Page 74 - FORE JAMES DETAYLI 2018

The James IQM & M-Meter System
The IQM System
Data uploaded directly to a laptop
74 NDT JAMES INSTRUMENTS INC.
emperature history is recorded by the IQM-4010 K
Thermocouple Module, which can store over eight
T thousand temperature readings. Intervals between
readings are specified by the user and can vary from one
minute to twenty-four hours. Designed with the latest in
microcomputer technology, the module is rugged enough
for the harshest construction environments.
The module is programmed with the required Equivalent
Age of the concrete under test. The red light on the
module will flash continuously once this number has been
reached. This provides a simple and effective automatic
indication that the concrete has reached the desired level
of maturity at that location.
Generally, sensors are inserted at critical points subject
to the most extreme temperatures. Using the modular IQM
Meter System, there is no limit to the number of sensors
that can be embedded in the wet concrete. The sensor
giving the lowest maturity number indicates the area
with the lowest strength, and this sensor will be the last
to signal that the desired maturity has been reached.
The economical M-IQM-4040 PC Software and cable
interface allow direct uploading of the data to a Windows
environment P.C. The data, then, can be easily imported
into any spreadsheet, word processor, or graphing
software package for further analysis. Temperature history
can also be graphically displayed with respect to time. The
IQM software will create maturity indices from the more
complex Arrhenius equation according to ASTM
procedure. Strength gain can also be calculated via
accepted methods. All of these parameters can be
graphically displayed with respect to time.
Theory
The maturity method is a technique for predicting
strength based on the temperature history of the concrete.
The extent of the cement hydration depends on how long
the concrete has cured and at what temperature. Maturity
is a measure of how far the hydration has progressed.
The equation developed by Arrhenius allows for greater
variation in cement types. It assumes a non-linear
relationship for the determination of a maturity index and
is suitable for a wide range of temperatures. The
mathematics of the Arrhenius equation is more complex
but it gives more accurate strength predictions over a
variety of cement types. The maturity index is expressed
as equivalent age in hours referred to a specific
temperature, and is a function of time, temperature and
the activation energy of the cement.
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