Size, Composition & Types Of Sand Used in Construction | Aggregate Size in Concrete
Types Of Sand Used in Construction |Grain of Sand Sizes | Uses of sand
What is Sand?
Sand is a granular material made of small fragments of rock and mineral. Sand is composed of a variety of different materials but is identified by its grain size.
The grains of sand are smaller than those of gravel and coarser than those of silt. Sand can also refer to a textural class of soil or a particular type of soil; for example, a soil that contains more than 85 percent sand-sized particles by mass.
Sand composition varies according to local rock sources and circumstances, but the most abundant ingredient in inland continental settings and non-tropical coastal settings is silica (silicon dioxide, or SiO2), typically in the form of quartz.
Calcium carbonate is the second most prevalent type of sand, for example, aragonite, which was primarily formed by various forms of life, such as coral and shellfish, over the last 500 million years.
For example, it is the predominant type of sand in regions such as the Caribbean where reefs have dominated the ecology for millions of years.
Sand may also be made of calcium sulfate minerals, such as gypsum and selenite, as is the case in areas such as White Sands National Park and Salt Plains National Wildlife Refuge in the United States.
Over human timescales, sand is a finite resource, and sand suited for concrete production is in great demand. Although desert sand is abundant, it is unsuitable for concrete. Each year, 50 billion tons of beach sand and fossil sand are used in construction.
Grain of Sand Sizes
Sand is a naturally occurring, finely divided rock composed of particles or granules measuring 0.0625 (or 16) to 2 millimeters in diameter.
A single particle in this size range is referred to as a sand grain. Silt is the next lower size class in geology, consisting of particles with a diameter of less than 0.0625 mm and a thickness of less than 0.004 mm.
Gravel is the next largest size class above sand, with particles ranging in size from 2 mm to 64 mm (see grain size for standards in use).
When rubbed between the fingertips, sand feels rough (silt feels like flour).
Sand is generally classified into five subcategories based on its particle size:
- Very Fine Sand (1/16 – 1/8 Mm),
- Fine Sand (1/8 Mm – 1/4 Mm)
- Medium Sand (1/4 Mm – 1/2 Mm)
- Coarse Sand (1/2 Mm – 1 Mm), And
- Very Coarse Sand (1/2 Mm – 1 Mm) (1 Mm – 2 Mm).
These dimensions are derived from the sediment size scale, which states that size in = -log base 2 of size in mm. On this scale, sand ranges from -1 to 4, with sub-categories denoted by full numbers.
Sand Size for Concrete
A good concrete mix requires clean, firm, strong aggregates that are free of absorbed chemicals or coatings of clay and other fine impurities that could cause concrete to deteriorate.
Aggregates are classified as ‘coarse’ or ‘fine’.
- Coarse aggregates are particles larger than 4.75mm in diameter. Typically, a diameter range of 9.5mm to 37.5mm is used.
- Fine aggregates are often sand or crushed stone with a diameter of less than 9.55mm.
The most often utilized aggregate size in construction is typically 20mm. In mass concrete, a greater size, 40mm, is more frequent.
Larger aggregate sizes use less cement and water.
The coarse aggregate size is the primary factor affecting the strength of your concrete. In general, stronger concrete requires smaller coarse particles, with 20mm aggregates meeting the threshold for strong concrete and 40mm aggregates meeting the threshold for normal strength concrete.
Different Sand Color
The common colors of the construction sand includes;
- White sand
- White sand
- Black sand
- Red-orange sand
- White grey color
- Light brown color
Sand Types and Classification
Sand Classification According to the Particle’s Grain Size
Sand is divided into three types:
- Fine Sand (0.075 to 0.425mm)
- Medium Sand (0.425 to 2mm)
- Coarse Sand (0.425 to 2mm) (2.0 mm to 4.75mm)
Sand Classification According to its Origin
Sand is divided into four categories: pit sand, concrete sand, river sand, desert sand sea sand, and synthetic sand.
River Sand: Sand from the River
River sand is a fine sand that is created as a result of corrosion caused by water currents. It is acquired from river streams and banks. It is often white-grey in color.
Unlike pit sand, river sand grains are smooth, rounded, and of high quality. As a result, it is used extensively throughout the world for a variety of construction tasks, including plastering.
Sand from rivers is obtained either directly from the river or from its flood plain, and accounts for the vast bulk of sand used in the building industry.
As a result, numerous minor rivers have been reduced, posing environmental concerns and resulting in economic losses for nearby area.
Sand mining in such places far outpaces the rate at which the sand replenishes, rendering it a non-renewable resource.
Desert Sand: Sands of the Desert
Sourced from desert areas and currently unsuitable for construction purposes due to the grains being too fine and too polished, although some are producing desert sand concrete replacements.
Sand dunes form as a result of drought or wind deposition. Due to its physical location and proximity to the equator, the Sahara Desert is extremely dry. It is famous for its massive sand dunes, which exist mostly as a result of a lack of flora and water.
Wind erodes tiny particles such as clay and decomposing organic matter over time, leaving only sand and larger boulders. Only 15% of the Sahara is covered in sand dunes, whereas 70% is bare rock.
The wind is responsible for sculpting these distinct settings and rounding and smoothing the sand. Due of these characteristics, desert sand is unsuitable for construction.
