Technical Perspective
Introduction:
The use of manufactured sand as a replacement for river sand is increasing with the ban on sand mining implemented by different states. The other factors are the general decline in the availability of river sand and pressure from active environmental groups to protect the nature.
Urban growth:
The phenomenal rise in the construction activity in the last decade has contributed to the wide gap between the supply and demand of river sand. A lot of damage has been caused to the eco-systems by carrying out dredging operations on the sand beds leading to the depletion of ground water levels in the country.
Role of fine aggregates in concrete:
It is accepted fact that sand plays a very important role in the production of concrete. The features of workability, strength and durability are directly dependent on the properties of the sand used in the making of concrete.
Concept of manufactured sand:
According to industry reports there is a major shift in the mindset of the Construction Industry towards exploring substitutes for river sand. Across the World there is growing support for the increased use of manufactured sand used in the production of concrete. The properties of particle shape, consistent gradation and zero impurities are the reason for the preference by structural consultants and concrete technologists. The imperative need for clean sand, eliminating the constraints of river sand like availability, price fluctuation etc, have made manufactured sand the perfect substitute for river sand.
Manufacturing process and its standards:
The sand is manufactured in a three stage crushing process. The raw material is either granite or basalt rock. The VSI which is also referred as sand making machine is in the Tertiary Stage. The process adopted is similar to the river sand generation by nature. The VSI applies the principle of rock on rock collision at a high velocity shaping the sand particles.
The plant works on the principle of continuous feed in closed circuit and adopts the technique synonymous and comparable to nature's production of river sand. The complete manufacturing process takes minutes when compared to the nature which happens over millions of years.
The product is produced to IS 383 standards.
Advantages-Manufactured sand
Impact on Concrete
Cubical particle shape
High compressive strength
Internal gradation IS 383
Reduction in voids increases workability
Surface Texture
Reduction in moisture absorption/lower water cement ratio
Greater durability
Longevity of structure/higher resistance to an aggressive environment
Zero impurities (marine and organic)
Reduction in wastage and increase in economic value
Comparison with river sand
Features
River Sand
Manufactured Sand
Source
Fragile river beds
Produced with special machines
Shape
Rounded
Cubical
Quality
Contains marine/ organic impurities
Zero impurities
Purity
Contains deleterious materials
Clean
Economy
Expensive
Competitive
Availability
Uncertain
On demand