In-Depth Look at Lime's Influence on Cement and Concrete

Introduction

We are familiar with lime. Lime is a versatile material that plays a significant role in various applications, including construction, agriculture, and industry. 

 

There are two primary types of lime: 

• Quicklime (calcium oxide, CaO) and hydrated lime (calcium hydroxide, Ca(OH)2).

Here are some key points about lime:

1. Production of Lime:

•    Quicklime is produced by heating limestone (calcium carbonate, CaCO3) in a kiln. The process, known as calcination, involves removing carbon dioxide from the limestone, leaving behind calcium oxide.
•    Hydrated lime is obtained by adding water to quicklime, causing it to undergo a hydration reaction. This results in the formation of calcium hydroxide.

2. Use in Construction:

•    Lime has been historically used in construction as a mortar for masonry and plaster in buildings. Lime mortar is known for its workability and flexibility.
•    It reacts with carbon dioxide in the air over time, turning back into calcium carbonate and providing additional strength to the construction material.

3. Soil Stabilization:

• Lime is often used to stabilize soil in construction projects. 
• It helps improve the engineering properties of soil, enhancing its strength and reducing plasticity.

4. Water Treatment:

• Hydrated lime is used in water treatment processes to adjust pH levels and remove impurities.

5. Agricultural Applications:

• Agricultural lime, which is primarily composed of calcium carbonate, is used to improve soil quality by neutralizing acidic soils and providing essential nutrients to plants.

6. Industrial Processes:

•  Lime is utilized in various industrial processes, including the production of chemicals, paper, and metals.

7. Environmental Benefits:

•  Lime can be used to reduce sulfur dioxide emissions in industrial processes and in flue gas desulfurization systems in power plants.

Lime's properties make it a valuable material in a range of applications, contributing to the strength and stability of construction materials and providing environmental and agricultural benefits.

 

 

Connection Between Lime and Cement

Lime and cement are both important materials in construction, and they have a historical relationship in the development of construction techniques. Here are some aspects of the relationship between lime and cement:

1. Historical Context:

•  Lime has been used in construction for thousands of years. Ancient civilizations, such as the Romans, used lime-based mortars and concrete in their structures.
• The Romans used a form of natural cement, which contained lime and volcanic ash, to create structures like the Pantheon and aqueducts.

2. Lime in Traditional Mortars:

• Before the widespread use of Portland cement, lime mortars were commonly employed in construction. 
• These lime mortars were known for their flexibility and ability to accommodate movement in masonry structures.

3. Introduction of Portland Cement:

• Portland cement, a key component of modern concrete, was developed in the 19th century. 
• It gained popularity due to its rapid setting and strength development compared to traditional lime-based materials.

4. Hydraulic Lime:

• Hydraulic lime is a type of lime that sets and hardens through a chemical reaction with water, similar to cement. 
• It is often used in restoration projects and applications where a more flexible and breathable material is desired.

5. Combined Use in Mortars:

• In some cases, lime and cement may be combined to create mortars with specific properties. This combination can provide a balance between the flexibility of lime and the strength of cement.

6. Historic Preservation:

• Lime is still widely used in the restoration and preservation of historic buildings. 
• It is chosen for its compatibility with older masonry materials and its ability to allow for natural moisture movement within the structure.

7. Soil Stabilization:

• Both lime and cement are used for soil stabilization, but they offer different advantages. 
• Lime is often preferred in situations where a more gradual and less rigid improvement is required.

8. Sustainability Considerations:

• Lime production generally has a lower environmental impact compared to cement production. 
• Lime-based materials can be more environmentally friendly, making them suitable for sustainable construction practices.

In summary, while cement, especially Portland cement, has become the predominant binder in modern concrete, lime continues to have a role in construction, particularly in specialized applications, historic preservation, and sustainable practices. The choice between lime and cement often depends on the specific requirements of a construction project and the desired properties of the material. 

