Precast concrete pile

Types of precast concrete pile

There are distinct types of precast concrete piles, and each is devised and perfected for use in particular conditions and with specific load requirements in mind.

Preston's pile

A type of lake known as cement pile construction, in which reinforced concrete piles are constructed at a plant and driven at the construction site into affected soil below the planned site floating-slab system, is commonly called Preston's pile. Characteristics include:

• H-bearing piles: Typical H-bearing precast concrete piles have two vertical flange sections and a bigger central web section; thus, they can carry large axial loads and lateral forces.
• Sp and section:In the middle of the construction of an S-section, the two spool-shaped flanges look like a spool of thread lying on its side. This shape helps reduce the piling resistance when driven, thus reducing the chances of resulting in a stuck pile, and also bearing well, enhancing stability against lateral forces.

Pipe piles

An alternative construction of precast concrete piles is circular or square hollow columns, known as concrete pipe piles, which resemble steel pipe piles' outer layer characteristics but water reinforced concrete internally.

• Benefits of pipe piles: Precast concrete pipe piles are lighter than denser steel piles, causing a reduction in transportation costs and ease of installation. The pile shape enhances stability when lateral loads are applied, and the center void allows easy handling of pile installation provisions.

Sheet piles

Concrete sheet piles have interlocking edges that are vertical and are driven to form a continuous wall to serve as a protective zone against erosion or to create walls for excavation in water and soil, such as centrals and other cribs.

• Accepted design and use:Recently, a precast concrete sheet pile was developed and is becoming increasingly accepted due to its lightness and ability to withstand design loads compared to the heavy wooden or steel alternatives.

Bored piles

Bored concrete piles are cast in-situ designated to reinforce building foundations. The difference is, while concrete piles are pre-cast in piles, bored piles are actually made by boring in the ground and then casting concrete.

• Construction method:The construction method for bored piles makes it possible to refer to them as ideal support systems for building structures in sensitive environments where driving vibrations from pile installation would be detrimental.

Material & Durability of precast concrete pile

The durability of precast concrete piles results from several critical design and material factors. In pile construction, cement concrete has been the main material used owing to its high strength and rigidness and also because it can be shaped constructively in various ways.

Cement concrete

The cement content in concrete occupies a very important place in the strength and durability of the concrete precast piles. Normally, precast piling concrete uses high-strength cement in H classes to improve the ultimate compressive strength of the pile to bear heavy loads. These cements also have specially formulated additives that enhance their ability to withstand water exposure.

Aggregate

The aggregates that constitute concrete precast piles provide volume. Their size, shape, and distribution impact many factors, including the concrete's workability, compressive strength, and durability against static and dynamic loading. Pumice, volcanic scoria, or expanded clay used in aggregate forms a lightweight but stable surface of the pile.

Reinforcement

High tensile steel reinforcements are embedded in the precast pile to improve its load-bearing capacity and resistance to cracking and structural failure. Poor piling structure can result in a precast pile that is susceptible to water damage. The use of galvanized steel or epoxy-coated rebar is standard in piles intended for hostile environments.

Water-resistant surfaces

Several constructions and materials make precast concrete piles extremely resistant to destruction or erosion from unfavorable elevation conditions such as constant immersion in water. Such features include:

• Dense concrete mix:The dense concrete mix reduces the penetration of water, which would cause steel reinforcements to rust or concrete to degrade.
• Protective coatings:Some precast piles may be coated with protective layers made of epoxy, polyurethane, or other water-resistant materials that act as barriers to water and chemicals.
• Antifreeze admixtures:Concrete admixtures that are anti-freezing and added to the mix of precast concrete during extremely cold conditions help to lower the risk of cracking due to freeze-thaw cycles, which could potentially destroy the concrete. This is done to make the concrete mix less porous and, thus, less able to absorb water.

How to use precast concrete pile

Precast concrete piles are conveniently and competently used in several construction-related applications as a vital aspect of foundation design and geotechnical engineering due to their great load-carrying ability and stacking strengths.

Deep foundations in high-rise buildings

• Application in deep foundations:Certain structures like high-rise buildings need deep foundations, which is a good use for precast concrete piles since they can easily carry huge loads and also reach down to stronger soils.
• Transfer of loads:When used in such situations, precast concrete piles favorably remove the building's load and transfer it to deeper, more compact soil layers to enhance its stability and safety.

Bridges and marine structures

• Crucial role: Precast concrete piles are an integral feature of the supported structure of bridges and marine structures such as piers and docks exposed to environmental elements, including water and weather.
• Durability:Bearing capacity, durability, and the ability to prevent water pile-induced deterioration make them ideal for such construction applications.

Soil and lateral loads

• Soil resistance:One of the key features of precast concrete piles is their ability to withstand both lateral and vertical loads while providing resistance to the surrounding soil, thus making it ideal for use in retaining walls.
• Retention:Concrete sheet piles, like a wall, interlock to form a continuous barrier that protects against erosion and helps retain soil in excavation zones.

Ground improvement and pile foundations

• Use in ground improvement:Concrete piles are also used in ground improvement techniques such as pile driving, where piles are driven into the ground to increase its bearing capacity and reduce settlement.
• Micropiles:Micropiles cement the surrounding soil and pile, improving the load-carrying capacity and providing a solid foundation for structures in unfavorable ground conditions.

Replacement & Maintenance of precast concrete pile

Poorly constructed concrete piles will pose a serious threat to the structure they are trying to support; thus, the need for replacement or maintenance to avoid collapse must be considered once such precast concrete piles are damaged or deteriorated.

Signs of deterioration

Some signs of premature precast concrete pile deterioration and indications often manifested include cracks, water seepage, and signs of rusting of reinforcement.

• Cracking:It can occur when there is too much load on the pile or when the surrounding soil shifts. Horizontal cracks indicate a pile under too much lateral pressure, while vertical cracks show tension or stretching of the pile.
• Water seepage:Water coming out of precast concrete piles indicates that the concrete is damaged and the water is penetrating into the concrete mix. This could lead to corrosion of the steel rebar inside the concrete and weakening it further.
• Rusting rebar:Rusting of the reinforcement bars is a clear indication of severe concrete deterioration. When water penetrates the concrete and gets to the rebar, it starts to rust. Rusting rebar will cause further cracking on the surface of the concrete as the rebar takes more space inside the concrete.
• Settlement:Settlement of precast concrete piles will occur when the supporting soil below the pile gradually gives way. In this case, the structure will become misaligned, leading to unequal floor levels and malfunctioning doors and windows.

Replacement

• Removing the pile:The first step in replacing precast concrete piles is to remove the damaged piles. This is done by using a pile extractor or vibrating rig to pull the pile out of the ground.
• Foundation work:
• Inserting a new pile:After preparing the foundation, a new precast concrete pile is positioned and driven into the ground using a pile driver, which compacts the soil around it to create a strong bond.