump cone is available, adjust water to achieve a 2" - 3" (51 - 76mm) slump. The final water content should be approximately 6 - 9 pt (2.8 - 4.3L) of water per 80 lb (36.3 kg) bag of concrete. The easiest way for you to achieve the best results is to use bagged pre-mix in 80 lb. bags. Each bag provides .60 cu. ft. of finished concrete. This translates to 15 bags of mix per batch. The current price today per bag is about $4. For small batch on demand concrete, it does not get much better.  

Water

The first time you create a batch it is advisable to use a 55 gallon barrel that is prefilled with water. Use a white 5 gallon pail and measure 4 gallons inside the pail and draw a line inside the bucket so you can scoop a predetermined amount each time you fill the bucket. The idea is to add enough water to the mix and keep track of how much water you have used so that each consecutive batch will be the same consistency. 

On-Site Mix

If you choose to mix the entire batch on your own, it is still advisable to buy your sand/gravel premixed to insure the quality you would expect for a professional batch. If you still would like to mix your own then scoop enough sand/gravel into your mixer to cover the paddles. Add 1.5 bags of Portland Cement per batch for 4000 psi concrete or 2 bags per batch for 5000 psi concrete. Once you have added water, the mixture will compress so you can add more sand/gravel mix to top off the batch. Once the batch is thoroughly mixed, it is safe to transport to the pour site.

Clean-up

Lots of water with some pea gravel added. Run the mixer for a few minutes and rinse any other spots that you see that have lingering traces of mix. A small spray bottle with diesel added will help to keep everything from rusting and sticking the next time you use your mixer.

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