Sand: Definition, Classification by Size, Source, Composition

• Sand is granular material formed from finely divided rock and mineral particles
• It is loose, fragmented, and naturally occuring
• The most common constituent is silica, or silicon dioxide (SiO2), which is usually found in the form of quartz

Definition of Sand

• Defined by size, sand particles are finer than gravel
• Sand particles are coarser than silt
• It is an engineering material and plays a vital role in engineering construction
• In concrete, sand is referred to as fine aggregates
• Sand grains feature sharp, angular, or rounded shapes

Classification of Sand

• Size refers to the particle size of the sand
• Source refers to where the sand was harvested from
• Composition refers to what the sand consists of

Classification Based on Size

• Varying sizes
• Very fine sand measures 1/16mm to 1/18mm
• Fine sand measures 1/8mm - 1/4mm
• Medium sand measures 1/4mm - 1/2mm
• Course sand measures 1/2mm - 1mm
• Very Coarse Sand measures 1mm - 2mm
• Very fine sand is used in plastering
• Fine sand is used for mortar in masonry work
• Very coarse sand is used in concrete

Sand Availability in Bangladesh

• Sand is available all over Bangladesh
• Rivers are the main source
• Good quality river sand is available in Dhaka, Mymensingh, and Sylhet (Jaflong, Bholagonj)
• Sylhet: Zafhlong, Bholagonj, Fajilpur, Moulivibazar, Shreemangal, Hobiganj, Chondisora
• Brahmanbaria: Meghna, area of the Titas River
• Comilla: Chauddagram, Gomoti river
• Dhaka: Gajaria, Savar, Gajipur, Kaliakair, Dulalpur
• Mymensingh: Bagunbari, Shomvoganj, Durgapur
• Faridpur: Kamarkhali, Alipur
• Khulna: Bockjuri
• Chapainawabgonj: Pagla, Mahanandapur
• Rangpur: Dumar
• Pabna: Shahbajpur
• Noagoan: Manda, Attrai river
• Panchgarh: Bogra: Kornofuli River
• Unit weight is 1450 to 1500 kg/m3
• Price is 18-25 Tk/cft

Properties of Good Sand

• Consists of pure silica (SiO2)
• Clean and coarse
• Doesn't include organic or vegetable matter; only 3-4% clay
• Chemically inert
• Sharp, angular, coarse, and durable grains
• Shouldn’t contain any salts to attract moisture from the atmosphere
• Well-graded
• Contain various sizes in proportions
• Strong and durable
• Clean and free from coatings of clay and silt

Testing Quality With Sieves

• The sand is filtered through a sieve of the correct pore size
• If the residue left is a higher quantity than the filtered sand, it is poor quality

Testing for Excess Silt or Clay

• Take some sand and add it to water
• Shake vigorously to allow all sediment to settle
• Acceptable sand should be no more than 5% clay and silt

Testing for Organic Matter

• Organic matter is tested using a straight-sided glass jar with a 130cc and 200cc mark
• The sample is added to sand up to the 130cc mark
• A 3% solution of caustic soda added until the mixture reaches the 200cc mark
• The bottle shaken thoroughly
• Allow the mixture to stand for 24 hours
• If it is colorless, the sand is free from organic/vegetable matter
• If it is straw-colored, it is considered objectionable, indicating vegetable matter in the sand
• If dark colored, the sand contains objectionable vegetable matter and should not be used

Qualities of Pitsand

• This is sand obtained by pit dredging on flood plains and lake sides
• Excavated at around 1meter to 2 meters from ground level
• It is sharp, angular, porous, homogenous, soft and free of salts
• It may contain clay and other materials that are screened and cleaned
• Light-brown or yellowish color
• Most suitable for mortar work

Qualities of River Sand

• Obtained by river dredging
• It has some of the best qualities and it is the least expensive
• Fine, round, and polished
• It may contain earthy materials like gravel and pebbles
• White, globular, and smaller in size compared with pit sand
• Suitable for plastering

Qualities of SeaSand

• It has the worst qualities of the three types of sand
• It contains salt, having been obtained from seashores
• Fine, round, and polished
• Contains sea salts, which absorb moisture, causing permanent dampness and disintegration
• It also contains shells or organic material
• Reduces the life and strength of mortar, plaster, and concrete
• Cleaner sand may be found near beaches and near the shore
• It is brown
• For non-structural purposes such as filing

Uses of Sand

• As the core component of Concrete
• Core component of glass manufacturing
• Filter media to filter water
• In the manufacturing of Plants to enhance a mixture of clays and other materials
• Mixed with paints and other materials to create textured finishing
• Can be used for plastering and mortar
• Filling in roads to brick selling points
• Traction improver to protect against floods and gunfire
• Alternative to gravel

Surkhi

• Fine powder made by grinding fresh and well-burnt bricks, brick bats, or burnt clay
• Do not use under-burnt or over-burnt bricks and avoid bricks with high sand content
• Acts as a substitute for sand
• Performs the same functions as sand but Improves mortar's strength and hydraulic property
• Must be clean
• Free of all foreign matter
• Should pass through an eight-sieve
• Largely used in lime mortar, lime plaster, and lime concrete
• Can disintegrate through humidity and air
• Should not be used for external plaster or pointing jobs

Mortar

• Mortar is a workable paste of binding and inert materials mixed in water
• Mortar = Binding material + Inert materials + Water
  • Binding materials comprise cement or lime
  • Inert materials comprise sand or surkhi
• Used as a mortar binding material

Sand, Surkhi and Cement Composition Proportions

• Cement / Lime comprises 9-15% of the total
• Cement is 1 part of the total ratio
• Sand / Surkhi comprises 3 parts
• Water comprises 3/4 part of the total mixture

What Is the Function of Sand in Mortar?

