aggregate, Building materials

Los Angeles abrasion Test on Aggregates

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Los Angeles Abrasion test is used to determine aggregates’ level of abrasion resistance and toughness. Los Angeles abrasion test of aggregate assesses the deterioration of aggregate standard gradings when subjected to abrasion and impact in a rotating steel drum containing an abrasive charge of steel balls. LA abrasion test on aggregates is the measure of aggregate toughness and abrasion resistance such as crushing, degradation and disintegration. Basically, finding the percentage wear as a result of relative rubbing between the aggregate and steel balls used as an abrasive charge is the primary objective of the Los Angeles abrasion test.

  1. Significance of Los Angeles Abrasion Test of aggregates
  2. Types of aggregate tests
  3. Los Angeles Abrasion tests on aggregates
    1. Codes and standards for Los Angeles Abrasion test of aggregates
    2. Working principle of LA Abrasion test
    3. The test procedure for the Los Angeles Abrasion test of aggregate
    4. The formula for LA Abrasion Test

Significance of Los Angeles Abrasion Test of aggregates

Aggregate is a fundamental and necessary component of concrete, flexible pavements, and other similar structures. More than 70% to 80% of the volume of concrete is aggregate. Quality matters when it comes to aggregates because they are the main component of concrete, flexible pavements, etc. Various tests are conducted to determine the following properties of Aggregates.

  • Strength
  • Toughness
  • Hardness
  • Shape
  • Water Absorption etc.

Related posts from Vincivilworld

Types of aggregate tests

The following are the various aggregate tests used to determine aggregate suitability:

This article is about Los Angeles Abrasion tests on aggregates

Los Angeles Abrasion tests on aggregates

The aggregate toughness and abrasion resistance such as crushing, degradation, and disintegration are evaluated by the Los Angeles abrasion test. Generally, this test is performed in accordance with AASHTO T 96 or ASTM C 131.

The Los Angeles Abrasion test determines the aggregate’s wearing resistance and hardness. Abrasion is indeed the wearing action on aggregate caused by vehicle movement. In order to resist abrasion, the aggregate should have an adequate abrasion value. The abrasion test value can ensure the quality and suitability of aggregates. Furthermore, aggregate with high abrasion resistance has a long life span.

Codes and standards for Los Angeles Abrasion test of aggregates

There are 3 tests commonly used to test aggregates for their abrasion resistance. (a) Deval Attrition Test (b) Dorry Abrasion Test (c) Los Angeles Abrasion Tests. However, Los Angeles abrasion test values are more realistic and correct.

Los angeles Abrasion testing apparatus
Los Angeles Abrasion Testing Apparatus
Los Angeles Abrasion Testing Apparatus

Working principle of LA Abrasion test

The principle of this test is to produce abrasive action using steel balls mixed with aggregates. Accordingly, the aggregate and steel balls are rotated in a drum for a specific number of rotations. The percentage of wear due to relative rubbing action between the aggregate and steel balls is recorded. This value is the Los Angeles Abrasion value.

Los Angeles Machine cross section
Los Angeles abrasion testing machine
Los Angeles abrasion testing machine
Los Angeles abrasion testing machine

The test procedure for the Los Angeles Abrasion test of aggregate

The Los Angeles abrasion testing machine consists of a hollow steel cylinder, closed at both ends, having an inside diameter of 700 mm and an inside length of 500 mm. The abrasive charge shall consist of cast iron spheres or steel spheres approximately 48 mm in. diameter and each weighing between 390 and 445 g. The number of balls to be placed shall be as per IS 2386.

Grading and number of abrasive charges
Grading and number of abrasive charges

The test sample shall consist of clean aggregate which has been dried in an oven at 105 to 110°C to substantially constant weight. They shall conform to one of the gradings shown in Table II.

GRADINGS OF TEST SAMPLES AS PER IS 2386PLES
GRADINGS OF TEST SAMPLES AS PER IS 2386
  • Firstly, place the specimen inside the horizontal drum.
  • Then, put the steel balls and rotate the cylinder for a total of 500-1000 revolutions at the speed of 30-33 rpm about its horizontal axis. For gradings A, B, C and D, the machine shall be rotated for 500 revolutions. However, for gradings E, F and G, it shall be rotated for 1000 revolutions.
  • After completing the specific rotations, collect the specimens from the cylinder.  
  • Then sieve on a 1.7 mm IS sieve and weigh the specimen.
  • Lastly, calculate the abrasion value using the formula below.

The formula for LA Abrasion Test

The original weight of aggregate sample = W1 g

Weight of aggregate sample retained = W2 g

Weight passing 1.7mm IS sieve = W1 – W2 g

Abrasion value = [(weight of sample taken – weight of sample retained on IS sieve) / weight of sample taken ] x 100

The difference between the original weight and the final weight (sieved through 1.7mm) is expressed as % of the original weight of the sample aggregate. Similarly, this value is called as Los Angeles abrasion value.

civil engineering

PCC Concrete – Plain Cement Concrete – PCC in Construction

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PCC concrete of Plain Cement Concrete (PCC) is without reinforcement steel. Plain cement concrete (PCC) is high in compression and very low in tension. Plain cement concrete is commonly used over the ground to keep footing reinforcement from coming into direct contact with the soil. The design mixes commonly used for Plain Cement Concrete (PCC) are 1:4:8, 1:3:5, 1:2:4, M7.5, M10 etc. PCC can also be used for grade slabs (floors) and concrete roads where the only load is compressive.

Concrete is a mixture of cement, sand, and aggregate (preferably broken stone) mixed with water in specific proportions. When poured into moulds or shuttered, the mixture consolidates over time to form a uniform mass known as concrete.

