Sand Strength Test Lab Report

Fig.4. Permeability Meter

This sand specimen is placed in the mercury cup of the permeability meter. The air drum is raised to take 2000 cm3 of air in to the air drum which will be indicated by the graduation on it. The whole air is then allowed to escape through the sand specimen with a pressure of about 10 g/cm3 and the time is recorded.

The permeability number of the sand sample can be calculated from the following equation:

P =V h/A t p (4.1)

Where P = AFS standard permeability number

V = Volume of air in cm3 = 2000 cm3 h = Height of specimen in cm = 5.08 cm (or, 2 inches)

A = Cross sectional area of specimen in cm2 = 20.268 cm2 p = Air pressure in g/cm2 = 10 g/cm2 t = Time in minutes

The above equation may be simplified as P =

Sand Strength Test Fig.5. Universal Strength Machine

Sand strength test is the measure of holding power of various bonding materials in green and dry sand. It determines the cohesiveness or natural binding capacity of the sand grains. There are four types of test for sand strength: (1) compression, (2) shear, (3) tensile, and (4) over-hang bar test. Of these tests, the compression test is by far most widely used and is very convenient for routine testing of all types of national bonded and synthetic moulding sand

For green compression strength test, the AFS Standard sand specimen is prepared. The test is performed on the sand specimen by using Universal sand strength machine. This machine consists of a pusher arm and weight arm, both hanging from a pivot bearing at the top of the machine. The weight arm applies load on the specimen while pusher arm pushes the specimen against the weight

As the weight arm is pushed up higher, the load increases until the specimen breaks. Then the compression strength in gm/cm2 may be read at the magnetic marker whose left side shows the maximum upward travel of the weight arm. For dry compression strength test, the AFS standard specimen is placed in the oven and dried it for about two hours at 110 C. The specimen is cooled and tested it on the same day they are made. The specimen is placed in the upper position of the sand strength machine and broken the specimen as in the case of green strength test. The dry strength values are read

Clay content test is carried out as follows: A portion of sand sample is thoroughly dried out at 220 C for about 4 h or until constant weight is attained. 50 g of this dried sand is placed in a wash bottle. To this sand, 475 c.c. of distilled water and 25 c.c. of 3.0 % caustic soda solution are added The mixture is stirred for 5 min in a rapid sand washer. Sufficient water is added up to the level line marked on the bottle. The liquid is then siphoned off after 10 min. The bottle is refilled twice more and siphoned the liquid off. The sand is placed in the oven for drying. The sand is weighed when it is completely dried and the percentage of clay is determined by the difference in the initial and final weights of the