Method of test for building limes, Part VIII: Determination of workability
1973 Edition

The apparatus essential for performing the workability test on building limes includes a Standard Flow Table engraved with three concentric circles for measuring flow spread and equipped with six equally spaced rivets. A truncated conical mould is used to shape the lime putty prior to testing, with dimensions specified by the standard. Additionally, a mixer conforming to IS 1625-1971 is required to thoroughly mix and "knock up" the lime putty by passing it twice through the mixer to attain plasticity. Clean water maintained at 27 ± 2°C is used to prepare the lime putty by mixing hydrated lime with an equal amount of water 24 hours before testing. A weighing scale capable of measuring 500 grams of lime sample is also necessary. This setup ensures consistent and reproducible workability testing.

Per IS 6932 Part 8 Clause 3.2.2, prepare lime putty by taking 500 grams of hydrated lime and mixing it thoroughly with an equal mass of clean water at 27 ± 2°C. The mixture should be allowed to rest for 24 hours to ensure proper soaking. After this period, the putty must be 'knocked up' or mixed vigorously using a mixer that complies with IS 1625-1971, passing the material twice through the mixer to achieve a plastic consistency. The putty is then adjusted to a standard plastering consistency where the spread on the flow table after one bump is 11.0 cm ± 0.1 cm. If the putty is too stiff, water should be added gradually; if too wet, excess water should be removed by placing the putty on a clean absorbent surface. Testing should be performed immediately after adjustment to ensure uniformity.

The standard consistency for lime putty, as defined in IS 6932 Part 8, is attained when the average diameter of the putty's spread on the standard flow table after one bump measures 11.0 cm with a tolerance of ± 0.1 cm. To adjust, if the measured spread is less than 10.9 cm, the putty is considered too stiff, necessitating the gradual addition of water. Conversely, if the spread exceeds 11.1 cm, it is too wet, and water should be removed by briefly placing the putty on a clean absorbent surface. After adjustment, the workability test is conducted promptly on a clean and dry flow table with the shaft oiled. The lime putty is applied centrally using the mould, which is then carefully withdrawn ensuring no significant residue remains inside; otherwise, the test must be repeated. This procedure guarantees consistent plastering performance.

To measure lime workability via the flow table method according to IS 6932 Part 8: First, prepare lime putty by mixing hydrated lime with an equal weight of water maintained at 27 ± 2°C and allow it to stand for 24 hours. Next, 'knock up' the putty using a mixer conforming to IS 1625-1971 to obtain plasticity. Adjust the putty to standard plastering consistency where its spread after one bump on the flow table is 11.0 cm ± 0.1 cm. Place a specified volume of the putty in the truncated conical mould on the flow table, then lift the mould vertically to allow the putty to spread. Apply one bump to the flow table and measure the average diameter of the spread. If the spread is less than 11.0 cm, add water and retest; if greater, remove excess water and retest. Equipment needed includes the standard flow table with engraved circles, the conical mould, and the mixer. This method ensures consistent and reliable workability assessment for plastering.

IS 6932 Part 8 mandates that during the workability test, the temperature of the lime material, the flow table apparatus, and the immediate test environment must be maintained at 27 ± 2°C. This thermal control ensures consistent test conditions and reproducible results. The uniform temperature helps prevent variability in the lime putty’s behavior during the test and guarantees accuracy in assessing its workability.