Concrete strength

[yanmars]

The concrete was for vertical columns. The concrete was to be 4000 psi, it was tested and none was below 3300 psi. The same are 1 footx1footx9 feet long. Four pieces of 5/8 inch rebar, he said 60 or 80. I am not a concrete man to know what that means. Said it had a ring embedded every foot. I am not too concerned about it handling my 1/2 ton pick up or 45 horsepower tractor in the short span. If I needed gravel or a concrete truck it could drive around when dry. Just curious of general strength, I can get them for between $100 to $75 depending on number purchased. He said they weigh about 1200 pounds apiece. Hope that helps some.

 

[bigdeano]

You could buy 1 and test it before investing in more.

 

[downsizingnow48]

There are online calculators the OP could use to assess the strength of those columns laid flat as beams. Dunno, maybe they would be safe, maybe not. Need to do the homework.

But only two of the nine would be working, the other seven are just sort of there. So total of 4 #5 rebars supporting the load for $700-$900. The beams have stirrups at 12" spacing which is good. Definitely safe for some loads. not sure I would put my $50k truck or $30k tractor on it.

Concrete and rebar are cheap building materials and easy to work with. If OP wants a concrete beam bridge, why not build it from scratch and make a couple proper beams with 3-8 rebars in the bottom or tension area.

 

[Streetcar]

The concrete was for vertical columns. The concrete was to be 4000 psi, it was tested and none was below 3300 psi. The same are 1 footx1footx9 feet long. Four pieces of 5/8 inch rebar, he said 60 or 80. I am not a concrete man to know what that means. Said it had a ring embedded every foot.

The rebar is either 60,000 or 80,000 psi strength. 60 is most common strength

 

[Egon]

Aggregate size is not factor in design strength. It is factor in workability of wet concrete

So, it still ends up being a factor in the design.

 

[LD1]

Too much guessing. Can never be 100% sure how they are made regardless of claims.

I'd but a couple, they'd make nice footings on either side. The build a proper bridge on top of that

 

[downsizingnow48]

That is another question if span is 7 and length is 9 hard to make a footing in crumbley edge.

 

[Streetcar]

So, it still ends up being a factor in the design.

Aggregate size is not considered in strength calculation.

 

[shadetree]

The concrete was for vertical columns. The concrete was to be 4000 psi, it was tested and none was below 3300 psi. The same are 1 footx1footx9 feet long. Four pieces of 5/8 inch rebar, he said 60 or 80. I am not a concrete man to know what that means. Said it had a ring embedded every foot. I am not too concerned about it handling my 1/2 ton pick up or 45 horsepower tractor in the short span. If I needed gravel or a concrete truck it could drive around when dry. Just curious of general strength, I can get them for between $100 to $75 depending on number purchased. He said they weigh about 1200 pounds apiece. Hope that helps some.

Anytime you use something in a way it was not designed for you are walking new ground. Buy a culvert (metal, concrete, or plastic) and be done with it worry free.

 

[Egon]

Aggregate size is not considered in strength calculation.

But it is a factor in the overall design.

 

[Streetcar]

Anytime you use something in a way it was not designed for you are walking new ground. Buy a culvert (metal, concrete, or plastic) and be done with it worry free.

A beam does not care what it was designed for, but I agree with the second sentence.
A lightly reinforced beam will not be able to support much weight

 

[Streetcar]

But it is a factor in the overall design.

Aggregate size and shape is factor in workability, but the discussion was about concrete strength

 

[Egon]

Aggregate size and shape is factor in workability, but the discussion was about concrete strength

When using rebar agregate size is all part and parcel of the overall design.

 

[rd_macgregor]

Unless there is some other factor militating against it, I would go with the culvert suggestion. It will be easier, cheaper, more trustworthy and make a wider crossing.

 

[Streetcar]

In most cases aggregate size is not considered, during design of reinforced concrete. In rare cases for appearance or clearance issues aggregate can be specified

 

[Renze]

Hmm two guys quabbling over the size of pebbles.. which shows free advice is worth just that...

 

[Egon]

Hmm two guys quabbling over the size of pebbles.. which shows free advice is worth just that...

Right on!:thumbsup:::cool2::cool2:

 

[Cord]

A beam does not care what it was designed for

Yea, but these were columns that were designed to be loaded linearly and the greatest lateral force was to control buckling. The loads were very light because there is so little rebar. Also, notice the design value of the concrete was 4,000 psi, but it tested "not less than 3,300 psi". This means the engineer rejected the concrete and these columns were removed from the building because they were defective.

Honestly, I'd guess that a good drop would crack these "beams".

 

[yanmars]

I anticipate going to a culvert/steel pipe system instead. Thanks for the inputs.

 

[shadetree]

Thank you, I feel better.