Repairing and strengthening St. Mark's Church in Zagreb

• Name

  St Mark's Church in Zagreb restored and refurbished

• Country

  Croatia, 2023

• Categories

  Structural Strengthening
  Masonry Systems

• Products

  Oxal VP I T
  Oxal VP III HS
  MC-RockMortar H
  MC-RockMortar HS
  MC-CarboSolid 1280

St Mark's Church is the parish church in the old town of Zagreb and is located on St Mark's Square. It is considered one of the oldest monuments in Zagreb and was built in the mid-13th century. In 1256, a fair was held here for the first time on the occasion of the feast of St Mark, which, according to medieval custom, took place near the church. The building has undergone several renovations over the centuries, so that the structure contains a variety of materials from different periods.

Repairing damage after the earthquake

The first earthquake in March 2020 caused considerable damage to St Mark's Church. The roof was damaged, the wall above the south portal collapsed and parts of the plaster and gilding inside fell down. The walls were cracked and the vault was severely damaged in places and separated from the wall. The earthquake in December 2020 exacerbated the damage and widened the existing cracks. This damage made extensive repairs and restoration essential. The building owners opted for MC's repair and restoration systems, which were used to seal the cracks and reinforce the masonry.

Cracks in the masonry repaired

As part of the restoration, the masonry joints on all the walls were first removed using small power tools. After removing the pointing mortar, Emcekrete SFM Thix was applied and spiral anchors, a helically moulded stainless steel used to repair cracked masonry, were inserted into the mineral pointing and adhesive. After inserting the spiral anchors, all the vaults and walls were injected with Oxal VP I T Flow, a highly flowable grout and injection adhesive, to fill cracks, joints and voids and provide additional consolidation.

 

Systematic repair and refurbishment

The FRCM system was then used to reinforce the structure of the vaults and the nave and gable walls. For this purpose, the special mortar MC-RockMortar L was used in combination with the high-strength carbon fibre mesh for structural reinforcement of masonry and concrete structures MC-CarboGrid 210 K and the carbon rope MC-CarboRope, which were bonded with MC-CarboSolid 1209TX and sprinkled with MC-Quartz.

 

FRCM stands for Fabric-Reinforced Cementitious Mortar and is a system consisting of a cementitious mortar combined with a two-dimensional fabric or scrim made of carbon fibres, alkali-resistant glass fibres or basalt fibres. The mineral matrix or mortar has the task of protecting the fibres and transferring stresses from the concrete or masonry to the fibres. The high strength-to-weight ratio of the FRCM system makes it possible to improve the mechanical properties of the reinforced component without increasing its mass or significantly changing its stiffness. Once this work was completed, anchor rods were inserted in the bell tower and at several other points in the church walls, which were injected with Oxal VP I T Flow grout and injection adhesive. This further improved the stability of the building and made it more resistant to earthquakes.

Preserving historical splendour for the long term

The restoration of St Mark's Church in Zagreb was a challenging project in which damage caused by earthquakes and historic fires had to be repaired. Thanks to the use of modern restoration techniques by MC, the structure of the church has been stabilised and its historic splendour has been permanently preserved. Today, one of Zagreb's most important historical landmarks shines again in its former splendour and tells an important chapter in the history of this fascinating city.