CEN/TR 16632:2014

Isothermal Conduction Calorimetry (ICC) for the determination of heat of hydration of cement: State of Art Report and Recommendations

1   Basic principle and key points of ICC
1.1   Basic Principle
The test method is designed to measure the heat of hydration of cement when mixed with water. The measurement takes place at essentially constant temperature, if the instrument and the measurement are well designed, therefore it is assumed to be the "isothermal heat of hydration of cement".
An isothermal heat conduction calorimeter (here called calorimeter) consists of a thermostatic heat sink upon which two heat flow sensors are placed. The sample is placed in an ampoule that is placed in an ampoule holder that is in contact with one of the heat flow sensors, and an inert reference is placed in contact with the other. The sample ampoule and the reference ampoule are thermally connected by heat flow sensors to a thermostatic heat sink. The output from the calorimeter is the difference between the outputs from the sample heat flow sensor and the reference heat flow sensor. A general scheme of a heat conduction calorimeter is given in Figure 1.
However the actual design of an individual instrument, whether commercial or home-built, may vary.
(...)
Most part of the calorimeters can measure the heat of hydration of samples mixed outside from the instrument therefore the heat produced during the mixing is not measured. It is not easy to solve this problem designing a calorimeter provided with an internally mixing device having the proper efficacy.
1.2   Key points of ICC
When performing ICC measurements on cement samples some key points have to be considered and correctly managed:
-   Constant value of the temperature of the thermostat;
-   Stability of the temperature of the thermostat all over the test duration;
-   Control of the maximum difference between sample temperature and thermostat temperature (isothermal conditions);
-   The baseline of the instrument (measured with an inert sample of similar thermal properties of test sample) should be both repeatable and stable;
-   Calibration of the calorimeter. The method currently used is based on the joule effect produced by a resistor feed with an electrical current; no standard material for the calibration is available for the time being;
-   Check that the ampoule is vapour tight enough (so that endothermic thermal powers of evaporation do not influence the measurements).

Bestimmung der Hydratationswärme von Zement durch isotherme Wärmeflusskalorimetrie: Stand der Technik und Empfehlungen

1   Grundprinzip und Eckpunkte der isothermen Wärmeflusskalorimetrie
1.1   Grundprinzip
Das Prüfverfahren wurde entwickelt, um die Hydratationswärme von Zement zu ermitteln. Die Messung findet bei weitgehend konstanter Temperatur statt, sofern die Messapparatur entsprechend dafür ausgelegt ist. Somit wird vorausgesetzt, dass es sich um eine „isotherme Bestimmung der Hydratationswärme von Zement“ handelt.
Ein isothermes Wärmeflusskalorimeter (im folgenden Kalorimeter genannt) besteht aus einer thermo¬statischen Wärmesenke, auf der zwei Wärmeflusssensoren angebracht sind. Die zu prüfende Probe (Prüfprobe) wird in eine Ampulle eingebracht, die durch eine Halterung mit einem der Wärmeflusssensoren in Kontakt steht. Eine inerte Referenzprobe wird in Kontakt mit dem anderen Wärmeflusssensor platziert. Die Probenampulle und die Referenzampulle sind durch die Wärmeflusssensoren thermisch mit einer thermostatischen Wärmesenke verbunden. Der Messwert des Kalorimeters ergibt sich aus der Differenz der Werte, die die Wärmeflusssensoren der Probe und der Referenz messen. Bild 1 zeigt ein allgemeines Schema eines Wärmeflusskalorimeters.
Die tatsächliche Gestaltungsweise einer Messapparatur, ob aus dem Handel oder dem Eigenbau, kann jedoch davon abweichen.

Določanje toplote hidratacije cementa z izotermno kondukcijsko kalorimetrijo (ICC): stanje tehnike in priporočila

Standard CEN/TR 16632 je zasnovan za določanje toplote hidratacije cementa pri mešanju z vodo. Merjenje poteka pri konstantni temperaturi, če sta instrument in merjenje dobro zasnovana, zato se predvideva, da gre za »izotermno toploto hidratacijo cementa«.

