ДСТУ Б EN 196-8:2015
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1 2 З? 4 5 6 7 8 1 Scope 1
2 Normative references 1
13 Principl 1
4 Materials 2
5 Apparatus 3
6 Calorimeter calibration 5
7 Determination of heat of solution .... 8
8 Heat of hydration 13
Bibliography 14 - - - -
Part 8: Heat of hydration - Solution Method 1 2 EN 197-1:2000 З? 1 SCOPE
This European Standard describes a method of determining the heat of hydration of cements by means of solution calorimetry, also known as the solution method. The heat of hydration is expressed in joules per gram of cement.
This standard is applicable to cements and hydraulic binders whatever their chemical composition.
NOTE 1 Another procedure, called the semi-adiabatic method, is described in EN 196-9. Either procedure can be used independently.
NOTE 2 It has been demonstrated that the best correlation between the two methods is obtained at seven days for the solution method (EN 196-8) compared with 41 h for the semi-adiabatic method (EN 196-9).
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies.
EN 197-1:2000, Cement - Part 1: Composition, specifications and conformity criteria for common cements
The method consists in measuring the heats of solution, in an acid mixture, of anhydrous cement and cement hydrated under standardized conditions for a predetermined period of time, e.g. seven days.
- - - 4 4.1 4.2 4.3 4.4 These standardized hydration conditions are as follows:
- water/cement ratio 0,40;
- use of neat cement paste;
- storage at constant temperature of (20,0 The heat of hydration for each period, /7,- , is obained from the difference between the heat of solution of anhydrous cement, Q a , and that of hydrated cement, Q,-.
4.1 Acid mixture
Analytical reagent quality acid mixture, obtained by adding 2,760 g of 40 % hydrofluoric acid (HF) for every 100,0 g of (2,00 WARNING - Hydrofluoric acid can cause painful skin burns which heal only with difficulty and precautions in handling this very corrosive substance should be strictly observed.
The quantity (mass or volume) of acid to be used, which is common to all tests, shall be measured to 4.2 Zinc oxide (ZnO)
Use zinc oxide of analytical quality to determine the thermal capacity of the calorimeter. Weigh 40 g to 50 g. Ignite at (950 4.3 Anhydrous cement
Store anhydrous cement, from which metallic iron has been removed with a magnet, in a sealed container to avoid absorption of water or carbon dioxide. Bring the test sample to ambient temperature and carefully homogenize it before use.
4.4 Hydrated cement
Prepare the hydrated cement test sample by vigrously mixing, either manually or mechanically, (100,0
5 5.1 (40,0 + 0,1) g of distilled or deionised water for 3 min at ambient temperature. Place the resulting paste in plastics or glass cylindrical vials (three for each hydration period to be tested) so that each vial contains 15 g to 20 g of material. Seal the vials by means of a stopper and, if necessary, with paraffin wax or similar material and store them horizontally in a thermostatic bath maintained at a temperature of (20,0 5 APPARATUS
5.1 Calorimeter
NOTE The method does not deal with the standardization of the calorimetric apparatus, or the measuring instruments. Insulated flasks with a volume of about 650 ml have proved to be suitable.
A suitable calorimeter (see Figure 1) comprises the following:
a) Dissolution vessel, consisting of: an insulated flask (e.g. Dewar flask), placed either in a heat insulated container set inside a box constructed of insulating material (e.g. wood, plastics), or immersed in a thermostatic water bath regulated to b) Thermometer, either a Beckmann thermometer with a 5 Express temperature readings with a resolution of с?) d) с?) Funnel, of acid mixture resistant plastics, through which the sample is introduced into the flask and which extends below the lower part of the stopper by 5 mm to 6 mm and is sealed during the test.
d) Stirrer, of acid mixture resistant plastics, positioned such that the blades are as close as possible to the bottom of the flask and rotated by a motor at a speed of (450
1 - 2 - З? - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 9 insulating material 10 flask support 11 ambient thermometer
12 stirrer motor
5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 6 6.1 6.2 5.2 Thermostatic bath, e.g. water bath, for storing the hydrated samples at a temperature of (20,0 5.3 Mortar or electric grinder, for crushing the hydrated samples.
