Concrete testing cubes

[pferdy62]

Hi, does anyone know where I can buy the metal molds to make the standard concrete cubes that are later crushed to measure their compressive strength?

 

[Kwasaki]

?

[eyecatcher]

Unless you are planning on doing something constructive rather than destructive then use the ones provided by your concrete supplier....free of charge

[pferdy62]

Do companies like CPAC loan them or supply single use plastic molds? I never thought to ask them. They were horrified when I started to slump test each delivery but a year later I see a lot of erosion in their concrete which makes me think they may not be supplying the correct mix


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[Kwasaki]

9 minutes ago, pferdy62 said:

1..Do companies like CPAC loan them or supply single use plastic molds? 

2.  I never thought to ask them.

3..They were horrified when I started to slump test each delivery

4.  but a year later I see a lot of erosion in their concrete which makes me think they may not be supplying the correct mix

1. Never seen it, guess you never will.

2. If you did they just think you crazy.

3. Not surprised as #2.

4. Could be a few reasons for that but frankly if you want a correct mix the best way is hire a mixer and do it or get someone to do it for you with you supervising.

[David B in Thailand]

Slump Test is readily available on Insee (Eagle) brand ready mix concrete in Buriram.  Perhaps other provinces in Thailand. The slump test cones can be purchased at a builders merchants store in Isaan. 

[eyecatcher]

Actually the truth is that concrete companies dont want anyone testing their mix.

my comment above actually is total <deleted> but they maybe willing to sell you them.

certainly in my experience of uk building, we had to produce 4 cubes for every pour.

Each cube was made only by the same person as there is a skill and technique involved.

At any one time as a builder you may need upwards of 30 steel moulds which had to be kept pristine and oiled.

As for testing...well that has to be independant of the connie company for obvious reasons.

I have taken the cubes many times one is tested at 7 days, then another at 14 days and then a final one at 28days, the fourth cube is a spare as a cube could have been made wrong and shows a drastic failure.

 

The irony is, a cube that fails to reach the 30N strength or whatever after 28 days represents a concrete pour that now has a month of building constuction on it, walls, floor build ups, back fills and its always a big  singing and dancing panic by the client until some engineer tells them that really it only needs to reach half strength as there is 100% safety and over engineering factor incorporated.

 

Have had loads fail in the past and when its thrown back to the concrete company, miraculously they did their own independent testing for the same pour.

 

Even here we criticise concrete knowledge and techniques but you kbow what.....its all still standing.

 

As westerners we are told to believe so much unnessary crap in our building education.

[sometimewoodworker]

1 hour ago, David B in Thailand said:

Slump Test is readily available on Insee (Eagle) brand ready mix concrete in Buriram.  Perhaps other provinces in Thailand. The slump test cones can be purchased at a builders merchants store in Isaan. 

CPac will do it in Issarn (udon province) but eagle will not.

 

It is free and get it done before accepting delivery.

[pferdy62]

I can do my own slump tests as I had the cone and rod custom built for me because I just couldn't find anyone that sells them in Lampang.

 

There is a concrete trade fair coming up in Bangkok in a couple of months, so I will drive on down and have a look at what's on offer.  Hopefully, I will find these cubes as well as some other goodies that I have been looking for.

 

While I understand that concrete is over-specified for a job, my concern is that the concrete that has been supplied in the past may not come close to 50% of the strength we paid for.  After a year, there is noticeable erosion of the upper surface and this only gets wet when I hose it down to clean it.  This is just a concrete floor in the dog's compound and they don't care about things like that, but I don't want houses that we are going to start building soon to have the same poor quality.

 

My next search will be to find a place where I can get the concrete cubes tested for a reasonable price.

 

 

[r136dg]

1 hour ago, pferdy62 said:

While I understand that concrete is over-specified for a job, my concern is that the concrete that has been supplied in the past may not come close to 50% of the strength we paid for.

I wouldn't put to much worry into it; but out of curiosity, what mixes are you ordering for what kind of work?

I'm sure you know there's lots of things that can weaken the surface, cause spalding, ect.. The worst IMO is all the bleed water you get here, even with a tight slump. If hand finishing your work, troweling that bleed water in over & over will weaken your surface significantly. There is things you can do to mitigate that a bit. Also, cure & seals will help.

Post or pm those mixes & the slumps you're pouring with.

