How to determine the compaction coefficient of crushed stone

An essential component of many construction projects, crushed stone is used to construct roads, building foundations, and other structures. Knowing the compaction coefficient of crushed stone is essential when working with it. For construction projects to be stable and long-lasting, it is important to know how much the material will compress under pressure, and this value helps with that determination.

When crushed stone is subjected to a particular compaction effort, its density is determined by its compaction coefficient. Building professionals can estimate the quantity of material required to achieve the appropriate level of firmness and support by knowing this coefficient. Additionally, it aids in averting possible problems like ground settling or shifting over time, which may result in structural issues.

Compaction coefficient can be found by a sequence of simple calculations and tests. These usually involve using a standard force and measuring the crushed stone’s volume both before and after compaction. One can compute the coefficient and use it to more efficiently plan and carry out construction projects by comparing these measurements.

Anyone working in construction or landscaping needs to know how to calculate the compaction coefficient of crushed stone. It guarantees that projects are constructed on a strong basis, offering comfort and long-lasting outcomes. Builders can contribute to the overall success of their projects by improving the quality and safety of their work by becoming proficient in this process.

Compaction during transportation

Crushed stone loses volume in transit from the point of production to the construction site, just like any other bulk material. The length of the trip and the state of the roads affect how much compaction occurs. GOST only specifies the maximum value of the compaction coefficient (Ku) during transportation, which cannot exceed 1.1 ÷ 1.15, regardless of the fractions’ sizes. Its value may be less than the GOST limit by agreement between the manufacturer and the customer (this needs to be documented in the supply contract).

Take the order for 10 mᶖ of crushed stone, for instance. Ten mᶖ of loose raw materials were loaded into the truck, and Ku during transit is 1.09, according to the documents that go with it. With the help of a tape measure and some basic math, you can quickly determine the volume of the delivered material, which is V = 9.3 mᶖ. We calculate the volume of shipped raw materials V₁ = V 1.09 = 9.3 1.09 = 10.14 mᶟ by applying the Ku stated in the documents. That is, every item for which you have paid has been delivered.

Compaction during ramming

Crushed stone is rammed when preparing the foundations of buildings or road surfaces (with a roller, vibratory plate or manual rammer). The volume of material naturally lowers after ramming. The compaction coefficient (Ktr) of crushed stone used in ramming is used to determine the amount of material needed. You have three options: order a laboratory measurement of the coefficient (which is economically justified during the construction of large construction projects or road works in large volumes), use the average tabular value of this coefficient (for a certain fraction and grade by strength), or calculate it yourself.

As an illustration, you choose to place a 0.3 m thick crushed stone cushion beneath a strip foundation that has external measurements of 8 ⅷ10 m and a 0.4 m strip width. Crushed stone with fractions of 20–40 mm and strength grade M1000 was chosen for the backfill. For this class of material, the compaction coefficient’s average tabular value during compaction is 1.38. Volume of compacted crushed stone (after compaction):

V₂ = 0.3 = 4.13 mᷟ (10 0.4 2 + 7.2 0.4 2)

The quantity of loose material needed to complete the work mentioned above must be purchased:

5.696 − 7 mᶟ = V₁ = V₂ 1.38= 4.13 1.38

For building projects to be stable and long-lasting, it is crucial to know the crushed stone’s compaction coefficient. This procedure helps builders determine the density and load-bearing capacity of the material by measuring how much the stone settles under pressure. Compaction coefficients are easily determined by anyone by following simple steps like setting up a sample, using a constant force, and measuring the volume change. Gaining an understanding of this crucial metric facilitates improved task planning and execution during construction, resulting in stronger and safer structures.

How to determine the compaction coefficient of crushed stone during compaction yourself

Assume, for the purposes of this example, that you are building a strip foundation and that you will need to use a hand rammer to compact the crushed stone cushion that you fill the bottom of the trench with. However, a valid query is how much cubic meters of building supplies to place an order with the closest supplier. You can perform the calculations on your own; just remember to account for the crushed stone’s compaction during the rammer process.

You behave as follows:

• First, make a box from boards with the following internal dimensions: width – 1 m, length – 1 m, height – 0.4 m.
• Load the box, hand tamper, shovel and thick lath 1.2÷1.3 m long into the trunk and drive to the crushed stone seller.
• Fill the box with crushed stone (usually a mountain of this useful building material is located next to the seller"s trailer) and level it with a lath (simultaneously removing all excess).
• Tamp the crushed stone in the box.
• Use a ruler or tape measure to measure the distance from the top edge of the box to the level of compacted crushed stone.
• Do simple calculations and get the desired Ktr.

For instance, following tamping, there was a 10 cm (0.1 m) gap between the top edge and the crushed stone level.

V₁ = 1·1·0.4 = 0.4 mᶟ is the volume of a full box filled with uncompacted crushed stone.

After compaction, the volume of crushed stone is V₂ = 1·1·0.3 = 0.3 mᶟ.

For our particular material (based on strength, humidity, and fractionation) and ramming device, the following is the compaction coefficient during ramming:

V₁ = 0.4: V₂ = 0.3 ≈ 1.33

Measuring the compaction coefficient in laboratory conditions

A unique vibration device is used in laboratory settings to measure the compaction coefficient during ramming. It is composed of:

• vibration table;
• measuring container (usually with a capacity of 50 liters);
• container lids with a built-in vibratory piston.

• The measuring container is filled with loosened material.
• The surface of the poured material is leveled along the upper edge of the container.
• Screw on the lid with the vibratory piston.
• Turn on the vibratory device and perform vibratory compaction (usually no more than 2-3 minutes).

Once the device has been turned off, use a ruler to measure the height of the free part of the container, compute its volume, and determine the compaction coefficient by dividing the volume of the crushed stone that has been compacted by the volume of the entire container filled with loose material.

For instance, the measuring container V₁ has a volume of 50 liters. V₀ = 14 liters is the volume of the free part after ramming. Compressed material volume V₂ = V₁ — V₀ = 50 — 14 = 36 liters.

Ktr = V₁: V₂ = 50: 36 = 1.3888 ∈ 1.39 is the result.

A solid and long-lasting foundation for building projects requires an understanding of the crushed stone’s compaction coefficient. Builders can make sure that the crushed stone is properly compacted and provide a stronger and more dependable base for any structure by knowing this coefficient.

There are a few simple steps involved in determining the compaction coefficient. The first is choosing a representative crushed stone sample. The maximum dry density and ideal moisture content are then determined by testing this sample using conventional techniques like the Proctor test. To evaluate how well the material can be compacted, these values are crucial.

Applying the compaction coefficient in real-world situations is much simpler once you have the required information. It makes it possible to forecast the behavior of the material under load, guaranteeing that the layer of crushed stone will sustain the weight of the structure above without settling or shifting over time. This information facilitates more effective and efficient project planning and execution in the construction industry.

Accurately calculating and applying crushed stone’s compaction coefficient enhances the general caliber and durability of building projects. It’s a tiny action that has a big impact on the stability and longevity of roads, buildings, and other infrastructure. Learning this part of construction, whether you’re an experienced builder or a do-it-yourselfer, will make a big difference in the outcome of your project.

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