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Reinforced Concrete Floor Reinforcement Systems
Reinforced concrete slabs are structural elements that span openings in buildings and transfer the vertical and horizontal loads they are subjected to—proportional to their stiffness—to columns or walls via beams located at their edges or beneath them. In addition to the traditional FRP method for reinforced concrete slab retrofitting, another system widely used worldwide is the FRCM retrofitting system. The FRCM retrofitting system, which stands for Fabric-Reinforced Cementitious Matrix, is a modern and up-to-date method for repair and retrofitting. The reinforcement matrix consists, in its simplest form, of textile reinforcement (also known as reinforcement fabric or technical textile) and a cement- or lime-based mortar.
FRCM systems are increasingly preferred over traditional polymer-bonded, fabric- or plate-reinforced (FRP) reinforcement systems due to their ease of application, removability without damaging the structure, greater resistance to high temperatures, resistance to UV radiation, vapor permeability, and suitability for use in damp areas.
PRINCIPLE APPLICATIONS
FRCM reinforcement systems, in principle, rely on the interaction between the mortar and textile reinforcement, similar to how concrete and steel work together in reinforced concrete. In this context, the mortar absorbs compressive stresses, while the textile reinforcement absorbs tensile stresses. In reinforced concrete slabs, continuous cracks, punching shear cracks, shear cracks caused by wall movement, and excessive deflections may be observed due to the loads they are subjected to. Additionally, the slab may have been designed thinner than required relative to its span, may lack sufficient reinforcement, or may have been removed from the formwork prematurely due to construction errors. While floor damage is not considered a primary structural failure from the perspective of the load-bearing system, it can pose a risk to the building’s usability. When reinforced with the FRCM system, the floor’s stiffness and load-carrying capacity increase, allowing it to efficiently transfer various applied loads to the relevant structural members.
RELEVANT STANDARDS
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CNR-DT 2000 R1 / 2013 “Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Existing Structures”
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ACI 549.4R-13 “Guide to Design and Construction of Externally Bonded Fabric-Reinforced Cementitious Matrix (FRCM) Systems for Repair and Strengthening Concrete and Masonry Structures”
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ICC-ES AC434 10-2018 “Acceptance Criteria for Concrete and Masonry Strengthening Using Fabric-Reinforced Cementitious Matrix (FRCM) and Steel Reinforced Grout (SRG) Composites”
The FRCM strengthening system is a well-established system recognized in the field of structural strengthening and included in international standards; the relevant application guidelines and engineering calculations are based on the standards listed above.
APPLICATION STEPS
For floor reinforcement:
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The surface to be treated is cleaned of all foreign matter and dust, then moistened.
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The selected reinforcement mesh is cut to the desired size using appropriate cutting tools.
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HPM100 or HPM120 is mixed with water in the ratio and for the duration specified on the package, then poured onto the reinforced concrete floor surface and spread to a thickness of approximately 5 mm.
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The reinforcement mesh is placed by hand onto the spread mortar surface, and a load-distribution plate is placed on top before anchoring it to the existing reinforced concrete floor using the selected mechanical anchoring elements.
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HPM100 or HPM120 is reapplied so that the final layer thickness is at least 10 mm, and the surface is sealed so that the anchors or mesh are not visible.
For under-slab reinforcement:
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The surface to be treated is cleaned of all foreign materials and dust and moistened.
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The selected reinforcement mesh is cut to the desired size using appropriate cutting tools.
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RPM40 or RPM60 is mixed with water in the ratio and for the duration specified on the package, then applied to the underside of the reinforced concrete slab using a trowel or by spraying to a thickness of approximately 5 mm.
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The reinforcement mesh is manually placed onto the applied mortar surface, and a load-distribution plate is positioned over it before anchoring it to the existing reinforced concrete slab using the selected mechanical anchoring elements.
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RPM40 or RPM60 is reapplied to ensure a final layer thickness of at least 10 mm, and the surface is finished so that neither the anchors nor the mesh are visible.
IMPORTANT DETAILS
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Reinforcement must be applied directly to the reinforced concrete slab surface.
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Any loose layers, plaster, ceramic tiles, paint, etc., on the surface must be removed.
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If rust formation and reinforcement corrosion are observed on the reinforced concrete slab, the loose rust layer must be removed, and the rust layer on the reinforcement surface must be cleaned using mechanical methods. When moistening the surface during slab reinforcement, free water must not be left on the surface.
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The reinforcement mesh must be applied over and under the reinforced concrete slab without leaving any gaps and with an overlap of approximately 20 cm.
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Anchors must be placed at a minimum of 4 per square meter.
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To prevent cracking of the mortar on the surfaces, the surface must be moistened 20 minutes after the initial curing is complete and the mortar has hardened.
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Where possible, the reinforcement mesh should not terminate at the slab plane but should be extended 20 cm into the wall plane and terminated at that plane.
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No additional additives such as cement should be added to the mortar, and the water-to-cement ratio must be strictly adhered to as specified in the technical data sheet.
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Mixing equipment must be capable of achieving the mixing speed recommended in the technical data sheet.
Sample Projects
