A Reactivity Test for Quicklime Used in Aircrete Production

A number of reactivity tests are used to characterise quicklime for use in the production of aircrete. Perhaps the most widely used is that specified in EN 459-2. That test, however, suffers from excessive thickening of the milk of lime with reactive limes, leading to poor repeatability between laboratories. The method used to obtain the curve in Fig. 26.7 has been found to give acceptable with high (but not very high) reactivity limes. 

The apparatus consists of a stirred 11 Dewar flask with a lid (see Fig. A3.1). The stirrer impeller consists of angled blades and is rotated at a speed which ensures that the surface of the contents is agitated throughout the test. The level of insulation of the apparatus is such that the rate of heat loss is within the limits described in section A.5 below. The temperature of the contents is measured using a thermometer or recording thermocouple, immersed 60 mm below the static meniscus. 

Add 750 5 ml of distilled water at 25 0.3 °C to the Dewar flask, switch on the stirrer and allow the apparatus to reach a steady temperature. If necessary, raise the temperature to 25 0.3°C by inserting a heated rod into the water. 

Weigh 150.0 0.1 g of the quicklime, which should be at a temperature of 15 to 30 °C. Switch off the stirrer and open the lid of the flask. Start the stop-clock and add the quicklime to the flask within 10 seconds. Close the lid and restart the stirrer after 20 seconds. 

Record the temperature either at 1 min. intervals, or continuously. Note 

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