Loughborough University
Leicestershire, UK
LE11 3TU
+44 (0)1509 222222
Loughborough University

Centre for Innovative and Collaborative Construction Engineering

2017

Wayne Dodds

Project

Durability assessment of concrete containing recycled materials and corrosion management of reinforced concrete structures

Company

AECOM Ltd

Supervisors

Academic:
Dr Chris Goodier
Prof Simon Austin

Industrial:
Dr Christian Christodoulou
Dr Gareth Glass

Director of Research
Professor Stephen Ison

Research Period

2013 - 2017

 

Durability assessment of concrete containing recycled materials and corrosion management of reinforced concrete structures

Company Background

AECOM Ltd, is a multi-disciplined international consultancy. The bridges and structures group is part of Transportation and it has been involved in the design, repair, refurbishment and rehabilitation of a large number of structures. The team operating from the Birmingham office (UK) have been involved for over 20 years with the maintenance of the UK’s Midland Links Motorway Viaducts (MLMV), which consists of 21 kilometres of elevated motorway bridge structures around the city of Birmingham. The company has been involved with the implementation of a number of corrosion management techniques and has historically been keen to develop new technologies and applications for the industry.

Current state-of-the-art:

Chloride-induced corrosion is the major contributing factor to the deterioration of steel-reinforced concrete structures. There are three main categories which can provide effective corrosion management and control:

  1. alkalinity of the reinforcement,
  2. transport mechanism, and
  3. reinforcement.

The alkalinity of the concrete is generally regarded as the primary line of defence against corrosion. Modern design standards such as BS 8500 and BS EN 206 deal with the durability requirements for a large variety of concrete mix designs given an environmental exposure class. However, with the increasing demand to improve the carbon footprint of concrete, the use of recycled materials is ever increasing. This includes blended cements and recycled aggregates.

Currently, there is limited information on the effects of recycled aggregates and blended cements (such as those containing silica fume, ground granulated blast furnace slag, metakaolin, and fly ash) on the durability of concrete structures. The current BS EN 201 (European Standard for Concrete Specification) states:

“other by-products of industrial processes, recycled materials etc. are in current use based on local experience. Until European specifications for these materials are available, this standard will not provide rules for their use, but instead refers to national standards or provisions valid in the place of use of the concrete.”

This statement indicates that further research is urgently required in this field. This will form the main aim and research work package of the EngD programme.

Aims and Objectives:

The overarching aim of this research programme is to investigate the effect of recycled aggregates and materials on the durability of reinforced concrete elements and their subsequent corrosion management strategies.

The objectives of the research programme include:

  • To conduct an extensive critical literature review to identify the state-of-the-art on the use of recycled aggregates and materials in concrete and their effect on durability.
  • Engage with UK industry, professional bodies and major asset owners such as the Highways Agency to identify the current levels of use of recycled aggregates and materials in construction.
  • Identify anecdotal industrial practices and limitations on full-scale reinforced concrete structures where site testing may be undertaken.
  • Undertake large scale laboratory testing using a variety of concrete mix designs, with blended cements, varying water/cement ratio and variety of recycled aggregates to determine their performance characteristics with respect to corrosion activity.
  • Undertake site-testing of full-scale RC structures with the aim of addressing the limitations of the previous research, which focused on the repair and corrosion management of reinforced concrete structures.
  • Provide scientific evidence on the effect of the performance of recycled aggregates which can influence the development of European standards and UK codes of practice.

Proposed Research Design and Methods:

Prior to laboratory work, an extensive and thorough review of the available literature will be undertaken to establish previous research work and limitations of existing knowledge and testing regimes.

An extensive laboratory programme will follow the findings of the state-of-the-art-review. The Research Engineer will be required to gain experience in the design of various concrete mixes, familiarising themselves with cement replacement products and recycled aggregates, in order to develop a testing programme that will include measurements of compressive strength, water absorption, electrical resistivity and steel potentials.

It is anticipated that initially concrete specimens from varying concrete mix designs will be cast, including various residual levels of chlorides. Following a period of environmental exposure, the specimens will be broken up to be used as recycled aggregate.

Concrete specimens will be cast with a variety of concrete mix designs such as CEM I, CEM II/A, CEM II/B-V, CEM III/A and CEM III/B, varying w/c ratios and including varying levels of recycled aggregates which are contaminated with chlorides.

Both unreinforced and reinforced specimens will be cast. The former will be tested for compressive strength, surface and bulk resistivity. The latter, will be tested for reinforcement corrosion by means of potential mapping.

Expected Benefits and Outcomes:

  • Influence on the use and interpretation of European standards for the specification of concrete.
  • Development of industry construction good practice guides for the use of recycled aggregates and their effect on the durability of ordinary and blended cement concrete mixesImprovements in the overall carbon footprint of concrete.
  • Enhance the current understanding and practice of corrosion management.
  • In addition, there will be opportunities for placements with the Industrial Sponsor where the research engineer can benefit from continuous professional development and gain hands-on experience on the design, assessment, repair, refurbishment and rehabilitation of reinforced concrete structures..
  • Production of papers in high-impact journals to promote the findings of the research and demonstrate the advantages of collaborative engineering between academia and universities.
  • Continuation of an already successful relationship between Loughborough University, Centre for Innovative and Collaborative Engineering and AECOM Ltd. This has the potential for further research programmes and access to major infrastructure projects.

 

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Loughborough University
Leicestershire
LE11 3TU

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