  1. What is PCC Concrete or Plain cement Concrete in construction?
  2. Properties of Plain Cement Concrete or PCC concrete
  3. Ingredients of Plain Cement Concrete or PCC Concrete
  4. Production of Plain Cement Concrete (PCC) in Construction
  5. Types of concrete in construction
  6. How to Decide On A Concrete Type
    1. Material Availability
    2. Strength Required
    3. Construction methodology to be adopted
    4. Type of structure
    5. Area of application
    6. Climate and pouring conditions
  7. Placing of Plain Cement Concrete (PCC)
    1. Level marking and dressing for PCC concrete
    2. Surface Preparation and shuttering
    3. Placing and Finishing of PCC Concrete
  8. Precautions while doing Plain Cement Concrete (PCC)

What is PCC Concrete or Plain cement Concrete in construction?

Concrete without reinforcement steel is called Plain Cement Concrete (PCC). Generally, design mixes commonly used for PCC are 1:4:8 , 1:3:5, 1:2:4, M7.5, M10 etc. Plain cement concrete is high in compression and very low in tension.

Plain cement concrete laying
Plain cement concrete laying

Properties of Plain Cement Concrete or PCC concrete

Plain cement Concrete (PCC) has compressive strengths ranging from 200 kg/cm2 to 500 kg/cm2. Likewise, tensile strength of PCC ranges from 50 kg/cm2 to 100 kg/cm2, and density ranges from 2200 kg to 2500 kg, depending on the grade of concrete and aggregates used.

Ingredients of Plain Cement Concrete or PCC Concrete

Basically, PCC is made from cement, coarse aggregate, and fine aggregate. Ordinary Portland cement is used as the binding material. Accordingly, as coarse aggregate, broken or crushed stone or brickbats must be used. However, fine aggregate must consist of coarse sand. Finally, these ingredients are combined in the appropriate proportions with potable water to make PCC.

Production of Plain Cement Concrete (PCC) in Construction

PCC can be manufactured in batching plants, mixer machines, or manually mixing. Generally, the thickness of PCC can range from 50 mm to 300 mm or more, depending on the design parameters.

Types of concrete in construction

The following are the main types of concrete used in construction

Plain cement concrete (PCC)
Plain cement concrete (PCC )

How to Decide On A Concrete Type

The type of concrete to be used on a particular work is decided based on following conditions.

Material Availability

Normally, the raw material (aggregate, sand, cement etc) availability decides the type of concrete to be used.

Plain cement concrete
Plain cement concrete


Strength Required

The concrete requires different strengths for different structures. However, the strength required for the particular structure decides the type of concrete to be used.

Construction methodology to be adopted

The construction technique to be adopted for a structure decides the type of concrete. Example Pre-stressed concrete etc.

Type of structure

Most of times the type of the structure decides the type of concrete to be used.

SELF COMPACTED CONCRETE (SCC) is preferred in structures where normal pouring is restricted due to rebar congestion or access restricted pouring area. SCC, when pumped from a single point, can fill every part of the structure. 

Area of application

The type of concrete shall be decided by the area where it has to be used. In some structures, the reinforcement is so dense that concrete may not pass through it. Mostly, In those cases, specially designed concrete with small-size aggregates or Self compacted concrete (SCC) may be used.

Climate and pouring conditions

The areas where there is extreme weather conditions like heavy rain , extreme cold, extreme hot specially designed quick setting concrete will be used.

Placing of Plain Cement Concrete (PCC)

The following steps are followed while placing Plain Cement Concrete (PCC)

Level marking and dressing for PCC concrete

After completing the excavation, the bottom level of the PCC shall be marked on the ground using a level machine. The centre line from the survey pillars shall be transferred to the ground where PCC has to be done. The surface shall be dressed manually to remove the loose soil the surface level to receive PCC.

Surface Preperation and shuttering

The surface shall be neatly dressed and supports has to be placed around using wooden battens. Accordingly, the battens used have to be the same size as PCC preferably. The battens shall be properly supported using proper supports (scrap steel can be used). The dressed surface shall be sprinkled with water to avoid absorption of concrete water by the soil.

Dressing for Plain Cement Concrete
Dressing for Plain Cement Concrete

Placing and Finishing of PCC Concrete

Concrete must be poured from one end to the other. For levelling purposes, level pillars at 2 metre intervals must be provided. The concrete must be levelled and rammed in accordance with the level pillars and end supports. The slump for PCC should be approximately 75 mm. Concrete must be poured within 30-45 minutes.

Precautions while doing Plain Cement Concrete (PCC)

  • When excavating, take care to only excavate to the required levels. However, avoid over-excavation. Backfilling with loose earth is not recommended if the excavation depth exceeds the required depth. In that case, we can place the PCC at the required level by doing a plum concrete. Backfilling with soil and compaction with plate compactors/walk-behind rollers/or Vibro rollers, depending on the situation, is required.
  • Before beginning excavation, the PCC level must be transferred to different locations. Before fine dressing with lime powder, the centerline and PCC dimensions must be marked on the ground to avoid reworks.
  • The surface on which PCC is to be laid shall be sprinkled with water.
  • Anti Termite chemical or LDPE sheets may sometimes be used before doing PCC. A confirmation has to be taken before doing the PCC from the clients/customers.
  • The free-falling height of concrete shall be restricted to 1.5 meters due to segregation issues.
bricks, Building materials

Testing of Bricks – Top 8 Test on bricks to ensure quality

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Testing of bricks is a crucial step both on-site and in laboratories to verify the quality and suitability of bricks for construction. Bricks are one of the oldest and most reliable building materials, valued for their strength, durability, and affordability. Typically made from clay, bricks usually measure 190 mm × 90 mm × 90 mm with sharp, rectangular edges. They serve as essential components in construction, acting as both load-bearing structures and means of load transfer. To ensure their effectiveness, several brick quality tests are conducted, including the compressive strength of bricks, water absorption test, efflorescence test, and brick durability test. These types of brick tests help assess the brick’s resistance, porosity, and overall performance under different conditions. Adhering to these testing methods guarantees that only high-quality bricks are used, leading to safer and more durable construction projects. Understanding the methods for testing bricks is vital for builders, engineers, and quality controllers.

