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This section is Under Construction, we apologize for any
inconvenience |
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The biggest economic impact maturity testing can have for a contractor is
realized when the test is routinely used to determine the soonest forms can be stripped or
post-tensioning can begin.
We find that contractors can save at least one day’s wait for each
pour. Why are contractors waiting so long to strip forms or stress PT? The answer lies in
the traditional method of testing concrete: field-cured cylinders.
Test cylinders have been used for decades as the benchmark of the
compressive strength of concrete. In fact, test cylinders remain the most widely used
barometer of concrete strength. And while test cylinders will always have a place in
constructing the world’s structures, maturity testing provides new and critical
information about the status of the concrete that is actually in the structure.
THE BATHTUB TEST
Imagine a bathtub full of hot water. If you were to scoop out a cup of the
hot water and place it on the counter beside the tub, which cools faster? The cup, of
course. If you want to know how hot the water is in the tub after one hour, you’d put
your hand in the tub, not the cup. This illustrates the difference between cylinder
testing and maturity testing, particularly for early-age strength determination.
Cylinders represent but a tiny fraction of the mass of a typical structure. They can lose
heat quickly, and even when well protected rarely do they have the same thermal history as
a larger concrete pour. They are subjected to any number of extraneous conditions not
found in the structure. And because concrete strength is proportional to the heat released
during hydration, in-place strengths are usually much higher. |
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We’ve tracked
the difference between strength gain in the structure vs. that of field-cured test
cylinders on many of the hundreds of jobs we’ve done. For post-tensioned (PT)
projects maturity testing is particularly beneficial. With PT, it is important to stress
tendons at the right time. Stressing too soon can be catastrophic, with great potential
for substantial damage to the structure and personal injury if the concrete should fail
near the PT cable heads. Stressing too late means the maximum benefit of PT is not
obtained, clearly wasting money and leading to potential design and engineering
implications. On most jobs, we found contractors needlessly waiting much longer than
necessary to safely begin stressing.
The graph below illustrates the significant time savings from using maturity testing to
properly time post-tensioning operations. 
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This section is Under Construction, we apologize for any
inconvenience |
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Con-Cure is allowing one contractor in St. Louis to strip tunnel forms
within 7 hours of end of finishing operations using immediate reshoring technique.
Con-Cure is allowing one contractor in California to speed construction of
new suspension bridge north of San Francisco by confirming in-place strength.
Very difficult working conditions at both sites make taking cylinders
virtually impossible.
Back to top
The biggest economic impact maturity testing can have for a contractor is
realized when the test is routinely used to determine the soonest forms can be stripped or
post-tensioning can begin.
We find that contractors can save at least one day’s wait for each
pour. Why are contractors waiting so long to strip forms or stress PT? The answer lies in
the traditional method of testing concrete: field-cured cylinders.
Test cylinders have been used for decades as the benchmark of the
compressive strength of concrete. In fact, test cylinders remain the most widely used
barometer of concrete strength. And while test cylinders will always have a place in
constructing the world’s structures, maturity testing provides new and critical
information about the status of the concrete that is actually in the structure.
THE BATHTUB TEST
Imagine a bathtub full of hot water. If you were to scoop out a cup of the
hot water and place it on the counter beside the tub, which cools faster? The cup, of
course. If you want to know how hot the water is in the tub after one hour, you’d put
your hand in the tub, not the cup. This illustrates the difference between cylinder
testing and maturity testing, particularly for early-age strength determination.
Cylinders represent but a tiny fraction of the mass of a typical structure. They can lose
heat quickly, and even when well protected rarely do they have the same thermal history as
a larger concrete pour. They are subjected to any number of extraneous conditions not
found in the structure. And because concrete strength is proportional to the heat released
during hydration, in-place strengths are usually much higher. |
|
We’ve tracked
the difference between strength gain in the structure vs. that of field-cured test
cylinders on many of the hundreds of jobs we’ve done. For post-tensioned (PT)
projects maturity testing is particularly beneficial. With PT, it is important to stress
tendons at the right time. Stressing too soon can be catastrophic, with great potential
for substantial damage to the structure and personal injury if the concrete should fail
near the PT cable heads. Stressing too late means the maximum benefit of PT is not
obtained, clearly wasting money and leading to potential design and engineering
implications. On most jobs, we found contractors needlessly waiting much longer than
necessary to safely begin stressing.
The graph below illustrates the significant time savings from using maturity testing to
properly time post-tensioning operations.
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Back to top
|
