Collection of used SiO2 SAND:
There are many types of waste sand is disposed in foundry. They are SiO2 sand, resin sand, baking sand, facing sand etc. But in general SiO2 sand is used in large quantity therefore SiO2 sand is collected from the foundry.
HAMMERING AND SIEVING:
Then the lumps are ground by hammering and screened to remove stone and other foreign bodies by sieving to 4.75mm of standard sieve size to maintain proper grain size of the sand.
MIXTURE IN FOUR DIFFERENT RATIOS:
From the journal and discussions four different ratios are selected. Then sieved foundry sand is mixed with red soil in three ratios such as 1:9, 2:8, 3:7 and 4:6. It kneaded without adding water till it get blended well with the red sand.
Then it is placed into a pug mill where it was mixed with water to obtain the right consistency for moulding.It was kneaded with the hands and feet to mix all the elements of the clay together. This step was called tempering or pugging. Then it is exposed to air for 48 hours to remove unwanted oxides.
Then four bricks are moulded for each ratio in standard brick size. Then it is stored in the area called a hack or a hack stead and the bricks were covered under roof or with straw to protect them from the rain or harsh sun.
FIRING THE BRICK:
After two weeks the bricks were ready to be burned. Then the bricks are placed in the kiln for burning for one week. Heated at 1800 F temperature. Then it is taken from kiln and placed in hack stead and exposed to open air for 24 hours.
TESTS TO BE CARRIED OUT:
Then it is given for testing and following tests are carried out
Specimen brick is immersed in water for 24 hrs.The frog of brick is filled flush with 1:3 mortar and brick is stored under damp jute bags for 24 hours followed by immersion in clean water for three days.The specimen is then placed between plates of compression testing machine.Load is applied axially at uniform rate till failure. Maximum load at failure divided by average area of bed face gives compressive strength.
The soluble salts if present in bricks cause efflorescence on the surface of brick.Brick is immersed in water for 24h. It is then taken out and allowed to dry in shade. The absence of grey or white deposits on its surface indicates absence of soluble salts. Observation is made with naked eyes and classified as below.
Nil – Imperceptible efflorescence
Slight – Deposit covers area < 10% of exposed area
Moderate – deposit covers exposed area 10% to 50%
Heavy – Deposit covers exposed area > 50%
Serious – Deposits are heavy and powder or flake away the surface
Dry bricks are oven dried at 105° ± 5° C.Room temperature cooled bricks weighed W1.Bricks immersed in water at 27° ± 2° C for 24 hrs.Soaked bricks weighed W2.Water absorption in % = (W2 – W1)/W1 x 100
This test is performed by striking two specimen bricks with each other. The bricks should not break and a clear ringing sound should be produced.
This test is performed by making a scratch on brick surface with the help of finger nail. If no impression is left on surface, the brick is considered to be sufficiently hard.
A specimen is broken and its structure is examined. It should be homogeneous, compact, and free from defects e.g. lumps and holes, etc.
From the obtained test result values are compared with the standard bricks. By the above comparison nearer to the best standard is selected.
RESULT AND DISCUSSION
The brick is fabricated with the four different ratios of used SiO2 sand and red sand. The fabrication is done by the same method as normal brick is fabricated. Then it is subjected to various tests and their comparison with the standard brick parameters.
|Parameters/ percentage of used SiO2 added||Standard brick||5%||10%||15%||20%|
|1.||Compression test||55.44 N/mm2||54.59 N/mm2||54.02 N/mm2||53.73 N/mm2||52.25 N/mm2|
|4.||Soundness test||Ring sound is produced.||Ring sound is produced.||Ring sound is produced.||A crack is formed.||Brick is broken into pieces.|
|5.||Structure test||Free from defects.||Free from defects.||Few lumps is identified.||Few lumps is identified.||Few lumps and holes are identified.|