4 different type of Physical Tests on Cement; setting time
Test: Cement is used widely for the construction work of various types of structures. Some of them are listed below: Cement slurry is used for filling cracks in concrete structures. Cement mortar is used for masonry work, plastering, and pointing. The Cement concretes are used for the construction work of various types of structures like construction buildings, all bridges. Big water tanks, All tunnels, many docks, the sea harbor is, etc. Also, Cement is used to manufacture lamp posts, Telephone posts, railway sleepers, Building piles, etc. For using manufacturing Big cement pipes, All garden seats, cement dust bins, Different types of flower pots, etc… cement is commonly used. It is very useful for the construction of road works, footpaths, courts for various sports, etc.
- Soundness Test
- Setting Time
- Soundness Test
- Crushing Strength Test
It is conducted by sieve analysis. 100 gems of cement are taken and sieved through IS sieve No. 9 for fifteen minutes. Residue on the sieve is weighed. This was should not exceed 10% by the weight of the sample taken.
The Initial setting time and the final setting time are the two are important physical properties of the cement. Initial setting time is the time taken by the cement from adding water to the starting of losing its plasticity. The final setting time is the time elapsed from adding the water to complete loss of plasticity. Vicar apparatus is used for finding the setting times. The Vicar apparatus consists of the movable rod to which any one of the three (3) needles shown in the figure can be attached. An indicator is attached to the movable rod. A vicar mold is associated with this apparatus which is in the form of a split cylinder.
Before finding the initial and final setting time it is necessary to determine water to be added to get standard consistency. For these 300(gms) of cement is mixed with about 30% (percentage) of water and cement paste prepared is filled in the mold which rests on non-porous in the plate. The plungers are attached to the movable stainless steel rod of the vicar apparatus and gently lowered to touch the paste in the machine mold. Then the plunger can move freely. If the penetration is 5 millimeters to 7 millimeters from the bottom of the machine mold, then cement is having standard consistency. If not, the experiment is repeated with a different proportion of water fill water required for standard consistency is found. After the tests for the initial setting and final setting, times can be taking out as explained below Test
2.1. Initial setting time.
300 gems of cement are thoroughly mixed with 0.85 times the water for standard consistency and vicar mold is filled and the top surface is leveled. The 1-millimeter square needle is fixed to the stainless rod and gently placed over the paste. Then it is freely allowed to penetrate. At the beginning of the test, the needle penetrates was the paste completely. As time lapses the paste starts losing its plasticity and resists penetration. When the needle can penetrate up to 5 to 7 mm above the bottom of the paste experiment is stopped and time elapsed between the addition of water and end if this experiment is noted at the initial setting time.
2.2. Final Setting Time.
The square needle is replaced between the annular collar. This type of experiment was continued by allowing this needle to freely moved after gently touching the surface of the paste in the testing machine. Time was elapsed between the addition of water and the mark of the needle but not of the annular ring is found on the paste of this test. This time is noted as the final setting time.
This test was conducted to find free lime in the cement, which is not desirable. Le Chatelet apparatus shown in Fig. 1.6 is used for conducting this test. It is consists of a split brass mold of diameter 30millimetres and height 30 millimeters. All either side of the split, there are two indicators, with pointed ends. The ends of indicators are 165 millimeters from the center of the mold.
Previously oiled Le Chatelet mold is placed on a glass plate in a test machine and is filled completely with a cement paste having 0.78 x times the water required for standard consistency. It was then covered with another glass plate and a small weight is placed over the test machine. Then the whole assembly is kept underwater for 24 hours. The temperature of the water should be between 24°C and 50°C. Note the distance between the indicators. After placing the testing mold again in the water and heat the assembly such that water reaches the boiling (24°C and 50°C) point in 30 minutes. Boil the water for one hour. The test molds are removed from the water and allowed to cool for heat reduction. The distance between the two pointers is measured.
4.Crushing Strength Test:
For this test procedure, 200 gm of cement is mixed with 600 gm of standard sand (fine aggregate) confirming An IS code 650–1966. After that mixing thoroughly in a dry condition for a minute distilled potable water P 4 + 3 percentage is added where P is the water required for the standard consistency.
They are mixed with a trowel for 3 to 4 minutes to get a uniform mixture. The cement mix paste is placed in the cube mold inner of 70.6 mm size (Area of 5000 mm2) after taking on a steel plate and prodded with 25 (mm) standard steel iron rod 20 times within 8 seconds. Then the mold is placed on a standard vibrating table that vibrates at a speed of 12000 ± 400 vibrations per minute.
it was secured at the top of the hopper and the required mortar is filled. The mold is vibrated for two minutes and the hopper removed. The top side is finished with a knife and a trowel and even level. After 24 hours that mold is removed, and the cube is placed under clean water for curing. After that specified period cubes are tested in compression in the testing machine, keeping the needed specimen (3 cubs) on its level edges.
The Average of three cubes is reported as crushing strength taking the value in N/mm2. The compressive strength at the end of the 3 days should not be less than 11.5 N/mm2 ( below this value is that cement is very low quality) and that at the end of the 7 days not less than 17.5 N/mm2.