Impact Products Digital Concrete Test Hammer CN652 - Manual (Page 22)

Standard Conversion Curve for Concrete Test Hammer Model LD
has already been corrected in relati ac
version
rve based on the average
e R
imits of Distribution
on to the imp t direction
Fig. 8.2 Model LD: Con
Mean value
cu
compressive strength of a
cylinder and the rebound valu
L
: The max. and m
alues are set so that 80
in.
% of
ll test results are included.
normal conversion curves occur
nder the following circumstances:
erform a separate series of tests for each
and
) result in a strength value lower than shown on the
r compressive strength which are lower than those scertained
gravel agglomerations which are not visible from
ntly
which has hardened under water. The
by
ever, these strengths cannot reliably be
v
a
8.3 Creating New Conversion Curve
Experience has shown that deviations from the
u
- Artificial stone products with an unusual concrete composition and small
dimensions. It is recommended to p
product in order to determine the relationship between the rebound value R
the resistance to pressure.
- Aggregates made from low strength, lightweight or cleavable stone (e.g.
pumice, brick rubble, gneiss
conversion curve.
- Gravel with a preponderance of smooth, polished surfaces and spherical shape
results in values fo
by the rebound measurements.
- A strong, dry mixed concrete (i.e. with low sand content) which has not been
worked adequately may contain
the surface. These affect the strength of the concrete without however
influencing the rebound values R.
- The concrete test hammer gives inadequate rebound values R on rece
applied, green concrete or concrete
concrete must be dried before the test.
- Very high values for compressive strength (> 70 N/mm2) can be achieved
adding pulverized fuel ash or silica. How
ascertained using the concrete test hammer.
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