Crushed stone - loose, inorganic and granular material obtained by artificial crushing. It is divided into primary and secondary. This is an important fact. Primary - the result of processing of natural stone: pebbles, boulders, pumice and other materials. Secondary is obtained by crushing construction waste, such as concrete, asphalt, brick.
Production method
For the production of crushed stone, the following method is used: the rock mined in the quarry is crushed to a certain state by screening. In the recycling of the above construction waste, a mechanized crusher is used.
Application area
Due to its high adhesive properties, i.e., its ability to firmly adhere to the surface, crushed stone is used in cement-sand compositions, in urban planning, in the construction of buildings, in the construction of roads and railways.
Material Features
The following main properties are distinguished:
- The density of crushed stone.
- Flattery (form).
- Frost resistance.
- Strength.
- Radioactivity.
These values fully characterize the specified material. Next, we consider in more detail such a property as crushed stone density. This is an unimportant definition.
Crushed stone density
This property of the material is directly related to its strength. Density is understood as the ratio of mass to volume. Measure it in tons or kilograms per cubic meter (t / m³, kg / m³). Distinguish the true density of crushed stone, excluding empty space, total and bulk, i.e., in an uncompressed state. Each of them has a corresponding meaning.
The true density of crushed stone is determined by the laboratory. That is , the mass is measured per unit volume of fine and dry material. This method eliminates the presence of voids filled with air. So determine the porosity.
The term "bulk density of crushed stone" is used to denote the relationship between the mass and the occupied volume, taking into account the free space between the particles. This parameter is necessary when calculating the composition of concrete mix.
Density measurement
In this case, there are several ways to determine:
- Using a measuring vessel.
- Using tables.
Let's consider the first method in more detail
To implement this process, it is necessary to completely fill a cylindrical measuring vessel with a volume of 5 to 50 liters until a cone is formed at the top. Then the excess on top of the form is removed. The vessel is weighed. To determine the density of crushed stone, the difference between a full and an empty vessel is calculated, which is divided by the volume of a given container. Nothing complicated here. The formula in this case is as follows:
where m 1 is the mass of the empty vessel; m 2 - with crushed stone, V - the capacity of the measured capacity.
Main criteria
To correctly measure bulk density, comply with the requirements of the state standard, these are:
- Use only specialized vessels, that is, a certain shape and size.
- The size of the tank depends on the grain size.
- Crushed stone in no case is specially compacted, since in this case the material will have other indicators.
- The total density is necessarily higher than bulk.
The results obtained in the laboratory are indicated in the accompanying passport of a particular batch.
In addition to crushed stone, the density of sand, concrete and other materials is likewise calculated. In this case, take into account the volume, granularity and the space between the particles.
Definition using tables
This calculation of the density of these materials is also important. For large volumes or in cases where an error of about 1% is not critical, resort to the help of measuring tables with conditional coefficients for translation. The advantage of this method is the saved time and simplicity. The minus is an approximate, inaccurate result.
Table: “Bulk density of crushed stone (GOST 9758)”| Type of crushed stone | Fraction, mm | Bulk density
kg / m³ | Mark |
| Granite | 20-40 | 1370-1400 | M 1100 |
| 40-70 | 1380-1400 | M 1100 |
| 70-250 | 1400 | M 1100 |
| Limestone | 10-20 | 1250 | M 1100 |
| 20-40 | 1280 | M 1100 |
| 40-70 | 1330 | M 1100 |
| Gravel | 0-5 | 1600 | M 1100 |
| 5-20 | 1430 | M 1100 |
| 40-100 | 1650 | M 1100 |
| more than 160 | 1730 | M 1100 |
| Slag | | 800 | M 800 |
| Expanded clay | 20-40 | 210-340 | M 200, M 300 |
| 10-20 | 220-440 | M 200, M 300, M 350, M 400 |
| 5-10 | 270-450 | M 250, M 300, M 350, M 450 |
| Secondary | | 1200-3000 | M 1100 |
Tip
It should be remembered that bulk density is a natural, natural quality that excludes the possibility of subsequent tamping to eliminate voids.
In building materials, it is one of the basic parameters. The strength of the final product and the indirect determination of voids filled with a less strong composition of other elements depend on this.
In the manufacture of concrete mixtures, they are guided by the rule: the higher the value of the fraction, the lower the bulk density parameters. Knowledge of its indicators can significantly save. For example, with a low fraction and a high bulk density, cement will require an order of magnitude less. Knowing the exact volumes simplifies transportation and storage. It becomes possible to calculate the material for transportation. Also in this case, you can take into account the carrying capacity of the vehicle.
Density coefficient
We will deal with this definition. The technical value used during measurements on the volume of crushed stone is called so: the coefficient of bulk density of crushed stone. This is an important parameter. Use its other name - the coefficient of compaction or translation (meaning the conversion of mass to volume, and vice versa).
Example
Suppose a car brought rubble to a construction site. How to make the necessary measurements? For this, the volume of cargo and the body along the filling border is calculated. Then the obtained values are multiplied by the compaction factor. It is clear that the numbers will be different due to the "shaking" of the cargo during movement, but it cannot lose in mass. In the first case, taking into account shrinkage, we can say that this is the total density of crushed stone or a value close to it. In the second - bulk.
For a better understanding, take another life example. Bought some sugar. Say a kilogram. Poured into a sugar bowl, received the primary volume. Shook, knocked, rammed. Measured. The resulting final volume was obtained.
Influencing factors
This is important to know. The density is also influenced by the rock from which crushed stone is made. With the same volume - 1 m 3 , the weight of granite will be 2.6 tons. However, limestone due to impurities of quartz, dolomites, etc. - 2.7-2.9 tons. With the same weight, the volume will vary.
As a result, large, unshredded rock takes up less space than recycled. This is due to the space between the elements. The true and bulk area of crushed stone will speak about the difference in volumes with the same mass. This is a reliable fact. So, for example, the true density of crushed granite with a fraction (grain size) of 5 to 20 mm will be 2590 kg / m 3 , and the bulk of the same material will be 1320 kg / m³. Thus, knowing this definition, one can significantly save on reducing costs in mixing concrete, as well as on transportation facilities and storage facilities.
Other options
In this case, the following can be distinguished:
- Fraction - grain size of the material. Distinguish between standard (5-10 mm, 10-20, 5-20 , etc.), non-standard (10-15 mm, over 15 to 20 mm, etc.) and euro-rubble (3-5 mm).
- Mark of crushed stone by strength. There are several types. Namely: ordinary strength M 800–1200; high - M 1400-1600; medium - M 600-800; weak - M 300-600; minimum - M 200.
The entire combination of fraction, grade and source rock will affect bulk density.