Pit sand is a gritty sand that is frequently found in a reddish-orange hue. It is extracted from deep holes dug between one and two meters below the topsoil.
Pit sand granules are coarse, angular, sharp, and abrasive. It is free of salts and other contaminants, which makes it a popular choice for concreting.
Concrete Sand: Sand for concrete
Concrete Sand is a form of sand composed of crushed concrete. It is a frequently used ingredient in cement and asphalt blends.
This sand is crushed and filtered at the quarry to remove large rocks and fragments. It is a coarse sand that can be combined with cement and water to serve as a leveling base for layers, patios, and walking paths.
When combined with cement and water, it creates a solid mass that is used to fill spaces between coarse aggregates. It has a finer grain than crushed stone sand and hence can be utilized to create softer pavements.
However, because it is larger than white sand, it can also be used as a filler. Due to the size and texture of this sand, it is an appropriate material for a variety of applications. It ensures the fundamental stability of a structure.
Sea Sand: Sand from the sea
Sea sand (alternatively called offshore sand) is sand that has been degraded by seawater. It is protected from seashores and is distinctively brown in color.
Sea sand grains are extremely thin in texture and have a round shape. Sea sand is composed of salt and other marine pollutants that absorb moisture from the air and produce dampness.
As a result, it is used sparingly in concrete structures and technical processes.
Manufactured sand is a form of sand that is created artificially by crushing hard granite stones. It is used in place of river sand in building.
It is prepared to the specified fineness, shape, surface smoothness, texture, and consistency, making it the ideal sand for construction while increasing the strength of the concrete by minimizing segregation during placement, bleeding, honeycombing, voids, and capillary.
Additionally, its use eliminates the need for dredging river beds to collect river sand, assisting in the avoidance of calamities such as groundwater depletion, water scarcity, and threat to bridge safety, making it a more environmentally friendly option to other sands.
Fill sand is composed of extremely tiny rock particles that have either decomposed into sand over time or have been crushed multiple times. Although this sand type has an exceptional compaction grade, it is prone to displacement and shifting.
Due to its attractiveness and affordability, many contractors favor fill sand. Additionally, fill sand is great for usage in moist locations with drainage issues. Typically, fill sand is used as a backfill material around septic tanks and as a foundation for the concrete.
Main Uses of Sand
- Sand is generally a major component of the aggregate used to prepare concrete. Sand is produced in rock crushing operations and is used as an aggregate.
- Molding sand, sometimes called foundry sand, is moistened or oiled before being formed into molds for sand casting. This sort of sand must be resistant to high temperatures and pressures, enable gases to escape, have a homogeneous, small grain size, and be inert to metals.
- Graded sand is used as an abrasive in sandblasting and in water filter media.
- Sand is added to a combination of clay and other minerals in brick making factories as an additive.
- Sand is occasionally combined with paint to give walls and ceilings a textured feel or to produce a non-slip surface.
- Sandy soils are suitable for certain crops, such watermelons, peaches, and peanuts, and are frequently favoured for intensive dairy production due to their superior drainage features.
- Sand is a material that is used in landscaping; it is used to create little hills and slopes (e.g. for making golf courses).
- It is the primary component used in the manufacture of glass.
- It is frequently moved to popular beaches, when periodic tides wash away the native sand.
- Sandbags are used to ward off floods and gunfire. When empty, they can be readily transported and filled with local sand.
- Sand castle construction is a popular activity, and there are even competitions for sand castle construction.
- Sand animation is a form of performance art and an animation method.
- Aquaria are frequently lined with sand rather than gravel; this is a cost-effective alternative that some claim is superior than gravel; railroads utilize sand to improve rail traction.
Sand Chemical Formula & Composition
Sand, the most common form of silicon dioxide, is composed largely of minute quartz crystals. Quartz has a tetrahedral crystalline structure: each silicon atom is bound to four oxygen atoms. Glass is another form of silicon dioxide, but its atomic structure is amorphous or irregular rather than crystalline
The main constituent of sand which is is silica (silicon dioxide, or SiO2), usually in the form of quartz, has chemical inertness and considerable hardness, is the most common mineral resistant to weathering.
Silica (Quartz) is chemical compound silicon dioxide SiO2. Silica is often found in nature as sand (non-coastal), usually in the form of quartz.
Characteristics & Properties of Sand in Construction
The following are some the Characteristics & Properties of Good Sand:
- The material should be absolutely inert. (i.e., it should be chemically inactive).
- Should be free of hygroscopic salts (i.e., CaCl2, MgCl2, etc.).
- Should be free of clay and silt; typically, a maximum of 3-4 percent clay and silt is tolerated for practical reasons.
- The grains should be pointed, angular, and gritty in texture.
- Sand should be devoid of clay and organic materials.
- The grains should be made of mineral that is resistant to corrosion.
- The grain size distribution should be such that voids are kept to a minimum.
- It should be clean and devoid of clay and silt coats.
- It should be completely devoid of organic stuff.
- Sand is made up of broken pieces of hard rock; it is composed of grains from the disintegrating rock.
- Sand should be of a size that it passes through I.S. sieve No.-480 [4.75mm] and retains its shape.