NDT James Instruments Cementometer L User manual

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T-C-20
Cementometer™ L
Operating Instructions
Original Instructions: Revision: May 2019

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Table of Contents
T-C-20 General Overview .....................................................3
Fine Aggregate.............................................................5
Coarse Aggregate ........................................................7
Mixing your Sample .............................................................8
Menu Items .......................................................................11
Unit Operation.............................................................11
Type I..........................................................................11
Type III........................................................................11
Direct… ......................................................................12
User Program .............................................................12
Change User Program ................................................12
Upload Data................................................................13
Change Date...............................................................13
PC Software Functions.………………………………………..15
Least Squares Analysis...……………………………………...17
Warranty Information ..........................................................18
Repair Policy ......................................................................22

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T-C-20 Cementometer™ L Instruction Manual
GENERAL OVERVIEW
The James®Instruments Cementometer™- L is a revolutionary
digital meter for low Water/Cement (or w/c) ration concrete. It allows
the user to measure the complex dielectric constant of the mixture of
water and material under investigation. As it has been shown in
many studies that the complex dielectric constant is directly related
to the amount of water present, the built-in microprocessor can
convert this value directly into the percentage of moisture.
The Cementometer™ L consists of a 100 MHZ probe and logging
unit that can process the data from the unit and can store it for later
retrieval.
The Cementometer™ L probe has 5 stainless steel prongs to insert
in the material to get a moisture content reading. Each prong is 3.5
inches in length with a diameter of 0.125 inches. They should be
inserted so that the entire prong is covered by the material under
investigation. The volume tested is that enclosed by the four outer
prongs of the sensor unit. The robust prongs have been designed to
be inserted into various materials. Most commonly used materials
are sand, aggregate, and gravel.
Proper cleaning and maintenance of probes is required for
accurate readings. Any contaminating material attached to the
probes can influence subsequent readings.
Stainless steel probes should be cleaned before and after testing
has been completed. The Cementometer™ L prongs cover a surface
depth of about 5 inches. Keep in mind that moisture always flows to
the bottom of these materials. The more moisture suspected in the
material, the deeper the depth you want your testing to be.
The unit comes from the factory with a variety of modes to assist
the user in determining the water/cement ratio. The unit comes
preprogrammed to analyze mixes of both Type I and Type III
cement. There is also a mode to read the output of the sensor
directly. The Cementometer™ L can also be programmed with up to
ten different user programs. These are correlation factors that
pertain to the direct material the user is dealing with and should be

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used for the most accurate readings. There are also the capabilities
to upload the data stored in the unit to a P.C. for later analysis, as
well as a clock to help synchronize and differentiate the data.
Finally, the unit comes with our P.C. software which simplifies
uploading of data to a Windows Compatible P.C. and analyzing the
data for later programming of the unit. When required, the software
will automatically monitor the serial communication port specified by
the user. Once transmission of data from the Cementometer™ L unit
has occurred, this information will appear in the edit window in the
software. This data can then be analyzed by the built in software
of the program or with a common spread sheet. The built-in
software will take the user step by step through each record and
allow the user to enter the moisture percentage associated with each
reading. Once all the readings have an associated moisture
percentage, the data can be graphically displayed, and the optimal
correlation relationship determined. Coefficients representing this
relationship are displayed for subsequent loading into the
Cementometer™ L unit.
The Cementometer™ L is an easy and accurate way of testing
for water / cement ratio in a controlled or uncontrolled environment.
Every effort has been made in providing a user friendly robust and
accurate system for the measurement of water / cement ratios in
fresh concrete. A robust sensor which responds to water content
has been created. This feeds into the main microprocessor unit of
the Cementometer™ L allowing the user an instantaneous direct
reading of the moisture under test.