General Information

• Status: Published
• Publication Date: 17-Jun-2014
• ICS: 91.100.10 - Cement. Gypsum. Lime. Mortar
• Technical Committee: CEN/TC 51 - Cement and building limes
• Drafting Committee: CEN/TC 51/WG 12 - Special performance criteria
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 18-Jun-2014
• Due Date: 20-Jan-2014
• Completion Date: 18-Jun-2014
• Ref Project: SIST-TP CEN/TR 16632:2014 - Isothermal Conduction Calorimetry (ICC) for the determination of heat of hydration of cement: State of Art Report and Recommendations

Overview

CEN/TR 16632:2014 - "Isothermal Conduction Calorimetry (ICC) for the determination of heat of hydration of cement: State of Art Report and Recommendations" - is a CEN technical report that reviews the principles, instrumentation and best-practice recommendations for using isothermal conduction calorimetry (ICC) to measure the heat of hydration of cement. The report combines a state‑of‑the‑art survey of available conduction calorimeters and inter‑laboratory data with practical recommendations aimed at improving reproducibility across laboratories. Key outcomes include unified guidance on apparatus performance, calibration practice and test procedures.

Key Topics

• Basic principle: ICC measures the heat released when cement is mixed with water under essentially constant temperature. A thermostatic heat sink supports two heat‑flow sensors - one for the sample and one for an inert reference - and the calorimeter output is the differential heat flow.
• Instrument design: Describes general calorimeter layout (thermostat, heat‑flow sensors, ampoules) and notes that commercial or custom designs may vary.
• Calibration: Current calibration commonly uses the Joule effect (controlled electrical heating via a resistor). No universal standard calibration material is available; calibration coefficient and time constant determination are discussed.
• Baseline and stability: Emphasizes repeatable, stable baseline measurements using an inert reference of similar thermal properties and control of baseline drift and noise.
• Isothermal control: Requires constant thermostat temperature, long‑term stability, and tight control of maximum temperature difference between sample and thermostat.
• Sample handling limitations: Most calorimeters measure specimens mixed externally, so heat generated during mixing is typically not recorded. Ampoule vapor‑tightness must be ensured to prevent evaporation artifacts.
• Performance data: Summarizes inter‑laboratory findings indicating ICC often gives better within‑lab repeatability (~5–6 J/g) and comparable or improved reproducibility (≈10–20 J/g) versus solution calorimetry (EN 196‑8).

Applications and Users

• Laboratories measuring heat of hydration of cements, including research, quality control and product development teams.
• Cement manufacturers, testing laboratories and academic researchers assessing hydration kinetics, early‑age heat evolution, admixture effects, and new cement formulations.
• Instrument manufacturers and calibration laboratories seeking guidance on performance requirements, calibration procedures and test comparability.
• Standards committees and regulatory bodies aligning test methods for cement thermal characterization.

Related Standards

• EN 196‑8 (solution calorimetry) - referenced for comparison of methods and precision.
• EN 196‑9 (semi‑adiabatic method) - discussed as another comparative approach in hydration heat testing.

CEN/TR 16632:2014 is a practical reference for implementing reliable isothermal conduction calorimetry testing workflows and improving inter‑laboratory comparability for cement hydration heat measurements.

Standards Content (Sample)

SLOVENSKI STANDARD
01-september-2014
'RORþDQMHWRSORWHKLGUDWDFLMHFHPHQWD]L]RWHUPQRNRQGXNFLMVNRNDORULPHWULMR
,&&VWDQMHWHKQLNHLQSULSRURþLOD
Isothermal Conduction Calorimetry (ICC) for the determination of heat of hydration of
cement: State of Art Report and Recommendations
Bestimmung der Hydratationswärme von Zement durch isotherme
Wärmeflusskalorimetrie: Stand der Technik und Empfehlungen
Ta slovenski standard je istoveten z: CEN/TR 16632:2014
ICS:
91.100.10 Cement. Mavec. Apno. Malta Cement. Gypsum. Lime.
Mortar
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL REPORT
CEN/TR 16632
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
June 2014
ICS 91.100.10
English Version
Isothermal Conduction Calorimetry (ICC) for the determination of
heat of hydration of cement: State of Art Report and
Recommendations
Bestimmung der Hydratationswärme von Zement durch
isotherme Wärmeflusskalorimetrie: Stand der Technik und
Empfehlungen
This Technical Report was approved by CEN on 26 November 2013. It has been drawn up by the Technical Committee CEN/TC 51.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2014 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 16632:2014 E
worldwide for CEN national Members.

