Aukstata went to the Kristiine boiler plant in Estonia to inspect and repair their 130-meter-high reinforced concrete smokestack. Plans were made to switch the burning fuel used for the structure, so the plant contracted our team of specialists for a detailed inspection of the stack in order to determine the current condition of the structure and provide recommendations on how to better prepare the chimney for the upcoming changes. This Estonian client has chosen our company as the most suitable candidate to carry out the necessary repairs according to our recommendations.

Aukstata was the ideal contractor choice for this type of work. Smokestack repairs and maintenance are the kind of services our team handles on a daily basis. We have many years of experience working with chimneys and other similar industrial structures, which is why we are able to promptly offer our clients the most efficient solutions and eliminate any existing problems for the successful continued operation of their structures.


During the initial stage, a thorough inspection of the chimney’s interior and exterior was performed. For the purposes of a comprehensive inspection, Aukstata specialists have used various methods and equipment that comply with the European Standards (EN) (e.g., Schmidt hammer, ultrasonic wall thickness gauge, 3D laser scanner, wall metal detector, etc.). The crew observed cracks in the concrete wall of the chimney, failure of the protective layers, open and unprotected reinforcement rods, etc. After assessing the present defects of the reinforced concrete chimney, it was determined that the technical condition of the structure is poor. Therefore, in order to operate the structure safely and reduce the impact of corrosive environmental, mechanical and operational factors, it was recommended to carry out repairs on the chimney and its structures.

For inspection and repair purposes, smooth access to the chimney was created via the installation of specially adapted GEDA platforms. A 360-degree work platform with elevators for liner installation was installed inside the stack. This platform provided the necessary access and safety to perform the works listed below.


To prepare the smokestack for repairs, we first removed the surface layer of broken concrete from the exterior of the structure. The reinforced concrete shaft was washed with a high pressure (1000 bar) water jet in order to remove the carbonized concrete layer, the old protective coating of the concrete, its crumbling particles, dust and any other dirt.

The open, corroded steel reinforcement rods had to be properly protected, therefore our specialists cleaned and coated them with two layers of anti-corrosion primer. Special inhibitors were used to stop the corrosion of the concealed reinforcement rods. This material chemically reacts with the concrete coating and inhibits the formation of rust.

We then began the renovation of the exterior concrete of the chimney. Our specialists restored the damaged concrete layer using a specialized repair mortar and carefully coated it with a high performance water resistant coating. The surface of the chimney was also appropriately painted according to the civil aviation regulations. All our repair works and methods comply with the EN 1504 standards and are applied to preserve the structures’ durability, structural stability and resistance against environmental and operational harm.

Since the stack was switching from burning coal to natural gas, it was necessary to install a steel liner inside the structure. After installing suspended work cradles, we prepared the necessary openings and structures inside the chimney to collect the accumulated debris from the demolition of the old masonry refractory. We washed the interior walls of the stack, repaired the existing concrete defects and covered the walls with a specialized gunite layer. After dismantling its old components, our team prepared the chimney for the installation of a new liner. With the help of a crane, we moved the liner into the structure section by section, which were tightened and welded together with steel rings and insulated with a thermal insulation layer. In addition, we installed spiral stairs and a ladder connecting all the interior platforms of the smokestack.

It is recommended to carry out similar inspections and maintenance work on a regular basis to ensure safe and efficient stack operation. They prevent minor problems developing into larger ones, as well as prevent dangerous incidents that would be much more costly for the facility. However, in this case, the works carried out by the team of Aukstata in a smooth and timely manner will ensure the safety, productivity and longevity of the stack.