Concrete experts...

Dave H (MI) · Feb 22, 2016

I mixes my own when I need it. Probably going to be doing a lot of it in the next few months. I mix 3-2-1...stone, sand and cement. Actually buy 60/40 mix to get the 3-2 part and then add the cement. Is the 3-2-1 supposed to be weight based or volume based? As much as I have mixed over the years it seems like a little late to ask...but still...

kruser · Feb 22, 2016

Dave,
3 2 1 is correct for the rock, sand and cement BUT if exposed to the elements, you need some air entraining. Reinforcing depends on the use.

YRMV

kruser · Feb 22, 2016

Duh - Volume

JD Seller · Feb 22, 2016

I am far from an expert on concrete but like Kruser it was always by volume. When we used a mixer we always counted shovels full. I have poured many a yard of concrete mixing it that way.

jeffcat · Feb 23, 2016

Gust make sure you get WASHED gravel and sand. If there is any dirt or clay in the sand you will have junk.

Billy NY · Feb 23, 2016

In the batch plant its actually done by weight per the design mix

dpendzic · Feb 23, 2016

as Billy said it is done by weight in the batch plant--but that is impractical in the field so volume is used
the most important factor on strength and durability is the water/cement ratio

Leroy · Feb 23, 2016

I have heard the term air entraining but what is it?

Steamboat · Feb 23, 2016

"Reinforcement depends on use." When I poured my garage floor, I used fiberglass instead of re-bar. I park cars, pick-up and medium sized tractors on it. 15 years and no cracking.

ed will · Feb 23, 2016

Hi, I just buy a load of 3/4" minus navy (best with lots of fracture in it). Then mix 4 1/2 shovels full to 1 shovel cement adding water as needed. Be sure to add some water and gravel to mixer first to each batch or the cement powder will start building up on the mixer bars. Bugger to clean up. At 4" thick, 100 sq ft = 1cu yd Ed Will Oliver BC

ed will · Feb 23, 2016

Hi, sorry! In previous post I said 100 sq ft = 1 cu yd at 4 " thick...Wrong ...It's 80 sq ft. 100 sq ft= 1 cu mtr. Ed Will

Billy NY · Feb 23, 2016

Agreed. Very wise to insure the correct amount of each are used. When I was involved with a NYS agency's design and construction division, the W/C ratio was one of the first things I looked at on the submitted for approval design mix, more so if it was not an approved mix design already in use. Many were in use with DOT approvals. It's true for this material no matter how you use it. The structural engineering department's lead engineer instructed me to do this on all contractor submissions.

Deutz Lover · Feb 23, 2016

If you need it hard and strong pozzolanic cement. It resists weathering. Roman type cement. The colosseum has been around a long time. look up pozzolan and fly ash.

Super Trucker · Feb 23, 2016

Dave if you would like a big load so you don't have to haul a bunch of little ones get a hold of me. Buno rd has the 60/40 and I would like to meet a neighbor.

ed will · Feb 23, 2016

Hi, sorry! In previous post I said 100 sq ft = 1 cu yd at 4 " thick...Wrong ...It's 80 sq ft. 100 sq ft= 1 cu mtr. Ed Will

ed will · Feb 24, 2016

Hi, sorry! In previous post I said 100 sq ft = 1 cu yd at 4 " thick...Wrong ...It's 80 sq ft. 100 sq ft= 1 cu mtr. Ed Will

Yukon3639 · Feb 25, 2016

(quoted from post at 07:04:44 02/23/16) I have heard the term air entraining but what is it?

Microscopic air bubbles that give concrete ability to expand and contract with the weather. Under a microscope it resembles a sponge
Never trowel air entrained concrete
Mag float only

Concrete experts...

Dave H (MI)

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kruser

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kruser

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JD Seller

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jeffcat

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Billy NY

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ed will

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Billy NY

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