Audio on test on bricks
Audio on test on bricks
  1. Requirement of Good Quality Bricks
  2. Testing of Bricks – Top 8 tests on bricks
    1. Water absorption testing of bricks
  3. Compressive strength of brick/Crushing strength of brick
  4. Efflorescence test on brick – Testing of bricks
  5. Hardness test on bricks
  6. Shape and size Testing of Bricks
  7. Colour test of bricks
  8. Structure Test on Bricks
  9. Soundness test of bricks

Requirement of Good Quality Bricks

Good quality bricks are essential in construction to ensure strong, durable, and safe structures. They provide a stable base and resist environmental stresses, contributing to the longevity of buildings. The requirement for good bricks includes uniformity in size and shape, strength, durability, and minimal water absorption to prevent damage from moisture.

  • Bricks should be homogeneous and compact.
  • They should have equal proportions of clay, sand, and silt. 
  • Bricks should have requisite plasticity.
  • They should be free from defects like lumps and holes. 
  • The shape of the brick should be rectangular. 
  • A good brick should not break if dropped from a one-meter height.
  • Brick should not possess internal cracking and shrinkage.
  • The brick should be fire and scratch-resistant.
  • Water absorption of brick should not exceed 20 per cent of its dry weight. 
  • The compressive strength of the brick should not be less than 3.5N/mm2.
Good quality bricks
Good Quality Bricks

To maintain these qualities, testing of bricks should be done. This article discusses the test on bricks that are carried out to ensure the quality of good bricks.

Testing of Bricks – Top 8 tests on bricks

Bricks must undergo various tests to ensure their quality, strength, and durability for safe and long-lasting construction. Proper testing helps identify defects, assess strength, and confirm compliance with standards, preventing structural failures and ensuring cost-effective use of materials.

  • Water absorption test of brick
  • Compressive strength test of brick/ crushing strength test on bricks
  • Hardness test of brick
  • Shape and size test of bricks
  • Colour test of bricks
  • Soundness test of brick
  • Structure of brick test
  • Efflorescence test of brick

Water absorption testing of bricks

A water absorption test of the brick is performed to determine the amount of moisture absorbed by the brick under extreme conditions. The purpose of the water absorption test of bricks is to determine their durability of the bricks. The water absorption test necessitates the use of a weighing machine and a drying oven.

  • Firstly, the brick specimen is dried in a drying oven 
  • After that, weigh the dry specimen using the weighing machine and mark it as W1.
  • Secondly, immerse the brick in water for 24 hours.
  • Then take the brick out and drain the water.
  • Similarly, measure the weight and mark it as W2.
  • Finally using the formula determine the water absorption.

Water absorption = (W1 -W2) / W1 x 100

The moisture content of the brick is thus determined by the difference between the dry weight and the wet weight. Water absorption for high-quality bricks should be less than 20% of the dry weight. This brick test ensures that the brick is long-lasting and can withstand extreme weather conditions.

Compressive strength of brick/Crushing strength of brick

The ability of the brick to withstand a particular load without failure is the compressive strength of the brick.

A compressive strength testing machine is the apparatus for determining the compressive strength of brick.

  • First, Take three sample specimens and submerge them in water. 
  • After 24 hours, drain the water. Fill the frog and void with mortar in a ratio of 1: 3. 
  • Subsequently, store the brick in jute bags for 3 days. 
  • Place the brick in the compression testing machine with the brick frog area facing upwards. After that apply the load slowly.
  • Note down the load at which the bricks break.
  • Finally, using the formula to determine the compressive strength of brick. 

Compressive strength (N/mm2) = Maximum load at bricks fail/ Loaded area of brick

For good quality bricks, the compressive strength should not be less than 3.5 N/mm2. 

Compressive strength of brick/Crushing strength of brick - Apparatus
Compressive strength of brick/Crushing strength of brick – Apparatus

Efflorescence test on brick – Testing of bricks

A good quality brick should be free of soluble salts. However, If soluble salts are present, they form a white substance on the brick surface. Generally, efflorescence on brick is the name given to this white formation. The test procedure for performing the Efflorescence test on brick is as follows.

  • First, take a brick specimen and submerge it in water for 24 hours. 
  • After 24 hours, drain the brick and allow them to dry.
  • Keenly observe the brick surface.
Brick surface conditionDegree of Efflorescence
No white substanceZero efflorescence
10% white substanceSlight efflorescence
50% white substanceModerate efflorescence
More than 50% white substanceHeavy efflorescence
Efflorescence test on brick – Range
Efflorescence Test on Bricks
Efflorescence test on brick

Hardness test on bricks

The hardness test on bricks is a field verification test. Hence they are performed on-site. A good brick should resist scratches against sharp things. The following is the test procedure for the hardness test on bricks.

  • At first, choose a brick randomly from the stack.
  • Using a nail or finger make a mark on its surface. 
  • If there is no scratch, then it is a good quality brick.

Shape and size Testing of Bricks

A good quality brick should be uniform in size and rectangular in shape. In order to check this, measure the brick on the field. The standard size of the brick is 190mm x 90mm x 90mm.

