Modified ACI Drop-Weight Impact Test for Concrete

This article reports on a study of a modified ACI drop-weight impact test for concrete. The industry standard, the ACI Committee 544’s repeated drop-weight impact test, is often criticized for large variations within the results. The authors of this paper identifed the sources of these large variations and developed modifications to the ACI test. The proposed modifications were evaluated by conducting impact resistance tests on 40 specimens from two batches of polypropylene fiber-reinforced concrete (PPFRC). The impact resistance of PPFRC specimens tested with the current ACI test exhibited large coefficients of variation (COV) of 58.6% and 50.2% for the first-crack and the ultimate impact resistance, respectively. The corresponding COV for PPFRC specimens tested according to the modified technique were 39.4% and 35.2%, indicating that the reliability of the results was significantly improved. Using the current ACI test, the minimum number of replications needed per each concrete mixture to obtain an error below 10% was 41, compared to 20 specimens for the modified test. The authors conclude that although such a large number of specimens is still not good enough for practical and economical reasons, the reduction presents a good step forward on the development of a standard impact test.


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  • Accession Number: 01002943
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 9 2005 7:08AM