Temperature Time Factor (TTF) calculations and compressive
strength results are used for estimating concrete strength gain using the
maturity method as outlined in ASTM C 1074.
To develop the data used for this type of evaluation, cylinders are cast
to be broken at certain intervals. The total curing time in either days or
hours and the average curing temperature in Celsius are recorded when cylinders
are broken. TTF is then calculated in
accordance with the ASTM C 1074 test method.
TTF numbers can either be calculated in degree hours or degree days
depending on the time interval used. We calculate
TTF in Degree hours to ensure compatibility with most of the hardware typically
used in the field.
The Datum temperature used in the TTF calculations can be
affected by several components in the concrete mix and may be an important
consideration when using this method for evaluating concrete maturity. If a datum temperature for the mix is not
entered, it is assumed to be 0 degrees Celsius.
Calculating the average temperature for the total cure time at the given
time interval may be a lengthy process unless the curing temperature remains
constant from the time the cylinders are cast.
Using temperature probes and hardware that will automatically calculate
a TTF value may greatly facilitate this process and can be quickly entered along
with concrete cylinder break information.
Please refer to ASTM C 1074 for more details and on how to determine the
Datum temperature appropriate for your concrete mix.
TTF data are especially useful for estimating the strength
of concrete in place. Ambient
temperatures on the job site often fluctuate greatly and will impact how
quickly concrete gains strength over time. By inserting temperature probes or
data loggers into the concrete placement, TTF values can be generated and then
evaluated within our software to estimate the actual strength of the concrete
in real time. For concrete pours such as
post tension decks or paving slabs, this often provides the assurance needed
that critical minimum strength values are met before placing the concrete in
service. Monitoring concrete in this way
also provides a means of measuring how effective curing methods are for the
concrete placement. The effects of
various concrete components on strength maturity also can be evaluated using
this method.
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| Figure 1. |
In Stonemont Software, TTF Values are either calculated or
entered on the concrete cylinder entry form along with the corresponding
compressive strength information as shown in Figure 1. Once this information is entered, it is automatically
associated with the final mix design for analysis. Up to five of the most recent maturity tests
are available for evaluations. Once a
maturity test is selected the results are
plotted on a graph as shown in Figure 2. For a given compressive strength value, a TTF value
can be interpolated from the data. For a
given TTF value, a compressive strength value can be interpolated from the
data. There are several options for
selecting the best-fit Line type used in the evaluation. The results of the
evaluation can then be exported as an image file. In the example shown in Figure 2, 3000 psi was used to
extrapolate the minimum estimated TTF value needed to reach that compressive
strength. The best-fit line for the data
used was point to point.
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| Figure 2. |
Since maturity testing is managed with the mix design in our
system, the user no longer needs to search for documentation elsewhere. Several evaluations can quickly be compared
to determine if any changes have been made that affect the maturity
results. No extra software is needed for
data entry or evaluations leaving the user free to choose the hardware they
want to use in the field for maturity monitoring. Managing maturity testing is a straight
forward and intuitive process in Stonemont Software V7.
For more information please contact Stonemont Solutions, Inc.