5.4 Plastics or glass vials, of capacity approximately 20 ml, for storing the hydrated paste.
5.5 Sieve, of mesh size 125 pm.
5.6 Sieve, of mesh size 600 pm.
5.7 Chronometer, graduated in seconds, for timing the temperature readings.
5.8 Two platinum crucibles, of capacity approximately 20 ml, for ignition of samples.
5.9 Electric furnace, naturally ventilated, capable of operating at (950 5.10 Analytical balance, capable of weighing to an accuracy of 5.11 Balance, of capacity 2 kg, capable of weighing to an accuracy of 6 CALORIMETER CALIBRATION
6.1 Principle
Calibration of the calorimeter is carried out in order to determine its thermal capacity and thermal leakage coefficient. These characteristics are determined by dissolving the ignited zinc oxide (4.2) in the acid mixture (4.1) and measuring the temperature of the calorimeter at fixed intervals of time. The temperature of acid mixture shall be so set that after the dissolution reaction the calorimeter temperature is at least 0,5 6.2 Procedure
Measure a quantity of acid mixture (4.1) by mass or volume to
Ь?) с?) d) е?) Carry out the procedure as follows:
a) Preliminary period
Stir the acid mixture for 40 min to 50 min.
b) Pre-period
When the rate of temperature increase is constant, start the timing using the chronometer (5.7) andrecord the initial temperature, T_ 15 .
c) Sample introduction
After 15 min record the temperature, T o , and immediately add the zinc oxide sample to the acid mixture, taking not more than 1 min.
d) Dissolution period
Stir the mixture for 30 min, after which the dissolution is considered as being complete, and then record the temperature, T 30 . Record the ambient temperature, T a . If the difference between T a and e) Post-period
Record the final temperature T 45 after a further 15 min.
In order to reduce reading errors, determine temperatures T_ 15 , T 3 Q and T45 as the average of five different readings recorded at intervals of 1 min over the period 2 min before to 2 min after the prescribed time, Tj(.e.Tj_ 2 , Tj.1, T h T /+1 , T j+2 ). Determine the value of T o by extrapolation of the function of temperature against time in the period T-4 to T_ v If the extrapolated value differs from the T o reading by more than NOTE The temperature readings will therefore effectively start 17 min before the zinc oxide sample is introduced and the last reading will take place 47 min after its introduction. The total duration of the calibration is 64 min.
6.3 Calculation of calibration characteristics
6.3.1 Corrected temperature increase, AT C
Calculate the corrected temperature increase, A7" c , in Kelvins, from Equation (2):
-2(T 45 -T 30 ), (2)
where
T 30 and T 45 are the average values of five measurements made at intervals of 1 min.
6.3.2 Thermal leakage coefficient, Calculate the thermal leakage coefficient, K, in Kelvins per 15 min per Kelvin temperature difference, (K/15minK -1 ), from Equation (3):
(3) 6.3.3 C = — [1077,43 +0,364(30-7>)+0,50(T a -T f )] , (4)
Ab L J
P- T f - 1077,43 - 0,364 - 0,50 - where:
T f is the temperature at the end of the dissolution period, in degrees Celsius ( T a is the temperature (i.e. ambient temperature) of zinc oxide when introduced into the calorimeter, in degrees Celsius ( 1 077,43 is the heat of solution of zinc oxide at 30 0,364 is the temperature coefficient of the heat of solution of zinc oxide, in joules per gram per Kelvin (J ■? g -1 ■? K -1 );
0,50 is the specific heat of zinc oxide, in joules per gram per Kelvin (J • g -1 • K -1 ).
Calculate the thermal capacity, C, expressed to two decimal places, and the thermal leakage coefficient, K, expressed to four decimal places, as the mean values of five calibrations of the calorimeter. If - - - 7 7.1 7.1.1 7.1.1.1 NOTE Calibration characteristics should be redetermined whenever:
- the thermometer has been recalibrated;
- either the thermometer, the stirrer or the flask have been renewed or modified;
- the operator considers that it is necessary.
7.1 Heat of solution of anhydrous cement
7.1.1 Procedure
7.1.1.1 General
Use acid mixture of the same composition, quantity and initial temperature as used for calibration of the calorimeter (see 6.2). The quantity of sample, weighed to
7.1.1.2 7.1.1.3 After the preliminary stirring period of the acid mixture (see 6.2, a)), follow the procedures given in 7.1.1.2 applicable to all cements and hydraulic binders or 7.1.1.3 applicable only to Portland cements.
7.1.1.2 Procedure applicable to all cements and hydraulic binders
Record the temperature, T_ 15 , and start the chronometer. Record the temperature, TO, after 15 min and immediately introduce the sample, taking not more than 1 min. Record the temperature, T 30 , after a dissolution period of 30 min. Follow the procedure for reading temperature given in 6.2 for the anhydrous sample, to avoid reading errors.
7.1.1.3 Portland cement (CEM I according to EN 197-1:2000)
Record the temperature, T o , start the chronometer and immediately introduce the sample, taking not more than 1 min. After a dissolution period of 30 min record the temperature, T 30 . After a further post-period of 15min record the temperature, T 45 .
Follow the procedure for reading temperature given in 6.2 for the anhydrous sample, to avoid reading errors.
7.1.2 7.1.2.1
7.1.2