This test method covers the determination of plate deflection resulting from the application of an impulse load. The deflection is measured at the center of the top of the load plate (see Note 1).

Note 1—If the load plate is in “perfectly uniform” contact with the unbound material under the plate, then deflection of the load plate should be equal to the deflection of the surface of the unbound material under test. However, with typical unbound materials a 100% uniform contact can seldom be achieved. Accordingly, the test surface shall be as clean and smooth as possible with loose granules and protruding material removed. For gravel surfaces it is recommended that a thin layer of fine sand be placed over the test point. For fine-grained materials, this will help in obtaining a reasonably uniform contact between the load plate and the surface. See 5.1 in Test Method .

Deflections may be either correlated directly to pavement performance or used to determine in-situ material characteristics of the pavement foundation layers. Some uses of the data include quality control and quality assurance of compacted layers, and for structural evaluation of load carrying capacity (see Note 2 and Guide ).

Note 2—The volume of the pavement foundation materials affected by the applied load is a function of the magnitude of the load, plate size and rigidity, loading rate, buffer stiffness, and the stiffness and shear strength of the pavement foundation materials. Therefore, care must be taken when analyzing the results because the data obtained by the Portable Impulse Plate Load Test may be obtained under substantially different conditions than when a heavy moving wheel load passes over the pavement surface after construction is complete.

1.1 This test method applies to measuring plate deflections using a Portable Impulse Plate Load Test device. The method covers the measurement of deflection of the load plate rather than the deflection of the surface of the pavement or foundation layers (see Note 1).

1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.