Anti-spalling of floor slabs: LIFE+ SYSTEM for an industrial warehouse from the 1960s-1970s.

Production sites built in the 1950s generally have a reinforced concrete structure and asbestos-cement infills. The main central complex of buildings constructed during that period for the production purposes of an important company in Modena also has these characteristics. Around a dozen unique gallery-like industrial buildings consist of a series of bays approximately twelve meters wide, with a total length of about 230 meters. The roofs are gable-shaped, constructed with very slender iron lattice structures, characterized by two changes in pitch interrupted by wide strip skylights, and coverings made of exposed asbestos-cement panels, without plaster finishes, which are relatively heavy compared to the supporting structures.

ISSUES AND DAMAGE

The age of the buildings has inevitably led to a series of deterioration issues that the company has addressed through necessary maintenance interventions. Among the problems that have arisen is the spalling of the asbestos-cement roof structures, which have been recurring in different areas of the buildings in recent years. The main cause of degradation is the infiltration of rainwater from the overlapping roofing sheets onto the asbestos-cement. Recently, the property owner decided to carry out a significant intervention to ensure the safety of its workers and provide a suitable environment for the activities, addressing all issues related to the inevitable deterioration of the historic company buildings. The executed intervention, categorized as extraordinary maintenance, involved the entire roofing package, working both on the underside with effective reinforcement measures to prevent the falling of material from the spalling panels and on the upper side by removing and replacing the external weather protection sheets. Considering the extensive surface area of the numerous industrial buildings, the roofing intervention is being executed in successive phases until the complete consolidation of the affected areas.

INTERVENTION

The anti-spalling intervention carried out on the underside of the roof involved the application of the LIFE+ SYSTEM, consisting of Glass Fiber Reinforced Polymer (GFRP) grids and specifically sized metal connectors. The GFRP grid, with a 99×99/33 mm mesh, is a preformed grid made of a monolithic square main mesh composite material produced using Textrusion® technology, composed of Alkali Resistant (AR) glass fiber and a vinyl ester-epoxy thermosetting resin. The selection and sizing of the connectors (galvanized steel and five per square meter) were based on pull-out tests performed on the asbestos-cement panels to assess their state of degradation and subsequently ensure the required strength characteristics of the system. Upon completion of installation, the anti-spalling GFRP grid was left exposed. The lightweight properties of the fiberglass grid and the necessary connectors were essential factors in choosing the anti-spalling system, considering that the roof structure could not be further burdened in terms of its own weight. In addition to this, the system’s effectiveness in preventing the falling of panels, especially from a workplace safety perspective, the certification of the LIFE+ system, and the ease and speed of installing the GFRP grid allowed the construction site to be organized without interrupting the ongoing production activities in the buildings, creating compartmentalized and non-interfering itinerant work areas through relatively simple coordination.

PROJECT DETAILS PROJECT Anti-spalling intervention at an industrial plant in the province of Modena CLIENT Private EXECUTION October 2017 – July 2018 (first phase)