The project was conducted by ENKA’s experienced personnel, certified for working at height and for steel welding.

The works that took place were the following: setup of safe access at the interior of the silo funnel, installation of hoisting equipment for personnel and machinery, cutting of the existing anti-friction sheet metal Hardox 400 of 20mm thickness and removal of the segments using crane (approximately 120m2 total surface), removal of the bauxite beneath the funnel (approximately 300m3) manually as well as by using special equipment, repair of the concrete surface of the silo and of the funnel base plate, installation of new steel beams and kicker braces for the support of the new funnel, construction and installation of the new funnel, Hardox 400 with 25mm thickness, steel connection and welding at the interior of the silo, connection of the funnel using chemical anchors on the circumferential concrete walls, encasements construction and installation of vibrators.

The works that took place were the following: removal of the loose concrete, sandblasting and cleaning of the corroded reinforcement, application of corrosion inhibitor onto the reinforcement, application of surface applied corrosion inhibitor, concrete sections restoration using R3/R4 repair mortars, dowels and new steel reinforcement installation, construction of shotcrete jackets, crystalline technology coating application (XYPEX) for protection against corrosion, repair and replacement of steel elements and structures.

The methods followed and the materials and systems used were in accordance with relevant standards (mainly EN 1504) and the Greek Technical Guidelines (ΕΤΕΠ).

The project took place inside an industrial building of plan dimensions 30m x 180m and height approximately 15m. The part of the new structure (walls, footings, conveyor belt) to be constructed had dimensions 7m x 200m along the main axis of the facility.

ENKA studied and composed a thorough method statement, regarding the execution of the project, that was checked and approved by a specialized international consulting office (AUXITEC Batiment – ARTELIA Group).

The scope of the project was the construction of new internal walls for the furnace using 118 precast concrete elements of 286cm length, 440cm height, 30cm thickness, and weight approximately 10tn each (constructed by Betofil). The ENKA method statement included guidelines for the transfer of the walls on the interior of the building on a horizontal position, and their hoisting and deposition on the furnace floor on a horizontal position. It also provided guidelines for the placement of the wall elements on a custom made metal table with rotation system around horizontal axis, their hoisting on a vertical position and their installation in temporary encasements. Moreover, provisions were given regarding the installation of the necessary kicker braces, the hoisting and placement of the walls on their specified position, the alignment of the walls, the adjustment of their height and verticality, the installation of the required expansion joints, >2cm between each wall element, and the installation of the gusset plates for connecting the wall panels. ENKA also studied a new technique to modify the initial footings of the precast walls provided by the consulting office. ENKA designed and constructed these special metal footings for the support of the walls, which were installed, based on high precision topographic instruments (www.aksm.gr), in each position and with predefined height according to the precise base level and the exact height of each wall panel. The acceptable tolerances regarding the installation of the walls were ±10mm in each direction. In total, 118 precast wall panels, of 10tn weight each, were installed.

The specification for the concrete of the foundation was quite strict due to the expected high operating temperature of the furnace (>500oC) and the constant heat cycles (from 50oC up to >500oC). More specifically, the specification called for pumpable concrete C35/45 with siliceous aggregates (calcium carbonate aggregates were prohibited) of maximum grain size 20mm. Moreover, due to the construction process and to other restrictions, the concreting should be able to last up to three hours after the loading of the concrete truck. ENKA conducted probationary mix designs, pumpings, and concretings for up to three hours after the production of the mix and the strength of the concrete was confirmed after 28 days. The tests took place in two ready mix concrete units in Thiva (Betofil) and Levadia (Spyridonos Bros) with siliceous aggregates from the quarry of Betofil in Aliartos. Special plasticizer (Sika Viscocrete Ultra 450) and retardant (SikaTard 930) were used. The final mix design comprised 420kg of cement I-42.5 and 4 sizes of siliceous aggregates (<20mm) without containing silica fume, because of washing, and the results of the tests showed concrete cube strength >60MPa. The 500m3 of special mix design C35/45 concrete were supplied by the ready mix concrete unit of Spyridonos Bros in Levadia. Another 330m3 C35/45 and C20/25 concrete with calcium carbonate aggregates were poured on the floor slab and on the composite slab of the conveyor.

The concrete pouring was performed using a concrete bucket hoisted from overhead travelling cranes inside the building, as concrete pumps could not be utilized. ENKA designed, constructed, and certified a concrete bucket of high capacity (3.0m3), in order to reduce the waiting time of the concrete truck and to pour more concrete per day.

The project was completed in 15 days, as scheduled, with continuous work 24/7 in two shifts.
More than 30 people (engineers, foremen, mechanics, and workers) worked for the project.

ENKA’s personnel received training regarding the special safety measures for the particular industry (general training, special training, training for working in enclosed and confined spaces, etc.) and received permission for working in the project after successfully participating in exams. The safety measures were fully abided by with daily presence of safety technician and constant on-site training based on risk analysis assessment of each work and project phase.