Contents Page
Foreword .4
Introduction .5
1 Basic principle and key points of ICC .6
1.1 Basic Principle .6
1.2 Key points of ICC .7
2 Normative references .7
3 Technical data sheets of available calorimeters .7
4 Experimental data .8
5 Calibration .9
5.1 Calibration of isothermal heat conduction calorimeters .9
5.2 Determination of the baseline . 11
5.3 Open question . 11
6 Final remarks . 12
7 Scope and field of application . 13
8 Terms and definitions . 13
9 Apparatus . 14
9.1 General . 14
9.2 Thermostat . 15
9.3 Calorimeter technical parameters . 15
10 Calibration . 16
10.1 General . 16
10.2 Steady state calibration . 17
10.2.1 General . 17
10.2.2 Calibration coefficient (ε) . 17
10.2.3 Time constant (τ). 17
10.3 Pulse calibration . 18
10.3.1 General . 18
10.3.2 Time constant (τ). 19
10.4 Determination of the calorimeter parameters . 19
10.5 Improvement of common calibration procedure . 19
11 Sample . 19
11.1 General . 19
11.2 Test sample . 19
11.3 Reference sample . 20
12 Testing procedure. 20
12.1 General . 20
12.2 Method A - “External mixing” . 20
12.3 Method B - “Internal mixing” . 21
12.4 Measurement . 21
12.5 Calculations . 21
12.6 Result . 22
Annex A (informative) Glossary . 23
A.1 Ampoule . 23
A.2 Ampoule holder . 23
A.3 Baseline . 23
A.4 Calibration coefficient . 23
A.5 Isothermal. 23
A.6 Reference . 23
A.7 Thermal power . 23
Bibliography . 24

Foreword
This document (CEN/TR 16632:2014) has been prepared by Technical Committee CEN/TC 51 “Cement and
building limes”, the secretariat of which is held by NBN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
It is divided into two sections. The first section is a State of Art Report of the test method based on the
collection of the technical data sheets of the calorimeters adopted in the European cement laboratories and
also on the collection of the results of several experimental activities. The second section is made of
recommendations for the measurement of heat of hydration of cement by ICC. Based on the State of Art
Report, this section provides some basic elements of the test procedure with the aim to become a first guide
for the laboratories that are currently using ICC or for those laboratories that would start to adopt this method.
By using the information and adopting the procedures given in the document it will be possible to compare in a
more reliable way both the performances of the different calorimeters and the test results.
Annex A (informative) provides a Glossary.
Introduction
In 2007, CEN/TC 51, through resolution 495, agreed that WG 12/TG 3 investigates the suitability for
standardization of the test method based on isothermal conduction calorimetry (ICC). The Task Group 3 has
been reactivated and held its first meeting in 2008.
Since no national standard on ICC for the determination of heat of hydration of cement was available, TG 3
started its activity on the item by gathering the available information on recommendations or published
scientific papers, inter-laboratory experimental exercises. The available information, collected into a State of
Art report, has been analysed and discussed in order to identify those aspects of the test method that can be
already considered consolidated as well as those elements that still need further development.
The second step of the activity was the redaction of a Recommendations document including a testing
procedure for the measuring of heat of hydration of cement by ICC. The circulation of this document in the
laboratory actually involved in ICC testing, would lead to the application of uniform general principles and,
therefore, to a better data reproducibility.
In this CEN/TR, the State of Art document and the Recommendations document are reviewed into a single
document divided into two parts:
a) State of art report on the application of ICC for the determination of heat of hydration of cement;
b) Recommendations for the measurement of Heat of Hydration of Cement by Isothermal Conduction
Calorimetry.
PART A
State of art report on the application of ICC for the
determination of heat of hydration of cement
1 Basic principle and key points of ICC
1.1 Basic Principle
The test method is designed to measure the heat of hydration of cement when mixed with water. The
measurement takes place at essentially constant temperature, if the instrument and the measurement are well
designed, therefore it is assumed to be the “isothermal heat of hydration of cement”.
An isothermal heat conduction calorimeter (here called calorimeter) consists of a thermostatic heat sink upon
which two heat flow sensors are placed. The sample is placed in an ampoule that is placed in an ampoule
holder that is in contact with one of the heat flow sensors, and an inert reference is placed in contact with the
other. The sample ampoule and the reference ampoule are thermally connected by heat flow sensors to a
thermostatic heat sink. The output from the calorimeter is the difference between the outputs from the sample
heat flow sensor and the reference heat flow sensor. A general scheme of a heat conduction calorimeter is
given in Figure 1.
However the actual design of an individual instrument, whether commercial or home-built, may vary.