Role of Lime on Cement functioning

Lime plays a crucial role in cement production, specifically in the production of clinker, which is the main component of cement. The production of clinker involves the heating of a mixture of raw materials, and lime contributes to the formation of key minerals during this process. The main raw materials used in cement production are limestone (calcium carbonate), clay, shale, and silica sand.

Here's how lime is involved in cement production:

1. Calcination of Limestone:

•    - The primary source of lime in cement production is limestone (calcium carbonate, CaCO3). During the first stage of cement production, limestone is quarried and then crushed to smaller sizes.
•    - The crushed limestone is then heated in a kiln to a high temperature (around 1450°C). This process is known as calcination, and it results in the decomposition of limestone into lime (calcium oxide) and carbon dioxide.

   `\[ CaCO_3 \rightarrow CaO + CO_2 \]`

2. Formation of Clinker Minerals:

•    - The lime (calcium oxide) produced during calcination combines with other minerals present in the raw materials, such as silica, alumina, and iron oxide, to form the main clinker minerals.
•    - Tricalcium silicate (C3S), dicalcium silicate (C2S), tricalcium aluminate (C3A), and tetracalcium aluminoferrite (C4AF) are the primary clinker minerals formed during the high-temperature reactions in the kiln.

3. Hydration Process:

•    - After the clinker is produced, it is finely ground to form cement powder. When this cement powder is mixed with water during the construction process, it undergoes a hydration reaction.
•    - The hydration reaction involves the reaction of the clinker minerals with water to form hydrated compounds, including calcium silicate hydrate (C-S-H) and calcium hydroxide (CH).
•    - The presence of lime in the clinker contributes to the formation of these hydration products, which provide strength and durability to the concrete.

`   \[ C_3S + H_2O \rightarrow C-S-H + CH \]`

`\[ C_2S + H_2O \rightarrow C-S-H + CH \]`

  ` \[ C_3A + 3H_2O \rightarrow C-S-H + \(OH)_6 \]`
  ` \[ C_4AF + 2H_2O \rightarrow C-S-H + \(OH)_6 \]`

The role of lime in cement production is essential for the formation of clinker minerals and, subsequently, the development of strength in the final concrete. The hydrated compounds formed during the hydration process contribute to the binding properties and overall performance of the cementitious material.

Role of Calcium Hydroxide (Ca(OH)₂) during construction and cement work

• Calcium hydroxide (Ca(OH)₂) is a byproduct of the hydration reaction in cement. It forms when water reacts with the clinker minerals in cement, particularly tricalcium silicate (C₃S) and dicalcium silicate (C₂S). The role of calcium hydroxide in cement is significant and has both positive and potential drawbacks in terms of concrete performance:

1. Positive Aspects:

•    - Early Strength Development: Calcium hydroxide contributes to the early strength development of concrete. It is responsible for the initial setting and hardening of the concrete mix.
•    - Alkalinity: The presence of calcium hydroxide increases the alkalinity of the concrete. This high pH is beneficial for the passivation of steel reinforcement, providing corrosion protection.

2. Potential Drawbacks:

•    - Long-Term Strength Gain: While calcium hydroxide contributes to early strength, it is not a primary contributor to the long-term strength of concrete. Over time, calcium hydroxide can leach out of the concrete, potentially leading to a decrease in strength and durability.
•    - Cracking and Durability Concerns: Excessive amounts of calcium hydroxide can contribute to the formation of cracks in concrete, especially in situations with drying and wetting cycles. These cracks may compromise the durability of the structure.

3. Leaching and Efflorescence:

•    - Calcium hydroxide is water-soluble, and in certain conditions, it can leach out of the concrete. This leaching may result in the formation of efflorescence on the concrete surface, which is a white, powdery deposit.

4. Use in Pozzolanic Reactions:

•    - In some cases, supplementary cementitious materials (SCMs) such as fly ash or silica fume are added to concrete mixes. These materials can react with calcium hydroxide to form additional cementitious compounds, enhancing long-term strength and durability.

