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

[epsilonGreedy]

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?

 

 

[Oz07]

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

[ToughButterCup]

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.

 

[epsilonGreedy]

  On 04/12/2019 at 20:52, 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.

 

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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.

[Mr Punter]

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

[ToughButterCup]

  On 04/12/2019 at 22:36, epsilonGreedy said:

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

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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

[Brickie]

  On 04/12/2019 at 19:17, 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?

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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. 

[epsilonGreedy]

  On 04/12/2019 at 19:51, 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

 

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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. 

[epsilonGreedy]

  On 04/12/2019 at 23:00, Mr Punter said:

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

 

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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. 

[epsilonGreedy]

  On 05/12/2019 at 07:17, AnonymousBosch said:

But doing it that way saves everyone time and money

 

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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 December 5, 2019 by epsilonGreedy