floor elevation compound

[releky]

What particular floor elevation compound do you use to make the floor or tiles higher? In my country. 100% of construction use sand mixed with cement as the filler. See the following picture:

http://www.pbase.com/rele/image/153741119

The tiles and sand elevation load is this.

15 kn/cubic meter x 0.05m = 0.75 Kn/m^2

The beam would have additional 0.75x20 = 15 Kn.

Do you think 0.75 KN/m^2 Superimposed Dead Load for a floor is low or high? what load do you typically use? And would elevation compound even be lower in weight? how low in square meter?

 

[hokie66]

A sand and cement thickset will weigh more that that. We typically use 24 kN/m^3 for concrete, and I think the sand/cement mortar would approach that density. What you have described is not uncommon for commercial construction with terrazzo tiles, marble tiles, etc. The actual setting method is something engineers are not so much involved in, as the trades have developed their own knowledge of what works and what doesn't. Saying that, there are examples of both good and poor flooring finishes wherever you go, so the competence of the tradesmen varies a lot.

 

[releky]

24 kN/m^3 is for concrete with fine and coarse aggregates (stones or gravels). If one use only sand and cement without stones (or gravels), the weight would be around 15 kN/m^3 only. Do you not agree with this?

 

[hokie66]

No, I don't agree. I always use 24 kN/m^3 for mortar, terrazzo, or ceramic tiles.

 

[releky]

I'm excluding the tiles for the 15 kN/m^3 but just the mortar. Let's break it down. What is the contribution of each to a concrete mix?

Water = ?
Sand = ?
Cement = ?
Coarse (stone) aggregates = ?

They should total 24 kN/m^3. But if you didn't include the coarse (stone) aggregates. Then a cubic meter should weight less. Why do you say it's still 24 kN/m^3? A cubic meter of sand is 13 kN/m^3. So add cement and few water and a cubic meter of concrete without coarse aggregates should weight about 15-18 kN/m^3.
Please elaborate details of where I analyze it wrong.

 

[hokie66]

If you don't believe me, just make your own samples and weigh them. It is the combination of materials that you want the density of, not the component parts. I think your sand density is low...19 is what I have used.

 

[releky]

Anyway. For just supporting tiles that require only very little compressive strength. Do you know of more lightweight compound like perhaps plastic? What are other possible substances to be put under the tiles just to elevate it a bit.. maybe even wood can be used?

 

[a2mfk]

Releky- why are you starting another thread on the same subject, when you got lots of input on it already?

http://www.eng-tips.com/viewthread.cfm?qid=356275

And my friend, if you honestly cannot figure out how to calculate dead load of floor toppings, you have bigger issues. You need a mentor engineer with local knowledge.

And what is with your superstructure design that it cannot handle the locally-used method of floor topping? The design should not be cutting it that close. The best floor leveling systems for floor tile, IMO, are self-leveling cementitious compounds (but they are expensive), or the method you posted would do the job. Wood is a bad idea usually because of moisture-related problems.

 

[releky]

I'm trying to figure out how to mix low-density concrete that can make it only 1/3 the weight of structural concrete which is 24kN/m^3.. so for 0.05m (2 inches) low density concrete of tile elevation, it is about 24kn/m^3 x 0.05 = 1.2 kN/m^2. I'd like to make it only 0.4 kN/m^2. In structural books, they mentioned about light weight concrete that is only good for insulation (about 8kN/m^3 or 50 pounds per cubic foot).. but the books never mentioned how exactly to mix it... now i'm looking for a compound that is even lightweight like only 0.2 kN/m^2. Something like lightweight plasticize liquid just to support the tiles and typical live load. Since no one mentions of this exact plasticized compound. I post it again. So how do you mix low-density concrete that is only 0.4 Kn/m^2? I have tried using volcano tuff with very few cement and water just to bind it enough (actually my country use this technique) and I wonder if there are techniques to make it even lower in weight (what ingredients to add)?

 

[Archie264]

In the US lightweight concrete is usually made by using lightweight aggregate in lieu of gravel. As I understand it the lightweight aggregate is slate that has been put into an industrial "popcorn popper". Concrete made using this method is usually on the order of 120 psf = 19 kN/m^3 if I've done the conversion properly.

 

[releky]

Archie, when you mentioned "lightweight aggregate".. are you referring to fine or coarse aggregates that are in lieu of gravel? What if all aggregates use is fine? Note lightweight aggregate include coarse aggregates. What would happen if all aggregates use is fine (super lightweight concrete), and there is less water and less cement just enough for cohesion and used just to support the tiles and 50 psf live load (which requires only mortar compressive strength of 0.5 psi (50/144)). How low the weight of this mix decrease? (15kN/m^3?)

 

[cvg]

there are products available such as: LevelLite®
3 lbs (1.36 kg) per square foot at 1/2" (13 mm) thickness

http://www.custombuildingproducts.c...nts/levellite-self-leveling-underlayment.aspx

 

[releky]

cvg.. it's great product.. unfortunately it's not available in my place to buy in the thousands of bags.... so how does one make such kind of product? What other ingredients do you add to cement and sands to make it low density.. something like an expanding plasticized soda? What ingredients have anyone actually tried (those without access to such commercially available product)?

