TECHNICAL | BTS/CONCRETE
those cast with normal OPC. The mix was a C50/60 concrete with 35kg/m3
of steel fibres and monofilament polypropylene (PP) fibres for fire resistance. See Figure 3.
Fire testing to RABT-ZTV curve at CSIRO, Australia Concrete panels were placed in the furnace and subjected to the RABT-ZTV (Eureka) fire curve for hydrocarbon fires in rail tunnels. The results for the steel fibre reinforced (SFR) EFC mix containing 1.5kg/m3
of PP fibres had similar magnitudes
of surface loss resulting from the exposure to fire as the other Portland cement-based concretes. After the fire tests, several cores were taken from
different depths within the concrete panels. The residual compressive strengths were determined for the different depths within the panels. The mean compressive strength of the EFC
Above, figure 3:
EFC Segments tested for Cross River Rail Project
EFC production
EFC can be produced with existing plants, albeit they need to be clean from OPC; they simply need an activator dosing unit to be added. Otherwise, EFC can be pumped and placed in the same way as traditional concrete. Use in Australia includes Toowoomba airport pavements where 50,000m3
geopolymer concrete prior to fire testing was 55.0MPa. After fire testing, the lowest residual strength occurred at the hot face section and showed a decrease of 25.4%.
has been poured, as well
as use in wharves, multi-storey buildings, and a road bridge. In the UK, it has been used for temporary works on HS2, London Power Tunnels (LPT), and for permanent works in piling.
EFC USE IN TUNNELLING APPLICATIONS Accreditation & standards For the DIBt approval process in Germany, full scale segments with EFC were cast, and sampling and testing undertaken. Data were submitted to DIBt, which in September 2019, wrote approved the components of the geopolymer “Wagners EFC binder” to produce concrete based on DIN EN 206-1 in conjunction with DIN 1045-2 for the following exposure classes: X0; XC1 to XC4; XF1 and XF3; XA1 to XA3; and,W0 and WF. Wagners is currently working with BUI (Brameshuber
+ Uebachs Ingenieure GmbH), DIBt, and the Building Research Establishment (BRE) in the UK to obtain a European Accreditation Document that would enable the BRE to issue a similar compliance with BS EN 206-1. Accreditation is anticipated shortly. EFC complies with the requirements and recommendations of the UK PAS 8820 ‘Alkali Activated Cementitious Material’. An Australian handbook entitled ‘Handbook for
the design of geopolymer and alkali activator binder concrete structures’ is scheduled for release in 2023. It has been developed by a sub-committee of the Australian Standard for Concrete Structures.
Segments for Cross River Rail Wagners won the concrete to supply segments to the Cross River Rail contract, in Brisbane, Australia, and used this as an opportunity to test EFC segments alongside
18 | July 2023
Beam Tests Three beams of the EFC mix were tested in accordance with BS EN 14651:2005, ‘Test method for metallic fibre concrete – Measuring the flexural tensile strength (limit of proportionality (LOP), residual)’. The results of the tests show that SFR EFC has similar
magnitude LOP and residual flexural tensile strengths to those of a typical C50/60 OPC-based concrete containing Dramix 4D steel fibres.
Comparative results: EFC v production concrete The comparative testing results of EFC and production concrete samples cast in May 2020 are summarised in Table 2. From the strength, beam and fire test results, it may be seen that EFC geopolymer concrete has comparable properties to those of the Portland cement- based concretes that were used to produce SFRC tunnel lining segments. The above, combined with the improved resistance to
exposure to chlorides and sulphates, give a compelling case for the use of EFC, regardless of carbon. Compared to OPC concrete, in terms of structural performance EPC is: 25MPa to 65MPa for all commercial grades; has 30% higher flexural tensile strength; low drying shrinkage – typically 350μɛ; similar modulus and Poisson’s ratio; and, high fire resistance. Also in comparison to OPC, in terms of durability it has: high acid resistance (sewer); high sulphate resistance; high chloride ingress resistance (marine), and low heat of reaction.
CO2 calculations for EFC By adopting the embodied CO2 values contained in
the EFC Carbon Footprint Declaration and the Mineral Products Association’s (MPA’s) published values, a carbon footprint table per tonne of binder material and binder content in various concrete mixtures has been developed by Wagners.
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