 

That's a really good slump in those pics above!

[sometimewoodworker]

 

 

This was about 6 years ago

[pferdy62]

The slump above is pretty good.  Once I started testing, every load came in good after the first one was reported as a "fail" on their paperwork.  We normally order 210 or 240 KSC if memory serves and get a slump of around 80 to 90mm which is within the specified range. 

 

I screed the surface to start with to get a moderately flat finish.  This is followed by a smoothing process using a home made bull wood bull float at intervals over the next hour.  Surface water is pulled off the concrete early on in the process.  

 

I am not trying to achieve super flat or polished finishes that I am used to with the warehouses I have worked on in Australia, but I am looking for a reasonably smooth finish that will last.  This is why I suspect that the concrete may have been light on cement powder which allows the surface to slowly deteriorate, but who knows, perhaps I am just a really bad finisher.

 

When we do start building houses, I want to get the concrete floor flat, similar to Australia which is probably the same as in countries like America and England.  This allows you to tile the floor using tile adhesive and a notched trowel which is very fast, efficient and accurate.  Anyone have any ideas on how to explain this properly to a builder so I can avoid the common practice of adding 3cm of mortar to bed the tiles onto?

 

[sometimewoodworker]

19 minutes ago, pferdy62 said:

When we do start building houses, I want to get the concrete floor flat, similar to Australia which is probably the same as in countries like America and England.  This allows you to tile the floor using tile adhesive and a notched trowel which is very fast, efficient and accurate.  Anyone have any ideas on how to explain this properly to a builder so I can avoid the common practice of adding 3cm of mortar to bed the tiles onto?

I tried that and you probably don't have a chance to get the concrete flat enough but we got a flatish screed on top, then used thinset. The full story with pictures is on a site devoted to building cool houses in Thailand.

[watcharacters]

On 7/20/2018 at 4:24 PM, David B in Thailand said:

Slump Test is readily available on Insee (Eagle) brand ready mix concrete in Buriram.  Perhaps other provinces in Thailand. The slump test cones can be purchased at a builders merchants store in Isaan. 

 

Thank you for an intelligent reply to the OP's question.

 

[Joinaman]

When i first came here i made the mistake of thinking i could leave a few guys to lay me a nice smooth brush finished driveway

Came back to see they had used anything they could find for the shuttering, used their usual 1.8m straight edges to try and make it level, then tried to brush it with one of those twig brushes, - never again 

When i did my extra rooms and area i went out and bought some lengths of 4x2 steel box sections and used these for the shuttering, so easy to get level and dead straight

I didn't do any slump test, but warned the concrete yard i would send back if they had added too much water to it, which seems to be a favorite trick here. Put lots of water in it, then it almost self levels itself, but then leaves a very poor finish on top

I also used one of these steels to level off the concrete, and then finish with a light float to leave flat

Was perfect to allow me to tile with standard tile adhesive straight on to the concrete

Takes a little longer to get smooth and level, but then saves time when wanting to tile

Got some funny looks from the village people, but they also commented how neat it was on completion

Also used the steels for doing some other paths and drives, but then  gave them a soft brush finish with a steel float border to the edges

Watched a guy build a house behind me, think he used a shovel to level the concrete

When it came to tile the floors, he used over 30 bags of cement and many cubes of sand, took him nearly 3 weeks just to tile the floors

 

 

[janclaes47]

On 7/20/2018 at 5:36 PM, eyecatcher said:

Even here we criticise concrete knowledge and techniques but you kbow what.....its all still standing.

 

Where I come from IU know many 100 year old buildings in pristine condition.........here I mostly see 20 year old construction that look as if they are 200 years old

[eyecatcher]

15 hours ago, janclaes47 said:

 

Where I come from IU know many 100 year old buildings in pristine condition.........here I mostly see 20 year old construction that look as if they are 200 years old

I think thats due to a general attitude here of failing to maintain and look after anything.

Theres not a lot of pride in peoples homes so that leaking gutter can leak for ten years.

[pferdy62]

One of the things that puzzles me is why so many concrete buildings have black stains running down the walls.  Can anyone explain what this is?

[sometimewoodworker]

16 hours ago, pferdy62 said:

One of the things that puzzles me is why so many concrete buildings have black stains running down the walls.  Can anyone explain what this is?

It is mould, or just possibly lichen.