This document discusses the properties and classification of aggregates used in concrete. It describes how aggregates can be classified based on size, weight, and composition. The key properties discussed include shape, texture, strength, density, moisture content, cleanliness, soundness, and thermal properties. Testing methods are provided for sieve analysis, grading, crushing strength, abrasion resistance, impact value, and soundness. The document also covers the workability of concrete and factors that influence it such as water-cement ratio, aggregate type and amount, cement type and amount, and use of admixtures.
The document summarizes the key properties and classifications of aggregates used to make concrete. It discusses that aggregates provide bulk and strength to concrete. It classifies aggregates based on their geological origin, size, shape, grading, and unit weight. The summary properties of fine and coarse aggregates are also provided, including requirements for good aggregates.
This document contains information about aggregates used in concrete provided by Deblina Dutta, a third year civil engineering student. It discusses the classification, properties, and uses of aggregates. Aggregates make up 70-80% of concrete by volume and include natural materials like sand, gravel, and crushed stone. They are classified based on their geological origin, size, shape, and unit weight. The properties of aggregates like composition, size, surface texture, specific gravity, bulk density, voids, porosity, absorption, and fineness modulus affect the properties of concrete. Aggregates are an important part of concrete as they give it body, make it economical, and contribute to its mechanical strength.
This document discusses the key materials used in concrete - cement, water, aggregates, and admixtures. It describes what concrete is, its types and uses. The main ingredients are described in detail, including their properties and how they affect the strength and performance of concrete. Aggregates make up the largest portion by volume and come in various sizes and grades. Proper mix design and material selection are important to produce durable concrete.
Concrete has several benefits including low cost, strength in compression, and ease of shaping when wet. However, it also has limitations such as low tensile strength and ductility. Concrete strength is determined by its compressive crushing strength and is affected by the materials and techniques used. It is strong in compression but weak in tension, so reinforcing with steel is common. Modern concrete contains aggregates, cement paste, water, and sometimes admixtures. Proper aggregate properties greatly influence the performance of concrete.
1) The document discusses different types of aggregates used in construction including their classification, physical properties, and testing methods.
2) Aggregates are classified based on size, source, and density. Common physical properties examined include shape, texture, strength, specific gravity, porosity, and moisture content.
3) Key tests described are for crushing strength, impact value, abrasion resistance, specific gravity, absorption, and moisture content. Proper testing ensures aggregates meet requirements for uses like concrete.
B-Tech Construction Material Presentaion.pptmosesnhidza
This document provides an overview of concrete, including its definition, properties, composition, testing, and uses. Some key points:
- Concrete is a mixture of cement, aggregates (sand and gravel), and water that can be used for load-bearing construction.
- Its properties depend on the mix proportions, water-cement ratio, and type of aggregates used. Good compaction and curing are important for strength.
- Concrete has high compressive strength but low tensile strength, so it is often reinforced with steel bars or prestressed using steel tendons.
- Aggregates make up the majority of a concrete mix by weight and influence properties like strength and durability. Proper testing of aggregates is
Aggregates are granular materials like sand, gravel, or crushed stone used with water and cement to make concrete. They come in two sizes: fine aggregates smaller than 5 mm and coarse aggregates larger than 5 mm. Aggregates provide strength, reduce cracking, and lower the cost of concrete. They are selected based on being hard, durable, and free of organic materials or other substances that could weaken the concrete. Aggregates are classified by size, manufacturing method, and density. Physical tests are conducted to determine properties like strength, hardness, porosity, and grading.
The document summarizes the key properties and classifications of aggregates used to make concrete. It discusses that aggregates provide bulk and strength to concrete. It classifies aggregates based on their geological origin, size, shape, grading, and unit weight. The summary properties of fine and coarse aggregates are also provided, including requirements for good aggregates.
This document contains information about aggregates used in concrete provided by Deblina Dutta, a third year civil engineering student. It discusses the classification, properties, and uses of aggregates. Aggregates make up 70-80% of concrete by volume and include natural materials like sand, gravel, and crushed stone. They are classified based on their geological origin, size, shape, and unit weight. The properties of aggregates like composition, size, surface texture, specific gravity, bulk density, voids, porosity, absorption, and fineness modulus affect the properties of concrete. Aggregates are an important part of concrete as they give it body, make it economical, and contribute to its mechanical strength.
This document discusses the key materials used in concrete - cement, water, aggregates, and admixtures. It describes what concrete is, its types and uses. The main ingredients are described in detail, including their properties and how they affect the strength and performance of concrete. Aggregates make up the largest portion by volume and come in various sizes and grades. Proper mix design and material selection are important to produce durable concrete.
Concrete has several benefits including low cost, strength in compression, and ease of shaping when wet. However, it also has limitations such as low tensile strength and ductility. Concrete strength is determined by its compressive crushing strength and is affected by the materials and techniques used. It is strong in compression but weak in tension, so reinforcing with steel is common. Modern concrete contains aggregates, cement paste, water, and sometimes admixtures. Proper aggregate properties greatly influence the performance of concrete.
1) The document discusses different types of aggregates used in construction including their classification, physical properties, and testing methods.
2) Aggregates are classified based on size, source, and density. Common physical properties examined include shape, texture, strength, specific gravity, porosity, and moisture content.
3) Key tests described are for crushing strength, impact value, abrasion resistance, specific gravity, absorption, and moisture content. Proper testing ensures aggregates meet requirements for uses like concrete.
B-Tech Construction Material Presentaion.pptmosesnhidza
This document provides an overview of concrete, including its definition, properties, composition, testing, and uses. Some key points:
- Concrete is a mixture of cement, aggregates (sand and gravel), and water that can be used for load-bearing construction.
- Its properties depend on the mix proportions, water-cement ratio, and type of aggregates used. Good compaction and curing are important for strength.
- Concrete has high compressive strength but low tensile strength, so it is often reinforced with steel bars or prestressed using steel tendons.
- Aggregates make up the majority of a concrete mix by weight and influence properties like strength and durability. Proper testing of aggregates is
Aggregates are granular materials like sand, gravel, or crushed stone used with water and cement to make concrete. They come in two sizes: fine aggregates smaller than 5 mm and coarse aggregates larger than 5 mm. Aggregates provide strength, reduce cracking, and lower the cost of concrete. They are selected based on being hard, durable, and free of organic materials or other substances that could weaken the concrete. Aggregates are classified by size, manufacturing method, and density. Physical tests are conducted to determine properties like strength, hardness, porosity, and grading.
