What Is Plum Concrete? Its Construction Procedure And Application

Plum concrete, an economical version of mass concrete, is a specialized type of concrete that employs large stones, often referred to as boulders or coarse aggregates. It becomes particularly advantageous when extensive leveling is needed, especially beneath foundations with steeply sloped strata.

Applications of Plum Concrete

• Foundation Leveling: Plum concrete is frequently employed to level uneven ground beneath foundations, even on steep slopes.
• Dam and Bridge Construction: In the construction of gravity dams and bridges, plum concrete is commonly used, though the plum size is typically limited to 150 mm.
• Water Channels: It serves as an excellent choice for creating water channels and surface bed building.
• Traffic Barriers: Plum concrete is utilized in the construction of traffic barriers and railroad crossing bridges.
• Machine Foundations: This construction method is ideal for machine foundations where bulk concrete is essential.

Specifications of Plum Concrete

Plum concrete must adhere to the following specifications:

• It should comprise black trap basalt with a crushing strength of at least 100 kg per square meter.
• The concrete should have a nominal mix ratio of 1:4:8 and contain aggregate with a maximum size of 25mm.
• The volume of plum in the concrete should not exceed 50% of the total concrete volume.
• Crevice width should not be less than 150 mm.
• The maximum layer thickness should not exceed 900mm.

Aggregate Size Considerations

In plum concrete, the size of the aggregate plays a vital role. According to International Standards Organization (IS code) recommendations, 20 mm aggregate size is suitable for most projects. However, when factors such as reinforcement or limited cover in relation to the formwork come into play, plum concrete with a nominal maximum size of 10 mm should be used. For plain concrete work, plums larger than 160 mm in diameter can be used up to 20% by volume if approved by the project engineer.

Construction Procedure for Plum Concrete

The step-by-step construction procedure for plum concrete involves the following:

Step 1: Large stones, neither too big nor too small, are manually placed on the ground.

Step 2: The area is meticulously cleared of soft soil to ensure proper bearing capacity. Sprinkling water maintains moisture for adherence, while anti-termite chemicals are applied to protect the foundation.

Step 3: Concrete is pumped into the spaces between the boulders in layers, gradually building up the desired level surface.

Step 4: Curing is essential for at least 7 days. Jute bags are used to retain moisture in the cured concrete. Prior to placement, boulders are inspected for dirt or clay and cleaned if necessary. High-quality, sturdy boulders are crucial due to the load they bear during construction.

By following these steps and adhering to specifications, plum concrete can be successfully used in various construction applications, providing stability and durability to a wide range of structures.