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Calibration Procedure
Preparation of Concrete Sample
Fine Aggregate (Sand)
We advise using ASTM C-128 & ASTM C-127 when preparing a
cement mix for calibration of a user mode for the Cementometer™
unit. A Saturated-Surface Dry (or SSD) condition is very important.
ASTM-C-128-15: Standard Test Method for Relative Density (Specific
Gravity) and Absorption of Fine Aggregate.
Step 1
Drying of the specimen is a very important step in this
procedure as values for absorption (SSD) may be higher for
aggregates not dried before soaking. This higher number could
lead to erroneous water/cement ratio reading when calibration
is in progress. Dry 1kg of fine aggregate in a suitable pan
at a temperature of 110 deg Celsius. Dry for 24 hours or until
sample stops losing water weight.
Step2
Remove sample from oven a let stand to cool to handling
temperature (approximately 50 deg C).
Step 3
Weigh and record the sample. Per ASTM C 128-15 8.1; which
states the following “…cover with water, either by immersion
or by the addition of at least 6% moisture to the fine
aggregate, and permit to stand for 24
± 4 hours…”.
Step 4
Remove excess water from sample but be careful not to
lose fine aggregate, now spread the sample on a flat non-
absorbent. Allow a warm breeze from a small table top fan
to flow through the sample. Stir the sample frequently to
allow homogeneous drying. This procedure should be done
until sample shows signs that it has reached SSD (step 6).

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Step 5
For proper SSD determination a commercially bought cone
should be used, ASTM C 128-15, 6.4 specs the mold as
follows.
“6.4 Mold and Tamper for surface Moisture Test - The metal
mold shall be in the form of a frustum of a cone with
dimensions as follows: 40 ± 3 mm inside diameter at the top,
90 ± 3 mm inside diameter at the bottom, and 75 ± 3 mm in
height, with the metal having a minimum thickness of 0.8 mm.
The metal tamper shall have a mass of 340 ± 15 g and a flat
circular tamping face 25 ± 3 mm in diameter.”
Step 6
ASTM C-128-15, 8.3 “Test for Surface Moisture - Hold the mold
firmly on a smooth nonabsorbent surface with the large
diameter down. Place a portion of the partially dried fine
aggregate loosely in the mold by filling it to overflowing and
heaping additional material above the top of the mold by holding
it with the cupped fingers of the hand holding the mold. Lightly
tamp the fine aggregate into the mold with 25 lights drops of the
tamper. Start each drop approximately 5 mm above the top
surface of the fine aggregate. Permit the tamper to fall freely
under gravitational attraction on each drop. Adjust the starting
height to the new surface elevation after each drop and
distribute the drops over the surface. Remove loose sand from
the base and lift the mold vertically. If surface moisture is still
present, the fine aggregate will retain the molded shape. Slight
slumping or the molded fine aggregates indicates that it has
reached a surface-dry condition.”
Step 7
SSD (Saturated–Surface Dry) the fine aggregate.
Absorption, % = [(B - A) / A] x 100
A = mass of oven dry test sample in air, g.
B = mass of surface-saturated-dry test sample in air, g.
Note: Allow your coarse aggregate to SSD for 24 hours prior to
adding to your mixture. (See below for more information.)
(EQUATION SHALL BE ADDED, SO CUSTOMER CAN
DETERMINE THEIR SSD VALUE.)

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Coarse Aggregate
The following procedure is used to determine the SSD of Coarse
Aggregate using ASTM C-127 standard. It is advised to use this
standard when preparing a cement mix for the calibration of a user
mode of the Cementometer™ L unit.
Step 1
Place the course aggregate sample in an oven safe tray
and dry the sample for 24 hr ± 4 hrs at 110 ± 5
deg C.
Step 2
Remove the coarse aggregate from the oven and let cool
to room temperature for 1 to 3 hrs for samples of 3.7 mm.
(Note: Larger size aggregates may require a longer
cooling time.) Record the aggregate weight at this point.
Step 3
After cooling, immersion of the coarse aggregates is
necessary. A sample container is required.
See ASTM C-127-15, 6.2 to 6.3 which specifies the sample
container and water tank as follows.
“6.2 Sample Container- A wire basket of 3.35 mm (No.6) or finer
mesh, or a bucket of approximately equal breath and height,
with a capacity of 4 to 7 L for 37.5 mm (1 ½ in.) nominal
maximum size aggregate or smaller, and a larger container as
needed for testing larger maximum size aggregate. The
container shall be constructed so as to prevent trapping air
when the container is submerged.”
“6.3 Water Tank - A water tight tank into which the sample
container is placed while suspended below the balance.”
The course aggregate sample should be immersed in the water
tank for 24 hr ± 4 hrs. The purpose of the 24 hr immersion is to
allow the aggregate’s pores to essentially fill.
Step 4
Remove the coarse aggregate from the sample container and
roll in a towel to dry until all visible films of water are gone.
Record the weight of the aggregate sample at this point.

