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Relaxation test on concrete prestressing steels

 

References of test methods: ISO 15630-3
Frequency: Each 3 years
Main characteristics ρ = ΔLo/Lo after loading during 1 min, 2 min, 4 min, 8 min, 15 min, 30 min, 60 min, 2h, 4h, 6h, 24h, 48h, 96h, 120h
Other characteristics -
Caution: The number of determinations may be low for the secundary characteristics, what may make inefficient the comparison between laboratories
                   
Determination of the assigned values (“true values” for each characteristic):
By statistical computation of the totality of the results with possible selection on competence criteria (accreditation, validation by a reference body, quantity of tests performed in the year), test to detect possible collusion, merging of results not obtained in reproductibility conditions, suppression of technically unvalid results.
Type of statistical computation:
Results are numerical. For each characteristic selected by the participant, 1 result shall be provided for each sample. The statistical computation will provide an assigned value with its attached uncertainty, values of standard deviations for repeatability, for reproductibility, limits of alerts for bias and repeatability of the participant, indiviual values for uncertainty of results of participants.
Number of samples per participant: 12
Product submitted to tests: Prestressing strand for concrete
Type of samples: Strands
Approximate dimensions of samples: T12,5 - L=2200 mm
Specific preparation to be performed by the participant:  None (other than possible necessity to adapt dimensions of the test specimen to the equipment of the participant)
                   
Special notice for this ILC: This ILC, which number of potential participants is low, is a continuation of the 2015 edition, using the same samples. The 2017 results will be merged with the 2015 ones to get a greater number of results, increase the accuracy of the assigned values and make the assessment more efficient. Consequently, the number of participants is limited by the availability of samples. Moreover, a participation is of low interest for those who participated in 2015.