The first stage of the project started on January 2017 and included the thorough visual inspection of the culverts and the assessment of the damages and of the structural integrity of the structures from ENKA engineers. The structural condition of the culverts was initially checked by the engineers of ENKA and afterwards, in cooperation with the engineers of DENCO P.C., rated in a 10-grade rating system. A technical report was compiled for each culvert, while for the whole project a general WMS was submitted. The works were completed in spring 2018.

The main works that took place are:

• Removal of the loose concrete and shoring of the existing culvert where necessary.
• Cleaning of the corroded reinforcement with sandblasting and application of corrosion inhibitor.
• Concrete sections rehabilitation with repair mortars R3/R4 (EN 1504-3) or shotcrete.
• Crack sealing with cement grout injections.
• Crack sealing with epoxy resin injections.
• Construction and expansion joints sealing and repair with polyurethane-based sealant.
• Concrete protection against water ingress with crystalline technology surface applied products by XYPEX.
• Reinforcement protection with surface applied corrosion inhibitor through impregnation.

For the culverts whose structural integrity was poor (rating < 5/10), structural retrofit designs were devised and the typical interventions that included the construction of a new reinforced concrete culvert (cast in situ or shotcrete) on the interior of the existing structure for its whole length or partially, were performed.

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

ENKA was asked to propose a methodology for filling and sealing the cracks. Epoxy resins from Chemco Systems were proposed, as they are suitable for application under low temperatures and in wet cracks, and the application took place during winter so most of the cracks were wet or damp. The applied epoxy resin of Chemco is approved by the German Highways for dynamic loads (e.g. bridges, pavements). The injection of the resin was performed with Chemco Pump B that provides controlled flow and pressure to avoid uplifting the pavement and to measure the injected material volume. At the end of the application, cores were drilled to confirm the sufficient filling of the cracks.

The certified crews of ENKA have installed a large number of bridge expansion joints since 2016.

Some of the highways in which ENKA has installed bridge expansion joints are: Olympia Odos, Aegean Motorway, Ionia Odos, Administrative Region of Attica. All the big construction companies in Greece in the segment of infrastructure (AKTOR, TERNA, J&P, etc.) are clients of ENKA.

The expansion joints of ARSAN have been used in bridge construction for several decades in more than 30 countries worldwide, mainly in Europe, proving their high quality and resilience.

The first stage of the project took place on November 2017 and included the thorough visual inspection of the culverts and the assessment of the damages and of the structural integrity of the structures from ENKA engineers. The structural condition of the culverts was characterized by the engineers of DENCO P.C. as “Very Poor (#2): Deteriorated with severe damages. Culvert integrity in risk”. The existing culverts could not safely bear the loads of the earth pressure and of the traffic of the highway. Moreover, due to the small embankment height up to the pavement (<1.0m), a potential failure of the culvert would jeopardize the highway operation. Olympia Odos asked for an immediate retrofit design and execution of the strengthening measures of the structure.

The required design and construction drawings were completed in 30 days. The design resulted in the construction of a new box-shaped culvert in contact with the existing one and with small thickness so that the hydraulic section in still sufficient. The existing structure was completely ignored as for its load bearing capacity.

The construction of the project took place on February-April 2018 and included:

• Removal of the loose concrete and shoring of the existing culvert.
• Cleaning of the corroded reinforcement with sandblasting and application of corrosion inhibitor.
• Shaping of the upstream and downstream river bed.
• Installation of Φ250 pipes on metal racks for retaining the culvert fully operational regarding floodwater flow rate during the works.
• For the new box-shaped culvert, expansion joints were constructed every maximum 7.0m and at all positions of the existing expansions joints, so that the latter are not affected.
• Construction of the floor slab of the new box-shaped culvert with cast-in-situ reinforced concrete.
• Construction of the side walls up to 25cm beneath their top side with cast-in-situ reinforced concrete.
• Construction of the upper 25cm of the walls and of the roof slab with reinforced shotcrete.
• The joints were sealed with PVC waterstop tape and with hand applied polymer modified bitumen sealant at the full perimeter of each segment of the new culvert.
• Addition of XYPEX Admix C-1000NF in all cast-in-situ concrete and shotcrete for permanent waterproofing and protection against future corrosion of the structure.
• Repair and strengthening of the wingwalls with cast-in-situ concrete or shotcrete.

The demolition and reconstruction of the three bridges was unachievable without creating detours of Olympia Odos through Egio city for a long time. The special design of the load bearing structure, with V-shaped piers, is the feature that made them the landmarks of the region, and the local community requested for a technical solution of preserving them while upgrading their operational and safety levels according to modern building codes.

A check of the structural integrity of the bridges, based on modern building codes and on requirements of road construction engineering, concluded that their preservation is feasible given a seismic resilience upgrade.

The interventions on the load bearing structure of each bridge were performed without interrupting the traffic of Olympia Odos and without altering their special design.

