Concreting of screw piles

Why concrete screw piles at all?

To understand whether it's necessary to concrete a screw pile, let's first understand what the process actually entails. It's simple: after the pile is screwed into the ground, concrete is poured into its shaft. It may seem like a small detail, but this pouring can significantly improve the characteristics of the pile foundation. In what cases is concrete justified?

Increasing Bearing Capacity

The first and most obvious advantage of concreting is increasing the bearing capacity of the pile foundation. If you're building a lightweight frame house, bathhouse, or gazebo on level and stable ground, the screw piles will easily withstand the load without any additional measures. But imagine a different situation: you're building a large two-story house from timber or brick, which places a significant load on the foundation. Or the site is challenging—peat, with a high water table, or clayey, unstable soil. This is where concrete becomes not just useful, but practically a must. When concrete hardens inside the pile shaft, the structure becomes much more rigid and resistant to loads. Concrete strengthens the metal shaft, making the pile less susceptible to lateral and vertical deformations and increasing its load-bearing capacity, which is especially important in difficult soil conditions.

Simply put: if the construction site is large or the soil is weak, concrete inside the pile is your guarantee of a long and trouble-free foundation.

Corrosion Protection and Extended Service Life

The second important advantage of pouring concrete inside piles is the protection of the metal shaft from corrosion. Metal, even protected with an anti-corrosion coating, is not indestructible. This is especially true in soils with high humidity, a high groundwater level, or aggressive environments, such as those found in marshy and peaty areas.

Concrete inside the pile acts as an additional barrier, preventing moisture and oxygen from penetrating the metal from within. Even if the pile's outer coating is damaged somewhere, the concrete will slow down the rusting process, significantly extending the life of the entire pile foundation.

When pouring concrete is necessary, and when it's not necessary

The most common mistake when working with screw piles is going to extremes: some customers consider concrete mandatory at all times, while others don't accept it at all. The truth, as usual, lies somewhere in the middle. Let's break down in simple terms when concrete is absolutely necessary, and when it can be dispensed with.

When concrete is absolutely necessary:

Here are the conditions under which concreting is not a luxury, but a necessity:

·         Heavy structures. If you're building a large house made of brick, aerated concrete, heavy timber, or logs, the pile foundation will be subject to very heavy loads. Concrete will help strengthen the piles and prevent deformation and subsidence.

·         Problematic soils. These include clayey, peaty, marshy areas, and areas with high groundwater levels. In such soils, piles corrode more quickly and are subject to greater lateral loads, so concreting is definitely justified here.

·         Climates with frequent temperature fluctuations.

When concreting is unnecessary:

There are situations when concrete inside the pile is an unjustified overpayment:

·         Lightweight structures. Are you building a gazebo, terrace, shed, or bathhouse from a frame or lightweight timber? In most cases, the loads will be minimal, and concreting will be unnecessary.

·         Good, stable soils. On sandy or well-compacted soils, screw piles perform excellently. In such conditions, concreting is an unnecessary step that will only increase the budget.

·         Temporary structures. If you are planning temporary structures, concrete will only complicate subsequent dismantling of the piles and significantly increase costs.

Let's summarize this section with a simple rule:

·         If you are building permanently, on difficult soils, with a high load, use concrete.

·         Easy to build, good conditions, temporary solution – no need for concrete.

Mistakes in Pile Concreting and How to Avoid Them

Mistakes in helical pile concreting can completely negate the advantages of this technology. Pouring concrete into a pile would seem like a simple task. However, even here, builders and clients often make common mistakes that later lead to problems and additional foundation repair costs. Let's look at the main pitfalls and offer advice on how to avoid these mistakes.

Mistake #1: Using the wrong concrete composition

A very common mistake is skimping on concrete mix. Some believe they can pour any mix they want into the pile, even the cheapest cement slurry. As a result, such concrete sets poorly, shrinks, and does not provide adequate strength or corrosion protection.

Mistake #2: Poorly prepared pile shafts before pouring

Workers are often in a hurry and fail to clean the piles of dirt, debris, soil, or water before pouring. As a result, the concrete inside is unevenly poured, creating voids and weakening the structure.

How to do it right: Before pouring concrete, the pile shaft must be clean and dry. Spend 10-15 minutes thoroughly preparing it: inspect the interior surface and remove any debris and soil. If there is water inside the pile, be sure to pump it out or remove it manually, otherwise the concrete will not set properly.

Mistake #3: Pouring Concrete Improperly

Some workers pour concrete into the pile quickly and without paying attention to the uniformity of the fill. The result: the concrete hardens unevenly, creating voids and areas of low density, which reduces the pile's load-bearing capacity.

How to do it right: Pour the concrete in small portions and immediately tap the pile with a hammer. This will help the mortar distribute evenly and fill all the voids. Don't rush—it's better to spend a little more time, but you'll get a reliable and durable structure. Mistake #4: Incorrect Pile Reinforcement

Some builders simply insert rebar into the pile, believing that's sufficient. However, if the metal touches the pile shaft walls, the protective layer of concrete won't form, and the rebar will quickly rust, weakening the pile.

How to do it right: Use special plastic or metal rebar spacers to ensure that the rebar is completely surrounded by concrete. The rebar should not touch the pile walls and should be positioned precisely in the center of the shaft.

Mistake #5: Neglecting Concrete Care After Pouring

Pouring concrete and forgetting about it is a common practice for many workers. However, concrete requires care in the first few days after pouring, otherwise it won't achieve the required strength, especially in hot or rainy weather.

How to do it right: For the first 24 hours after pouring, cover the pile with film or other material to protect it from the sun and precipitation. Avoid subjecting the pile to any loads for at least 3-7 days to allow the concrete to fully strengthen.

By following these simple guidelines, you'll avoid most common mistakes and ensure a truly reliable pile foundation that will last for many years.