CONST. MTRLS. & TESTING: SAND

Although sand is a major component in the fabrication of concrete, its main purpose is to be a filler for the voids created between the coarse aggregates. The quality of coarse aggregates dictates the strength of concrete while cement glues the aggregates together. However, using cement alone will be very costly for the construction. 

courtesy of India Today

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Another purpose is to increase workability of concrete. Imagine placing high amounts of aggregates in concrete thinking that cement will be bonding these particles together. With coarse aggregates alone, small spaces between reinforcing bars and intersections of sections will make it hard to be filled with concrete (that is, smaller spaces will be poured of cement alone without any kind of aggregate). Thus, the need for sand.

From the three general classifications of stones, long processes of sedimentation and deposition of these create sand. Natural sand is further classified as:

a. Pit sand which is deposited with soil.
b. River sand obtained from river banks or beds.
c. Sea sand are those found in seashores.

For construction, the most ideal sand grade is river sand which can be checked with fineness modulus between 2 and 3. The perfect sand for construction should be free from salt deposits, soil, or vegetable matter.

According to grade, concrete works require gravelly sand. This type has the average diameter size which is suitable to work as a smaller size aggregate in concrete. Coarse sand, on the other hand, which is about 3.175mm in size is more used for brick laying. And finally fine sand is best used for plastering work as this kind of job would require minute sizes of sand.