Title:
Measurement of Flexural Toughness of Fiber-Reinforced Concrete Using a Novel Technique—Part 1: Assessment and Calibration
Author(s):
Nemkumar Banthia and Ashish Dubey
Publication:
Materials Journal
Volume:
96
Issue:
6
Appears on pages(s):
651-656
Keywords:
concrete; fibers; tests; toughness.
DOI:
10.14359/790
Date:
11/1/1999
Abstract:
It is now widely accepted that the measured postpeak response of fiber-reinforced cement-based composites carrying low fiber volume fractions of steel or synthetic fibers is greatly affected both by the test and the machine configurations. For such composites, the postpeak load response obtained from open-loop testing machines tends to be very unreliable given the sudden release of energy in these machines at the occurrence of the peak load; only a properly run closed-loop, displacement-controlled test can capture the true postpeak response. Because most testing laboratories are equipped only with open-loop test machines, however, a new methodology that provides a valid postpeak response using such machinery should be highly valued. Recently, a new ASTM technique has been approved to obtain the postpeak response of fiber-concrete composites. In this technique, termed the residual strength test method (RSTM), a stable narrow crack is first created in the specimen by applying a flexural load in parallel with a steel plate under controlled conditions. The plate is then removed, and the specimen is tested in a routine manner in flexure to obtain the postcrack load-displacement response. In this paper, experimental results obtained from this new technique are compared with those obtained by testing identical specimens in a closed-loop machine with proper displacement control. A very good agreement between the two methods was observed. Part 2 of this paper will present comprehensive data on fiber-reinforced concrete with various volume fractions of polymeric and steel fibers obtained using the RSTM.