Key
1 thermostat
2 heat flow sensors
3 heat sunk
4 sample
5 reference
Figure 1 — A schematic drawing of a heat conduction calorimeter
Most part of the calorimeters can measure the heat of hydration of samples mixed outside from the
instrument, therefore the heat produced during the mixing is not measured. It is not easy to solve this problem
designing a calorimeter provided with an internally mixing device having the proper efficacy.
1.2 Key points of ICC
When performing ICC measurements on cement samples some key points have to be considered and
correctly managed:
— Constant value of the temperature of the thermostat;
— Stability of the temperature of the thermostat all over the test duration;
— Control of the maximum difference between sample temperature and thermostat temperature (isothermal
conditions);
— The baseline of the instrument (measured with an inert sample of similar thermal properties of test
sample) should be both repeatable and stable;
— Calibration of the calorimeter. The method currently used is based on the joule effect produced by a
resistor feed with an electrical current; no standard material for the calibration is available for the time
being;
— Check that the ampoule is vapour tight enough (so that endothermic thermal powers of evaporation do
not influence the measurements).
2 Normative references
Not applicable.
3 Technical data sheets of available calorimeters
One of the expected results from this CEN/TR is a general and comprehensive overview of the technical data
sheets of the currently existing conduction calorimeters because the quality of the test results of ICC is
strongly influenced by the characteristics of the apparatus, where the word “characteristics” has to be intended
in the sense of “fit for use” when measuring heat of hydration of cement.
A number of instruments that have been used for calorimetric measurements on cement have been
considered and their technical specifications have been compared. The list of the instruments that have been
considered is given in Table 1.
Table 1 — List of Instruments considered for the analysis of technical data sheets
Instrument Manufacturer
Thermal Activity Monitor TAM AIR Thermometric, Sweden
Thermal Activity Monitor TAM 2277 Thermometric, Sweden
Thermal Activity Monitor TAM III TA instruments
ToniCAL 7338 Toni Technik
MS 80 Calorimeter Setaram
C 80 Calorimeter Setaram
Calorimeter Italcementi Italcementi
Basically the relevant specifications of each instrument are useful to describe two main aspects:
— sensitivity and related uncertainty;
— stability (Baseline drift, Baseline noise).
The final result of this activity should be the identification and definition of performance requirements for ICC
suitable for the determination of heat of hydration of cements, but with reference to this expected result, the
collected data does not allow to reach this objective.
Unfortunately the data provided by the technical sheets are not expressed in a standardised way, so any
comparison of the characteristics of the calorimeter has to be preceded by a unification of the definitions and
expression of the main instrumental parameters.
TG 3 has already defined a program of the activity suitable to fill the gap related to:
— unified procedures for the determination of fundamental technical specifications;
— technical specifications for performances related to Sensitivity and Stability.
4 Experimental data
Several inter-laboratories round-robin exercises have been collected:
— International inter-laboratory trial 2003 by Lund University;
— Swiss inter-laboratory trials 2005/2006 (Cemsuisse);
— German inter-laboratory trials 2006/2007 (VDZ);
— NL reference test on cement;
— Experiences from US (PCA);
— Validation of conduction calorimetry (VDZ).
All these tests had two main objectives:
— determination of precision data of ICC method;
— comparison of ICC test results with the corresponding results of the reference methods: solution method
(EN 196-8) and semi-adiabatic method (EN 196-9).
In practice, only few data are available for semi-adiabatic method, therefore no comparison can be made for
semi-adiabatic method and ICC, while for the solution method there is a lacking of data for Type II, Type IV
and Type V cements.
Focusing only on the comparison of ICC with solution method, the following considerations can be made:
1)
1) repeatability (within-laboratory precision) is better than for solution calorimetry ((5 ÷ 6) J/g for ICC vs. 8
J/g for EN 196-8);
2) reproducibility (inter-laboratory precision) is somewhat better than for solution calorimetry (ranges from 10
to 20 J/g1 for ICC vs. 18 J/g for EN 196-8);
3) comparative testing data with solution method (EN 196-8) are quite limited and even more limited with
semi-adiabatic method (EN 196-9);