  • Randomly, choose 20 bricks from the stack.
  • Sort them in length, width and height wise.
  • If the sizes are the same, Then they are good bricks.
shape and size test of bricks
shape and size test of bricks

Colour test of bricks

Normally good quality bricks are deep red or copper colour. The colour test is a field test. Therefore, it can be observed visually.

Structure Test on Bricks

Homogeneity and compact structure are the quality of good bricks. 

  • Randomly, pick one brick from the stack.
  • Cut the brick into two pieces at the centre. 
  • Then observe its inner side.
  • They should be free from defects such as lumps, holes etc. 

Soundness test of bricks

The soundness test of bricks is a field test used to determine the strength of the bricks.

  • In this test, choose two bricks randomly without damage or break.
  • Hit the bricks with each other. 
  • Then, listen to the sound the brick produce. 
  • If a metal ringing sound is produced, then it is good quality bricks. 
dams, Hydrauilics

Components of dam – 12 dam components explained

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Components of dams have specific functions in managing their primary responsibility of water management. Dams are structures built across water bodies to control water flow and levels. Furthermore, dams are also required for a wide range of projects, including small irrigation and water supply schemes as well as larger hydropower and disaster management schemes. Dams’ primary responsibility of managing water is managed by each component in a specific way. The components of the dam and their functions are discussed in this article.

The upstream side of a dam is the area where the water is collected. The water level is high on the upstream side. The downstream is the section of the barriers with low water levels.

Components of Dams - Audio
Components of Dams – Audio
  1. Advantages of Dams
  2. Components of Dams
    1. Water-retaining structure – Components of Dam
      1. Heel 
      2. Toe
      3. Abutment
      4. Crest/Roadway of Dams
      5. Cut off 
      6. Parapet wall
    2. Water-releasing structure: Components of dams
      1. Galleries
      2. Spillway
      3. Diversion tunnel
      4. Sluice way
      5. Free board
    3. Water conveying structure – Components of dams
      1. Conduit
  3. Examples of some major dams
    1. Bhakra Dam ( Gravity dam )
    2. Idukki dam ( Arch dam )
    3. Nagarjuna Sagar Dam (Masonry Dam)
    4. The Hirakud Dam (Earthern dam)
    5. KARIBA DAM (Double curvature arch dam)
  4. Key Takeaways
  5. Conclusion

Advantages of Dams

The dams provide a range of environmental, economic and social benefits. One of the most important benefits of dams is water storage. The stored water is used for drinking, cleaning, bathing, gardening, irrigation purposes, and industrial purposes.

Dams may be constructed to meet the following functions

  • Water storage: Dams are one of the major sources of water for domestic uses. These include cooking, cleaning, bathing, washing, and drinking water. They are also used for gardening, agricultural uses, and industrial purposes. The water is supplied through the canal or with the help of a pipe system from the dam.
  • Irrigation – The water from the dams is diverted through canals. It is directed to fields where the water level is low. This process is used for irrigation purposes.
  • Hydroelectric power – The water stored in the dam is passed through turbines for hydroelectric power generation.
  • Flood prevention – The water level of rivers, streams, etc is maintained by constructing dams across it. This prevents the loss and damage from unexpected floods. 
  • Recreation – The water stored in the dam is used for fishing, boating, and other recreational activities.
  • Debris control – The dam also provides the retention of hazardous material and protects the environment.

Components of Dams

The components of dams play an important role in maintaining the primary responsibility of water management. The parts of the dams are broadly classified as follows.

  • Water-retaining structure
  • Water-releasing structure
  • Water conveying structure
Components of a dam

Components of Dam – Youtube video

Water-retaining structure – Components of Dam

The water-retaining structure is the dam’s walled structure that resists water while allowing a controlled amount to flow downstream. The side of the barrier where water is collected is known as the upstream side. Where the water flows is known as the downstream side. Generally, the following component of dams makes up the dam’s water-retention section

  • Heel
  • Toe
  • Abutment
  • Crest
  • Cutoff
  • Parapet wall
Components of dams
Components of dam
Sluice way
Sluice way

Heel 

The part of the dams meeting with the groundwater or upstream side is called the heel. (Ref fig.)

Toe

The portion of the dams meeting with the groundwater or downstream side is called the Toe.(Ref fig)

Abutment

Abutments support the lateral pressure. These are the sides of the valley. These are concrete or masonry structures. 

Crest/Roadway of Dams

The section of the dams used as a roadway or walkway is the crest. It is the upper area of the dam.

Cut off 

The cut-off is an impervious barrier constructed beneath the earthen dams. The main function is to reduce the loss of stored water in the reservoir by preventing seepage.

Cut off of earthen dams
cut off – Earthen dams

Parapet wall

The parapet wall is seen below the crest near the roadway. This assists in the dam investigation and safety barriers.

Water-releasing structure: Components of dams

Mainly, the components of dams that allow water to flow downstream are known as the water-releasing structure. These dam components are technically known as the dam’s spillways. The spillway’s mechanism allows for controlled water volume. A spillway contains the following components.

  • Galleries
  • Spillways
  • Diversion tunnel
  • Sluice way
  • Free board

Galleries

These are hollow openings passing through the dam as shown in fig. The main purpose of providing a drainage gallery is to collect seepage water from the foundation and body of the dam and drain it out. The seepage water received by foundation galleries is drained away under gravity. The galleries are broadly divided into …

  • Grouting gallery
  • Inspection Gallery
  • Drainage gallery
  • Valve gallery
  • Transformer Gallery

Spillway

The role of the spillway is to convey excess water and prevent damage. The water passes from upstream to downstream. The spillway helps in the emergency discharge of water. 