5. Role in Autogenous Healing:

•    - Calcium hydroxide participates in autogenous healing, a process where cracks in concrete can self-heal to some extent. The chemical reactions involving calcium hydroxide contribute to the sealing of microcracks.

In summary, calcium hydroxide is an integral part of the hydration process in cement, contributing to early strength and alkalinity. However, its potential drawbacks, such as leaching and long-term durability concerns, are important considerations in concrete mix design. Engineers and concrete practitioners often balance the benefits and drawbacks of calcium hydroxide to optimize concrete performance for specific applications.

"Lime can be used to reduce sulfur dioxide emissions in industrial processes and in flue gas desulfurization systems in power plants"

Application of lime in addressing air pollution, specifically sulfur dioxide (SO2) emissions.

Here's a breakdown of the key components of the statement:

1. Sulfur Dioxide (SO2) Emissions:
   - Sulfur dioxide is a harmful gas produced by the combustion of fossil fuels containing sulfur, such as coal and oil. It is a major contributor to air pollution and can lead to environmental and health issues.

2. Lime's Role:
   - Lime, or calcium oxide (CaO), can be used in industrial processes and power plants to reduce sulfur dioxide emissions.

3. Flue Gas Desulfurization (FGD) Systems:
   - Power plants often use flue gas desulfurization systems to control and reduce sulfur dioxide emissions from the combustion of fossil fuels.
   - In these systems, lime is commonly used as a reagent in a process known as "flue gas desulfurization" or "scrubbing."

4. Flue Gas Desulfurization Process:
   - The flue gas, which contains sulfur dioxide, is passed through a system where lime is introduced. Lime reacts with sulfur dioxide to form calcium sulfite (CaSO3) and, further, calcium sulfate (CaSO4), also known as gypsum.
   - The reaction is often represented as follows:
    ` \[ CaO + SO2 \rightarrow CaSO3 \]`
    ` \[ CaSO3 + 1/2O2 + H2O \rightarrow CaSO4 \cdot 2H2O \]`

5. Formation of Gypsum:
   - Gypsum is a solid byproduct that can be easily removed, and it has commercial value in various industries, such as construction and agriculture.

6. Environmental Benefits:
   - The use of lime in flue gas desulfurization helps to mitigate the environmental impact of sulfur dioxide emissions. By converting sulfur dioxide into solid gypsum, the harmful gas is removed from the flue gas, reducing air pollution.

In summary, lime plays a crucial role in reducing sulfur dioxide emissions in industrial processes, particularly in power plants equipped with flue gas desulfurization systems. The use of lime helps control air pollution, improve air quality, and mitigate the environmental impact of combustion processes that release sulfur dioxide into the atmosphere.

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Lime - Tests on Limestone

Tests on Limestones 

The following practical tests are made on limestones to determine their suitability:

• (i) Physical tests 
• (ii) Heat test 
• (iii) Chemical test 
• (iv) Ball test. 

 

(i) Physical Test: 

    Pure limestone is white in colour. Hydraulic limestones are bluish grey, brown or are having dark colours. The hydraulic lime gives out earthy smell. They are having clayey taste. The presence of lumps give indication of quick lime and unburnt lime stones. 

 

(ii) Heat Test: 

    A piece of dry stone weighing W1 is heated in an open fire for few hours. If weight of sample after cooling is W2, the loss of weight is W2 – W1. The loss of weight indicates the amount of carbon dioxide. From this the amount of calcium carbonate in limestone can be worked out. 

 

(iii) Chemical Test: 

    A teaspoon full of lime is placed in a test tube and dilute hydrochloric acid is poured in it. The content is stirred and the test tube is kept in the stand for 24 hours. Vigourous effervescence and less residue indicates pure limestone. If effervescence is less and residue is more it indicates impure limestone. 

    If thick gel is formed and after test tube is held upside down it is possible to identify class of lime as indicated below: 

• Class A lime, if gel do not flow.