The project took place inside an industrial structure of plan dimensions 30m x 180m and height approximately 15m. The part of the existing facility that was removed had dimensions 7m x 200m along the main axis of the structure.

ENKA studied and composed a thorough method statement regarding the execution of the project. The project concerns the removal of refractory brick masonry walls and of reinforced concrete walls, slabs, beams, and foundations. In total, more than 4.000 tn of materials were removed, from which 1.500m3 of reinforced concrete were removed using non-vibrating cutting. Special caution was given in the sequence of the elements removal using non-vibrating cutting and in the hoisting technique, given their poor condition (loose and cracked concrete, corroded reinforcement, etc.).

The main aspects of the methodology of the project are:

• Shoring and bracing of slabs and walls using PERI systems.
• Removal of refractory brick masonry walls using 7tn loaders, 7,5m3 debris dumpsters, and overhead bridge cranes.
• Repeated phases of non-vibrating cutting of walls and slabs, and removal, with hoisting, through overhead bridge cranes.
• Partial non-vibrating cutting of footings, in order to avoid inducing any damage in the remaining segment of the footing. Removal using mechanical means, debris dumpsters, and overhead bridge cranes.

The project was completed in 18 days, as scheduled, with continuous work 24/7 in two shifts.

More than 50 people (engineers, foremen, mechanics, and workers) worked for the project. For the non-vibrating cuttings of concrete 3 diamond wall saws of Hilti were constantly operating.

ENKA’s personnel received training regarding the special safety measures for the particular industry (general training, special training, training for working in enclosed and confined spaces, etc.) and received permission for working in the project after successfully participating in exams. The safety measures were fully abided by with daily presence of safety technician and constant on-site training based on risk analysis assessment of each work and project phase.

All the removed materials were delivered for recycling after thorough grading.

Most of the pedestals had already been repaired with shotcrete approximately 10-15 years ago. In 2017 new repair measures were deemed necessary to elongate the life expectancy of the structures for ten more years.

The works performed were removal of the loose concrete, cleaning of the corroded steel reinforcement, protection of the steel reinforcement with corrosion inhibitor, addition of new steel reinforcement wherever necessary, concrete section rehabilitation with repair mortar, sealing of voids between pedestals and steel tanks and drainage pipe installation for the collection of the rain water from the voids, mechanical anchoring repair and replacement, and XYPEX application for the waterproofing of the concrete pedestals as an extra measure of protection against corrosion and life time prolong.

The methods followed, and the materials and systems used were in accordance with relevant standards (mainly EN 1504) and the Greek Technical Guidelines (ΕΤΕΠ).

In 2018 ENKA executed the restoration and strengthening of silo No2 and of the top beam ring of silo No10.

The works that took place were the following: scaffolding installation at the full height of the silos, removal of the loose concrete, sandblasting and cleaning of the corroded reinforcement, application of corrosion inhibitor onto the reinforcement, installation of new steel reinforcement and dowels, and construction of 15cm thick jacket with shotcrete, with its pour in-situ foundation.

At the beginning of the 2000’s, repairs of the silos comprising corrosion inhibitors, repair mortars, and coatings that protect against carbonation took place, but 15 years later new and more extensive damages appeared. Thus, Xypex Concentrate was applied at the whole surface of the shotcrete jacketing of silo No2 to permanently waterproof and seal it and, so, protect it from any kind of water ingress. That way, the steel reinforcement was protected against corrosion and the life expectancy of the structure was largely prolonged.

In general, the chloride concentration inside the existing concrete was below the max acceptable limits.

The process followed and the materials and systems used were in accordance with relevant standards (mainly EN 1504) and the Greek Technical Guidelines (ΕΤΕΠ).

The works that took place were removal of the loose concrete, sandblasting and cleaning of the corroded reinforcement, application of corrosion inhibitor onto the reinforcement, corrosion inhibitor coating on the concrete surface, concrete restoration with repair mortars R3/R4, strengthening using shotcrete jacketing, strengthening with FRP, and application of final paint coatings suitable for limiting carbonation.

Where the chloride content inside the concrete was above the allowable limits, special techniques and materials were used to reduce this content.
The process followed and the materials and systems used were in accordance with relevant standards (mainly EN 1504) and the Greek Technical Guidelines (ΕΤΕΠ).

In the wastewater treatment facility of Kalamata works of repair and strengthening of concrete on the reservoir of the stable sewage took place. The works specifically included the strengthening of the perimeter wall and of the walls controlling the sewage overflow by using reinforced shotcrete. Furthermore, the concrete structure controlling the overflow of the reservoirs and the perimeter walls were rehabilitated with repair mortars. Following the repair works, a crystalline technology product was applied on the concrete surface for reservoir waterproofing.