Base for a new machine shop aka “shed”!

[BazyleParticipant @bazyle]

Few questions arise from Bill's post, not necessarily directed at him.

What is MPA 25 in amateur terms ie bags of cemont per cubic yard of aggregate?
How much free water is left in concrete after say the 24 days that is still going to come out and cause rust?
After keeping it wet during the curing stage how soon before it would be ok to put a dehumidifier on to protect the contents?
How long before the sealer can be applied as presumably the residual moisture would be trapped or cause some problem with the sealer adhesion?

[“Bill Hancox”Participant @billhancox]

Paul

I come from a long line of English and Irish stone masons and concrete finishers so I have picked up a little knowledge and experience over the years. I did not take up either trade but rather opted for becoming a sign painter; in the days when we hand lettered signs with brushes, quills and stripers. I digress. At the risk of being too long-winded for some members who do not appreciate quality English composition, I offer the following.

Unless the floor area is extremely small, I strongly recommend that you do the preparation yourself but purchase your concrete premixed. This allows for a quick and steady pour and eliminates the risk of unplanned interruptions such as equipment failure, calls to nature etc; not to mention nosey neighbors. You can tell the company the strength of the mix that you want (eg MPA 32) and you need not calculate the required amount; the company will do that for you if you provide them with the dimensions. If you haven't done this work before, I also recommend that you engage a local concrete finisher who will have all the necessary tools and equipment to do the job quickly and properly. Start to finish, the pour should not take long. The finisher will probably need to leave after the pour and initial trowel is complete and return a bit later (depending on the weather and temperature) for the final finish trowel. You will be busy enough wheeling the concrete unless the truck can get close enough to pour directly on the floor using the chute. If at all possible all equipment should be removed from the work area until the floor is completely finished, cured, sealed and painted. While the floor is curing as per my previous thread, the area should be ventilated to allow excess moisture to dissipate. Whereas you intend to pour inside an existing structure it is prudent to apply poly 3 to 4 feet up the walls to catch the inevitable splatter from the pour.

You can set up a dehumidifier any time after the slab is hard enough to walk on; bearing in mind that the slab should still be kept moist and covered in poly. Despite having a warm and dry 24 X 24 workshop in my basement, I have a dehumidifier in my shop set at about half-throttle year round and have absolutely no problems with rust even during the most humid weather.

I am enclosing a few links that explain the terminology and the technology of concrete work.

**LINK**

**LINK**

**LINK**

**LINK**

**LINK**

Wee Willie Winkle must now go tinkle.

Cheers

[Paul MajorParticipant @paulmajor25237]

Thanks for all the info Bill and everyone

Had a friend who is a QS come round to give some advce on the structure and he also suggested that by the time I have faffed about trying to implement alternatives it will be quicker and no more expensive to get a truck load of pre mix in.

So, plan is to hardcore, 50mm sand blind, dpc, kingspan then 150mm C30 with mesh. May run it a bit thinner in the store and woodwork parts of the shed to keep it to 1 load.

Hopefully get this sorted in the next 4 weeks so will let you know how I get on!

Cheers,

Paul.

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