• Class B lime, if gel tends to flow down. 

• Class C lime, if there is no gel formation. 

 

(iv) Ball Test: 

    This test is conducted to identify whether the lime belongs to class C or to class B. By adding sufficient water about 40 mm size lime balls are made and they are left undisturbed for six hours. Then the balls are placed in a basin of water. If within minutes slow expansion and slow disintegration starts it indicates class C lime. If there is little or no expansion, but only cracks appear it belongs to class B lime.

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Building with Lime: Past, Present, and Potential, Types and Properties

 

Building with Lime: 

Past, Present, and Potential, Types and Properties

Lime

It is an important binding material used in building construction. Lime has been used as the material of construction from ancient time. When it is mixed with sand it provides lime mortar and when mixed with sand and coarse aggregate, it forms lime concrete. 

Lime is a versatile material that finds applications in various fields, including construction, agriculture, and chemistry. There are two primary types of lime: quicklime (calcium oxide, CaO) and hydrated lime (calcium hydroxide, Ca(OH)2). Let's explore some aspects of lime:

Production:

• Quicklime (CaO): Produced by heating limestone (calcium carbonate, CaCO3) at high temperatures (typically around 900–1000°C) in a process known as calcination.
• Hydrated Lime (Ca(OH)2): Produced by treating quicklime with water.

Uses:

• Construction: Lime has been traditionally used in construction for various purposes, such as mortar and plaster. It reacts with carbon dioxide in the air and slowly turns back into calcium carbonate, resulting in a durable and stable material.

• Soil Stabilization: Lime is used to stabilize soil in construction projects, improving its engineering properties and reducing plasticity.

• Water Treatment: Hydrated lime is often used in water treatment processes to adjust pH levels and precipitate impurities.

• Agriculture: Agricultural lime (usually in the form of crushed limestone) is added to soil to neutralize acidity, providing essential nutrients for plant growth.

• Chemical Industry: Lime is used in various chemical processes, including the production of calcium-based chemicals and as a reactant in industrial processes.

Chemical Properties:

• Quicklime is highly reactive and exothermic when it reacts with water, producing heat.
• Hydrated lime is a dry powder that results from the chemical transformation of quicklime in the presence of water.

Safety Considerations:

• Quicklime is caustic and can cause burns. Proper safety measures, including protective equipment, should be used when handling it.

It's important to note that the application and properties of lime can vary based on the specific type of lime used and the intended use.

 

 

Types of Limes and their Properties 

The limes are classified as fat lime, hydraulic lime and poor lime: 

 

(i) Fat lime: 

It is composed of 95 percentage of calcium oxide. When water is added, it slakes vigorously and its volume increases to 2 to 2.5 times. It is white in colour. 

Its properties are:

• (a) hardens slowly 
• (b) has high degree of plasticity 
• (c) sets slowly in the presence of air 
• (d) white in colour 
• (e) slakes vigorously. 

 

(ii) Hydraulic lime: 

It contains clay and ferrous oxide. Depending upon the percentage of clay present, the hydraulic lime is divided into the following three types: 

• (a) Feebly hydraulic lime (5 to 10% clay content) 
• (b) Moderately hydraulic lime (11 to 20% clay content) 
• (c) Eminently hydraulic lime (21 to 30% clay content) 

The properties of hydraulic limes are: 

• • Sets under water
• • Colour is not perfectly white 
• • Forms a thin paste with water and do not dissolve in water. 
• • Its binding property improves if its fine powder is mixed with sand and kept in the form of heap for a week, before using. 

 

(iii) Poor lime: 

It contains more than 30% clay. Its colour is muddy. It has poor binding property. The mortar made with such lime is used for inferior works. 

 

IS 712-1973 classifies lime as class A, B, C, D and E. 

 

Class A Lime: 

It is predominently hydraulic lime. It is normally supplied as hydrated lime and is commonly used for structural works. 

