To determine the popping and pitting of a lime sample IS-6932-Part-10
This test is a measure to study the healthiness of the manufacture of limes. Bursting, pitting and blowing are caused by the presence of coarse uneducated or only partially extinguished particles. Upon final slacking, these cause displacement of fragments across the plaster surface, usually in the form of a cone.
In this test, pat is prepared by mixing 70 gram of hydrated lime with 70 ml of water and 10 g of plaster of paris, They are subjected to steam action and checked for disintegration, popping and pitting. Any of these occurrences is a sign of the malaise of the lime.
step 1 [Gauging/Mixing of Plaster]
The gauging plaster used for the popping and pitting test, when measured with 50 percent of its mass by distilled water and tested by wicket needle, shall have an initial setting time of not less than 15 minutes. The gauging plaster shall be free from cracks and pits. Fresh, fine, white and good quality plaster of paris can be used, which shows no pops or pits when tested without lime.
step 2 [Preparation of Test Pats/Specimens]
Four test samples shall be prepared separately in the manner described below.
The 70 g of hydrated lime under test was given 27 ± 3. Mix thoroughly with 70ml clean water at temperature0c and let soak for 2 hours.
At the end of 2 hours, the lime putty thus obtained should be thoroughly mixed and knocked down with a trowel with a small addition of clean water, if necessary, to obtain a plastic mass. It will then be spread over a non-porous surface. 10 gm Approved Grade Plaster of Paris (as prepared in Step-I) will be added, Plaster being spread evenly over the putty and the whole shall be mixed rapidly and thoroughly with a trowel for 2 minutes,
The gauged material will then be formed into a flat pat by pressing it into a ring mold of 100 mm diameter and 5 mm deep, greasing from the inside and placing it on a well greased non-porous plate. One gram of petroleum jelly/pat is suitable for greasing each time it is renewed.
The measured putty shall be pressed in small quantities at a time with the help of a wide palette knife or spatula in such a way that avoid air bubbles, It will then be leveled along the top edge of the ring with no more than 12 strokes of the knife, removing any excess material in the process. Total time should not exceed 5 minutes From the time of pouring plaster of paris to the last stroke of the knife for a single pat.
step 3 [Drying of Pats]
The four patties thus formed will be left to set for half an hour. They will then be transferred to a well-ventilated drying oven maintained at a temperature between 35 and 45 with or without their ring molds on their base-plates.0c Dry thoroughly. a period amount 16 hours should be sufficient for this purpose but at least four hours is sufficient in many cases.
Pat can be left in the oven before drying or in between drying periods.
Any test pat that shows shrinkage cracks before steaming will be discarded and replaced with a new pat.
step 4 [Placing Pats in Steam Boiler]
The four pats, still on their base-plates, shall be placed horizontally in a suitable steam boiler, with the water already boiling, and subjected to the action of steam introduced at atmospheric pressure. 3 hours duration, The steaming vessel should be arranged in such a way that the condensed water does not drip back onto the faces of the plates.
Patts will then be examined in good light for disintegration, popping and pitting.
The ring mold and the non-porous plate should be greased evenly with petroleum jelly.
Press the putty into the ring mold with a wide spatula to avoid ingress of air bubbles.
IS: 6932-Part-10 Test method for the determination of popping and pitting of hydrated lime.