Introduction

The Swedish reuse pilot, a temporary exhibition pavilion for the H22 city expo in Helsingborg, Sweden, was constructed in 2022 and used reclaimed elements from two donor buildings and factory-rejected hollow core slabs.  

The Swedish reuse pilot was  a temporary exhibition building for the city expo H22 in Helsingborg in 2022. The structure served two main purposes:

1) to show the feasibility of reusing precast concrete elements from the existing building stock

2) a pilot project used for data gathering about different aspects of the reuse process for the ReCreate project.

Located in area Drottninghög, it was built with 94% reused building material by weight and included salvaged concrete elements from four different sources: demolished housing block on Drottninghög (donor building 1), a raft foundation from a deconstructed preschool on the building site (donor building 2), salvaged columns and beams from an industrial building in Helsingborg (donor building 3), and reclaimed hollow core slabs from Strängbetong’s factory (so-called factory rejects).

The H22 pilot project represents a hybrid between the two main design approaches in reuse, namely (i) designing from stock material and (ii) sourcing the stock material to fit a given design. Sourcing construction material is not part of the usual tasks of architects but in the H22 pilot, the team of architects at KTH took on an active role in the inventory and sourcing of concrete elements. The successful incorporation of reclaimed components from the third donor building, the industrial building in Helsingborg, was made possible by devising a method of collecting demolition permits in a selected catchment area.

After the H22 City Expo, the pilot building was disassembled by the contractor. The concrete elements were transported to the municipality’s facility for reuse of products and materials for intermediate storage in waiting for a new purpose. After a year in storage, without any new possibilities for reuse, the elements were eventually transported to a processing facility to be crushed and used as recycled aggregate in new concrete.  

Deconstruction and Storage

Drottninghög  

The two pieces of wall elements and a floor element were reused from a block of flats that stood in ‘Drottninghög Västra 1’ area, built in the period of 1967-69. The building had three floors with a cross-wall structure: transverse load-bearing internal walls perpendicular to the lateral axis of the building.

First, all the light weight façade elements were removed to reveal the precast concrete structure of the multifamily apartment building. Of all the precast concrete elements (walls and floor slabs) only a handful were deconstructed for reuse, mainly because the decommissioning was to move forward. The lifting of the solid concrete floor slabs was done by installing fasteners into the slabs for lifting the slabs. Only two fasteners were used in order to limit possible damage to the elements themselves as well as the amount of drilling. This meant that the positioning of the fasteners needed to be rather accurate to keep the slabs level during the lifting process.

Testing and Digitalisation

No load tests were carried out for the elements in the Swedish pilot. The properties of the reused elements were only obtained from original documents and by in-situ investigation, i.e. sampling of cores. However, compressive strength, chloride content and hazardous and toxic substances were studied from the samples taken during in-situ investigation.

Compressive strength was tested from the salvaged wall element (V7D) and floor element (P2). A total of 6 cores were used in the compressive strength assessment. The compressive strength testing was done according to EN 12390-3:2019 (2019) and the density was measured from the same samples according to EN 12390-7:2019 (2019).

The potential presence of chlorides, which can be a risk factor for corrosion and durability, was investigated on the salvaged wall and floor element. Chloride content was measured at 3 depths from the same 3 core samples obtained from wall and slab elements that were also used in the carbonation depth measurements. The result of the test is a ratio of chlorides to cement weight. The chlorides were measured from a cylindrical sample of 10 mm from the core, and the content was determined by a potentiometric method (with an ion-selective electrode). The cement content was determined by titration with ethylenediaminetetraacetic acid (EDTA) and photometric measurement of the colour change from murexide indicator.

Hazardous substances were measured from the concrete of the wall and slab elements from the Drottninghög donor building. A total of four samples were investigated. The occurrence of hazardous substances was measured with a method that is referred to as ‘Bygg-IS-1’ (ALS, 2024) that relies on the use of inductively coupled plasma mass spectrometry (ICP-MS). The tested substances are arsenic, barium, cadmium, cobalt, chrome, copper, mercury, nickel, lead, vanadium, and zinc. The accuracy of the method (i.e. reporting limit) for the 11 tested substances is given in the report along with the results, and more information can be found in ALS (2024). 

Precast concrete reuse in the design and construction of new buildings

The main contributions of the H22 pilot consist in demonstrating that it is feasible to source and implement concrete elements from multiple donor buildings and in demonstrating a method for identifying possible donor buildings by collecting demolition permits. 

Check out the YouTube videos showcasing the disassembly and deconstruction of the Swedish donor building

Swedish Country Cluster Partners