 

[jimstructures]

releky and cvg

If my math and conversion are correct 3 lbs at 1/2" thick per square foot work out to 72 lbs. per ft^3.

That gives 11.3 kN per m^3. Better but no where near 0.2 kN per m^3.

Jim H

 

[releky]

If you will check my message again. I mentioned "0.2 kN/m^2", not m^3. To make it m^3, change 50mm (approx 2") to 1 meter so multiply 0.2 by 20 to make it 4Kn/m^3. So I'm looking for a special plastic compound that is only 4kN/m^3 instead of the normal concrete 23kN/m^3 which I don't need this much compressive strength. I'm sure chemists can synthesize such. Meanwhile, What I do is use volcano cinders as fine aggregate, mix it 5 bags to 1 bag cement and little water just enough to cause cohesion. This would be controlled honeycombs but have enough compressive strength for the tile and live load. If anyone has done something like this, please share the technique. I want to make it even lighter by including plastic compound.

 

[Ron]

Releky...adding coarse aggregate usually reduces the density (and thus, the unit weight) as compared to a sand-cement mortar, unless the coarse aggregate has a specific gravity greater than the sand specific gravity....bottom line, hokie66 is correct.

 

[hokie66]

releky,
You are contemplating the impossible. If my car only weighed 100 kg instead of 2000, it would use a lot less fuel. But that won't happen, and neither will your gravity defying levelling compound.

 

[releky]

Huh? I don't understand what you are saying. Let me type the following for context of what I read in a reference on "Design of Concrete Structures" (note I'm basically just discussing of one creates low-density concrete):

"A variety of lightweight aggregates are available. Some unprocessed aggregates, such as pumice or cinders, are suitable for insulating concretes, but for structural lightweight concrete, processed aggregates are used because of better control. These consist of expanded shales, clays, slates, slags, or pelletized fly ash. They are light in weight because of the porous, cellular structure of the individual aggregate particle, which is achieved by gas or steam formation in processing the aggregates in rotary kilns at high temperature (generally in excess of 2000F). Requirements for satisfactory lightweight aggregates are found in ASTM C330, "Standard Specification for Lightweight Aggregates for Structural Concrete.

Three classes of lightweight concrete are distinguished in Ref. 2.2: low-density concretes, which are chiefly employed for insulation and whose unit weight rarely exceeds 50 pcf; moderate strength concretes, with unit weights from about 60 to 85 pcf and compressive strengths of 1000 to 2500 psi, which are chiefly used as fill, e.g., over light-gage steel floor panels; and structural concretes, with unit weights from 90 to 120 pcf and compressive strengths comparable to those of stone concretes."

Ok, so how do you create low-density concrete for insulation that rarely exceeds 50 pcf?

 

[Ron]

hokie66...you realize we've been sucked in again from the same place!

releky....you clearly do not understand concrete technology, to include any cementitious material such as mortar, lightweight insulating concrete, lightweight structural concrete, grout or similar.

Just because you might be able to make a cementitious material lighter in weight does not mean it will work for your application. If you are going to put tile on the material, it has to be durable and has to have a reasonable compressive strength, and thus, a reasonable tensile strength to allow tile bonding and to withstand loading and cyclic movement.

Consider how poor your construction quality control appears to be, your floor slabs likely move a lot....therefore placing a lot of need on the mortar bed to be robust for the sake of the tile.

Yes...there are many lightweight aggregates available (mostly coarse aggregates). They are generally expensive and somewhat difficult to work with, but can be very effective in certain applications. This is not one of them. Just because you read something in a particular treatise doesn't mean you can grossly apply it to your situation without appropriate experience and judgment.

 

[releky]

If you are going to put tile on the material, it has to be durable and has to have a reasonable compressive strength, and thus, a reasonable tensile strength to allow tile bonding and to withstand loading and cyclic movement.

Yes, We have taken care of it. We use adhesive below the 2" of grout and above it and the tiles stick to it. This is used in 100% of hotels in our country which often has 2" of tile beddings. The reason the floors are not leveled is because traffic in streets usually makes the ready mix concrete come late and we have to hurry up to put it so the slabs are mostly not leveled with some parts higher. Traffic also caused many honeycombs in the columns of most hotels to form because it hardens fast and consolidation problems occur. It is solved by inserting fresh concrete but I think the old and new concrete are not really connected, so I believe that in the event of strong seismic movement, the columns moment magnification factor can go overboard with loss of moment of inertia. Now the subcontractor for tile don't know how to trim the high slab parts so they just call in the contractor to put mortal bedding. Note Laborers, carpenters, and masons in my country usually come from poor community so they don't have any skills but just know enough how to use hammer, nails, wood and mix concrete. We live in very poor third world country with daily wage of workers averaging just $8 (eight dollars) for 15 hours of work daily.

Anyway. Since we don't have the lightweight mortar compounds available commercially. I have to mix stuff and asking which can have the lowest weight. Again, adhesive below and above the mortars solve the problems of tensile strength, tile bonding, loading and compression strength. Note the compressive strength of the mortals don't have to be 4000 psi for example.. they just need to be good for 100 psf (4.8 Kpa) live load.