Aggregates make up 70-80% of concrete by volume and can be classified by source, size, shape, and other properties. Their properties affect the workability, strength, and economics of concrete. Igneous, sedimentary, and metamorphic rocks are common sources. Aggregate size, shape, texture, strength, and durability all impact the performance of concrete. Tests are used to evaluate aggregate crushing strength, impact resistance, and abrasion characteristics important for different concreting applications. Proper aggregate selection and testing are essential for producing high quality concrete.
Concrete is a composite material made of aggregates, sand, cement, and water. It has high compressive strength but low tensile strength. Proper mixing and compaction are required to produce durable concrete. Mixing involves blending the ingredients into a uniform mass and coating aggregates with cement paste. Compaction removes air pockets and achieves maximum density. It is done through tamping, rodding, or vibrating the fresh concrete. Vibration uses internal or external vibrators to penetrate and settle the concrete mixture.
The document provides information on aggregates used in concrete, including their definition, classification, properties, grading, and tests. It defines aggregates as materials such as sand and gravel used to make concrete and mortar. Aggregates are classified by their geological origin, size, and shape. Their properties including strength, absorption, and density are described. The importance of proper grading of aggregates for density and strength of concrete is discussed. Common tests on aggregates like crushing value, impact value, and abrasion value are outlined.
Introduction To Aggregates Its Properties And Effectson ConcreteUmar Ahad
Introduction to use of aggregates in concrete. Various Properties of aggregates and their effect on fresh and hardened concrete. Flakiness and Elongation Index of Concrete have also been discussed. Various tests performed for suitable usage of concrete in Civil engineering projects have also been discussed.
This document provides an overview of concrete technology. It defines cement and concrete and describes their composition and manufacturing processes. It discusses the properties and types of cement and concrete, how workability is measured, and testing methods for fresh and hardened concrete, including compressive strength, slump, and rebound hammer tests. The document also outlines the processes for mixing, transporting, placing, compacting, curing, and finishing concrete.
Highway Materials: Desirable Properties, Testing Procedures, Standards, and standard values relating to Soil, Stone Aggregates, Bitumen and Tar, fly- ash/pond-ash. Role of filler in Bituminous mix, materials of filler.
Specifications of DLC and PQC for rigid pavement
This document provides information on aggregates used in traditional building materials. It defines aggregates as fillers used with binding materials that are derived from rocks. Aggregates make up 70-80% of concrete's volume and influence its properties. Aggregates are broadly classified into fine aggregates smaller than 4.75mm and coarse aggregates larger than 4.75mm. The document discusses various types of coarse aggregates based on geological origin, size, shape, and unit weight. It also covers properties of aggregates like strength, shape, specific gravity, moisture content and tests conducted on aggregates. Alkali aggregate reaction and measures to prevent it are summarized.
The weekly report summarizes activities from site visits and trainings. On May 14, the group observed soil, asphalt, and concrete testing rooms at AACRA and learned about testing procedures and equipment operation. On May 16, the group visited the Legetafo site where black cotton soil was being excavated to a depth of 1.6m for a 60m long section of roadwork. Rock was also discovered during excavation. On May 21, the group visited the Balderas site where a 1km long road with a 20m span was under construction, including a retaining wall, water segregation, and base course preparation to a thickness of 25mm. Trainees names were signed and the report was
In its simplest form, concrete is a mixture of paste and aggregates, or rocks. The paste, composed of portland cement and water, coats the surface of the fine (small) and coarse (larger) aggregates
The document provides information on various materials used in highway construction. It discusses the types and functions of pavement, including flexible and rigid pavements. It describes the requirements of ideal pavements. It also discusses various pavement materials like soil, aggregates, bitumen and their properties. It outlines various tests conducted on these materials like penetration test, abrasion test, crushing test, to evaluate their suitability for pavement construction.
This document discusses materials used in highway construction. It outlines seven major materials: bituminous materials, soil, aggregates, Portland cement concrete, admixtures, pavement marking materials, and structural steel. For each material, it provides details on composition, properties, and relevant tests used for evaluation and quality control of the material. Key tests discussed include moisture content value, California bearing ratio, Los Angeles abrasion value, and specific gravity and water absorption.
This document discusses various types of special concretes used for specific purposes, including lightweight concrete, high density concrete, mass concrete, plum concrete, fibre reinforced concrete, polymer concrete, and ferroconcrete. Lightweight concrete uses lightweight aggregates to reduce density, while high density concrete uses heavy aggregates. Mass concrete structures require measures to cope with heat generation during curing. Fibres are added to concrete to improve properties like ductility, toughness and crack resistance. Polymer concrete uses polymers instead of or along with cement. Ferroconcrete consists of wire meshes embedded in cement mortar. Each type has distinct composition, properties and applications.
1. Concrete is a composite material consisting of cement, water, fine aggregate (sand), and coarse aggregate (gravel). It constitutes 30-40% paste and 60-70% aggregates by volume.
2. The selection of concrete proportions involves balancing economy, workability, consistency, density, strength, and durability. Key factors are water-cement ratio, which controls strength, and durability to withstand weather conditions.
3. Aggregates are relatively inexpensive fillers that provide volume stability, abrasion resistance, and reduce volume changes in concrete. Their properties like density, grading, shape, and texture influence the properties of fresh and hardened concrete.
Aggregates are a combination of different sized stones used in construction. They are classified based on size, source, and density. Common types include natural and crushed coarse and fine aggregates. Aggregates must be hard, durable, and free of organic matter or other impurities. Tests are conducted to determine properties like strength, hardness, porosity, and water absorption. Sieve analysis tests the particle size distribution and grading of aggregates.
The aggregate is a relatively inert material and it imparts volume stability.
The aggregate provide about 75% of the body of the concrete and hence its influence is extremely important (70 to 80 %)
An aggregate should be of proper shape and size, clean, hard and well graded.
It must possess chemical stability and it must exhibit abrasion resistance.
Classification of Aggregate
I. Classification Based on Size
a. Fine aggregates:
b. Coarse aggregates:
II. Classification Based on Shape
a. Rounded aggregate:
b. Irregular aggregates
c. Angular aggregates
d. Flaky and elongated aggregates
III. Classification based on unit weight
a. Normal weight aggregates
b. Heavy weight aggregates
c. Light weight aggregates
The physical properties of aggregates are;
1. Shape
2. Size
3. Color
4. Texture
5. Gradation
6. Fineness modulus
Effect of aggregate properties on concrete
a. Particle Size, Grading and Dust Content
b. Particle Shape
c. Particle Surface Texture
d. Water Absorption
fineness modulus - According to IS 2386-1963, the sieves that are to be used for the sieve analysis of the aggregate for concrete are 80mm, 40mm, 20mm, 10mm, 4.75mm, 2.36mm, 1.18mm, 600m, 300m and 150m.
