4.1 The rebound hardness method provides a means for rapid classification of the hardness of rock during site characterization for engineering, design, and construction purposes, geotechnical mapping of large underground openings in rock, see Guide D4879, or reporting the physical description of rock core, see Practice D4543.
4.2 The rebound hardness number, HR, can serve in a variety of engineering applications that require characterization of rock material. These applications include, for examples, the prediction of penetration rates for tunnel boring machines, determination of rock quality for construction purposes, grouping of test specimens, and prediction of hydraulic erodibility of rock.
4.3 This test method is of limited use on very soft rock or very hard rock, which is defined as having uniaxial compressive strengths less than approximately 1 MPa or greater than 100 MPa.
4.4 The results of this test method are not intended for conversion to strength data suitable for design.
1.1 This test method covers the testing apparatus, sampling, test specimen preparation, and testing procedures for determining the rebound hardness number of rock material using a spring-driven steel hammer, referred to variously as a rebound hammer, impact test hammer, or concrete test hammer.
1.2 This test method is best suited for rock material with uniaxial compressive strengths ranging between approximately 1 and 100 MPa. Test Method D7012 provides more information on compressive strength of rock.
1.3 The portable testing apparatus may be used in the laboratory or field to provide a mea......
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