• Skip to main content
  • Skip to footer

Sandberg

Materials Testing and Consultancy

Menu
  • Home
  • About
      • About Us

      • Sandberg Today
      • Sandberg History
      • Opportunities
      • Memberships and Associations
    • Sandberg Key Personnel
        • Neil Sandberg
        • Paul Bennett-Hughes
        • Simon Clarke
        • Julie Dell
        • Mike Eden
        • David Ellis
        • Jayne Fagan
        • Mariachiara Faliva
        • Julian French
        • Rom Gostomski
        • Kevin Green
        • Yohann Guellil
        • Ian Hudson
        • Sam Hudson
        • Marion Ingle
        • John Jones
        • Ashfaq Khokhar
        • Daniel Kinnersley
        • Ewa Krylowicz
        • Sebastian Kwincinski
        • Graham Lee
        • Roger Lucas
        • Dr Ewan Maclean
        • Gavin Mayers
        • Gregory Moor
        • Chris Morgan
        • Simon Morris
        • Tony Pitman
        • Steve Pringle
        • Richard Rogerson
        • Mohamad Sabra
        • Panos Sotiropoulos
        • Connor Walden
    • News & Information
        • Reinforced Autoclaved Aerated Concrete (RAAC)
        • London Legal Walk
        • Sam Burdett appointed to IOM3 advisory council
        • Tony Willmott 1949 – 2021
        • Structural Steelwork – Specifying the Future
        • Head Office
        • COVID-19 Update
        • Client Satisfaction Survey
        • UKAS Accreditation
        • Midland Corrosion Services Ltd
        • Pension Scheme Documents
    • Vacancies
        • Conservation Architect
        • (Mechanical) Load-testing Lead
        • GPR Surveyor
        • Materials Consultant
        • Building Inspector
        • Head of Facades
  • Laboratory
    • Stone
      • Building Stone
      • CE/UKCA Marking Stone
      • Stone Testing
      • UKAS Stone Testing
    • Chemistry
      • Cement Testing
      • Chemical Testing
      • Chloride Testing
      • Efflorescence
      • Hardened Concrete Analysis
      • Infrared Spectroscopy
      • Lead in Paint
      • Mortar Testing
      • Rock Salt Testing
      • Screed Analysis
      • Water Testing
    • Construction Materials
      • Agglomerated Stone CE Marking
      • Aggregate Testing
      • Bricks, Blocks, Flags & Pavers
      • Laboratory Concrete Testing
      • Fresh Concrete Testing
      • Hardened Concrete Testing
      • Chloride Diffusion and Chloride Migration Testing
      • Masonry Testing
      • Screed Testing
      • Terrazzo/Agglomerated Stone
    • Geomaterials
      • Concrete Petrography
      • Mica and Pyrite Blocks
      • Mundic Concrete
      • SEM and X-Ray
      • Sulfate Attack
    • Metallurgy
      • Laboratory Services
      • Bolt Testing
      • Metallographic Analysis
      • Metals and Weld Testing
      • Scaffold Component Testing
      • Tensile Testing of Metals
    • UKAS Testing
  • Site
    • Ground Penetrating Radar
      • GPR Surveys
      • GPR Principles
      • Building Investigation
      • Chimney Flue Location
      • Concrete Imaging
      • Concrete Slab Surveys
      • Ferroscan/GPR Compared
    • Inspection
      • Abseil Inspection
      • Bedding Mortar
      • Building Inspection
      • Bridge Inspection
      • Cladding Inspection
      • Concrete Floors
      • Ferroscan Surveys
      • Fire Damaged Concrete
      • GFRC Inspection
      • HAC Concrete
      • NDT Weld Inspection
      • Paint Inspection
      • Precast Concrete Inspection
      • RAAC Identification Surveys
      • Woodwool
    • Leak Detection
      • Defect and Leak Location
      • Waterproof Membranes
    • Load Testing
      • Buildings
      • Balconies and Barriers
      • Car Park Barriers
      • Sports Ground Barriers
      • Cladding Systems
      • Foundations
      • Glass Panels
    • Specialist Testing
      • Data Logging
      • Slip Resistance
      • Thermography Surveys
    • Steelwork/Metallurgy
      • Steelwork Services
      • Sampling and Testing
      • Safe Working Loads
      • Steel Fire Damage
  • Consultancy
      • Building Envelope
        • Building Fire Safety Audits
        • Condensation Risk Analysis
        • Facade and Roofing
        • Thermal Analysis of Facades
        • Thermography Consultancy
      • Building Retrofit
        • Retrofitting of Buildings
        • Sustainable Construction
      • Conservation
        • Building Conservation
        • Stone Conservation
        • Historic Mortars
        • Historic Metals Conservation
      • Expert Services
        • Expert Witness
        • Independent Advice
      • Stone Consultancy
        • Building Stone (new projects)
        • Building Stone (existing)
        • Building Stone Suitability
        • Building Stone – Source Matching
      • Geology/Geomaterials
        • Geology/Geomaterials Services
        • Materials for Coastal Engineering
      • Specialist Services
        • Building Damage Assessment
        • Demolition and Refurbishment
        • Glass and Glazing
        • Pavement Consultancy
      • Quality Assurance
        • Contract Administration
        • Materials and Workmanship
    • Polymers
      • Polymer Consultancy
      • Polymers in Construction
      • Polymer Failure Analysis
      • Polymer Identification
      • Polymer Microscopy
    • Concrete
      • Alkali Aggregate Reactivity
      • Concrete Consultancy
      • Concrete Durability
      • Concrete Strength Assessment
      • Steelwork
        • CE/UKCA Marking of Steel
        • ISO 3834 Services
        • Failure Investigation
        • Welding Coordinator (RWC)
        • Steelwork Consultancy
      • Sandberg Consultants
  • Contact

