TM 5-809-3/NAVFAC DM-2.9/AFM 88-3, Chap. 3
(a) Can establish the state of
the voltage change is proportional to the amount of
steel and the distance from the steel to the probe.
compressive stress, in-situ, with reasonable
The application of the test is done by cover meters
accuracy.
(b) Inexpensive materials and equipment.
used to locate the presence of vertical and
(c) Uncomplicated to use.
horizontal reinforcement, joint reinforcement, and
(d) ASTM standards currently being
metal ties or connectors. The equipment is compact
and portable, allowing the operator to quickly map
developed.
(2) Disadvantages.
reinforcing locations and patterns. Cover meters
(a) Somewhat time-consuming to
will, however, locate all steel present, not just the
reinforcing bars. Some care needs to be taken not
prepare the test, when compared to other methods.
(b) Requires removal of mortar from ma-
to identify metal ties, nails, electrical conduit, etc.,
as reinforcing steel. While cover meters are able to
sonry bed joint with a saw or drill.
(c) Requires repair of the mortar joint
accurately determine the presence of reinforcing
steel, some interpretation is needed if either the size
after testing.
c. Double Flatjack in-situ deformability test.
of the reinforcement or the depth within the
(1) Advantages.
masonry is to be estimated. A weak signal can
(a) Can establish deformation properties,
indicate either a small bar close to the surface, or a
larger bar located farther from the probe. Hence, it
in-situ, with reasonable accuracy.
(b) Inexpensive materials and equipment.
may be necessary to expose the reinforcement at
(c) Uncomplicated to use.
trial locations to verify assumptions regarding size
(d) ASTM standards currently being
and location.
g. Nuclear methods. Although not related di-
developed.
(2) Disadvantages.
rectly to structural properties of materials, the
(a) Somewhat time consuming to
Neutron-Gamma technique shows great promise
for certain aspects of masonry evaluation. The
prepare the test, when compared to other methods.
(b) Requires removal of mortar from ma-
technique measures element concentrations in ma-
sonry walls, and thus gives information about
sonry bed joint with a saw or drill.
(c) Requires repair of the mortar joint
moisture content, presence of salts, and elemental
composition of the masonry materials. The tech-
after testing.
d. In-place shear test.
nique has been shown to be complementary to
(1) Advantages.
structural evaluation techniques by aiding the
(a) Can establish joint shear strength in-
interpretation of results from tests such as the
mechanical pulse technique.
situ.
(b) Equipment is inexpensive and readily
available.
10-6. Advantages and disadvantages of all NDE
(c) Uncomplicated to use.
tests.
a.
Schmidt Hammer test.
(2) Disadvantages.
(1) Advantages.
(a) Somewhat time consuming to
(a) Simple to use. No special experience
prepare.
(b) Requires removal of a masonry unit
is needed to conduct the test.
(b) Establishes uniformity of properties.
and a head joint.
(c) Equipment is inexpensive and is
(c) Restricted to masonry with low
readily available. It is relatively simple and
cement content mortar.
(d) Requires
inexpensive to conduct a large number of tests. The
unit
and
mortar
equipment for the test is readily available.
replacement after the test.
(2) Disadvantages.
(e) State of compressive stress on the
(a) Evaluates only the local point and
test unit must be estimated.
(f) Contribution of the collar joint is un-
layer (wythe) of masonry to which it is applied.
(b) No direct relationship to strength or
known.
e. Two Flatjack modified in-place shear test.
deformation properties.
(c) Unreliable for the detection of flaws.
(1) Advantages.
(d) Evaluates only the layer (wythe) of
(a) Can establish the joint shear strength
masonry to which it is applied, and is unreliable for
in-situ with reasonable accuracy.
(b) Permits control of compressive stress
detection of flaws or for investigation of inaccessi-
ble masonry wythes.
on test unit.
b. Single Flatjack in-situ stress test.
(c) Determines the Coulomb failure
(1) Advantages.
surface for the material.
10-11
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