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Advice and suggestions needed for cement "bridge"


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I have a small garage directly alongside the National Highway. I park my Innova there.  The highway has been widened, and the contractor is constructing the drainage canal now.  Once the canal is completed, I will need to build a small "bridge" to cover the gap between my garage and the highway.

I am going to use marine plywood as a base onto which I will pour the cement.  

I have a few questions regarding the thickness of the "bridge", the size of the rebar to be used and how long the cement should cure.  I guess the cement mix/ratio is also a question.

i figured I’d use some 10mm and 12mm rebar.

How should the mix be prepared?  

How close should the rebar be placed?

How thick should the slab be?

How long should the cement cure?

I am very familiar with Pinoy style of construction work, so I wanted to compare this to advice from members who may have genuine knowledge and experience.  

 

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Couldn't you get something similar to a metal grate they use for covering drainage canals with.

Use a cement drainage pipe., then cover it with cement. It's what we did, supported a cement truck.

If it was me I`d weld 16mm rebar into the exact size grid and tie flat GI sheet underneath that grid..Put the grid in place and concrete over.

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Salty Dog
14 minutes ago, Jawny said:

I have a small garage directly alongside the National Highway. I park my Innova there.  The highway has been widened, and the contractor is constructing the drainage canal now.  Once the canal is completed, I will need to build a small "bridge" to cover the gap between my garage and the highway.

I am going to use marine plywood as a base onto which I will pour the cement.  

I have a few questions regarding the thickness of the "bridge", the size of the rebar to be used and how long the cement should cure.  I guess the cement mix/ratio is also a question.

i figured I’d use some 10mm and 12mm rebar.

How should the mix be prepared?  

How close should the rebar be placed?

How thick should the slab be?

How long should the cement cure?

I am very familiar with Pinoy style of construction work, so I wanted to compare this to advice from members who may have genuine knowledge and experience.  

 

Couldn't you get something similar to a metal grate they use for covering drainage canals with.

4c664b1bab96b9d556d383433967.jpg

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I can answer the mix ratio question with a high degree of certainty as I recently read it on the side of a cement bag.The ratio is 1 part cement, 2 parts sand, 3 parts gravel by volume.

I like SDs solution better.

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A grate is not available nearby.  

The gap is likely to be around 50cm between the two sides of the canal.  I can’t rely upon the canal to be strong, so the bridge will need to be supported by a stronger base, such as the floor of the garage and a portion of the highway.  

 

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RogerDat

Use a cement drainage pipe., then cover it with cement. It's what we did, supported a cement truck.

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A pic of the conditions of where the bridge is to be constructed might be helpful.

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trthebees

I'm just wondering, as you say the drainage channel is being constructed now, whether the contractor is going to install access bridges across the channel FOC afterwards. 

I can see that's a bit of a "will they, won't they and how strong if they do" question.

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Enuff

My contract built us a drain cover using steel bar. 50cm is about 20", no reason steel bar wouldn't work.54f773cc5fd8dd5c6c3a5766d8c55d08.jpg

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The only images I have were hurriedly taken late today.  Besides, they only show an open pit into which the canal will be constructed.  This is the same process being done on most national highways as they are being widened to four lanes.  By tomorrow or the next day, the canal construction will begin.

Basically, there is a frame in a sort of flattened u shape.  This will have cement  poured to make the base and walls.  That’s it.  A canal is made.  In my case, directly in front of the garage.  Of course, the same concerns are for homes with access from the highway,.  In these cases, it is just foot traffic.

The contractor is not going to make the bridge.  It is my problem and my materials.

Can’t use a drainage pipe, as the canal is a standard size and being constructed by the DPWH. 

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The image of the steel bar was interesting.  Is this for a car to be driven over?

The width of the canal is around 50cm. I’d much prefer to have a cement cover.  

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SkyMan

One lane?  For your multicab, right?  No need to pay extra for marine plywood.  I'd say 10mm rebar in 10 inch grid with 4 inches of concrete would be fine, probably overkill.

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5 minutes ago, SkyMan said:

One lane?  For your multicab, right?  No need to pay extra for marine plywood.  I'd say 10mm rebar in 10 inch grid with 4 inches of concrete would be fine, probably overkill.

The plywood is the base onto which the cement will be poured.  This is not being poured onto ground, but over a gap (the canal). The only support for the vehicle, an Innova, is the slab I’ll construct.  It’s like a roof, that will be driven on.

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Enuff
The image of the steel bar was interesting.  Is this for a car to be driven over?
The width of the canal is around 50cm. I’d much prefer to have a cement cover.  
The 1/2 bar is about 2" between. As long as the cross member bar supporting is enough, I don't see a car tire doing any damage to the 1/2 steel bar

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SkyMan
10 minutes ago, Jawny said:

The plywood is the base onto which the cement will be poured.  This is not being poured onto ground, but over a gap (the canal). The only support for the vehicle, an Innova, is the slab I’ll construct.  It’s like a roof, that will be driven on.

Yes, no need for marine ply.  I would cut a strip of 3/8" ordinary plywood just wide enough to fit into the canal.  Then nail the ends to 2X4 cocos longer than the canal width.  Perhaps very long if you plan to pave from the hiway garage..  Then stack rocks or blocks of scraps of wood in the canal enough to support the plywood with the cement on it.  Put your form down with the strip just in the top  of the canal.  Lay on the rebar and tie.  Put some smallish, 3/4" stones under the rebar to raise it slightly so the cement will pour around the bars.  Brush used motor oil on the plywood liberally.  Pour, screed along the tops of the 2X4s and brush lightly with a broom.  After a couple days remove the blocks under plywood and then the plywood..  

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36 minutes ago, SkyMan said:

Yes, no need for marine ply.  I would cut a strip of 3/8" ordinary plywood just wide enough to fit into the canal.  Then nail the ends to 2X4 cocos longer than the canal width.  Perhaps very long if you plan to pave from the hiway garage..  Then stack rocks or blocks of scraps of wood in the canal enough to support the plywood with the cement on it.  Put your form down with the strip just in the top  of the canal.  Lay on the rebar and tie.  Put some smallish, 3/4" stones under the rebar to raise it slightly so the cement will pour around the bars.  Brush used motor oil on the plywood liberally.  Pour, screed along the tops of the 2X4s and brush lightly with a broom.  After a couple days remove the blocks under plywood and then the plywood..  

That’s the way I’ve done this many times for countertops and such.  Pinoy construction techniques. What I don’t know is the amount of rebar to use, cement mix and that sort of stuff.  My concern is the ability of the slab to support the weight of a car. 

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