For many reasons, warehouses can face various structural problems that can damage the interior and exterior walls of the warehouse, foundations, columns, concrete slabs, etc. The most common problems are sinking concrete and cracking slabs, caused by a difference in concrete levels.

A difference in concrete levels can occur when there is an uneven settlement of the soil under the structure’s foundation, which causes parts of the structure to collapse differentially and can lead to cracks, trip hazards and other related problems.

This uneven or differential settlement can affect the efficient operation of mobile machinery and cause instability of equipment such as shelving and racking systems. Adding shims or replacing the concrete slab under the column base plates can be attractive solutions. However, these solutions can be difficult, expensive, time-consuming and have limited success. Especially if the underlying cause of weak ground hasn’t been addressed.

Here’s how you can overcome the difference in unlevel concrete with the solutions below. Before we proceed, let’s have a quick overview of why differential settlement occurs in warehouses.

Why Does Differential Settlement Occur in Warehouses?

Many factors cause differential settlement, including inadequate site preparation, inhomogeneous subsoil properties, poor soil quality, and uneven distribution of loads on the floor,

Warehouse settlement can potentially be avoided if a comprehensive geotechnical investigation can be undertaken to assess the soil quality before construction.

However, in some cases, it is observed that pallets are constantly placed and stacked on the floor, which makes the area more sensitive. In addition, some drivers push the pallets directly onto the floor with the forklift to save time, which damages the concrete slab and causes uneven settlement in the future.

Fortunately, we have two powerful solutions to deal with sinking concrete and unlevel slabs.

What is the solution to a subsiding concrete slab (Sinking Concrete Slabs)?

Mud jacking:

This is the process in which a mixture of water and high compressive strength cementitious materials are hydraulically pumped or injected directly below the slab. These include sandy loam, pond sand, topsoil mixtures, limestone or Portland cement which is injected under the concrete slab at high pressure to regain its previous position using a hydraulic lift.

Mud jacking includes the following steps:

1. Drill 10-20mm diameter holes directly into the concrete slab.

2. Prepare the mix and load it into the portable pump.

3. Pour and pump the mix into the holes until the concrete is releveling.

4. Finally, fill the drilled holes with concrete mix or epoxy.

Expanding Structural Foam Leveling using Polyurethane Resin:

Like mud jacking, polyurethane resin injection, which is also known as slab jacking, involves injecting the mixture into drilled holes to raise the concrete slab. However, polyurethane resin is used instead of cement grout.

Slab Jacking is a two-part polymer (i.e., resin and activator) that produces a closed-cell polymer foam. The movement of two separate liquids through the pipes results in this polymer foam that mixes in the nozzle to seal the cells together. As the mix is injected through the injection tube and into the ground it begins to gel into an expanded solid-state with great force, permeating the weak layers of ground and densifying it to the extent that the reaction generates upwards force and relevels the sunken slab above it.

Moreover, Slab Jacking will remove excess water and moisture and mitigate erosion. You will need an experienced, professional technician to perform this process.

This process consists of the following three steps:

1.Drill 16mm diameter holes in the concrete slab at specific locations.

2. Pump two parts of the polymer into the holes. This mixture of two liquids will create an expanding foam that results in concrete releveling.

3.Fill the drilled holes with a concrete mixture.

Bottom line! 

Even after all the precautions and considerations, other factors can cause the concrete slab to settle. These factors include soil settlement or concrete creep. These problems usually occur 2 to 5 years after construction. However, the solutions mentioned above will help you solve your problems.