ISO 5091-2:2023

Overview

ISO 5091-2:2023 - Structural intervention of existing concrete structures using cementitious materials - Part 2: Top‑surface overlaying provides international guidance for the design and execution of top-surface cementitious overlays used to increase the thickness and performance of existing concrete members. The standard defines principles and methods to improve safety, serviceability and durability when attaching a cementitious layer (typically with internal tension reinforcement) to the top surface of slabs, decks and other horizontal elements.

Keywords: ISO 5091-2:2023, top-surface overlaying, cementitious materials, concrete repair, structural intervention, concrete strengthening.

Key topics and technical requirements

ISO 5091-2:2023 addresses the full life‑cycle of top-surface overlay interventions, including:

• Investigation of existing structure
  • Document review and on-site inspection to identify defects, deterioration and original construction issues.
• Intervention design
  • Structural plans and detailed reinforcement layout for overlay thickness, cover and jointing.
• Materials
  • Requirements for cementitious repair materials, reinforcing materials, bonding products, waterproofing and pavement finishes; guidance on characteristic/design values for repaired parts.
• Actions and deterioration mechanisms
  • Consideration of mechanical (fatigue, impact, seismic, settlement), chemical/biological (sulfate attack, alkali‑aggregate reaction), physical (freeze–thaw, thermal cracking, moisture, salt crystallization, fire, erosion) and corrosion-driven damage.
• Performance verification
  • Verification of structural response, durability (including corrosion control), safety (including failure and fatigue checks), serviceability (stress limits, appearance) and restorability.
• Construction & quality control
  • Pre-construction planning, surface preparation, reinforcement assembly, mix production, placement, compaction, finishing, curing, inspection and record keeping.
• Maintenance and records
  • Guidelines for inspection, maintenance planning and documentation after intervention.

Practical applications and users

ISO 5091-2:2023 is intended for practitioners involved in concrete repair and strengthening, including:

• Structural and repair engineers designing overlays
• Contractors and site supervisors executing cementitious overlays
• Inspection and asset-management teams assessing remaining service life
• Material and bonding-product manufacturers supplying repair systems
• Owners and facility managers planning maintenance and upgrades

Typical applications include strengthening slabs and decks for increased load capacity, restoring deteriorated concrete surfaces, improving durability against environmental attack, and prolonging service life with minimal demolition.

Related standards

• ISO 5091 series (Part 1: common issues; Parts 3 and 4: other attachment methods)
• ISO 16311 umbrella code (notably ISO 16311‑3 and ISO 16311‑4) for conformity with overarching intervention principles

For implementers, ISO 5091-2:2023 is a practical reference for standardized, performance‑based top-surface overlaying of existing concrete structures.