Gradation of aggregates
Gradation refers to the particle size distribution of aggregates.
The gradation of coarse aggregate plays an important role in workability and paste requirements.
The gradation of fine aggregate affects the workability and finishing ability of concrete.
Types of gradation:
a. Well graded
b. Poor / Uniform graded
c. Gap graded
Mechanical Properties
The following are the properties to be analyzed for aggregates, they are
a. Toughness
b. Hardness
c. Specific gravity
d. Bulk Density
e. Porosity and absorption of aggregates
f. Moisture content of aggregate
Mechanical Strength Test
a. Crushing strength Test
b. Impact strength Test
c. Abrasion Test (Los Angeles Test)
Water (for concrete)
Water is the most important material for construction, especially for making concrete.
The purpose of water in concrete are
a. It distributes the cement evenly.
b. It reacts with cement chemically and produces calcium silicate hydrate (C-S-H) gel which gives the strength to concrete.
c. It provides for workability, i.e., it lubricates the mix.
d. Hence, for construction, quantity and quality of water is as important as cement.
As water quantity goes up in a mix (ill effect), the following are the effects:
a. Strength decreases
b. Durability decreases
c. Workability increases
d. Cohesion decreases
e. Economy may increase at the expense of quality and reliability.
Quality of water for concrete (IS10500:2012)
a. Chlorides: They can cause corrosion of steel reinforcement, can accelerate setting.
b. Sulphates: They reduce long-term strength levels.
c. Organic matter: If an alga is present, water should not be used. It will affect the setting and strength development.
d. Sugar: It will retard setting time.
e. Wastewater: It should never be used in construction.
Aggregates such as sand and gravel are mixed with cement and water to form concrete. There are several key properties of aggregates including being clean, hard, durable, and having a shape that provides good workability and strength. The most common aggregate sources are river stones or crushed rock. Proper grading of aggregate sizes is important to prevent voids when mixed. Concrete is formed by mixing aggregates, cement, and water. The exact proportions and mixing process affect the workability and strength properties of the resulting concrete. Curing the concrete is also important for the hardening and strength development process.
This document discusses aggregates and bituminous materials used in construction. It describes various types of aggregates including sand, gravel, crushed stone, and recycled concrete that are used as a base material or to extend asphalt and concrete. It outlines important properties of aggregates like density, absorption and shape. It also discusses uses of aggregates in bases, asphalt, and Portland cement. Further, it describes types and testing of bituminous materials like penetration graded bitumen, viscosity graded bitumen and modified bitumens used in construction.
This document discusses aggregates which are inert materials mixed with cement to produce concrete. It defines aggregates and describes their properties and types. Aggregates can be classified based on grain size, origin, density or shape. The main types are fine aggregates like sand, and coarse aggregates like gravel. Fine aggregates pass through a 4.75mm sieve while coarse aggregates are retained. Properties of aggregates that affect concrete like composition, size and texture are also covered. The goal is to educate civil engineers on aggregates used in construction.
Concrete is made up of ingredients like Cement, Fine Aggregate (Sand), Coarse Aggregate, Water and admixtures. Concrete mix design is done to Optimize the requirements of Cement, Sand, Aggregate and Water in order to ensure that concrete parameters in both Plastic Stage (like workability) and in Hardened Stage (like Compressive Strength and durability) are achieved. The Concrete mix design is as per Indian Standards (IS 10262) and might vary from country to country. The nominal mix design ratios available for concrete less than M30 in strength are only thumb rules and are generally over designed. As the actual site conditions vary and the mix design should be adjusted as per the location and other factors.
Aggregates are granular materials such as sand, gravel, crushed stone and recycled concrete used with cementing materials like cement or asphalt to produce concrete or asphalt. They make up 75% of concrete and over 90% of asphalt. Aggregates must be strong, durable and meet certain shape and size requirements. Common tests evaluate properties like strength, hardness, absorption and abrasion resistance. Sources of aggregates in Pakistan include limestone from Margalla Hills and Salt Range as well as dolomite deposits in Hazara and Kashmir regions.
Data Communication and Computer Networks Management System Project Report.pdfKamal Acharya
Networking is a telecommunications network that allows computers to exchange data. In
computer networks, networked computing devices pass data to each other along data
connections. Data is transferred in the form of packets. The connections between nodes are
established using either cable media or wireless media.
Cricket management system ptoject report.pdfKamal Acharya
The aim of this project is to provide the complete information of the National and
International statistics. The information is available country wise and player wise. By
entering the data of eachmatch, we can get all type of reports instantly, which will be
useful to call back history of each player. Also the team performance in each match can
be obtained. We can get a report on number of matches, wins and lost.
Aggregates make up 70-80% of concrete by volume and can be classified by source, size, shape, and other properties. Their properties affect the workability, strength, and economics of concrete. Igneous, sedimentary, and metamorphic rocks are common sources. Aggregate size, shape, texture, strength, and durability all impact the performance of concrete. Tests are used to evaluate aggregate crushing strength, impact resistance, and abrasion characteristics important for different concreting applications. Proper aggregate selection and testing are essential for producing high quality concrete.
Concrete is a composite material made of aggregates, sand, cement, and water. It has high compressive strength but low tensile strength. Proper mixing and compaction are required to produce durable concrete. Mixing involves blending the ingredients into a uniform mass and coating aggregates with cement paste. Compaction removes air pockets and achieves maximum density. It is done through tamping, rodding, or vibrating the fresh concrete. Vibration uses internal or external vibrators to penetrate and settle the concrete mixture.
The document provides information on aggregates used in concrete, including their definition, classification, properties, grading, and tests. It defines aggregates as materials such as sand and gravel used to make concrete and mortar. Aggregates are classified by their geological origin, size, and shape. Their properties including strength, absorption, and density are described. The importance of proper grading of aggregates for density and strength of concrete is discussed. Common tests on aggregates like crushing value, impact value, and abrasion value are outlined.
Introduction To Aggregates Its Properties And Effectson ConcreteUmar Ahad
Introduction to use of aggregates in concrete. Various Properties of aggregates and their effect on fresh and hardened concrete. Flakiness and Elongation Index of Concrete have also been discussed. Various tests performed for suitable usage of concrete in Civil engineering projects have also been discussed.
This document provides an overview of concrete technology. It defines cement and concrete and describes their composition and manufacturing processes. It discusses the properties and types of cement and concrete, how workability is measured, and testing methods for fresh and hardened concrete, including compressive strength, slump, and rebound hammer tests. The document also outlines the processes for mixing, transporting, placing, compacting, curing, and finishing concrete.