1) Determined for duration of test ranging from 3 d to 7 d.
4) solution method data at 7d and ICC data at 7d do not match very well;
5) some systematic deviation seems to exist between the data of two methods: values from ICC are higher
than those from Solution Method;
6) for the time being no sound correlation has been found between ICC data and solution method data;
characteristics of instruments seem to play a role;
7) some doubts still exist about the capability of the method to measure with the needed accuracy the heat
of hydration in the time interval 3 d - 7 d when the heat flow developed by the cement paste is very low.
5 Calibration
5.1 Calibration of isothermal heat conduction calorimeters
Calibration is in general a fundamental activity of a test method. The ICC of cement does not represent an
exception to this rule.
This test method is completely automated and, therefore, the precision intended as repeatability and
reproducibility (or extended uncertainty) is determined by:
1) design and construction of the calorimeter;
2) proper use and maintenance;
3) calibration procedure.
Points 1) and 2) depend on manufacturer activity and training of users, while point 3) should be considered at
a more general level.
Currently the calibration is made by producing a known electrical thermal power close to where the sample will
be placed in the calorimeter and measuring the electrical signal by the data acquisition equipment. Heaters
can be placed in sample ampoules with inert contents or fixed in the ampoule holders.

Key
1 calibration heater 1
2 calibration heater 2
Figure 2 — A schematic drawing of the set-up for the simultaneous calibration of two calorimeters
There are two ways of calibration: steady-state calibration that is convenient for manual calibration and pulse
calibration that is done on automated systems. These two ways of calibrating give the same result.
before the calibration. The current to the
Steady-state calibration is made by first measuring the baseline U
heater is then turned on until a new stable output value is obtained. When the output is constant, its value is
. The current is then switched off and the signal returns back to the baseline. The baseline U after
noted as U
C 2
the calibration is then measured. Figure 3 shows such calibration schematically.

Key
X time [s]
Y output voltage [V]
Figure 3 — Schematic steady-state calibration
The calibration coefficient ε is calculated as the produced thermal power ( P) divided by the resulting output:
P
ε= (1)
U −+UU / 2
( )
c 12
Pulse calibrations are made by producing a pulse of heat in the calorimeter, without attaining steady-state,
and dividing the heat input by the integral of the output peak. This, in principle, will give the same value of the
calibration coefficient as the steady-state method given above. Figure 4 shows such a non-steady state
calibration schematically. As the calibration current is constant the heat is the product of the input thermal
power and the duration of the calibration (Δt):
Q IR∆t (2)
H
For the non-steady state calibration the calibration coefficient ε is calculated as the produced heat (Q) divided
by the integral of the resulting output above the baseline:
Q
ε= (3)
Udt
∫
=
Key
1 ∫Udt [V s]
X time [s]
Y output voltage [V]
Figure 4 — Schematic of pulse calibration
The calibration peaks can have different input thermal powers and different durations.
The described procedures are theoretically simple and also practically simple to apply, nevertheless some
aspects still need to be understood and clarified.
For example it seems that the calibration coefficient is depending from the intensity of the thermal power.
During the hydration process of the cement the thermal power varies in the range of mW to the tenths of mW
but usually a unique coefficient of calibration is applied in the calculation of the heat produced (see 5.3).
5.2 Determination of the baseline
Baseline noise (BN) and baseline drift (BR) are determined with reference ampoules in both the sample and
reference positions, and the suggested output recording should be at least 24 h long.
In any case there is no generally accepted procedure for the determination of the baseline and for the
expression of the two parameters BN and BR (W or W/g).
5.3 Open question
Basic assumption of the calibration procedure is that the behaviour of the thermal sensor is linear. This means
that the ratio between the thermal power and the voltage output is constant or slightly variable.
In practice this seems to be true only when considering a limited range of thermal power. On the other hand
the heat of hydration of cement has a peculiar pattern that covers a large range of thermal power: high during
the main hydration peak period and low in the following. Nevertheless this secondary hydration phase covers
a long time period so its contribution to the total heat of hydration is relevant.
2)
There is some experimental evidence of the fact that the response of sensor is not linear below a limit
threshold of thermal power. Therefore an accurate evaluation of the impact of this non-linearity of the
calorimeter sensitivity on the ICC test results is needed.
6 Final remarks
Th
...