Specification for calorimeter for the determination of heat of hydration of hydraulic cement
1985 Edition

As per IS 11262 Clause 2.1 and Table 1, the calorimeter components must be made of the following materials: the calorimeter itself is a glass vacuum flask with a 40 mm thick cork stopper; the insulated container consists of wood with insulating layers such as cork or cotton wool; the thermometer used is of the Beckmann type; the stirrer is made from glass or polyethylene, designed as a double-bladed propeller approximately 40 mm in diameter with a 6 mm shaft diameter and 400 mm length, with the glass parts inside the flask coated to resist hydrofluoric acid; and the funnel is a Gooch type made of glass or polyethylene, featuring a 6 mm internal diameter stem, about 25 mm in body diameter and length, with the stem extending no more than 3 mm below the cork stopper. This combination ensures chemical resistance, efficient thermal insulation, and accurate measurement of heat during cement hydration tests.

According to IS 11262 (Clause 6.5), the vacuum flask's inner surface and the underside of the cork stopper are coated with a thin, uniform layer of an acid-resistant substance, typically paraffin wax with a melting point around 60°C. This protective lining serves as a barrier against hydrofluoric acid attacks on the glass. It is critical that this coating remains intact and free of cracks. If damage is detected—often indicated by abnormal temperature rises during testing—the coating must be completely removed and reapplied by melting and renewing the paraffin wax layer. This design ensures both chemical durability and reliable thermal performance.

Per IS 11262 Clause 4.3, temperature measurement precision relies on two thermometers: a differential Beckmann thermometer and a reference thermometer. The Beckmann thermometer must have graduations of at least 0.01°C and cover a range of around 6°C. It is protected against hydrofluoric acid exposure and equipped with a reading lens. The reference thermometer should have a graduation of 0.1°C and an appropriate temperature range. The Beckmann thermometer must be securely fitted to avoid contact with the stirrer and is typically mounted using a split cork stopper for easy removal. These stringent requirements allow for detection of minute temperature changes essential for accurate heat of hydration measurements.

Per IS 11262, the stirrer must be a double-bladed propeller constructed from glass or polyethylene. It should have a diameter of approximately 40 mm, a shaft diameter of 6 mm, and a shaft length of 400 mm, extending to within 40 mm of the bottom of the flask. The glass portion of the stirrer inside the calorimeter must be coated with an acid-resistant layer to protect against hydrofluoric acid. The blade pitch should be set to provide effective stirring without generating excessive heat. Importantly, the stirrer’s operation must not cause the temperature of the flask contents to increase by more than 0.001°C per minute beyond the unstirred baseline, ensuring minimal heat interference during measurement.

According to IS 11262 Clause 5.1, each component of the calorimeter apparatus must be clearly and permanently marked with the manufacturer's name or registered trademark, or both, along with the date of manufacture. These markings must be applied in a manner that does not impair the performance or integrity of the apparatus. This ensures traceability, accountability, and quality control throughout the lifecycle of the equipment.