 

Class B Lime: 

It contains both hydraulic lime and fat lime. It is supplied as hydrated lime or as quick lime. It is used for making mortar for masonry works. 

 

Class C Lime: 

It is predominently fat lime, supplied both as quick lime and fat lime. It is used for finishing coat in plastering and for white washing. 

 

Class D Lime: 

This lime contains large quantity of magnesium oxide and is similar to fat lime. This is also commonly used for white washing and for finishing coat in plastering. 

 

Class E Lime: 

It is an impure lime stone, known as kankar. It is available in modular and block form. It is supplied as hydrated lime. It is commonly used for masonry mortar

 

 

Structure where  Lime is Used

One of the most iconic and well-known structures that extensively used lime as a binding material is the Roman Pantheon. The Pantheon is an ancient temple located in Rome, Italy, and is renowned for its architectural and engineering marvel.

The Pantheon:

1. Construction Period:

   • The Pantheon was commissioned during the reign of Emperor Hadrian in 118–128 AD. However, the original structure on the site was built by Marcus Agrippa around 27 BC and later rebuilt by Emperor Hadrian.

2. Architectural Features:

   • The Pantheon is known for its remarkable dome, which was the largest unreinforced concrete dome in the world for many centuries.
   • The dome has a central oculus (circular opening) at the top, allowing natural light to enter the interior.

3. Use of Lime in Construction:

   • Lime played a crucial role in the construction of the Pantheon. The Romans used a type of mortar known as pozzolana mortar, which consisted of lime, volcanic ash (pozzolana), and water.
   • Pozzolana mortar is highly durable and has excellent hydraulic properties. The addition of pozzolana allowed the Romans to create concrete that could set underwater and gain strength over time.

4. Concrete Construction:

   • The Pantheon's dome is made of concrete, and the Romans employed a method of constructing concrete using a mixture of lime, pozzolana, and aggregates such as crushed volcanic rock and bricks.
   • The use of this concrete allowed for the creation of large and stable structures, and the Pantheon's dome is a testament to the engineering expertise of the Romans.

5. Durability and Longevity:

   • The Pantheon stands as a testament to the durability of Roman concrete and lime-based mortar. Despite its age, the structure has survived earthquakes and the test of time.

6. Symbolic Importance:

   • The Pantheon has been repurposed over the centuries and is now a Christian church (Basilica di Santa Maria ad Martyres). Its conversion contributed to its preservation.

The Pantheon remains an architectural marvel, and the use of lime-based materials in its construction highlights the ingenuity of ancient Roman engineers. The properties of lime and the technology used in structures like the Pantheon have influenced construction practices throughout history

 

Historical Use of Lime

Lime has a rich history dating back thousands of years, and its use has evolved over time. Here's a brief overview of the history of lime:

1. Ancient Uses:

   • The use of lime can be traced back to ancient civilizations. The Egyptians used a form of lime for various construction purposes, and evidence suggests that lime mortars were used in the construction of the pyramids.
   • The Greeks and Romans also extensively used lime-based materials in their construction projects. The Romans, in particular, developed advanced techniques for producing lime and pozzolana-based concrete, as seen in structures like the Pantheon.

2. Middle Ages:

   • The knowledge of lime production and use continued into the Middle Ages. Medieval builders in Europe used lime mortar for constructing cathedrals, castles, and other structures.
   • Lime kilns, used to produce quicklime by heating limestone, became more widespread during this period.

3. Renaissance and Early Modern Period:

   • The Renaissance saw a revival of interest in classical architecture, and the use of lime continued to be prominent. The development of lime-based plasters and finishes contributed to the aesthetic aspects of buildings during this period.

4. 18th and 19th Centuries:

   • The Industrial Revolution brought about advancements in lime production. Lime kilns became more efficient, and the demand for lime in construction, agriculture, and industry increased.
   • Lime was a key component in mortar for brick construction during the 19th century, contributing to the growth of urban areas.

