FPA-SC-02-0 Test Methods for Evaluating Existing Foundations 29 November 2010 Issued for Website Publication Foundation Performance Association - Structural Committee Page 25 of 76 7. Many factors could affect the results of this method such as concrete resistivity, temperature,

carbonation, oxygen content, type of steel, presence of coating, and degree of water saturation (moisture content).

8. Accuracy decreases with depth of steel reinforcement.

Relative Cost Purchase: $$ Additional Resources ASTM C876 Standard Test Method for Half-Cell Potentials of Uncoated Reinforcing Steel in Concrete 2.10 HAMMER SOUNDING

General Description and Applications

Hammer Sounding (Figure 2.10.1) consists of striking the bare surface of a concrete foundation with a hammer in order to evaluate the presence of delamination and voids. Variations of the sound from the hammer striking the concrete surface are used to qualitatively determine the possible presence of delamination and voids in concrete. Typically hammer sounding is used to delineate the boundaries of delamination and voids in a concrete slab-on-ground.

Figure 2.10.1 Hammer Sounding Test on a Concrete Slab

FPA-SC-02-0 Test Methods for Evaluating Existing Foundations 29 November 2010 Issued for Website Publication Foundation Performance Association - Structural Committee Page 26 of 76 Some Considerations

1. The equipment is easy to use and portable.

2. Different size hammers could be used to investigate different depths of delamination.

3. The test is not efficient to survey large areas.

4. The results may need to be verified with other methods.

5. The results do not provide quantitative data, so the depth of defects is unknown.

6. The test is relatively inexpensive, does not require special equipment or specific equipment training, and is non-invasive.

Relative Cost

Purchase: $ Additional Resources

NACE Publication 6G191 (withdrawn), Surface Preparation of Contaminated Concrete for Corrosion Control 2.11 IMPACT ECHO General Description The Impact-Echo (IE) method involves introducing mechanical energy, in the form of a brief impact, to the structure. When a material, such as concrete, is subject to a surface impact, stress waves propagate through the material at a finite speed. The velocity of these waves is a characteristic of the material through which the waves propagate. Typically, the higher the velocity the more dense the concrete. In isotropic solids, elastic theory indicates propagation of three types of waves: primary or P-waves, secondary or S-waves (shear waves), and surface or R-waves (Raleigh waves). The P-waves are those in which particle motion is parallel to the direction of impact. S-waves are those in which particle motion is normal to the direction of impact. The R-waves propagate along the free surface of the material and decay exponentially with depth from the surface. When a concrete surface is impacted, a transducer acoustically mounted on the same surface receives the primary or P-wave energy reflections from discontinuities within the panel. Therefore, with the knowledge of the propagation velocity through the material, the amplitude spectrum can be evaluated to determine the location of discontinuity or flaws within the concrete.