Professor of civil engineering, University of Calgary, Calgary, Alberta
The variability of parameters used to define the toughness of fiber reinforced concrete under static flexural loading is examined to establish the precision statistics needed for ASTM standards dealing with toughness measurement. Included in the anlaysis of single-operator precision are first-crack strength, deflection, and toughness, the toughness index recommended by the American Concrete Institute Committee 544, and a number of other toughness indices that have been shown in a previous paper to define flexural toughness more completely. The single-operator 1S% value defined according to ASTM Standard Practice for Preparing Precision Statements for Test Methods for Construction Materials (C 670) is used as the measure of precision throughout, the bulk of the data being obtained from testing of 300- by 100- by 100-mm (12- by 4- by 4-in.) steel fiber reinforced beams under third-point loading. However, the effects of beam size, shape, span, and mode of loading on both the actual values of the toughness indices and their variability are also discussed. Single-operator levels of precision achievable in flexural toughness tests by an experienced operator using good equipment are summarized to provide input to precision statements for a future ASTM standard dealing with the measurement of flexural toughness under static loading.
Paper ID: CCA10229J