Highway Materials: Desirable Properties, Testing Procedures, Standards, and standard values relating to Soil, Stone Aggregates, Bitumen and Tar, fly- ash/pond-ash. Role of filler in Bituminous mix, materials of filler.
Specifications of DLC and PQC for rigid pavement
This document provides information on aggregates used in traditional building materials. It defines aggregates as fillers used with binding materials that are derived from rocks. Aggregates make up 70-80% of concrete's volume and influence its properties. Aggregates are broadly classified into fine aggregates smaller than 4.75mm and coarse aggregates larger than 4.75mm. The document discusses various types of coarse aggregates based on geological origin, size, shape, and unit weight. It also covers properties of aggregates like strength, shape, specific gravity, moisture content and tests conducted on aggregates. Alkali aggregate reaction and measures to prevent it are summarized.
The weekly report summarizes activities from site visits and trainings. On May 14, the group observed soil, asphalt, and concrete testing rooms at AACRA and learned about testing procedures and equipment operation. On May 16, the group visited the Legetafo site where black cotton soil was being excavated to a depth of 1.6m for a 60m long section of roadwork. Rock was also discovered during excavation. On May 21, the group visited the Balderas site where a 1km long road with a 20m span was under construction, including a retaining wall, water segregation, and base course preparation to a thickness of 25mm. Trainees names were signed and the report was
In its simplest form, concrete is a mixture of paste and aggregates, or rocks. The paste, composed of portland cement and water, coats the surface of the fine (small) and coarse (larger) aggregates
The document provides information on various materials used in highway construction. It discusses the types and functions of pavement, including flexible and rigid pavements. It describes the requirements of ideal pavements. It also discusses various pavement materials like soil, aggregates, bitumen and their properties. It outlines various tests conducted on these materials like penetration test, abrasion test, crushing test, to evaluate their suitability for pavement construction.
This document discusses materials used in highway construction. It outlines seven major materials: bituminous materials, soil, aggregates, Portland cement concrete, admixtures, pavement marking materials, and structural steel. For each material, it provides details on composition, properties, and relevant tests used for evaluation and quality control of the material. Key tests discussed include moisture content value, California bearing ratio, Los Angeles abrasion value, and specific gravity and water absorption.
This document discusses various types of special concretes used for specific purposes, including lightweight concrete, high density concrete, mass concrete, plum concrete, fibre reinforced concrete, polymer concrete, and ferroconcrete. Lightweight concrete uses lightweight aggregates to reduce density, while high density concrete uses heavy aggregates. Mass concrete structures require measures to cope with heat generation during curing. Fibres are added to concrete to improve properties like ductility, toughness and crack resistance. Polymer concrete uses polymers instead of or along with cement. Ferroconcrete consists of wire meshes embedded in cement mortar. Each type has distinct composition, properties and applications.
1. Concrete is a composite material consisting of cement, water, fine aggregate (sand), and coarse aggregate (gravel). It constitutes 30-40% paste and 60-70% aggregates by volume.
2. The selection of concrete proportions involves balancing economy, workability, consistency, density, strength, and durability. Key factors are water-cement ratio, which controls strength, and durability to withstand weather conditions.
3. Aggregates are relatively inexpensive fillers that provide volume stability, abrasion resistance, and reduce volume changes in concrete. Their properties like density, grading, shape, and texture influence the properties of fresh and hardened concrete.
Aggregates are a combination of different sized stones used in construction. They are classified based on size, source, and density. Common types include natural and crushed coarse and fine aggregates. Aggregates must be hard, durable, and free of organic matter or other impurities. Tests are conducted to determine properties like strength, hardness, porosity, and water absorption. Sieve analysis tests the particle size distribution and grading of aggregates.
The aggregate is a relatively inert material and it imparts volume stability.
The aggregate provide about 75% of the body of the concrete and hence its influence is extremely important (70 to 80 %)
An aggregate should be of proper shape and size, clean, hard and well graded.
It must possess chemical stability and it must exhibit abrasion resistance.
Classification of Aggregate
I. Classification Based on Size
a. Fine aggregates:
b. Coarse aggregates:
II. Classification Based on Shape
a. Rounded aggregate:
b. Irregular aggregates
c. Angular aggregates
d. Flaky and elongated aggregates
III. Classification based on unit weight
a. Normal weight aggregates
b. Heavy weight aggregates
c. Light weight aggregates
The physical properties of aggregates are;
1. Shape
2. Size
3. Color
4. Texture
5. Gradation
6. Fineness modulus
Effect of aggregate properties on concrete
a. Particle Size, Grading and Dust Content
b. Particle Shape
c. Particle Surface Texture
d. Water Absorption
fineness modulus - According to IS 2386-1963, the sieves that are to be used for the sieve analysis of the aggregate for concrete are 80mm, 40mm, 20mm, 10mm, 4.75mm, 2.36mm, 1.18mm, 600m, 300m and 150m.
Gradation of aggregates
Gradation refers to the particle size distribution of aggregates.
The gradation of coarse aggregate plays an important role in workability and paste requirements.
The gradation of fine aggregate affects the workability and finishing ability of concrete.
Types of gradation:
a. Well graded
b. Poor / Uniform graded
c. Gap graded
Mechanical Properties
The following are the properties to be analyzed for aggregates, they are
a. Toughness
b. Hardness
c. Specific gravity
d. Bulk Density
e. Porosity and absorption of aggregates
f. Moisture content of aggregate
Mechanical Strength Test
a. Crushing strength Test
b. Impact strength Test
c. Abrasion Test (Los Angeles Test)
Water (for concrete)
Water is the most important material for construction, especially for making concrete.
The purpose of water in concrete are
a. It distributes the cement evenly.
b. It reacts with cement chemically and produces calcium silicate hydrate (C-S-H) gel which gives the strength to concrete.
c. It provides for workability, i.e., it lubricates the mix.
d. Hence, for construction, quantity and quality of water is as important as cement.
As water quantity goes up in a mix (ill effect), the following are the effects:
a. Strength decreases
b. Durability decreases
c. Workability increases
d. Cohesion decreases
e. Economy may increase at the expense of quality and reliability.
Quality of water for concrete (IS10500:2012)
a. Chlorides: They can cause corrosion of steel reinforcement, can accelerate setting.
b. Sulphates: They reduce long-term strength levels.
c. Organic matter: If an alga is present, water should not be used. It will affect the setting and strength development.
d. Sugar: It will retard setting time.
e. Wastewater: It should never be used in construction.
