What is Dry Lean Concrete (DLC)

In today’s rigid pavement, dry lean concrete (DLC) plays a significant role. In general, it is utilized as the base or sub-base of rigid pavement. It is plain concrete with a higher aggregate-to-cement ratio than conventional concrete.

Rigid pavements (roads made of Portland cement concrete) are being built in many new projects these days because of their added benefits of having a longer lifespan, a smoother riding surface, and requiring little to no maintenance. Even at the village and municipal levels, the Indian government promotes the construction of cement concrete roads. Currently, dry lean concrete (DLC) is used as a base course over which concrete slabs of pavement quality are placed when building cement concrete roads for highways in India. It is a typical and well-liked cement-treated sub-base or base for concrete paving.

With a high aggregate-to-cement ratio, DLC is a no-slump plain concrete. Compared to traditional concrete, it includes less cement paste. A crucial component of contemporary stiff pavements is the DLC layer. The main benefits of using DLC as a base layer include providing strong, uniform support, high resistance to deformation, improved load transfer efficiency at joints, proper fixing of formwork and proper placement of dowel bar cradles in semi-mechanized construction, movement of construction equipment during the construction of the roads, all-weather construction and finally a reduction in the depth of pavement slab required from the point of view of axle load consideration.

Today, DLC is also utilised for the rehabilitation and fortification of damaged bituminous roads that already exist, but with a white coating.

Ordinary Portland Cement (OPC) is often used to create DLC in accordance with IRC: SP-49: 1998 specification. The specification [IRC SP-49, 1998] encourages the use of alternative cement in the production of DLC, such as portland pozzolana cement (PPC) and portland slag cement (PSC). It establishes a 7-day DLC compressive strength requirement of 10 MPa. It must have a minimum ordinary portland cement (OPC) concentration of 150 kg/m3. However, it does not provide information on DLC made with PPC and PSC, such as cement content, aggregate-to-cement ratio, moisture content, etc.

OPC is currently rarely accessible in the open market, not even in a large metropolis like Delhi. To obtain OPC from its makers in small towns and cities, dealers must make full payment (one to two months in advance). Customers have no choice but to utilise PPC because there is a severely limited supply of OPC available on the open market. The presence of fly ash and the significantly higher value of PPC’s typical consistency are just two of the clear distinctions between these two varieties of cement (PPC and OPC). Table 1 lists some values for the fundamental characteristics of OPC and PPC that are codal as well as frequently encountered.

Dry Lean Concrete Mixing Ratio:

The DLC mix’s design cannot be compared to that of a typical concrete mix. In contrast to typical concrete combinations, the DLC mixture is designed using the optimal moisture content (OMC), which ensures that the concrete under the lamination is completely compacted.

Because it sticks to the roll drums, the mixture shouldn’t be too moist. In order to achieve the necessary compaction and compressive strength of the concrete, it is crucial to ascertain the optimal moisture content for the correct compaction and mixing ratios, i.e., the aggregate/cement ratio.

Where to use?

• Rigid pavement typically uses DLC as a base or sub-base.

• It prevents mud pumping and provides stability for heavy machinery and solid pavement.

The procedure of DLC:

The prepared sub-grade is sprinkled with water to moisten the surface prior to the building of a dry lean concrete sub-base.

A paver evenly distributes DLC material without any sorting.

The liquid curing agent can be sprayed on the surface to cure the DLC, or wet gunny bags can be used to cover the surface.

Advantages of DLC

• It gives the stiff pavement more even and robust support.
• It is highly deformation resistant.
• At the joints, it has great improved load transfer efficiency.
• All weather conditions benefit from it.
• Because DLC serves as the base layer, the depth of the pavement slab is finally reduced.