They are two varieties

  • Controlled spillway 
  • Uncontrolled spillway

In a controlled spillway the flood flow is regulated by the gate. 

Also Read : Spillway types and features – A comprehensive guide

Diversion tunnel

The purpose of the diversion canal is to redirect the water. Diversion tunnels are constructed during the construction stage of dams.

A diversion tunnel may also be constructed to divert floodwater. It can redirect water from mountainous regions to low-lying areas experiencing a water shortage supply.

Sluice way

The role of the sluiceway is to remove the silt accumulated. 

Free board

The interval between the dam heads to the maximum water level on the upstream side.

Water conveying structure – Components of dams

Water-conveying structure mainly conduit and conveys the water from reservoirs through, around, or under an embankment dam

Conduit

These are closed pipe structures. Conduits act as a passage for the water supply. Bottom discharge conduits are pipes. They cross the body of the dam from the upstream to the downstream sides. This enables water flow.

Examples of some major dams

Bhakra Dam ( Gravity dam )

The Bhakra Dam is an Indian gravity dam built across the river Sutlej in Himachal Pradesh. This dam is constructed in 1963. The height of the dam is 226 meters. The length of the dam is 518 meters.
Gobind Sagar is a reservoir of this dam. The Bhakra Dam is composed of alternating layers of light red clays and sandstone.
This dam has four spillways. It helps in irrigation, hydroelectric power generation and recreation. The major source of irrigation water supply in Haryana, Punjab and Rajasthan is this dam.

Idukki dam ( Arch dam )

Idukki dam is an arch dam constructed across the Periyar river in Kerala. It is 554 feet high. One of the biggest arch dams in Asia. The dam provides hydroelectricity, irrigation and tourist destinations. It is built between Kuravan and Kurathi hills.

Idukki Dam - Arch dam
Idukki dam

Nagarjuna Sagar Dam (Masonry Dam)

Nagarjuna Sagar Dam is a stone masonry dam completed in 1967. The dam is a symbol of modern architecture. The purpose of this project was to generate hydroelectricity. It has a 26-crest gate.

The Hirakud Dam (Earthern dam)

The Hirakud dam is located in Orissa state over the river Mahanadi near Sambalpur. The length of the dam is 4800 meters and 59 meters high. It is the oldest multipurpose dam completed in 1957.
The Hirakud Dam is the 4800-meter long and 59 meters high. The gross storage capacity of the dam is 1841 million cum.

KARIBA DAM (Double curvature arch dam)

Kariba Dam is a double curvature arch dam constructed in 1960. It has been built over the Zambezi river. The crest length is 620m and 128m high. The dam provides an example of improving the quality of rocks.

Key Takeaways

  1. Primary Functions: Dams manage water for various uses, including storage, irrigation, hydroelectric power, flood prevention, recreation, and debris control.
  2. Components: The main components include water-retaining structures such as the heel, toe, abutment, crest, cutoff, and parapet wall. Water-releasing structures include galleries, spillways, diversion tunnels, sluice ways, and freeboard. Water-conveying structures are conduits.
  3. Types of Dams: Dams vary by construction and purpose. Examples include gravity dams, arch dams, masonry dams, earthen dams, and double curvature arch dams.
  4. Examples: Major dams include Bhakra Dam, Idukki Dam, Nagarjuna Sagar Dam, Hirakud Dam, and Kariba Dam.
  5. Environmental and Economic Benefits: Dams provide essential benefits like water supply, power generation, flood control, and recreational opportunities.

Conclusion

Dams are crucial infrastructure for effective water management and offer significant environmental, economic, and social benefits. We can appreciate the role of dams by understanding their various components and functions. They are important for water storage, irrigation, hydroelectric power, and flood prevention. Each component plays a vital part in the dam’s functionality. From the water-retaining to the water-releasing and conveying structures, they ensure efficiency. Examples like Bhakra Dam, Idukki Dam, and Kariba Dam demonstrate the diverse applications and benefits of these impressive engineering feats. Effective dam management is essential for sustainable development and environmental protection.

geotechnical, RAFT FOUNDATION

Types of Raft Foundations – Advantages and features

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Types of Raft Foundation are chosen based on a variety of criteria, including bearing capacity, applicable loads, site conditions, cost-effectiveness, etc. A raft foundation is a continuous slab resting on the soil and covering the entire area of the proposed structure. This is one of the most commonly used types of foundation in construction. Raft foundation types are classified according to their application.

But what is a raft foundation? It is a large concrete slab that spreads the load of the building over a wide area. This helps prevent uneven settling. There are various types of raft foundations, each with its unique features. Understanding raft foundation types is crucial for selecting the right one for your project. Raft foundations are versatile, cost-effective, and efficient. This blog will explore the different types of raft foundations, their advantages, and features, helping you make an informed decision for your construction needs.

  1. What is a raft foundation?
  2. Types of raft foundation – Principle
    1. Soil Stress Calculation
  3. Why choose Raft Foundations?
  4. Types of Raft foundations
  5. Types of raft foundations: Solid slab raft foundation
    1. Flat raft mat foundation
    2. Wide-toe raft
    3. Blanket raft foundation
    4. Slip plane rafts
  6. Slab beam-type raft foundation
  7. Piled raft foundation
  8. Cellular raft foundation
  9. Balancing or floating raft foundation
  10. Advantages of the Raft foundation
  11. Disadvantages of raft foundations
  12. Key Takeaways
  13. Conclusion

What is a raft foundation?

A raft foundation/mat foundation is a solid slab that is placed at a specific depth and spreads across the entire structure. Raft foundations have shear walls and columns to transfer loads from the structure to the ground. These foundations are typically used when the soil’s bearing capacity is low and it becomes challenging for individual footings to handle the loads. The raft foundation aids in transferring the entire load of the structure to a larger area. This type of foundation helps prevent uneven settling.