Aggregates such as sand and gravel are mixed with cement and water to form concrete. There are several key properties of aggregates including being clean, hard, durable, and having a shape that provides good workability and strength. The most common aggregate sources are river stones or crushed rock. Proper grading of aggregate sizes is important to prevent voids when mixed. Concrete is formed by mixing aggregates, cement, and water. The exact proportions and mixing process affect the workability and strength properties of the resulting concrete. Curing the concrete is also important for the hardening and strength development process.
This document discusses aggregates and bituminous materials used in construction. It describes various types of aggregates including sand, gravel, crushed stone, and recycled concrete that are used as a base material or to extend asphalt and concrete. It outlines important properties of aggregates like density, absorption and shape. It also discusses uses of aggregates in bases, asphalt, and Portland cement. Further, it describes types and testing of bituminous materials like penetration graded bitumen, viscosity graded bitumen and modified bitumens used in construction.
This document discusses aggregates which are inert materials mixed with cement to produce concrete. It defines aggregates and describes their properties and types. Aggregates can be classified based on grain size, origin, density or shape. The main types are fine aggregates like sand, and coarse aggregates like gravel. Fine aggregates pass through a 4.75mm sieve while coarse aggregates are retained. Properties of aggregates that affect concrete like composition, size and texture are also covered. The goal is to educate civil engineers on aggregates used in construction.
Concrete is made up of ingredients like Cement, Fine Aggregate (Sand), Coarse Aggregate, Water and admixtures. Concrete mix design is done to Optimize the requirements of Cement, Sand, Aggregate and Water in order to ensure that concrete parameters in both Plastic Stage (like workability) and in Hardened Stage (like Compressive Strength and durability) are achieved. The Concrete mix design is as per Indian Standards (IS 10262) and might vary from country to country. The nominal mix design ratios available for concrete less than M30 in strength are only thumb rules and are generally over designed. As the actual site conditions vary and the mix design should be adjusted as per the location and other factors.
Aggregates are granular materials such as sand, gravel, crushed stone and recycled concrete used with cementing materials like cement or asphalt to produce concrete or asphalt. They make up 75% of concrete and over 90% of asphalt. Aggregates must be strong, durable and meet certain shape and size requirements. Common tests evaluate properties like strength, hardness, absorption and abrasion resistance. Sources of aggregates in Pakistan include limestone from Margalla Hills and Salt Range as well as dolomite deposits in Hazara and Kashmir regions.
Data Communication and Computer Networks Management System Project Report.pdfKamal Acharya
Networking is a telecommunications network that allows computers to exchange data. In
computer networks, networked computing devices pass data to each other along data
connections. Data is transferred in the form of packets. The connections between nodes are
established using either cable media or wireless media.
Cricket management system ptoject report.pdfKamal Acharya
The aim of this project is to provide the complete information of the National and
International statistics. The information is available country wise and player wise. By
entering the data of eachmatch, we can get all type of reports instantly, which will be
useful to call back history of each player. Also the team performance in each match can
be obtained. We can get a report on number of matches, wins and lost.
Covid Management System Project Report.pdfKamal Acharya
CoVID-19 sprang up in Wuhan China in November 2019 and was declared a pandemic by the in January 2020 World Health Organization (WHO). Like the Spanish flu of 1918 that claimed millions of lives, the COVID-19 has caused the demise of thousands with China, Italy, Spain, USA and India having the highest statistics on infection and mortality rates. Regardless of existing sophisticated technologies and medical science, the spread has continued to surge high. With this COVID-19 Management System, organizations can respond virtually to the COVID-19 pandemic and protect, educate and care for citizens in the community in a quick and effective manner. This comprehensive solution not only helps in containing the virus but also proactively empowers both citizens and care providers to minimize the spread of the virus through targeted strategies and education.
Sri Guru Hargobind Ji - Bandi Chor Guru.pdfBalvir Singh
Sri Guru Hargobind Ji (19 June 1595 - 3 March 1644) is revered as the Sixth Nanak.
• On 25 May 1606 Guru Arjan nominated his son Sri Hargobind Ji as his successor. Shortly
afterwards, Guru Arjan was arrested, tortured and killed by order of the Mogul Emperor
Jahangir.
• Guru Hargobind's succession ceremony took place on 24 June 1606. He was barely
eleven years old when he became 6th Guru.
• As ordered by Guru Arjan Dev Ji, he put on two swords, one indicated his spiritual
authority (PIRI) and the other, his temporal authority (MIRI). He thus for the first time
initiated military tradition in the Sikh faith to resist religious persecution, protect
people’s freedom and independence to practice religion by choice. He transformed
Sikhs to be Saints and Soldier.
• He had a long tenure as Guru, lasting 37 years, 9 months and 3 days
Online train ticket booking system project.pdfKamal Acharya
Rail transport is one of the important modes of transport in India. Now a days we
see that there are railways that are present for the long as well as short distance
travelling which makes the life of the people easier. When compared to other
means of transport, a railway is the cheapest means of transport. The maintenance
of the railway database also plays a major role in the smooth running of this
system. The Online Train Ticket Management System will help in reserving the
tickets of the railways to travel from a particular source to the destination.
Better Builder Magazine brings together premium product manufactures and leading builders to create better differentiated homes and buildings that use less energy, save water and reduce our impact on the environment. The magazine is published four times a year.
This is an overview of my current metallic design and engineering knowledge base built up over my professional career and two MSc degrees : - MSc in Advanced Manufacturing Technology University of Portsmouth graduated 1st May 1998, and MSc in Aircraft Engineering Cranfield University graduated 8th June 2007.
Particle Swarm Optimization–Long Short-Term Memory based Channel Estimation w...IJCNCJournal
Paper Title
Particle Swarm Optimization–Long Short-Term Memory based Channel Estimation with Hybrid Beam Forming Power Transfer in WSN-IoT Applications
Authors
Reginald Jude Sixtus J and Tamilarasi Muthu, Puducherry Technological University, India
Abstract
Non-Orthogonal Multiple Access (NOMA) helps to overcome various difficulties in future technology wireless communications. NOMA, when utilized with millimeter wave multiple-input multiple-output (MIMO) systems, channel estimation becomes extremely difficult. For reaping the benefits of the NOMA and mm-Wave combination, effective channel estimation is required. In this paper, we propose an enhanced particle swarm optimization based long short-term memory estimator network (PSOLSTMEstNet), which is a neural network model that can be employed to forecast the bandwidth required in the mm-Wave MIMO network. The prime advantage of the LSTM is that it has the capability of dynamically adapting to the functioning pattern of fluctuating channel state. The LSTM stage with adaptive coding and modulation enhances the BER.PSO algorithm is employed to optimize input weights of LSTM network. The modified algorithm splits the power by channel condition of every single user. Participants will be first sorted into distinct groups depending upon respective channel conditions, using a hybrid beamforming approach. The network characteristics are fine-estimated using PSO-LSTMEstNet after a rough approximation of channels parameters derived from the received data.
