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Concrete In Australia : June 2008
TECHNICAL 52 Concrete in Australia Vol 34 No 2 Table 4. Common test methods used in Australian concrete specifi cations for durability related parameters. Property Common reference Chloride diffusion or penetration AASHTO T277 Test type Presaturate sample within tolerance, measure electrical charge passed through specimen of defi ned geometry over 6 hours under 60 Vdc gradient. Assessment from tabulated criteria. ASTM C1202 As AASHTO T277. “TEL Immersion Test” Presaturate sample to constant weight, expose to simulated seawater for at least 28 days. Chloride diffusion coefficient determined by measurement and non-linear regression analysis of chloride concentration profi le using Fick’s Second Law. NT Build 443 Presaturate sample within tolerance, expose to sodium chloride solution for at least 35 days. Chloride diffusion coeffi cient determined by measurement and non-linear regression analysis of chloride concentration profile using Fick’s Second Law. NT Build 492 Presaturate sample of defi ned geometry to tolerance, pass electrical current at driving voltage and for duration as specifi ed. Locate chloride front by breaking sample and spraying with silver nitrate solution, calculate chloride penetration coeffi cient using this value and equations given. ASTM C1556 As NT Build 443. Water permeability “TEL/GHD Method” Dry samples of defi ned geometry to constant weight, apply water under pressure (usually 950kPa) to one face and measure uniaxial fl ow through sample periodically over 7 days. D’Arcy permeability at 7 days from pressurisation is the most common compliance criterion. DIN 1048.5 Apply water pressure (500kPa) to a defi ned area on one off-form face of a water cured cube or block for 72 hrs. Test perpendicular to direction of casting. Assessment by depth of water penetration. Drying temperature N/A N/A N/A Comment Now only occasionally specifi ed, generally replaced in specifications and in practice by ASTM C1202. ASTM adoption of AASHTO T277. Often referred to as the “Rapid Chloride Permeability Test” or “RCPT”. Occasional references appear, but now supplanted by NT Build 443 since the late 1990’s. Originally developed to overcome test duration and data misinterpretation issues in the earlier membrane cell method, which has not been generally used since the early 1990’s. N/A Current industry default prequalifi cation test method for determination of chloride diffusion coeffi cient. Not generally used as a production QA test due to time required to complete – about 11 weeks minimum for concrete tested at 28 days age, or 15 weeks if tested at 56 days age. N/A References have started to appear over last 12 months or so, claims to be able to derive chloride diffusion coeffi cients from an electrically accelerated test. Potentially suffers similar limitations to ASTM C1202 in relation to concrete mix design parameters. N/A 105°C ASTM adaptation of NT Build 443, currently rarely specified in Australia by reference to this standard. Currently one of the most commonly used water permeability test methods, especially in Western Australia. Nomenclature is an historical issue dating back to the 1980’s, arising from original introduction of method and availability of public testing services. N/A Very little historical use in much of Australia, but has appeared in recent specifi cations in Western Australia. A standard RTA durability criterion for shotcrete. Adopted as EN12390-8:2000 and BS EN 12390-8:2000.