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Having your aggregates at SSD when mixing is very important
and the following equation should be used to determine the
percentage of moisture required to SSD your aggregate.
Absorption, % = [(B - A) / A] x 100
A = mass of oven dry test sample in air, g.
B = mass of surface-saturated-dry test sample in air, g.
Allow your coarse aggregate to SSD (Saturated-Surface Dry)
for 24 hours ± 4 hours prior to adding to your mixture.
Mixing Your Sample
Proper mixing of your concrete sample is a very important
process for the calibration of a user mode in the
Cementometer™ unit. Your mixture should be that of 1 cubic
foot and it is suggested to start at the 0.20 W/C ratio.
Example mixture design
* Material needed for approx. 1 cubic foot of concrete:
2 cubic feet commercially available tilting mixer
59 lbs surface-saturated-dry fine aggregate
46 lbs surface-saturated-dry coarse aggregate
29 lbs cement paste
5.8 lbs of water
As stated in an earlier paragraph the material above equals a
1 cubic foot of 0.20 w/c concrete mix. The following order
should be followed to properly mix the concrete.
Step 1
Spray down inner dome of tilting mixer to moisten drum.
Step 2
Remove any excess water from the drum and start revolving the
mixer.
Step 3
Add 10 % of the water and coarse aggregate in to the
drum.

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Step 4
Add 50 % of the fine aggregate and cement into the drum.
Step 5
Add 60 % of the coarse aggregate and the remaining water
until approximately 1/4 to 1/3 of the water is remaining in the
reservoir being used to contain water.
Step 6
Add the remaining fine aggregate and cement to the drum
followed by the remaining coarse aggregate and water.
Step 7
Let sample mix properly until a proper paste has been
achieved.
Again, this is a 0.20 w/c ratio mix. Remove enough the
fresh concrete from mixer and place in a nonconductive
bucket (1 gallon or more, 4 liters or more) for testing with
the Cementometer™.
Using up or down arrows, scroll through the menu selection
until Direct mode appears on the T-C-20 display. (It is
recommended to erase all prior data saved in the T-C-20).
Take 10 readings for this w/c mixture, store each reading by
pressing enter. Then the readings can be uploaded to the
PC. The readings can be recorded manually with the
corresponding w/c ratio.
Uploading can be done by connecting the instrument to the
P.C. using the supplied USB cable.
Step 8
Once the sample has been put back into the drum, start
rotating drum.

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Step 9
For the mixture design presented in the example, add 1.45 lbs of
water to the mix, or the corresponding amount of water to increase
the w/c of your mix to 0.25 and let the drum rotate for 1 minute.
This is now 0.25 w/c ratio concrete mix, and it is ready for
testing with the Cementometer™. Repeat steps 7-9 until value
on Cementometer™ display reaches 409.5. This is the
saturation point of sensor probe.
* Materials used for research and development may vary
depending on aggregate types.
After the data has been collected, a correlation relationship
needs to be established. This is a linear relationship of the
form
w/c ratio = Gain * Direct Reading + Offset
Where:
W/C ratio – Final Value
Gain – Multiplier obtained from the Data
Direct Reading – Value obtained from the meter
Offset – additive factor from gathered data
From the data generated above a best fit line through data
can be generated. This can be accomplished either with a
spreadsheet, or with the accompanying software. When
inserting the moisture percentage with the software, the time
and date stamp field can be used to identify which tests were
associated with which moisture percentages.
The Gain and Offset parameters are the two values that need
to be programmed into the Cementometer™ to define the
User program (see Ch. User prog).
Once the analysis has been completed with the T-C-20 P.C.
Software, the Gain and Offset values will be displayed. Write
these values down for future reference; in the event they are ever
lost.
Return to the T-C-20 and enter a user program. (See T-C-20
manual “Change user program”)
Once the Gain and Offset values have been entered into the
T-C-20, the calibration has been completed.