Thorough inspection of damages and extensive repairs took place at the whole structure.

The existing foundation, comprising shallow footings, was strengthened with Φ80 piles and with reinforced concrete jackets on the footings.

The cold joints and any voids of the 15-20m high abutments were repaired and filled with cementitious grout injections (compression strength of grout ~ 90MPa), corrosion inhibitor was applied, and CFRP jackets of < 5mm thickness were applied to enhance their shear capacity and ductility.
The 75m long superstructure comprises a prestressed concrete slab 1.20m thick with circular voids. The longitudinal beams of the superstructure were strengthened, in terms of shear strength, with Φ16 galvanized threaded rods anchored on the bottom side of the beam at gusset-plates, placed at preformed indentations, and then the holes were filled with epoxy resin. Before holes drilling, thorough mapping of the prestress tendons took place with GPR (Ground Penetrating Radar) to avoid causing any damage at the tendons. The transverse beams at the supports were strengthened with reinforced shotcrete jacket.

Several meters of cracks were filled with epoxy resin system approved for bridges applications (dynamic loads) with special equipment of Chemco Systems USA providing flow and pressure control. ENKA SA is the exclusive certified applicator of Chemco in Greece. The crack filling quality control was performed by Φ32 core drilling every 30m, as required by the relevant Greek Technical Guidelines (ΕΤΕΠ).

The FRP fabrics were impregnated with special equipment (saturator) suitable for providing the proper ratio fibers/resin in relation to the ambient temperature. Before the commencement of the works, mock-ups of FRP application, pull-off tests, and testing of samples strength in the laboratory were performed as a proof regarding the crew’s experience. The quality control of the project required daily worksheet recording (Inspection Check List), ambient conditions recording, and samples of pull-off and FRP coupons samples preparation. Approximately 1,000m2 of concrete were repaired, 2,000m2 of FRP fabrics were applied, and 2,000m of cracks were filled.

The circular columns of one of the piers of the airport flyover of Attiki Odos were found to suffer from extensive concrete cover deterioration and stirrups corrosion. The diameter of the columns is 1.2m and their height is 6m. In order to address the problems the following works took place:

• Corroded reinforcement cleaning and protection with corrosion inhibitors, and local rehabilitation of the concrete section cement repair mortars per EN1504.
• Confinement of the circular columns along their full height with several layers of Carbon Fiber Reinforced Polymers (CFRP).

ENKA was urgently asked to offer its services on the immediate repair of the New Jersey barriers, so that the new segment of the highway could be delivered fully operational as soon as possible. To accomplish that, rehabilitation of the New Jersey type barriers took place, on the new highway connecting Corinth to Patras. The works included the opening of the cracks and their rehabilitation by using a two component epoxy paste. In cases where the cracks extended to the full section of the barriers, a crack injection method of a two component epoxy resin was applied. Finally, the resurfacing of the barriers was done by using repair mortars.

The demolition of the existing bridge and the construction of a new one in the same position was found to be cost-ineffective and troublesome due to the high traffic volume needed to be channeled through diversions. On the one hand the bridge geometric characteristics could fulfill the new highway design parameters with minor interventions. On the other hand the structural assessment of the bridge per the new bridge and seismic codes concluded that the bridge could be retained with a retrofitting cost being approximately half of what is required for the construction of a new one.

The superstructure of each bridge section consists of five simply-supported prestressed in-situ concrete main girders per span, supported on elastomeric bearings. The superstructure reinforced concrete slab is supported monolithically on the main girders. Extensive surveying of the damage and required repair took place. The bearing capacity of the main girders and some parts of the concrete slab of the deck was enhanced by using Fiber Reinforced Polymers (FRPs). The impregnation of the fabrics was done with a proprietary machine (saturator), properly calibrated per the project temperature conditions in order to ensure a steady specified fabric/epoxy resin ratio. To enhance the durability of the concrete structure in the specific areas where the concrete cover was less than required, a layer of FRP was applied for protection. Prior to project commencement, trial applications of FRPs to confirm the experience of the application team, on site pull-off testing and FRP coupons specimens tensile testing in accredited laboratory took place. The quality control of the project included daily inspection check list, recording of ambient conditions, preparation of pull-off testing samples and FRP coupons samples. Furthermore, trial applications took place under dynamic traffic loading to confirm that FRPs could be applied and develop the minimum required composite technical properties and bonding on concrete substrate while the bridge is in operation. The total area of concrete surface repaired was 3,000m2. Approximately 13,000 m2 of FRPs were applied in addition to 4,000 composites fiber anchors (40cm length each) and 2,000m of NSM (Near Surface Mounted) strips. For the quality control purposes more than 50 pull-off tests were performed and more than 60 FRP double layered specimens 30x30cm were produced, from which more than 300 coupons of FRP were sent to the laboratory for testing.