Keywords
Signal to Noise Ratio (SNR), Bit Error Rate (BER), mm-Wave, MIMO, NOMA, deep learning, optimization.
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This study Examines the Effectiveness of Talent Procurement through the Imple...DharmaBanothu
In the world with high technology and fast
forward mindset recruiters are walking/showing interest
towards E-Recruitment. Present most of the HRs of
many companies are choosing E-Recruitment as the best
choice for recruitment. E-Recruitment is being done
through many online platforms like Linkedin, Naukri,
Instagram , Facebook etc. Now with high technology E-
Recruitment has gone through next level by using
Artificial Intelligence too.
Key Words : Talent Management, Talent Acquisition , E-
Recruitment , Artificial Intelligence Introduction
Effectiveness of Talent Acquisition through E-
Recruitment in this topic we will discuss about 4important
and interlinked topics which are
This study Examines the Effectiveness of Talent Procurement through the Imple...
Aggregates
1. UNIT-III
INTRODUCTION
Aggregates are the important constituents in concrete. They give body to the
concrete, reduce shrinkage and effect economy, It occupy 70-80% of the volume of
concrete, Cement is the only factory made standard component in concrete other
ingredients namely water and aggregates are natural material and can vary to any
extent in many of their properties. The study of aggregates can best be done under
the following sub-headings
Classification
Source
Size
Shape
Texture
Strength
Specific gravity and bulk density
Moisture content
Cleanliness
Soundness
Chemical properties
Thermal properties
Durability
Sieve analysis
Grading
Classification
Aggregates can be classified based on the size of the aggregates as coarse
and fine aggregates
2. Aggregates can be also classified based on the weight of the aggregates as i)
Normal aggregates
ii) Light weight aggregates iii) Heavy weight aggregates
Normal weight aggregates can be further classified as natural aggregates and
artificial aggregates
Natural aggregates- sand, gravel, crushed rock such as granite, quartzite,
basalt, sandstone
Artificial aggregates- Broken bricks, slag, fly ash, bloated clay
Source
Natural aggregates originated from bed rocks
Three kinds of rocks namely Igneous, sedimentary and metamorphic rocks
These classification based on the made of formation of rocks
Igneous rocks: The igneous rocks are formed by cooling of molten magma or lava at
the surface of the earth
Sedimentary rocks: They are formed originally below the sea bed and subsequently
lifted up
Metamorphic rocks: They are originally either igneous or sedimentary rocks
which are subsequently metamorphosed due to extreme heat and pressure
Aggregates from igneous rocks
Most igneous rocks make highly satisfactory concrete aggregates because they
are normally hard, tough and dense
The igneous rocks have massive structure
3. They may occur light coloured or dark coloured
The igneous rocks is one of the widely occurring types of rocks on the rocks on
the faces of the earth bulk of concrete aggregates that are derived from igneous
origin
Aggregates from sedimentary rocks
Igneous rocks and metamorphic rocks are subjected to wearing agencies such
as sun, rain and wind
Due to these weathering agencies transport and deposit the particle of rock,
deep beneath the ocean bed where they are cemented together by some of the
cementing materials
Aggregates from metamorphic rocks
Igneous and sedimentary rocks may be subjected to high temperature and
pressure which causes metamorphic which changes the structure
Metamorphic rocks shows foliated structure
Size
The maximum size of aggregates used for plain cement concrete is 80mm
The maximum size of aggregates used for reinforced cement concrete is
20mm Using the largest possible maximum size will result in:
i. Reduction of the cement content
ii. Reduction in water requirement
iii. Reduction of drying shrinkage
4. The maximum size of the aggregates may be limited by following condition
i. Thickness of section
ii. Spacing of reinforcement
iii. Clear cover
iv. Mixing, handling and placing techniques
Bigger than 4.75mm is considered as coarse aggregates and less 4.75mm is a fine
aggregate
Shape
The shape of the aggregates is an important characteristic since it affect the
workability of concrete
The shape of the aggregates depending upon the parent rocks and type of
crusher
Shape of particle
i. Rounded
ii. Irregular or partly rounded
iii. Angular
iv. Flaky
By using the rounded shape aggregates the cement content is less required and
5. angular shape aggregates more cement is required
But angular shape aggregates gives more strength compare than rounded shape
Angularity number is based on the percentage voids in the aggregates after
compaction in a specified manner
Texture
Particle surface are smooth or rough
Surface texture depends on hardness, grain size, pore structure, structure of
rock and degree of forces acting on the particle surface
Hard, dense, fine grained materials will generally have smooth fracture surface
Surface smoothness increases, contact area decreases, and have less bonding
area and require a thinner layer of paste
Strength
The strength of the rocks does not exactly represent the strength of the
aggregates in concrete
Since concrete is an assemblage of individual piece of aggregates bond
together by cementing material
The strength is dependent also on the bond between the cement paste and
aggregates
If either the strength of the paste or the bond between the paste and aggregates
is low, a concrete of poor quality
When the cement paste of good quality and the bond between cement paste
and aggregates is satisfactory, the concrete of good quality
6. Conclude that while strong aggregates cannot make strong aggregates are an
essential requirements
Bulk density
The bulk density or unit weight of an aggregate gives valuable information
regarding the shape and grading of aggregates
The bulk density depends on the particle size and shape of the particle
The higher the bulk density the lower is the voids content
Specific gravity
Average specific gravity of the rocks vary from 2.6 to 2.8
Specific gravity of aggregates is used for design calculations of concrete
Specific gravity of aggregates is required to be consideration when deal with
light weight and heavy weight concrete
Moisture content
Some of the aggregates are porous and absorptive
Porosity and absorption of aggregates will affect the water/cement ratio
The water absorption of aggregates is determined by measuring the increase in
weight of an over dry sample when immersed in water for 24 hours
Bulking of aggregates
The bulking increases with the increase in moisture content upto certain limit and
beyond that the further increase in the moisture content result in the decreases in the
volume and at a moisture content representing saturation point
7. Cleanliness
Fine aggregates obtained from natural source is likely to contain organic
impurities in the form of silt and clay
Coarse aggregates stacked in the open and unused for long time may contain
moss and mud in the lower level of the stack
Sand is decayed with vegetable matter, humus, organic matter and other
impurities
Fine aggregates contains permissible quality of organic impurities or not a
simple test known as colorimetric test is made
Soundness
Soundness refers to the ability of aggregates to resist excessive change in