There are different types of raft foundations, each designed for specific needs. Knowing the various raft foundation types is essential for choosing the right one for your project. Raft foundations are cost-effective and versatile, making them a popular choice in construction. By understanding what a raft foundation is, you can make informed decisions for your building’s foundation needs.

Types of Raft foundation
Types of Raft foundation

Types of Raft foundations – Youtube video

Video of Raft foundation- Types and Advantages

Types of raft foundations – Related articles from vincivilworld

Types of raft foundation – Principle

The raft foundation distributes the total loads from the structure over the entire area of the structure. When compared to other types of foundations used in civil construction, they can reduce soil stress. Raft foundations differ from other foundations due to this mechanism of stress distribution.

Soil Stress Calculation

stress = total load coming on the structure + self-weight of raft/ Area of raft foundation

Consider a total load is 300 T and a foundation size

Size : 20 m x 10 m

Stress on the soil = 300/200 = 1.5 t/sqm

The same structure supported with 8 individual footing

Size : 2m x 2 m

Total area = 8 x 4 = 32 sqm

Stress on soil = 300/32 = 9.375 t/sqm

This shows that same load we are getting stresses of 1.5 T/sqm for raft and 9.375 T/sqm for individual foundations.

As the contact area of the raft is more the load is distributed over a larger area and hence stresses coming on the soil are very less.

Why choose Raft Foundations?

Raft foundations are typically preferred over other foundations when one of the following situations arises.

  • Individual footing design and pile foundation construction can be expensive when the soil’s bearing capacity is very low.
  • When the soil’s bearing capacity is less and it is essential to minimise stresses that have been induced into the soil.
  • The columns, shear walls, and so on are so close to each other that individual footings may overlap.
  • Any other type of foundation may cover more than 50% of the total ground area beneath the structure.
  • When a possibility of unequal settlement exists.
  • Preferred for complex equipment foundations.
  • Used when the proposed structure includes basements.

Raft foundations are appropriate for basement buildings where the foundation slabs will be subjected to direct live loads depending on the utility of the building. Raft foundations are a better choice because excavations can be finished with the aid of light excavators in areas with poor soil conditions and limited access to heavy excavation equipment.

Types of Raft foundations

The types of raft foundations are chosen based on a variety of factors, including bearing capacity, applications, cost-effectiveness, and so forth. Raft foundations are broadly categorized as follows.

  • Solid Slab Raft Foundation
  • Slab Beam Raft Foundation
  • Piled Raft foundation
  • Cellular Raft Foundation
  • Balancing or Floating raft foundation

Types of raft foundations: Solid slab raft foundation

In a Solid slab raft foundation, the columns and walls are equally spaced, and the load distribution is also equal. Because they are designed as slabs of uniform thickness, these raft foundations are known as solid slab raft foundations. These foundations are reinforced with a bottom layer and a top layer.

Solid slab raft foundations are classified into four types.

  • Flat raft mat foundation
  • Wide toe raft
  • Blanket raft foundation
  • Slip plane rafts

Flat raft mat foundation

Flat raft mats are used for small buildings with uniform column spacing and a foundation that covers the entire structure. These foundations have bottom and top reinforcements.

Types of raft foundation - Flat raft mat
Types of raft foundation – Flat raft mat

Wide-toe raft

A wide-toe type of raft foundation is used when the structure needs to be economical. A full-size solid slab mat foundation may not be required to support the structure’s loads. In that case, a heavily reinforced toe is provided on both sides, as shown in the figure, to handle the loads.

Types of raft foundation - Wide-toe raft
Wide-toe raft

Blanket raft foundation

blanket raft foundation
blanket raft foundation

Blanket rafts are used when the surface has unequal settlements or nonuniform strata. In this type of situation, stone blankets will be laid as shown in the figure on a compacted surface. The stone blankets and raft shoes help to distribute the load on the structure.

Slip plane rafts

The slip plane raft foundation has a fully compacted sand bed beneath the raft. To facilitate the transfer of loads, the sand bed size should be slightly larger than the raft size. The sides of the foundation can be filled with any compressible material.

Slip plane raft foundation
Slip plane raft foundation

Slab beam-type raft foundation

slip plane raft foundation
slip plane raft foundation

Slab beam-type raft foundations are used when the loads are unequally distributed and the foundation is prone to distortions. Beams included with the slabs serve as stiffeners. The raft is reinforced with two layers of mesh, one at the bottom and one at the top. The beams can offer additional stiffness and guard against distortion.

Piled raft foundation

piled raft foundation
piled raft foundation

Rafts are supported by pile foundations in this type of Mat Foundation, as illustrated in the figure. When the loads on the structure are extremely high, the soil bearing capacity is very low, and the water table is very high, these foundations are used. Piled raft foundations are ideal for high-rise buildings, and heavy industrial structures such as high-rise RCC chimneys, silos, and storage tanks that are typically supported by a single foundation element. Due to their high cost, they are not commonly used in residential applications. Piled raft foundations eliminate the need to design a very heavy raft foundation or a very conservative pile foundation with larger depths.

Instead, they opt for a combination of an optimised raft foundation and a pile foundation capable to share the loads. Over the pile foundation, the raft foundation floats. Typically used in structures such as chimneys, silos, bunkers, and overhead storage tanks where even minor soil settlement may cause the structure to fail.

Cellular raft foundation

cellular raft foundation
cellular raft foundation

A cellular raft is made up of two-way foundation beams with a solid slab on the ground below and a suspended slab on top. The upper and lower slabs are joined by intermediate beams, transforming the foundation into an I-beam structure.

