MICROHARDNESS TESTING OF FIBER-REINFORCED CEMENT PASTE

Microhardness testing of polyolefin fiber-reinforced Type III cement paste was performed. Type III cement with two water-to-cement ratios (w/c)--0.38 and 0.46--was tested. For 0.38 w/c cement aged for 7 days, the mean Vickers microhardness found with a 0.981 N load was 620 MPa. For 0.46 w/c cement, the mean Vickers hardness with a 100 gf load was determined to be 435 MPa. The Vickers microhardness data obtained at both w/c's were not normally distributed, but were, instead, distributed according to a lognormal distribution. The data at each w/c, however, displayed the same mean and variance at 95% confidence, as determined by the Kruskal-Wallis test. The indentation size effect was quantified, and the exponent n was found to be 2.24; while the load necessary to give a 2 micrometer indentation diagonal KL was 0.062 N. The minimum edge-to-edge distance between indentations at which the indentations did not affect each other was measured and found to be less than 12.5 micrometers, which was the smallest distance that could be measured with the microhardness tester utilized. Also, the Young's modulus was estimated from Knoop microhardness tests and was found to be approximately 11 GPa for w/c = 0.38, and 18 GPA for w/c = 0.46, although there was no significant difference between the two values at 95% confidence. The second part of the experimental work consisted of microhardness testing in the interfacial transition zone (ITZ) of polyolefin fiber-reinforced Type III cement paste. The Knoop microhardness of the ITZ was measured using 0.245 N load. The mean Knoop microhardness (HK25) of the bulk paste was found to be 542 MPa. Within the ITZ, a statistically less hard region was found to exist approximately 40-65 micrometers from the polyolefin fiber surface. The mean HK25 of this region was 393 MPa. The region less than 40 micrometers from the surface could not be investigated because of the indenter head impinging on the fiber.

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  • Supplemental Notes:
    • This work was supported by the National Science Foundation under Grant No. CMS-9453467.
  • Corporate Authors:

    American Concrete Institute (ACI)

    38800 Country Club Drive
    Farmington Hills, MI  United States  48331
  • Authors:
    • Cross, W M
    • Sabnis, K H
    • Kjerengtroen, L
    • Kellar, J J
  • Publication Date: 2000-3

Language

  • English

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Filing Info

  • Accession Number: 00792306
  • Record Type: Publication
  • Contract Numbers: 95-C-001, NSF/GER-9023496-02, CMS-9453467
  • Files: TRIS
  • Created Date: May 10 2000 12:00AM