Is all cement, from a big truck, the same?

[chingmai331]

I see many cement trucks in the city and countryside, some small but some  very big.  All with rotating tub on back, full of cement.

But is all that cement the same stuff?  Could i order a better grade, or cement for roadway not walls, etc?

What I'm needing to know is can i get better quality cement, if any exists, from common cement vendors?  And, if you know, how much more expensive is the better stuff?

thnx.

[Kwasaki]

You order the mix you want from the nearest readymix company & if there is no company near you mix yourself.

[JWRC]

Cement comes in various strengths and you can ask for the right one for the job, depending of course that you stick with the standard laying procedures, for instance a house pad at 4 inches thick, with the correct size rio bar you would be looking at a 20 MPA mix.  It goes up from there depending on the use.

[Farangwithaplan]

Like most things there are different specifications for cement / concrete. Two common specs that are important for design are "slump" or how wet (basics here only) the mix is. This can also affect overall strength when cured.

 

The other important factor is the amount of pressure concrete can withstand. This is usually defined in megapascals or mPa. Less often is is in Newtons per square mm or N/mm.

 

Choose the correct concrete for the correct task at hand. The person who designed the structure will advise you on requirements.

[sometimewoodworker]

Also not all RMC companies are equal in general CPac is the best, other companies may well supply concrete soup, adding more water than should be in the mix.

 

the prices are not greatly different for different strengths.

 

Many buildings have concrete that is much weaker than it could be because of poor curing practices. That is why often structures here have oversized beams and columns.

[chingmai331]

So is 20 MPA = 20 mPa (megaPascals)?  And is that considered 'strong' or average?

 

If i'm doing the ordering and i am not a structural engineer, what do i tell the CPAC desk?  No soup, but strong plz?

[emptypockets]

 

1 hour ago, chingmai331 said:

So is 20 MPA = 20 mPa (megaPascals)?  And is that considered 'strong' or average?

 

If i'm doing the ordering and i am not a structural engineer, what do i tell the CPAC desk?  No soup, but strong plz?

it will depend on what the concrete will be used for. A house slab or a vehicle access road may have different requirements.

I've never dealt with cement companies in Thailand, but in Australia I told them what I was building and followed their recommendations. Its probably the same here allowing for language differences. Call around and ask.

These days (say the last 30 years that I know of) for a house driveway you can get a concrete mix with fibres in it and don't need any reinforcing steel at all. Try this link for some information.

https://www.ccaa.com.au/imis_prod/documents/Library Documents/CCAA Datasheets/Residential Concrete Driveways and Paths.pdf

[Farangwithaplan]

1 hour ago, chingmai331 said:

So is 20 MPA = 20 mPa (megaPascals)?  And is that considered 'strong' or average?

 

If i'm doing the ordering and i am not a structural engineer, what do i tell the CPAC desk?  No soup, but strong plz?

Without knowing what you are using the product for in or in what context, order 25 mPa from a reputable supplier.

 

 

[CharlieH]

I concur and have used CPAC and told them whats it for etc and cubic metres or area etc and they do the rest. Never had any issues, other than getting it down fast enough for the driver ! 

[chingmai331]

Good info here, thnx. 

 

I'm not too familiar with concrete requirements for a  house slab but have read that many Thais use poor technique or low quality concrete resulting in slab cracks, settling and wall cracks.  Those i must avoid so if i order mPa 30 will that give me more protection against failure?  Or maybe i should make the slab thicker, or use a better sub-layer of ??rocks??.  Well, lots of Qs but figure it's a 'one-time' shot, so make it the best possible.

 

Found this:

https://www.nrmca.org/aboutconcrete/cips/35pr.pdf

 

Which tells me more, but no mention of cost increase when mPa increases.  How much more expensive is 25 mPa compared to 20 mPa, same volume?  And any negative features of higher compressive strength concrete?

[Farangwithaplan]

3 hours ago, chingmai331 said:

Good info here, thnx. 