For covering the top slab, precast soffits can be used. The top slab is cast using precast soffits or other types of permanent formwork or sacrificial formwork, and it is filled with lightweight infill blocks.

Typically used in areas subjected to heavy mining activity and with poor soil-bearing capacities. The foundations must withstand massive bending moments. They are the preferred option in these cases. Cellular rafts are used when removing overburdens resulting in increased bearing capacity. Cellular rafts can be used to control soil uplift pressure.

Balancing or floating raft foundation

Balancing rafts or floating foundations are used in areas where the soil’s bearing capacity is very low and the soil settlements must be kept within an acceptable range.

The floating foundation operates on the principle that the total weight of the soil and water removed from the excavated area must equal the weight of the proposed structure.

Advantages of the Raft foundation

completed raft foundation.
completed raft foundation.
  • Raft foundations are a safe and cost-effective alternative to other shallow and deep foundation types.
  • Raft foundations are preferred in areas with low soil bearing capacity, uneven settlement, and mixed soil types. The load-bearing capacity of these foundations is achieved by distributing stresses over a larger area.
  • In densely populated urban areas, access to the sites is frequently restricted, making it impossible to mobilise heavy equipment for foundation construction using other techniques. Raft foundations can be built with very little equipment because of their low heights.
  • Raft foundations, when compared to other isolated foundations, provide a much-needed option for designers in terms of limiting settlement limits within the codal provisions.
  • When deciding on settlement values, the designers have the option to choose higher values when compared to standard foundations. The raft foundation prevents uneven settlement.
  • Raft foundations are a very flexible design option that can be customised to the soil conditions and workability.
  • The execution of a raft foundation is simpler than that of individual footings. This, in turn, can speed up the project.

Disadvantages of raft foundations

Most of the time, raft design is not considered economically when the soil conditions are extremely poor. Complex raft foundations consume a large amount of concrete and steel and necessitate precise professional/technical supervision and workmanship. As a result, the structure is more expensive than any other alternative foundation. The soil beneath the foundation, especially near the edges, must be preserved.

Key Takeaways

Understanding the types of raft foundations is crucial for making informed decisions in construction. Raft foundations are continuous slabs of concrete that distribute loads across a wide area, preventing uneven settling and providing stability in poor soil conditions. They are versatile and cost-effective, making them popular in various construction projects. Different types of raft foundations, such as solid slab, slab beam, piled, and cellular rafts, each offer unique advantages tailored to specific structural and soil requirements. By choosing the appropriate raft foundation type, you can ensure the stability and durability of your building while optimizing construction costs and efficiency.

Conclusion

Raft foundations are an essential element in modern construction, particularly in areas with challenging soil conditions. They provide a robust solution for distributing loads evenly, preventing differential settling, and ensuring the structural integrity of buildings. Understanding the various types of raft foundations, from solid slab to piled and cellular designs, allows for tailored applications that meet specific project needs. While they offer numerous advantages, including cost-effectiveness and versatility, it is important to consider site-specific conditions and professional expertise in their design and implementation. By doing so, you can achieve a durable, stable foundation that supports your building efficiently and effectively.

civil engineering

Prefabricated and modular houses – 10 Amazing designs. | Advantages and Disadvantages

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Prefabricated and modular houses, as found in New City Paradise, are like putting together a puzzle. But best of all is that from one or more pieces, it is you who decides the final image. The future of housing design will probably be increasingly closer to the modality of prefabricated and modular houses.

And the reasons are simple and appeal to our old friend: common sense.

  1. Significance of Prefabricated and Modular Houses
  2. Disadvantages of Prefabricated and Modular Houses
  3. 10 Very Good Designs of Prefabricated and Modular Houses
    1. #1. CPH Shelter House
    2. #two. Modular Ecological Houses
    3. #3. The Smart Shelter
    4. #4. The Unseen House
    5. #5. House M2
    6. #6. The Big Box
    7. #7. Prefabricated House C6
    8. #8. Modular House in Container
    9. #9. The Arch House
    10. #10. Prefabricated Single Family Home

Significance of Prefabricated and Modular Houses

There are many advantages to this constructive modality:

  • Construction times are greatly reduced
  • The house (in its entirety or parts) is built in a workshop and not on the land
  • Less environmental impact due to: waste of materials, water contamination, less noise, and less energy consumption
  • There is greater control of the energy and bioclimatic behaviour of the house
  • Construction labour costs are reduced
  • The fieldwork is much less compared to the traditional way of building a house
  • It is very easy to expand the house since being modules; it is only enough to “add” one or more to the house
  • There are fewer construction labour conflicts because the entire construction process is done in the factory, in a scheduled and standardized manner

Disadvantages of Prefabricated and Modular Houses

And like everything in this life, prefabricated and modular houses also have their disadvantages:

  • In many cases, you must choose between pre-established designs
  • Costs are increased in the quality of the materials used. (Which is also an advantage regarding the quality that the house will have)
  • In matters of legislation, it is worth reviewing when you buy models of prefabricated and modular houses outside the country where you live
  • Local weather conditions should also guide you when choosing the prefabricated and modular home option. Not all houses will be designed according to the climate of the place where you live
  • The costs of moving the house to the land must be considered

In conclusion, and weighing both the advantages and disadvantages of the prefabricated and modular home design modality, it seems to me that there are more advantages than disadvantages.

So it is worth considering this alternative when building your house.

And to give you an idea of ​​the versatility offered by the prefabricated and modular home modality, here is a selection of 10 good designs that I have compiled for you.

I hope you enjoy them and tell me if it is easy for you or not to choose the one you like the most.

