dear sir,

If you type " apparent density" in the google search machine, you will find quit a few sites, stating the definition.

Indeed, apparent density and bulkdensity should be the same.

Although I could think of another type of apparent density.

The density of a material submerged in a fluid has apparently a lower density than not submerged.

best regards ■

I venture out on the limb to say: There is no universal "apparent" or "bulk" density standard that classifies many of the relavant factors into a common test procedure and which agrees on a common identification.

The apparent density can be altered by handling and test procedures.

Often academic and standards (ASTM, et al) literature refers to "apparent" density when describing their research.

A summary of the minimum factors worth consideration:

1. particle size distribution incl: coarse, coarse and fines, fines

2. particle shapes - degree of surface area to classified size

3. particle structure - agglomeration of specific shapes during storage or testing

4. inherent moisture

5. surface moisture

6. particle to particle attraction and repulsion

7. ph influence - zeta potential

8. particle packing action during density tests - standardized compaction pressure and methods

9. segregation of particles during handling and testing

10. coordination number theorectically achievable verses actual

as measured by gas absorbtion

11. degree of compaction during tests - noting all solids compact when in a pile or storage vessel or subjected to a above ambient pressure activity

12. degree of vibration to ideally align or consolidate particle groups

13 time during testing for: moisture, strength, pressure and elasto-plastic relaxation of particle to particle interactions

14. yield locii influence on density - J & J, Schultz, others

15. tapping or vibration testing vs volume change of finer particle groups as has been noted in earlier forum responses.

I am sure Mr. Lynn Bates and others who contribute to the forum, have more to say.

Note: Jenike & Johanson test procedures, that measure apparent shear strength, suffer from human variances during their simple measurements as do other soil mechanics testing.

In summary, the subject of "apparent" or "bulk" density is very complex.

. ■

"What is relation between Apparent Density and Bulk Density"

But what is the material? If it is a bulk solid then the material has a Bulk Density measured in mass per unit volume (typically kg/m3, te/m3 etc). You measure it by finding the mass that is contained in a known volume.

But that only applies to the sample you measured. If you used a different sample you may get a different bulk density.

Depending on the size distribution you may get different results according to the size of container you use, so its important to use a container suitably sized according to the lumps the bulk solid contains. I used to like using a 1ft3 container, it was big enough for most lumpy materials I came across yet not too big to manhandle onto a scale!

At the end of the day the bulk density is what you measured from the sample you were provided with and the container you used. ■

Good point on sample bias or variance.

Also, besides the preparation, the shape of the container biases the result such as loading a cylinder versus box, etc.

Vibration from the application can bias the result, such as the container mounting in a vibration zone al la trains.....

So, the container shape and environment will vary the result as was suggested on container size.

The ore or granular material elastic constants by size and shape will have an effect.

How the container is loaded ,as has been discussed in the forum, with the preference for higher density below the filling spout and coarse particles migrating to the outer field. ■

For most applications, apparent or bulk density are technically the same.

However, most means of obtaining the apparent or bulk density will not deliver the appropriate value unless the many qualifying conditions are considered.

So, what is the density when many factors are omitted or the measurement is flawed? ■

Dear Surri

Density = mass per unit of volume(kg/m3) (of 1 material)

bulk-density = mass per unit of volume, whereby voids are included. in the volume (kg/m3)

additional conditions to the figure of density have to be given, f.i. settled, consolidated, fluidized, poured, etc.

material-density = mass per unit of volume, whereby voids are excluded. from the volume (kg/m3)

For instance Alumina :

bulk-density = 1220 kg/m3

material-density = 3400 kg/m3

particle size = 90 micron median

Concentration is part or percentage of one material, mix with another material.

Normally this ratio is based on volume or mass and in principle dimensionless.

Example : m3 material 1 / m3 material 2

kg material 1 / kg material 2

Another example is : x kg of material 1 / y m3 of material 2

The name of a presented figure is not really important, as long as the physical and mathematical description is also clearly stated.

In case someone presents you with a figure and the definition is not clear, just ask for the explanation.

Influences on the various densities is already mentioned in the previous posts

success ■

Dear Mr. Surri

If the mass of 1.5 is really a powder, then it consists of many particles.

Between the particles are the voids.

With this powder, including the voids between the particles, 1 m3 can be filled.

Thus :

BULK-density = (mass of bulk powder) / volume of bulk-powder) = 1,5/1 = 1,5 kg/m3

If the mass of material consists of one solid block (without any voids), weighing 1,5 kg, copying 1 m3 of volume, then ;

Material-density =

(mass of material powder) / volume of material-powder) = 1,5/1 = 1,5 kg/m3

Stating just “density” is in almost all cases NOT sufficient to explain the nature of the presented value of density, because there are so many kinds of density.

all for now ■

Some very interesting and useful comments have been made on this subject but I would add that I can only see the term ‘apparent density’ being meaningfully when applied to particles, rather than a bulk material. In the case of particles there is a clear distinction of meaning between the ‘apparent density’, when the particle may contain enclosed pores or voids, and the ‘solid density’ of the material of composition. The different terms are necessary in these circumstances.

Voids are inevitable in a bulk material, so the term ‘apparent density’ can only mean the value measured under given circumstances, but what is this to be compared with other than the density of the material of composition because, whilst ‘Bulk density’ is the weight of a mass divided by the volume that it occupies, in the case of bulk solids the expression has to be further qualified by the manner of formation. Apart from the geometry of the container that influences the order of particle packing against the wall surfaces, see ‘The packing of particles’ by Grey, the degree of compaction attained depends on many factors, such as the magnitude, orientation and pattern of applied forces, bulk porosity, particle isotropy and the nature of the component particles. This leads to various definitions of ‘Bulk density’, such as ‘Fluidised Bulk Density’, ‘Aerated Bulk Density’, ‘Dilated Bulk Density’, ‘Loose Poured Bulk Density’, ‘Settled Bulk Density’, Tapped Bulk Density’, ‘Consolidated Bulk Density’, ‘Time Consolidated Bulk Density’, ‘Compacted Bulk Density’, each of which required the conditions of formation to be clearly and closely specified. Standard or reference conditions may be adopted for comparative or design purposes.

The actual value of ‘Bulk Density’ of interest in a specific application is usually related to a particular situation, of which there may be more than one.

In summary, I would not recommend the use of the term ‘apparent bulk density’ in relation to a mass of bulk material, unless there was a particular reason that should be stated, but consider that it had a simple meaning with respect to a particle, but begged the question as to whether the material of composition had the same value. ■

As Lord Kelvin said "We only know what we can measure." so if you have weighed a known volume then you know the density regardless of whether it results from time consolidation, mechanical compaction, excavation or whatever other learned confusion you want to add. The figure that a customer passes on to suppliers has its origin in the process operated by that customer & the onus is always on the customer to provide the correct data for input to the equipment sought. Density is density, as measured at the time & place. It is never apparent, break bulk, consolidated or whatever; simply mass per unit volume, voids, warts & all.

If the forums continue along the previous lines we will finish up with statistically probable Gaussian-Nyquist incidences of density. All for a bucket of coal. Come on.

Mind you, Lord Kelvin also affirmed that heavier than air flight was not possible. ■

Well said John. Yet it is amazing how a figure can be taken as gospel when it only relates to a particular condition. ■