1. Rationale
The basis for the proposed change in the specification for data acquisition for ASTM C1609/C1609M is a paper recently published by Bernard, E.S. & Coleman, R. (Effect of Data Acquisition Rate on Apparent Performance of Fiber Reinforced Concrete Beams and Panels, JAI, Vol. 8, No. 7, 2011) which highlighted the inadequacy of the current specification for data acquisition in this standard. This work indicated that the current specification results in too few data points representing a continuous record after L/900 central deflection is reached, thereby introducing unnecessary errors. Further consideration of the minimum number of points required to record the pre-cracked region of the curve has indicated that a higher rate of data acquisition is needed to reduce the error in the Modulus of Rupture to less than 2%. At present the rate of data acquisition is set at fixed rates of 2.5 Hz declining to 1.0 Hz beyond L/900. The initial rate of 2.5 Hz is inadequate to record sufficient points in the pre-cracked region of the curve thereby leading to unnecessary errors in the Modulus of Rupture, and the rate of 1 Hz after L/900 is inadequate in the latter part of the curve. The inadequacies in data acquisition caused by the present specification in Section 6.3 can easily be reduced by increasing the minimum required rate of logging to 5 Hz up to L/900 reducing to 2 Hz in the remainder of the test so that more data points are used to represent the load-deflection history of the specimen. Higher rates of data acquisition can be used if desired. A copy of the paper listed above can be obtained from ASTM assistant Lindsey Limone at LLimone@astm.org.
Keywords
fiber-reinforced concrete; first-peak strength; flexural toughness; peak strength; residual load; residual strength; Beam test; Concrete; Concrete (fiber-reinforced); Flexural testing ;
Citing ASTM Standards
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