Metakaolin - measuring the total quantity of fixed Calcium Hydroxide (Chapelle testmodified) Referring to the French norm NF P 18-513, Annexe A

1. Principle

The measure of the fixed quantity of calcium hydroxide on pozzolanic materials helps to define theirpozzolanic activity.1 g metakaolin is reacted with 2 g CaO in 250 ml of water. The non reacted lime is then measuredand the result expressed in mg Ca(OH)2 fixed by the metakaolin.A blank experiment is done symmetrically without metakaolin

2. Equipment

This consists of: - heated stirrer with a Teflon magnet - thermometer (scaled from 0 to 100C) - cooling column - Erlenmeyer in stainless steel with smooth inner surface (volume of 750 ml) - tap with 2 holes o one for the cooling column o one for the thermometer - balance e=0,1 mg

3. Reagents

- calcium carbonate for analysis - distilled water without CO2. Prepare the water by passing it over an ion exchange resin. Use this water for all reactions. - Saccharose for analysis - Hydrochloric acid (decinormal) - Indicator solution: 0,1 % phenolphthalein in 50% alcohol solution

4. Working method

- the apparatus id regulated to a temperature of 90C - weigh exactly 1 g of metakaolin in powder form into the dry clean Erlenmeyer - use a calibrated pipette to add 250 ml of the above water - add about 2 g of CaO exactly weighed - prepare the CaO the following way: o weigh 3,6 g of CaCO3 in a platinum crucible with known tare o calcine for about 30 minutes at 1000C o weigh and verify that the LOI (loss on ignition) be 44% - place the stirrer in the Erlenmeyer - place the tap with the thermometer and the cooling column and homogenise the content of the Erlenmeyer - place the apparatus on the heated stirrer and start heating - verify that the temperature gets to 85C5 - stir and heat for 16 hours - cool to room temperature - add to the Erlenmeyer 250 ml saccharose solution freshly prepared (60 g saccharose dissolved in exactly 250 ml water) - stir for 15 minutes on the magnetic stirrer. Filter about 200 ml take out 25 ml with a calibrated pipette.

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- Make the same proceeding without metakaolin

4.2. Titrating the solution

- titrate with a burette using the HCl 0,1N solution using the phenolphthalein as indicator

5. Calculations

Definition:

- V1 (ml) is the volume of 0,1N HCl necessary for the 25 ml of solution obtained by the blank sample - V2 (ml) is the volume of 0,1N HCl necessary for the 25 ml of solution obtained by the reaction of the metakaolin

The titration reaction is:

CaO + 2HCl CaCl2 + H2O

Ca(OH)2 + 2 HCl CaCl2 + H2O

Check of the blank reaction

56 2 x V1 must be under 1000Trial with metakaolin:

Mg of Ca(OH)2 fixed = 2 x V1 - V2 x 74 x 1000 V1 56

6. Results

The results are expressed in mg Ca(OH)2 fixed by the metakaolin

7. Precision

The results should have a variation of 10%.

more info: Dr. Denis Bezard - questions@metakaolin.info - phone: +43 (0)2252 45970

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