21
votes
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When pouring concrete, is it safe to add large rocks to increase volume?
Concrete is a mix of large aggregate, small aggregate, and cement (a 4:2:1 ratio is a good approximation - though designed mixes will be more calculated than that).
The size of the large aggregate ...
- 2,390
18
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What is this white powder on my foundation?
Looks like effloresence to me, which itself is not harmful, but possibly a symptom, mainly of water movement; I would check perimeter walls for further signs of water infiltration, and make sure water ...
- 1,262
16
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Contractor is installing a vinyl fence and posts but is not using any water with concrete. Is he doing it right?
I put some posts into concrete - made a dry mix and tamped it down.
Next day it was just about done - the mix absorbed moisture from the surrounding soil and was fine.
If you need a really smooth ...
- 24.8k
12
votes
When pouring concrete, is it safe to add large rocks to increase volume?
With regard to using wood posts in concrete:
Image Source
Note that any water that drains down the side of the wood post will drain through to the subsoil. The post should be in a collar, not a cup......
- 1,020
12
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How much does cement weigh after it has set?
Several things affect the final weight of concrete.
Concrete has many different densities based on its composition. Standard "ready mix" concrete is often engineered for structural strength of ...
12
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Contractor is installing a vinyl fence and posts but is not using any water with concrete. Is he doing it right?
Unless you are in a extremely dry area this is fine.
The concrete mix will absorb moisture from air and surrounding soil and will slowly set. Usually a couple of days is all it takes.
Some rain or a ...
- 735
11
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Contractor is installing a vinyl fence and posts but is not using any water with concrete. Is he doing it right?
This is a common technique for setting posts in the ground.
Here is a video from Quickcrete that explains how to do it:
Quickcrete Dry Mix Post Setting
- 23k
8
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How much does cement weigh after it has set?
You could make a pretty simple test to get almost exact data for your situation. My guess is that you are planning to use the pre-mixed stuff in the bags that you buy from the big box home store. ...
- 63.6k
8
votes
What is this white powder on my foundation?
Efflorescence, salts rising to the surface due to presence of moisture. Common in cementitious materials where water is present.
You can wash it away with mild HCL solution but the stains will remain....
- 33.9k
8
votes
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Is it OK if my Durock cement board got wet?
Durock and similar cement-based products are designed for uses where it may be exposed to water. It's not waterproof but it will not disintegrate or lose its strength when wet.
You should allow it ...
- 23k
7
votes
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Is mortar waterproof?
Mortar is not waterproof. However, there are products that can be applied to mortar (and other concrete materials), that can make the mortar waterproof.
- 130k
7
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How do I start making cement on my own?
Well, you have to mix lime and sand. If you want concrete you add rocks.
So you will need to find a source of lime, limestone will work. The ancient Romans used volcanic ash.
Powderize the limestone ...
- 33.9k
6
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How much does cement weigh after it has set?
According to my research, about 95% of the water used in the concrete mixing process will be in the final result, so you basically need to directly calculate how much you want the plates to weigh by ...
- 161
6
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When pouring concrete, is it safe to add large rocks to increase volume?
It is not good practice to bury wood in concrete as you depict. Best to use
metal anchored in the concrete and attach the wood to the metal. Your result
will be inevitable rot and failure, probably ...
- 69
6
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Quikrete didn't absorb much water. What did I do wrong?
It's fairly simple if your going to put it in dry like that. Put a bag in, then a gallon in, and so on. Don't put 4 bags in a narrow hole and expect 4 Gallons of water to penetrate all the way through ...
6
votes
Contractor is installing a vinyl fence and posts but is not using any water with concrete. Is he doing it right?
This is perfectly fine unless you live in a desert where it never rains.
I've seen Florida Public Works workers build a concrete catch basin for a large pipe that passed under a road, and they used ...
- 8,493
5
votes
When pouring concrete, is it safe to add large rocks to increase volume?
Reducing the amount of Portland Cement in the concrete will reduce its strength. That is, adding rocks to an already-blended mixture of concrete will reduce its strength over the same mix without the ...
- 932
5
votes
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Will a cement mixer extend the working life of mortar?
A mixer might help you mix smaller batches more quickly, so that you can easily adjust the size of a batch and keep up. But most mixers will make you think you should be making an even larger batch, ...
- 174k
5
votes
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How can I fill this gap between concrete and cement board?
I ended up filling the gap with tile thinset and cement board tape.
- 195
4
votes
Is mortar waterproof?
Yes, mortar is waterproof. It is "relatively unaffected" by water "under specified conditions".
Water-proof or water-resistant describes objects relatively unaffected by water or resisting the ...
- 13.2k
4
votes
Accepted
Quikrete didn't absorb much water. What did I do wrong?
Bagged concrete dumped in hole dry can work but is not ideal. With a clay base the hole is like a pipe. Adding water to the top the mixture will absorb water a few inches down then create a seal. It ...
- 101k
4
votes
Disposal of hydrochloric acid
You can neutralise the acid by mixing with alkali. However, be careful.
You will need quite a lot of something like baking powder. Or if you have any left over - cement powder.
Add a small amount ...
- 1,294
4
votes
Accepted
Is this retaining wall failing?
The wall may have been built that way but I doubt it, the wall may have shifted over the years and is stable now.
The only way to know is to drop a plumb bob from the upper decking just in front of ...
- 101k
4
votes
Can I create concrete driveway with forms to get the paver stone look without the need for all the aggregate beneath?
If this was just a patio I'd say you have a good chance of getting some satisfactory results except for the fact that it would be about 2.5" above grade and there's be the possibility of tripping over ...
- 71.9k
4
votes
Proper deck post installation
If I understand your description you're concerned because the posts are encased in concrete with no gravel under the posts.
It would have been good to have gravel under the posts for drainage but it's ...
- 8,652
4
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Should Cement Patio be Poured Level with Foundation?
I would pour it below the foundation level for several reasons.
First if the same level it would be easy for a heavy rain to end up inside.
In my current state and 2 others I have lived in the ...
- 101k
3
votes
How much does cement weigh after it has set?
Adding different amounts of water will change the strength of the concrete. So you probably don't want to change that.
I don't know if there is a way to calculate the final weight, but the easiest ...
- 5,589
3
votes
how to make a half circle tunnel through a cement slab?
Rather than try to shape the slab so it conforms to the pipe, cut the slab slightly wider and deeper than the pipe. Mix a loose batch of cement, pour into slab cut, and embed pipe into concrete.
- 10.9k
3
votes
When pouring concrete, is it safe to add large rocks to increase volume?
People have bound stone in concrete since...well, since they started using concrete. I don't think adding rock is a bad idea in principle but it matters what sort of rock you are adding. Adding ...
- 31
3
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When pouring concrete, is it safe to add large rocks to increase volume?
It is pier size that matters. My God, yes to the above answers if you were building a very serious structure. Yes less Portland the less PSI. 6 sack Portland cement is about 4000 psi. You can drive a ...
- 71
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