What Is The Thickness Of DLC?

Dry lean concrete (DLC) is a type of concrete that has a low water-cement ratio and a high aggregate-cement ratio. It is used as a sub-base or base layer for pavement construction, especially for rigid pavements. DLC provides strength, stability and durability to the pavement structure.

One of the important factors that affects the performance of DLC is its thickness. The thickness of DLC depends on several factors, such as:

- The design traffic load and volume

- The subgrade soil type and condition

- The climatic conditions and drainage

- The quality and gradation of aggregates and cement

- The compaction and curing methods

According to the Indian Roads Congress (IRC), the minimum recommended thickness of DLC for rigid pavements is 150 mm. However, this may vary depending on the site-specific conditions and requirements. For example, if the subgrade soil is weak or expansive, the thickness of DLC may need to be increased to provide adequate support and prevent differential settlement. Similarly, if the traffic load is heavy or frequent, the thickness of DLC may need to be increased to resist fatigue cracking and rutting.

The thickness of DLC should be determined by using empirical or mechanistic methods based on field tests and laboratory experiments. Some of the commonly used methods are:

- California Bearing Ratio (CBR) method:

CBR Test Machine

This method uses the CBR value of the subgrade soil to estimate the required thickness of DLC. The CBR value is a measure of the bearing capacity of soil under standard loading conditions. The higher the CBR value, the stronger the soil and hence less thickness of DLC is needed.

- Modulus of Subgrade Reaction (K) method: This method uses the K value of the subgrade soil to estimate the required thickness of DLC. The K value is a measure of the stiffness or elasticity of soil under repeated loading conditions. The higher the K value, the stiffer the soil and hence less thickness of DLC is needed.

- Layered Elastic Theory (LET) method: This method uses a mathematical model that considers multiple layers in pavement structure with different material properties and stresses. It calculates the required thickness of DLC by considering various factors such as traffic load, temperature variations, moisture changes etc.

The thickness of DLC should be checked and verified by using non-destructive testing methods such as falling weight deflectometer (FWD), dynamic cone penetrometer (DCP), ultrasonic pulse velocity (UPV) etc. These methods can measure various parameters such as deflection, penetration resistance, wave velocity etc., which can indicate whether the DLC layer has achieved sufficient strength and uniformity.

The thickness of DLC is an important parameter that affects its performance as well as that of pavement structure. Therefore, it should be carefully designed, constructed, and tested to ensure optimal results.