volume as a result of changes in physical conditions
These physical condition that affect the soundness of aggregates are the
freezing the thawing, variation in temperature, alternate wetting and drying
under normal condition and wetting and drying in salt water
Grading
The particle size distribution of aggregates is called grading
The grading determine the paste requirement for a workable concrete since the
amount of voids requires needs to be filled by the same amount of cement
paste in a concrete mixture
To obtain grading curve for aggregates, sieve analysis has to be conducted
Fine different kinds of size distribution, dense graded, gap graded, uniformly
graded, well graded and open graded
8. UNIT-III
Chemical properties
The chemical properties of aggregates have to do with the molecular structure of the
minerals in the aggregates particles, Reaction with asphalt and cement, There are
several types of substance found in mineral aggregates which may have a negative
effect, Most are rarely significant but varies organic substance may retard hardening,
reduce strength development or cause excessive air entrainment in Portland cement
concrete
Composition
Some aggregates have minerals that are subject to oxidation, hydration and
carbonation
Thermal properties - There are three thermal properties
i)Coefficient of thermal expansion ii)specific heat iii)thermal conductivity
The coefficient of thermal expansion of aggregates influences the value of such
a coefficient of concrete containing the given aggregates
The higher the coefficient of aggregates the higher the coefficient of the concrete
The linear thermal coefficient of expansion of concrete may be taken as 9.9x10-6
per0
c but the range may be from about 5.8x10-6
per0
c to 14x10-6
per0
c
Sieve analysis
Sieve analysis is conducted to a aggregates, which we call gradation
The aggregates used for making concrete are normally of the maximum size
80mm,40mm,20mm,10mm,4.75mm, 2.36mm, 60micron, 300micron and
150micron Coarse aggregates and those fractions from 80mm to 4.75mm
Fine aggregates and those fraction 4.75mm to 150µ
9. UNIT-III
Testing of aggregates
In order to decide the suitability of the aggregate for use in pavement
construction, following tests are carried out:
Crushing test
Abrasion test
Impact test
Soundness test
Shape test
Specific gravity and water absorption test
Bitumen adhesion test
Crushing test
One of the model in which pavement material can fail is by crushing under
compressive stress. A test is standardized by IS: 2386 part-IV and used to
determine the crushing strength of aggregates.
The aggregate crushing value provides a relative measure of resistance to
crushing under gradually applied crushing load.
The test consists of subjecting the specimen of aggregate in standard mould to
a compression test under standard load conditions.
Dry aggregates passing through 12.5 mm sieves and retained 10 mm sieves
are filled in a cylindrical measure of 11.5 mm diameter and 18 cm height in
three layers.
Each layer is tampered 25 times with at standard tamping rod. The test sample
is weighed and placed in the test cylinder in three layers each layer being
tampered again.
The specimen is subjected to a compressive load of 40 tonnes gradually applied
10. at the rate of 4 tonnes per minute. Then crushed aggregates are then sieved
through 2.36 mm sieve and weight of passing material (W2) is expressed as
percentage of the weight of the total sample (W1) which is the aggregate
crushing value.
Aggregate crushing value =W1 /W2 x 100
Abrasion test
Abrasion test is carried out to test the hardness property of aggregates and to
decide whether they are suitable for different pavement construction works.
Los Angeles abrasion test is a preferred one for carrying out the hardness
property and has been standardized in India (IS:2386 part-IV).
The principle of Los Angeles abrasion test is to find the percentage wear due to
relative rubbing action between the aggregate and steel balls used as abrasive
charge.
Los Angeles machine consists of circular drum of internal diameter 700 mm and
length 520 mm mounted on horizontal axis enabling it to be rotated.
An abrasive charge consisting of cast iron spherical balls of 48 mm diameters
and weight 340-445 g is placed in the cylinder along with the aggregates.
The number of the abrasive spheres varies according to the grading of the
sample. The quantity of aggregates to be used depends upon the gradation and
usually ranges from 5- 10 kg.
The cylinder is then locked and rotated at the speed of 30-33 rpm for a total of
500 -1000 revolutions depending upon the gradation of aggregates.
After specified revolutions, the material is sieved through 1.7 mm sieve and
passed fraction is expressed as percentage total weight of the sample. This
value is called Los Angeles abrasion value.
A maximum value of 40 percent is allowed for WBM base course in Indian
conditions. For bituminous concrete, a maximum value of 35 is specified
Impact test
11. The aggregate impact test is carried out to evaluate the resistance to impact of
aggregates. Aggregates passing 12.5 mm sieve and retained on 10 mm sieve is filled
in a cylindrical steel cup of internal dia 10.2 mm and depth 5 cm which is attached to a
metal base of impact testing machine.
The material is filled in 3 layers where each layer is tamped for 25 numbers of blows.
Metal hammer of weight 13.5 to 14 Kg is arranged to drop with a free fall of 38.0 cm by
vertical guides and the test specimen is subjected to 15 numbers of blows.
The crushed aggregate is allowed to pass through 2.36 mm IS sieve. And the impact
value is measured as percentage of aggregates passing sieve (W2) to the total weight
of the sample (W1).
Aggregate impact value =W1/W2 x100
Aggregates to be used for wearing course, the impact value shouldn't exceed 30
percent. For bituminous macadam the maximum permissible value is 35 percent. For
Water bound macadam base courses the maximum permissible value defined by IRC
is 40 percent
Soundness
Soundness test is intended to study the resistance of aggregates to weathering
action, by conducting accelerated weathering test cycles.
The Porous aggregates subjected to freezing and thawing are likely to
disintegrate prematurely. To ascertain the durability of such aggregates, they
are subjected to an accelerated soundness test as specified in IS:2386 part-V.
Aggregates of specified size are subjected to cycles of alternate wetting in a
saturated solution of either sodium sulphate or magnesium sulphate for 16 - 18
hours and then dried in oven at 105 -110oC to a constant weight.
After five cycles, the loss in weight of aggregates is determined by sieving out
all undersized particles and weighing. And the loss in weight should not exceed
12 percent when tested with sodium sulphate and 18 percent with magnesium
sulphate solution.
Shape tests
12. The particle shape of the aggregate mass is determined by the percentage of
flaky and elongated particles in it.
Aggregates which are flaky or elongated are detrimental to higher workability
and stability of mixes.
The flakiness index is defined as the percentage by weight of aggregate
particles whose least dimension is less than 0.6 times their mean size.
Test procedure had been standardized in India (IS:2386 part-I)
The elongation index of an aggregate is defined as the percentage by weight of
particles whose great dimension (length) is 1.8 times their mean dimension.
