BTS/CONCRETE | TECHNICAL


Table 1: Chloride penetration tests at UNSW Australia, with excellent chloride ion ingress results GP


Binder solids (kg) w/b ratio


Slump (mm) 28d Comp (MPa)


Chloride ion migration


coefficient (1012


m2 /s)


Chloride ion diffusion


coefficient (1012


m2 /s) 4.6 1.4 1.2 1.6 0.48


Cement 450


0.36 230 87.5


5.4


GP; Flyash (FA); Silica Fume (SF)


450 0.36 220 78.0


1.7


SF + Biocide 454


0.35 220 77.5


1.5 GP; FA;


Aluminate cement 450


0.42 220 74.5


0.70


Calcium


Wagners EFC®


450 0.43 140 53.0


0.84


attack is generally attributed to the reaction of sulphate ions with calcium hydroxide and calcium aluminate hydrate to form gypsum and ettringite) and chlorides in conventional concretes, there are additional advantages of durability. More than 100,000m3


of EFC has been poured in


Australia with the first permanent works structural application being the construction of the Global Change Institute building at the University of Queensland, in 2012. Figure 1 shows the CO2


emissions of a range of


concrete binders, including EFC. Alkali activated cements were developed in the


1930s and slag use increased several decades later with cement shortages. Research has increased considerably since the 1990s. Commercialisation has occurred with products no longer confined to laboratories. EFC is currently available in the UK with strength


grades up to C60/75. Initial trials and applications were conducted in early 2020 in London for temporary piling works. Further applications have been in temporary works for a number of projects, including the southern section of HS2 high-speed rail project where the Skanska/Costain/Strabag JV has installed approximately 3000m3


of C32/40 EFC in the temporary piling mat


works at the Euston approaches section. The first permanent works installation of EFC in


the UK occurred on 30 November 2020, at the new Tesco petrol station at Canada Water, in London, where C32/40 EFC was installed in permanent piles by Keltbray Piling. Extensive testing of the EFC prior to the commencement of the project enabled the design engineers to be satisfied with the structural and durability performance of the material.


Compliance Prescriptive specifications limit the potential use of AACM. Performance-based specifications are needed to allow their use through testing, which is allowed by EC2. Extensive studies have been undertaken by approved


test houses, independent experts and universities (including fire and durability testing), including: RMIT in Melbourne, Australia; Aachen University, in Germany; UNSW Australia; Aecom Australia; UQ Water Management Centre, in Australia; and, Dr James Aldred.


7 6 5 4 3 2 1


0 -1 Days


This testing and research has led to successful


Deutsches Institut fur Bautechnik (DIBt) certification in Germany, which is aligned to EN:206 and can act as a foundation for wider European accreditation. Furthermore, this complies with the recently released Australian Standard TS199 2023 ‘Design of Geopolymer Concrete Structures’.


Properties and testing Biogenic corrosion was tested at the University of Queensland through 12 months of exposure to a sewage environment and EFC performed significantly better than other concretes. Chloride penetration tests showed similarly


impressive results at UNSW Australia, with excellent chloride ion ingress results as shown in Table 1: As mentioned, the mechanism for sulphate attack on


concrete. This doesn’t occur with EFC (due to the lack of calcium) as is shown in Figure 2. The different chemistry of EFC also provides a


different temperature profile; EFC exhibits under half the temperature rise of comparable 65% slag mixes, which in turn can aid reduction of early age thermal cracking.


Below, figure 2:


Reaction of sulphate ions with calcium hydroxide and calcium aluminates in different concrete mixes (EFC, PFA)


500 Na EFC


5000 Na EFC 50000 Na EFC 500 Na PFA 5000 Na PFA 50000 Na PFA


July 2023 | 17


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