 

I'm not too familiar with concrete requirements for a  house slab but have read that many Thais use poor technique or low quality concrete resulting in slab cracks, settling and wall cracks. 

You are throwing up many more questions than answers. Without knowing seeing your detailed plans people would just be guessing.

 

I assume you want a concrete slab on the ground for a house. There are a lot of variables on this. First is the soil type which is generally terrible in Thailand. So you will need embedded piers to support the slab. At what centres or distance between each pier do you expect to use? What is the area between load bearing walls or piers.

 

Then you will need to know the weight or dead load of all the materials hat will be sitting on the slab. Think of the roofing material, the steel roof frame, the beams, the ceiling material and insulation, the weight of the walls. When that is considered you will need to have the footing designed.

 

All that plays a role in the slab thickness, embedded steel requirements and concrete used. Then there are considerations such as "slab heaving' if you want to avoid cracks in walls and floors. I have seen significant slab heaving in tropical areas with high rain fall in other parts of the world and it can cause significant aesthetic and sometimes structural damage.

 

 

[eyecatcher]

Forget all that megapascals rubbish, strength (steng) are measured as 180,200,210,240,280,300,320 etc

For general concreting a weaker 180 or less is the way to go

For columns and structural beams 200-240 is normal

And high strength work, bridges, multi storey etc then 300-400

 

Higher the strength often a much higher proportion of cement.

 

I have a list from my local yard which has at least 20 different mixes and strengths for different situations.

[Farangwithaplan]

16 hours ago, eyecatcher said:

Forget all that megapascals rubbish, strength (steng) are measured as 180,200,210,240,280,300,320 etc

 

And tell me, do you ignore all that cubic metre malarky and just order a 'big pile' or a "little pile" of material from the yard when you need some? ????

 

And don't get me started on tape measures. What a farce they are!

[eyecatcher]

30 minutes ago, Farangwithaplan said:

And tell me, do you ignore all that cubic metre malarky and just order a 'big pile' or a "little pile" of material from the yard when you need some? ????

 

And don't get me started on tape measures. What a farce they are!

dont be pathetic.

And do you go an order concrete here in megapascals, of course you dont.

If you ever order concrete here my numbers are what they need to know and the strength it arrives at.

[Fruit Trader]

19 hours ago, eyecatcher said:

Forget all that megapascals rubbish,

Why is MPa rubbish?

[eyecatcher]

12 minutes ago, Fruit Trader said:

Why is MPa rubbish?

Not sure how long MPa has been around but as a Brit we favour Newtons as the unit of strength......pretty much like the Americans still favour feet and inches when the rest of the worlrd went metric in 1971

 

The point about it being rubbish, is that you are not going get very far when you walk into your concrete plant and ask for 40mpa mix after 28days.

But....maybe there are some forward thinking light bulbs here

[Farangwithaplan]

47 minutes ago, eyecatcher said:

Not sure how long MPa has been around but as a Brit we favour Newtons as the unit of strength......pretty much like the Americans still favour feet and inches when the rest of the worlrd went metric in 1971

 

The point about it being rubbish, is that you are not going get very far when you walk into your concrete plant and ask for 40mpa mix after 28days.

 

Ummm megapascals or mPa has a direct correlation to newtons.

 

newtons or kiloNewtons measure force. Pascals / megaPascals measure pressure.

 

1 Pascal = 1 Newton/meter²

1 megaPascal (MPa) = 1000 kiloNewtons (kN)/m².

 

You will get very far ordering the correct mPa concrete because that is what an engineer will have referenced for the design to work in conjunction with the embedded steel.

 

What you are referring to in the way of straight numbers will have some reflection to the mPa rating of the material.

 

 

3 hours ago, eyecatcher said:

dont be pathetic.

And do you go an order concrete here in megapascals, of course you dont.

If you ever order concrete here my numbers are what they need to know and the strength it arrives at.

 

 

 

3 hours ago, eyecatcher said:

dont be pathetic.