• Primarily functions as an inert material providing volume for economic purposes
• Subsidizes cementing material into a thin film
• Offers surface areas for the cementing material to adhere to
• Prevents shrinkage and cracking during mortar setting
• Helps achieve density of the mortar and aids in settings

Functions of Surkhi in Mortar include

• Volume
• Imparts strength and hydraulic properties to mortar

Functions of Mortar

• Binds bricks or stones together, provides structure
• Homogenous mass for structure and withstand loads
• Essential requirement to masonry plastering and pointing work

Ideal Mortar Qualities

• Durably adheres to masonry units, ensuring stability
• Remains workable
• Quickly provides adequate strength
• Accommodates irregularities
• Resistant to climate conditions
• Resists rain penetration in size of masonry unites and provides aesthetic appearance
• Cost-effective

3 Main Uses of Mortar

• Binding the material together
• Provide soft layers between brick to balance the load
• Improving and protecting joints

Common Precuations in Mortar Mixtures

• Small quantities that will be used quickly for setting
• Bricks and stones should be soaked for 12 hours before application
• Prevents moisture absorption
• Mortar should be stiff and all joints filled
• Keep surfaces wet after application to prevent quick drying

Pointing

• Raking out mortar joints is used to fill in the same joints to protect against environmental impact
• Types of joints used in mortar include
• Concave Pointing
• Extruded Pointing
• V Groove Pointing
• Beaded Pointing
• Weathered Pointing
• Struck Pointing

Concave Joint

• The most common type of joint
• Formed in mortar and is known for highlighting quality
• Waterproof and compacted

Vee Joint

• Known for its ability to hide imperfections
• Use of V-shaped
• Contains V Jointer

Flush Joint

• Commonly used when it's known the wall will be painted
• Has great aesthetic qualities

Raked Joint

• For uniform depth and water resistance with wheeled jointer
• Usually uncompressed for compact

Extruded Joint

• Formed by excess mortar when bricks are put under pressure
• Not recommended for the exterior

Beaded Joint

• Creates an interesting look
• Prone to erosion and falling out

Struck Joint

• Not effective for outside conditions due to poor insulation

Weather Joint

• Not water-resistant
• Primarily for decoration

Plaster

• A thin coat of mortar (cement, lime or gypsum, sand, surkhi, and water mix) applied to outside and inside wall
• Protects ceilings, columns and staircases etc
• Termed as Plastering
• Must be Cured for protection otherwise cracks may develop

Qualities of Plaster

• Cement and lime
• Water and aggregate qualities

Objectives of plastering

• Give and smooth even and durable surfaces for walls
• Seal against humidity and the outside air
• Preserve surfaces from weathering
• Moulding
• Decoration or artistic walls

Desirable Properties for Good Plaster

• Hard, and durable
• Can be applied any day rain hail or shine
• Good insulation against climate conditions
• Inexpensive and ecological to the environment
• Able to good insulation against heat and sound
• Prevents moisture

Plaster Classification

• Material used for the mixture includes
• Lime
• Surki
• Cement
• gypsum

Lime Plaster

• Sand and lime ratio is all proportions
• Some Cement helps improve small quantities for durability
• Must be in 13-16mm

Cement Plaster

• Powdered cement and lime mix in a ratio of at least 1:3 and 1:4 volume when using hard
• Suited for damp conditions

Gypsum Plaster

• Mineral product made for walling and ceilings
• Used commonly for coating that is finished and ready to go

Mudplaster

• Must not be contaminated using small loose objects
• Kept out for multiple days

Stucco Plaster

• Formed using an excellent finishing which may be used for outside conditions
• Has 3 coating which has total thickness of 25mm

Finishes Include

• Smooth, Sand, Depeter, Scrapped
• Followed using various steps

Defect Prevention Include

• Damp continuous
• Ensure the mixtures are adequate
• Imperfection adhesion
• Good workmanship
• Apply enough pressure to the plastic
• Ensure all areas are accounted for
• Smooth cast finish
  • Utilizes a Mortar, 1x 3 ratios for finishing a smooth surface
    • Involves skimming the water after cement is applied
  • Best suited for tools include wooden floats

Rough Cast Finish

• Mortar mixture consisting of coarse aggregates
  • Mixture ratio of 1 : 1.5 : 3
  • Coarse size is generally 12mm
• Using a wooden float and trowel to distribute quantity on the surface

Sand Faced

• This kind of finish may require a two coating system - Cement to sand ratio 1 to 4 then left to set for a week to be cured
• Involves sand in a one to one ratio which will require some wooden sand and then skim
  • Sponges are used for the surface

Pebble Dash Mixture

• Molar based with both sand and cement
  • 12 mm on the coating
• Then pressure as well the area
• Wooden floats are needed