This test is applicable to aggregates larger than 6.3 mm
This test is also specified in (IS:2386 Part-I). However there are no recognized
limits for the elongation index
Specific gravity and water absorption test
The specific gravity and water absorption of aggregates are important properties
that are required for the design of concrete and bituminous mixes.
The specific gravity of a solid is the ratio of its mass to that of an equal volume
of distilled water at a specified temperature. Because the aggregates may
contain water- permeable voids, so two measures of specific gravity of
aggregates are used: apparent specific gravity and bulk specific gravity.
Water absorption, the difference between the apparent and bulk specific
gravities is nothing but the water permeable voids of the aggregates.
The specific gravity of aggregates normally used in road construction ranges
from about to 2.9. Water absorption values ranges from 0.1 to about 2.0 percent
for aggregates normally used in road surfacing.
Bitumen adhesion test
Bitumen adheres well to all normal types of road aggregates provided they are
dry and free from dust.
Bitumen adheres well to all normal types of road aggregates provided they are
13. dry and free from dust. In the absence of water there is practically no adhesion
problem of bituminous construction.
Adhesion problem occurs when the aggregate is wet and cold.
This problem can be dealt with by removing moisture from the aggregate by
drying and increasing the mixing temperature.
14. UNIT-III
Workability of concrete
It is desirable that freshly mixed concrete be relatively easy to transport, place,
compact and finish without harmful segregation
A concrete mix satisfying three conditions in said to be workable
Workability is the most important property of freshly mixed concrete
There is no single test method that can simultaneously measure all the properties
Involved in workability
It is determined to a large extent by measuring the consistency of the mix
Consistency
Consistency is the fluidity or degree of wetness of concrete
It is generally dependent on the shear resistance of the mass
Its major factor in indicating the workability of freshly mixed concrete
Factors affecting concrete workability:
1. Water-Cement ratio
2. Amount and type of Aggregate
3. Amount and type of Cement
4. Weather conditions
5. Temperature
6. Wind
7. Chemical Admixtures
8. Sand to Aggregate ratio
1. Water content or Water Cement Ratio
More the water cement ratio more will be workability of concrete. Since by simply
adding water the inter particle lubrication is increased. High water content results in a
higher fluidity and greater workability. Increased water content also results in
15. bleeding. another effect of increased water content can also be that cement slurry will
escape through joints of formwork.
High water content results in a higher fluidity and greater workability. Increased water
content also results in bleeding. another effect of increased water content can also be
that cement slurry will escape through joints of formwork.
2. Amount and type of Aggregate
Since larger Aggregate sizes have relatively smaller surface areas (for the cement
paste to coat) and since less water means less cement, it is often said that one
should use the largest practicable Aggregate size and the stiffest practical mix. Most
building elements are constructed with a maximum Aggregate size of 3/4" to 1", larger
sizes being prohibited by the closeness of the reinforcing bars.
Because concrete is continuously shrinking for years after it is initially placed, it is
generally accepted that under thermal loading it will never expand to it's originally-
placed volume. More the amount of aggregate less will be workability.
Using smooth and round aggregate increases the workability. Workability reduces if
angular and rough aggregate is used.
Greater size of Aggregate- less water is required to lubricate it, the extra water is
available for workability
Angular aggregates increases flakiness or elongation thus reduces workability. Round
smooth aggregates require less water and less lubricationand gretaer workability in a
given w/c ratio
Porous aggregates require more water compared to non absorbent aggregates for
achieving same degree of workability.
16. 3. Aggregate Cement ratio
More ratio, less workability. Since less cement mean less water, so the paste is stiff.
4. Weather Conditions
1. Temperature: If temperature is high, evaporation increases, thus
workability decreases.
2. Wind: If wind is moving with greater velocity, the rate of evaporation also
increase reduces the amount of water and ultimately reducing workability.
5. Admixtures
Chemical admixtures can be used to increase workability.
Use of air entraining agent produces air bubbles which acts as a sort of ball bearing
between particles and increases mobility, workability and decreases bleeding,
segregation. The uses of fine pozzolanic materials also have better lubricating effect
and more workability.
6. Sand to Aggregate ratio
If the amount of sand is more the workability will reduce because sand has more
surface area and more contact area causing more resistance. The ingredients of
concrete can be proportioned by weight or volume. the goal is to provide the desired
strength and workability at minimum expense. A low water-cement ratio is used to
achieve a stronger concrete. It would seem therefore that by keeping the cement
content high one could use enough for god workability and still have a low w/c ratio.
the problem is that cement is the most costly of the basic ingredients. The dilemma is
easily seen in the graphs below.
17. VOLUME CHANGES IN CONCRETE
Concrete changes slightly in volume for various reasons, and understanding the
nature of these changes is useful in planning or analyzing concrete work
Cracks develop because concrete is relatively weak in tension but quite strong
in compression
Concrete volume changes due to thermal properties of aggregates and concrete
due to alkali/aggregates reaction due to sulphate action etc.,
Most objectionable defects in concrete is the presence of cracks
The cracks in floor and pavements is than due to shrinkage
The term shrinkage is loosely used to describe the various aspects of volume
changes in concrete due to different reasons
Shrinkage can be classified into following reasons
i. Plastic shrinkage
ii. Drying shrinkage
iii. Autogeneous shrinkage
iv. Carbonation shrinkage
Plastic shrinkage
Loss of water by evaporation from the surface of concrete is to be reasons of
plastic shrinkage
Loss water results in the reduction of volume
Water at the surface dries out the surface concrete collapses causing cracks
18. Prevention
Plastic shrinkage can be reduced mainly by preventing the rapid loss of water
from surface
This can be done by covering the surface with polyethylene sheeting
immediately on finishing operation
Monomolecular coating by fog spray that keeps the surface moist and also use
of small quality of aluminium power
Drying shrinkage
The loss of water contained in hardened concrete does not result in any
appreciable dimension change
It is the loss of water held in gel pores that causes the change in the volume
Under drying conditions the gel water is lost progressively over a long time as
long as the concrete is kept in drying conditions
Autogeneous shrinkage
Where no moisture movement to or from the paste in permitted when
temperature is constant some shrinkage may occur
The shrinkage of such conservative system is known as a autogeneous
shrinkage
Autogeneous shrinkage is of minor importance is not applicable in practice to
many situations except that of mass of concrete in the interior of a concrete dam
Carbonation shrinkage
Carbon dioxide present in the atmosphere reacts in the presence of water with
hydrated cement
Carbon hydroxide gets converted to calcium carbonate and some other cement