 

Well I must admit my tape measure and pile lines were foolish, but you started it. I just added to it for comedic value.

 

 

3 hours ago, eyecatcher said:

 

And do you go an order concrete here in megapascals, of course you dont.

 

Anyone in the metric world does

 

3 hours ago, eyecatcher said:

 

If you ever order concrete here my numbers are what they need to know and the strength it arrives at.

Okay, so please explain what the 200 figure relates to.

[sometimewoodworker]

6 hours ago, Farangwithaplan said:

You will get very far ordering the correct mPa concrete because that is what an engineer will have referenced for the design to work in conjunction with the embedded steel.

No you will not. Just because mPa is a measurement of concrete strength does not mean that the CPac company will understand what you are taking about.

 

You could try specifying thickness of material in Angstroms or temperatures in degrees Kelvin and have equal lack of success while being technically accurate, Steng is the strength measurement used for concrete here so it is what you need to use

[chingmai331]

There will be no structural engineer on my job, so it sounds like i will shop at CPAC and order 'steng 200' for my slab. Should any slab piers be stronger steng?

[Fruit Trader]

19 hours ago, sometimewoodworker said:

No you will not. Just because mPa is a measurement of concrete strength does not mean that the CPac company will understand what you are taking about.

From the local CPAC rep, Thai to English verbal.

 

We choose most orders from our standard application list but are familiar with all common measurements used in construction specification including Mpa. Our process will be in kg/sq cm but will discuss any engineering detail or conversion as required. Level of technical service varies depending on size of orders. For critical applications we would ask your structural engineer to make unit conversions to match our process.

[emptypockets]

On 10/31/2019 at 7:20 PM, eyecatcher said:

Forget all that megapascals rubbish, strength (steng) are measured as 180,200,210,240,280,300,320 etc

For general concreting a weaker 180 or less is the way to go

For columns and structural beams 200-240 is normal

And high strength work, bridges, multi storey etc then 300-400

 

Higher the strength often a much higher proportion of cement.

 

I have a list from my local yard which has at least 20 different mixes and strengths for different situations.

What do those numbers refer to? What does 180,200 etc actually mean? What are the units they are in? 180 what? 20MPa is just over 2 million Kg force per square meter according to an online conversion calculator, Which doesn't seem to match your numbers.

[sometimewoodworker]

9 hours ago, emptypockets said:

What do those numbers refer to? What does 180,200 etc actually mean? What are the units they are in? 180 what? 20MPa is just over 2 million Kg force per square meter according to an online conversion calculator, Which doesn't seem to match your numbers.

The numbers are nicely explained Here on the CPac website and by Fruit Trader just before your question!!!

[Thian]

On 10/29/2019 at 12:44 PM, sometimewoodworker said:

Many buildings have concrete that is much weaker than it could be because of poor curing practices. That is why often structures here have oversized beams and columns.

I see the opposit, undersized beams and columns...and that's special concrete designed for it.

 

If you want a concrete floor to be extra hard you spray water on it when it starts to dry, it will become blue and extreme hard.

 

But the main trick is it has to dry slowly, so best is to cover it or at least keep it out of draft. Also the right thickness, good rebar which is 10 cm away from the edges..and so on. Also compacting it by vibration is good..the ground underneath also should get stamped/compacted by a machine and covered by plastic or at least be humid...

 

 

[sometimewoodworker]

2 hours ago, Thian said:

But the main trick is it has to dry slowly

You don’t want it to dry, apart from the initial surface water, you want it to cure. So after the initial couple of hours keeping a floor flooded for a week at least will get one of the best beginnings of a cure, of course few people will or can do that.

[Thian]

17 minutes ago, sometimewoodworker said:

You don’t want it to dry, apart from the initial surface water, you want it to cure. So after the initial couple of hours keeping a floor flooded for a week at least will get one of the best beginnings of a cure, of course few people will or can do that.

If it becomes 'blue' it is sooo hard that even a jackhammer has a hard time to demolish it....i don't want to have blue concrete.