Method of test for building limes, Part VI: Determination of volume yield of quicklime
1973 Edition

IS 6932 Part 6 (1973) outlines the scope and essential parameters for determining quicklime's volume yield, expressed as milliliters per gram of quicklime. It introduces critical formulas and describes the main testing equipment, including the Southard viscosimeter and density vessel, with their dimensions and functions. The procedure involves preparing lime putty according to IS 712-1973, adjusting consistency, measuring density, and calculating volume yield, with tests conducted at both 50°C and 100°C to select the maximum yield.

Preparation of lime putty samples follows IS 712-1973 and IS 6932 Part III protocols, involving the use of filter cloth bags for draining and moderate hand pressing to remove excess water. Consistency is precisely controlled to achieve a slump of 1.3 cm ± 0.2 cm by adding or removing water and thorough mixing using a mixer complying with IS 1625-1971. The Southard viscosimeter is employed to verify slump, ensuring uniformity before testing.

The volume yield of quicklime is calculated using the density of lime putty, measured by weighing a known volume in the density vessel. The key formula is volume yield (ml/g) = 0.70 divided by the density (g/ml). Testing involves eliminating air bubbles for accuracy and conducting duplicate tests at 50°C and 100°C, with the higher yield being reported. Distilled water as per IS 1070-1960 is used to prepare lime putty to maintain reagent quality.

The Southard viscosimeter consists of a vertical metal cylinder with 50 mm internal diameter and a metal piston with 65 mm stroke, operated by a screw with 2 threads/cm at a rate of 1 turn per second over 10 seconds to measure slump. The volume yield vessel is a tinned iron cylinder with a diameter of 63 ± 1 mm and a capacity of 250 ml, reinforced with a brass rim. These ensure consistent measurement of putty density and consistency.

Following IS 6932 Part III, lime putty is prepared and placed in a filter cloth bag for draining. The bag is suspended and gently pressed by hand to expedite water removal. Consistency adjustment targets a slump of 1.3 cm ± 0.2 cm using the Southard viscosimeter. Water content is modified by trial and thorough mixing using a small mixer (IS 1625-1971). Excess water is absorbed by placing the putty on a clean absorbent surface, ensuring uniform consistency.

The putty is filled into the viscosimeter cylinder avoiding air entrapment, smoothed on top, and the piston lowered to the bottom. The piston is then raised steadily at 1 turn per second for 10 seconds to eject the putty, and the slump height is measured. Density is determined by weighing a known volume of putty in the density vessel. The volume yield is then calculated using the density value and corresponding conversion tables, ensuring reliability and repeatability.

Volume yield is expressed in milliliters per gram of quicklime and derived from the measured density of lime putty. Table 1 provides volume yield values corresponding to lime putty densities ranging from 1.20 to 1.55 g/ml. Results should be reported with proper rounding as specified. Duplicate tests at 50°C and 100°C are performed, with the higher volume yield recorded as the final result.

Volume yield is computed using the formula: Volume yield (ml/g) = 0.70 divided by the density (g/ml) of lime putty at standard consistency. Density is measured by weighing a fixed volume of putty in the density vessel, ensuring no air bubbles. Duplicate slakings at 50°C and 100°C are performed, with the highest volume yield considered. This calculation reflects the expansion characteristics of quicklime upon hydration.

The standard includes a detailed table correlating lime putty density values (from 1.20 to 1.55 g/ml) with their respective volume yields (ml/g). Intermediate values can be interpolated. This table assists in converting density measurements into volume yield values for reporting and comparison purposes.