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Concrete In Australia : September 2013
42 Concrete in Australia Vol 39 No 3 CONFERENCE TECHNICAL PAPER Figure 10. Products which are similar to alkali-aggregate reaction (AAR) products. Counts1000 Si 800 O 600 400 C 200 0 Na Al Mg SCl CaCa 0 2 4 6 8 10 E (k V) Counts1000 Si 800 O 600 400 C 200 0 Na Al Mg SCl CaCa 0 2 4 6 8 10 Energy(keV) Counts1000 Si 800 600 O Ca 400 C 200 0 Al Na Cl MgS Ca 0 2 4 6 8 10 Energy(keV) amounts of sodium silicate activator in the mix, as the aggregate is non-reactive in OPC concrete. Information from published literatures shows that slag-based geopolymer concrete can undergo deleterious AAR, but low- calcium fly ash-based concrete is less prone to AAR. In conclusion, the concrete developed satisfactory compressive strength; the VPV values for the blended slag cement concrete meet the criterion of a max value of 16%, specified by VicRoads Specification Section 610, for structural concrete of VR400/40 grade; the geopolymer concrete had a VPV of 18.9% and did not meet the above requirement. Nevertheless, it is argued that the higher VPV is not due to larger interconnected pore volume, but due to additional loss of water from the gel-like materials present in the geopolymer concrete. It is likely that an excess amount of sodium silicate was used in the geopolymer formulation, which was not fully assimilated into the geopolymer binder and remained as a hydrous gel, which lost water during the drying phase of the VPV test and caused the value of the VPV to appear high. is is consistent with the large amounts of water-soluble alkali found in the geopolymer concrete. is argument is in agreement with our very low chloride penetrability results (ASTM C1202) and very low chloride diffusion coefficient, determined using the NT Build 443 test method. Another possibility is that the relatively large amount of water used in the concrete mix (Table 3) actually resulted in