10 Very Good Designs of Prefabricated and Modular Houses

#1. CPH Shelter House

Prefabricated and Modular Houses
Prefabricated and Modular Houses – A very good design. A mobile, flexible and sustainable house. Built by the Danish firm CPH Shelter

A very good design. A mobile, flexible and sustainable house. Built by the Danish firm CPH Shelter

Building based on containers has many advantages:

  • Its construction is fast, flexible and modular
  • In most soils, very simple and inexpensive foundations are required
  • The assembly of the house on the ground takes very little time
  • They are very easy to move from one place to another

Being houses built in a modular way, they can easily be transformed into larger houses and adapted to the needs of each family.

This house is a passive design; that is, it makes the most of the use of clean energy, also taking care of the materials used, coatings and paints.

It has large windows and includes a kitchen, bathroom, living room, and bedroom, plus plenty of storage space.

#two. Modular Ecological Houses

Modular Ecological Houses
A house generates more energy than it consumes

The main idea of ​​this house is to maximize passive design strategies and the creation of spaces that flow through the house.

The walls are mobile so that the spaces grow as needed, making the rooms larger or smaller depending on the activity.

All this facing north and the winter garden, not only a place to air-condition the house but also to grow vegetables, to rest, relax, etc.

This design has been developed by the Australian company ArchiBlox.

#3. The Smart Shelter

Prefabricated and Modular Houses - The Smart Shelter
A 96m2 house was built in 10 months

The construction has been defined as a place to share leisure time enjoying the landscape.

The S-SE orientation maximizes thermal comfort in winter, and the sun protection ensures enjoyment in the summer season.

A very good design where simplicity and functionality prevail.

This project was designed and built by the Spanish company NOEM. 

NOEM’s motto reads:

«Design, modern, ecological and prefabricated wooden houses. High energy efficiency custom projects equipped with the most advanced eco-technology and designed under passive house standards.”

Your work is worth knowing!

#4. The Unseen House

Prefabricated Modular Houses - The Unseen House
The Unseen House

Casa Invisible is a flexible housing unit consisting of a prefabricated wooden structure designed for turnkey execution at any designated site

Maximum flexibility and spatial quality are the critical elements in its development concept.

This provides custom design options for the housing units as well as flexible pricing options.

The total dimensions are 14.50 x 3.50 meters, which facilitates transport by truck.

The key factors in this proposal are its uncomplicated assembly, its attractive price, and the free choice of location.

This design was developed by the Austrian firm DMAA. 

#5. House M2

Prefabricated Modular Houses - House M2
Prefabricated Modular Houses – House M2

The house has 2 bedrooms and 1 and a half bathrooms. It has a total area of ​​115 m2

The living/dining rooms and bedrooms are connected by a fibreglass “suspended bridge”.

Method Homes is one of North America’s most prestigious manufactured home companies.

They are specialists in modular houses, built in an artisanal way by authentic professionals, with excellent value for money.

Its quality and precision are unquestionable.

#6. The Big Box

Prefabricated and modular houses - The big box
A house with 2 bedrooms and a total area of ​​73m2

Clad in wood both outside and inside the house, which gives it a rustic and very modern design at the same time.

An outside terrace helps to “extend” the house outside.

The Bert & May Group (London) are specialists in modular manufacturing of houses with a very modern aesthetic.

The construction of this “ecological mobile home” takes only 14 weeks, and it can be assembled in a single day. Incredible!!!

Enjoy this Very Good Design!!!

#7. Prefabricated House C6

Prefabricated House - C 6

This design is part of the C6 series of model homes designed by the LivingHomes staff in collaboration with Make It Right, a non-profit organization founded by Brad Pitt and architect William McDonough.

The C6 series is the lowest cost design.

They combine clean and modern design, have floor plans adaptable to each client, improved finishes and artefacts, and many warehouses for storage.

The new C6 model is larger than the original C6 and features a streamlined roof and exterior.

#8. Modular House in Container

Modular house in container
Modular House in Container

This design is the smallest of the modular houses built by the company Nova Deko, in Australia

They use a 40-foot container and come up with good space-saving solutions that make the house compact and large at the same time.

Thanks to mechanisms such as folding doors and fitted wardrobes, the house offers a living space that does not feel claustrophobic.

There is a lot of efficiency in this design. Less is more!!!

#9. The Arch House

A prefabricated house, small and simple, but at the same time self-sufficient and intelligent

It can have a surface between 37 and 46m 2, depending on the model.

Solar panels make it energy self-sufficient. It also has good thermal insulation.

The house has the basic amenities of a house and the “California codes of modular construction”.

The design was made by the company Shelter Dynamics. 

#10. Prefabricated Single Family Home

Prefabricated single family Home
Prefabricated single-family Home

This house was designed by the Berlin-based studio  Brandt + Simon Architekten.

A design that seeks (and succeeds) to integrate with the landscape through a pixelated facade

The façade combines sustainable technologies with traditional cladding and hides a light timber frame construction.

In addition, a series of green building strategies are incorporated: layers of recycled paper are used for insulation, while solar panels support the heating system.

The internal structure allows a flexible organization of the rooms.

The kitchen and dining room are open to the terrace, while the ground floor spaces overlook a small part of the garden

I hope that this visual walk through these 10 Prefabricated and Modular Houses has inspired you.

I think it is worth considering this option when evaluating different modalities to build the house of your dreams.

But above all, I would like you to know that there are always alternatives.

There are always options when what guides you is the dream of building your own house.

And do not forget that whatever method you choose to build your house, try to have a good design and quality.

A good design will make your home a beautiful, welcoming place, a place where you can be happy with the people you love. For more home ideas, please visit New City Official Site.

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