Concrete Strength Assessment

Compressive strength test of concrete core

An estimate of the in-situ strength of concrete may be required for several reasons:

  • When an assessment of the in-situ concrete strength is needed during construction
  • When an existing structure is to be modified or redesigned
  • To assess structural adequacy when doubt arises about the compressive strength in the structure due to defective workmanship or deterioration of concrete due to fire or other causes
  • To assess structural adequacy in the case of non-conformity of the compressive strength obtained from standard cube test specimens (or when cube results are not available)

The most contentious issues normally arise when cube results are not available or when they are below specified strength.

Historically, Concrete Society Technical Report 11 (CSTR 11) was used in the UK to interpret core strength results, but it was superseded in part by BS EN 13791 and BS 6089. Following extensive research, BS 13791 was again revised in 2019 to incorporate features of BS 6089 and current thinking. At the same time, the concrete core testing standards were revised. The BS EN 12390 standards changes were primarily editorial and minor technical and did not significantly affect the test methodology. However, the changes to BS EN 12504-1 were significant. In particular, handling/storage/moisture conditions at test are clearly defined. There are no longer corrections for length/diameter ratio and reinforcement but defined rules relating to core length/diameter and reinforcement content.

BS EN 12504-1:2019 Testing concrete in structures, Part 1: Cored specimens – Taking, examining and testing in compression This includes a National Annex NA, which gives a method for visual assessment of excess voidage (formerly in BS 1881-120 and before that CSTR 11).

BS EN 13791:2019 Assessment of in-situ compressive strength in structures and precast concrete components.

Core samples tested in the laboratory are used to obtain a ‘core compressive strength’ which provides a measure of the actual strength of the concrete as it presently exists in the structure and is the value that is then used for any assessment of structural integrity.

The BS EN 12504 series also covers indirect non-destructive methods – Rebound Hammer to measure surface hardness and Ultrasonic Pulse Velocity (UPV). Guidance for establishing the relationships between test results from indirect test methods and the in-situ strength is included in BS EN 13791.

Sandberg can offer a full testing and consultancy service comprising:

  • Initial review
  • Planning a suitable test programme
  • UKAS accredited core sampling and laboratory testing
  • Full interpretation of results

Two assessments can be carried out – one for the in situ strength and the other for conformity:

  • Estimation of compressive strength for structural assessment of an existing structure – For use where there is none or very little information about the concrete used in the structure or where the supplier has declared a non-conformity and cannot provide data to support an acceptable estimated characteristic in-situ compressive strength.
  • Assessment of compressive strength class of concrete in case of doubt – For use where there is doubt over the compressive strength of recently supplied concrete resulting from identity testing or problems suspected in the execution of the works.

The two assessments use different design principles and analyses and should be treated separately as there will be significantly different outcomes depending on the method used.

An important point to remember is that the compressive strength of cores and the in situ strength will generally be less than that measured on standard test specimens taken from the same batch of concrete. This is due to a range of factors, including the degree of compaction and curing in practical site conditions and dependent on the location in the member where in-situ strength is determined.

For more information contact our in-house experts:

Julie Dell

Julie Dell

Direct Tel: 020 7565 7068
Email: julie.dell@sandberg.co.uk
Mohamad Sabra

Mohamad Sabra

Direct Tel: 020 7565 7098
Email: mohamad.sabra@sandberg.co.uk
You are here: Home / Consultancy Services / Concrete / Concrete Strength Assessment

Footer

Registered in England and Wales
Partnership No: OC304229

About | Laboratories | Site | Consultancy | People | Contact

Share on X (Twitter) Share on Facebook Share on LinkedIn Share on E-mail Share on WhatsApp

Copyright © 2023 Sandberg LLP · Privacy Policy