During the past 30 years, there has been a lot of research into replacing some of the Portland Cement used in concrete with alternative components such as ‘fly ash’, ‘blastfurnace slag’, ‘silica fume’, polymers, recycled car tyres and fibres. Some of this research has been published through the ACA.
‘Fly ash’ is a by-product from burning coal at a power station and incorporating fibres into a mix is similar to the old practice of adding horse hair to wet plaster. One particular area of research is in the field of geopolymer concrete, utilising alkali-activated binding agents.
According to Andrews-Phaedonos, the enhanced characteristics of fibre reinforced polymer (FRP) concrete include increased flexural and shear capacity of beams and slabs. FRP concrete is now regularly specified by VicRoads for repair and strengthening works.
“The material is thinner, lighter, non-corrosive and easier and quicker to install,” he said. “It also has increased axial load, bending, shear and confinement capacities.”
As a result of the research into concrete additives, construction companies and engineering consultancies have access to all the latest technologies that yield a suite of proactive and reactive processes and procedures to maximise the effectiveness of reinforced and pre-stressed concrete.
“If you have all the appropriate specialists involved at the design stage it is very possible to have a design life of 100 years or more,”
said Warren Green, a Director and Corrosion Engineer at engineering consultancy, Vinsi Partners.
By incorporating the by-products of other processes into the concrete mix, it has been possible to get “green star” ratings for different types of concrete. There is the challenge of ‘thinking outside the box’ as to what might be incorporated into concrete in order to enhance sustainability and durability.
In addition to new materials being incorporated into the concrete mix, other additives have created ‘self-compacting’ and ‘self-levelling’ concrete which can save both time and money. Off-site construction of pre-stressed concrete panels, under factory conditions, permits a far greater degree of quality control.
“Advances in admixtures means that we can build almost anything out of concrete these days,”
“The Australian Standards for concrete work gives basic guidance for normal situations, but in aggressive environments such as tropical, coastal, acid-sulphate soils, etc., a structure will not necessarily achieve its design life if simply designed and constructed to comply with the Standards,”
To complement the Standards and support designing for maximum durability in specific situations, the Concrete Institute of Australia is developing a range of ‘recommended practice’ guidelines.
“VicRoads was the first State Road Authority in Australia to publish standard specifications for concrete maintenance work and has made a significant contribution to the preparation of Standards such as AS 5100 Part 8,”
As concrete infrastructure ages, corrosion prevention has to be as cost effective as practical. Owners and operators are being challenged to find better ways to maintain the integrity of their assets. Some of the factors that need to be considered include how long the asset has to remain in operation and would a shorter life extension be acceptable if maintenance has to be repeated more frequently.