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How long should it take to mix 0.4 cubic meter of concrete?


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Today I had planned to fill a shallow trench with concrete. Some simple sums suggested it would require 0.4 m3 and when estimating the job I thought as my Belle electric mixer has a 130 litre drum then 4 to 5 full loads should fill the trench.

 

I seem to be out by a factor of 2 or 3. Would I be correct in thinking that the rated 130l capacity of a mixer drum is highly theoretical and relates to the water capacity of the drum filled to the brim when sitting upright on its axis in a rain catching position?

 

I have re-calibrated my concrete mixing capability and reckon that when working solo and filling a trench 30m away from the mixer I should allow 4 hours per 0.5 m3. How does that compare with others?

 

 

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1 hour ago, AnonymousBosch said:

How does it compare?

Takes me about 10 minutes to order the tail end of a part load ( half price), and a further 20 to chat to the driver, 5 minutes to wash up the coffee cups.

 

A part load "tail end" concrete order, had not heard of that. I assumed ordering such a small quantity would be a daft price. Makes sense though as my garden develops in advance of the house the post delivery wagon wash-out would involve killing green stuff.

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8 hours ago, epsilonGreedy said:

A part load "tail end" concrete order, had not heard of that. ...

Knowing the despatcher well enough to ring and ask if any truck has a part load " left" .

Yes I have to wait until Someone doesn't use as much as they'd ordered. But doing it that way saves everyone time and money

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12 hours ago, epsilonGreedy said:

I have re-calibrated my concrete mixing capability and reckon that when working solo and filling a trench 30m away from the mixer I should allow 4 hours per 0.5 m3. How does that compare with others?

If possible,I’d set the mixer up so it’s tipping directly into the trench,with a water butt next to it & the cement bags stacked there. Much easier to barrow  the dry ballast than to barrow the mixed concrete the same distance. 

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14 hours ago, Oz07 said:

If say you get about 87.5 kg in a drum of dry materials. Just basing a 6:1 mix filling the drum. So around 8/9/10 for .4m3 based on weight

Yes I would assume 130l is horizontal complete volume

 

 

Your calculations look sound. If the the dry materials have a density of 1.6 tons per m3 then:

 

87 / 1.6 = 54 litres and 9 x 54 = approx my trench capacity which increased to 0.45 m3 after the shuttering was pegged in place. 

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11 hours ago, Mr Punter said:

You need to fill the mixer. Is your estimate out by time or volume?

 

 

Yes nearly full, the limiting factor is my ability to tip the loaded barrow over the trench which is about a 100kg barrow load.

 

I am not sure of the water volume used, all I know is 17 seconds with the Gardena hose nozzle on jet is about right for a mix a touch more moist than a kerb mix. 

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3 hours ago, AnonymousBosch said:

But doing it that way saves everyone time and money

 

 

But I won't loose 2 pounds of winter flab picking up the phone ?

 

I will remember the tail end load tip next year however at this time of year the pouring/set time window is short, for the past week on my plot this has been 12pm to 3pm because of overnight frosts. I wrapped the trench in a quadruple layer hessian ground blanket last night. A small test tub of water placed under the blanket remained liquid through the night even though the car displayed -2 (c).

 

Last night I was reading up on cold weather concrete handling techniques and read that I should have used warmed water to accelerate initial hardening. 

Edited by epsilonGreedy
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