5. 20th Century:

   • Portland cement, an alternative to lime-based mortars, gained popularity in the construction industry during the 20th century. However, lime continued to be used in heritage restoration and conservation projects due to its compatibility with historic structures.

6. Contemporary Uses:

   • Today, lime is still utilized in various industries. In construction, lime is employed for mortar, plaster, and soil stabilization. It remains an essential material in the restoration of historic buildings.
   • Agricultural lime, which is crushed limestone or dolomite, is used to neutralize soil acidity and improve crop yields.

Throughout history, lime has played a crucial role in the development of architectural and construction practices. Its enduring popularity is attributed to its versatility, durability, and compatibility with a wide range of materials. The historical use of lime in iconic structures highlights its significance in the built environment.

 

Chemical Constituents of Lime

Lime is a general term that refers to a range of calcium-containing inorganic materials. The two primary types of lime are quicklime (calcium oxide, CaO) and hydrated lime (calcium hydroxide, Ca(OH)2). Let's delve into the constituents of each:

1. Quicklime (Calcium Oxide, CaO):

   • Chemical Formula: CaO
   • Production: Quicklime is produced by heating limestone (calcium carbonate, CaCO3) in a lime kiln at high temperatures (typically around 900–1000°C) in a process known as calcination.
   • Properties:
     • Quicklime is a white, crystalline solid at room temperature.
     • It is highly reactive with water, producing heat in an exothermic reaction.
     • When quicklime reacts with water, it forms hydrated lime (calcium hydroxide).

2. Hydrated Lime (Calcium Hydroxide, Ca(OH)2):

   • Chemical Formula: Ca(OH)2
   • Production: Hydrated lime is produced by adding water to quicklime. This process is known as slaking or hydration.
   • Properties:
     • Hydrated lime is a dry, fine powder.
     • It is less reactive than quicklime but still exhibits some reactivity with water.
     • The chemical reaction between quicklime and water results in the formation of calcium hydroxide.

3. Pozzolana (Optional Constituent in Lime-Based Materials):

   • Definition: Pozzolana refers to siliceous or siliceous and aluminous materials that, in themselves, possess little or no cementitious value but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties.
   • Examples: Volcanic ash, fly ash, and certain natural clays are examples of pozzolanic materials.
   • Use: Pozzolanic materials are often added to lime-based materials, like mortars and concretes, to enhance their properties, such as setting time and strength.
     

The chemical reactions involved in the production of lime and its subsequent use in construction involve the transformation of calcium carbonate into calcium oxide and, eventually, into calcium hydroxide. These reactions are fundamental to the functionality and versatility of lime-based materials in various applications, from traditional mortar and plaster to more advanced construction techniques.

 

Clay and Lime Reactivity

The presence of clay in Lime Affect:

The presence of clay in lime can significantly influence the properties and performance of lime-based materials. While lime is often used in construction for its binding and stabilizing properties, the addition of clay can affect various aspects, such as workability, strength, and durability. Here are some effects of the presence of clay in lime:

1. Workability:

   • Positive Aspect: Small amounts of clay can enhance the workability of lime mortars. Clay acts as a plasticizer, making the mix more malleable and easier to work with.
   • Negative Aspect: Excessive clay content can lead to poor workability, making the lime mix difficult to handle and apply.

2. Setting Time:

   • Positive Aspect: Clay can contribute to the setting and hardening of lime-based materials by promoting pozzolanic reactions. Pozzolanic reactions involve the combination of lime with silica and alumina in the clay, forming compounds with cementitious properties.
   • Negative Aspect: Excessive clay content may lead to delayed setting times, affecting the construction schedule. It's crucial to find the right balance to achieve a reasonable setting time.

3. Strength:

   • Positive Aspect: The addition of clay can enhance the strength of lime-based materials. Pozzolanic reactions contribute to the development of additional cementitious compounds, improving the overall strength and durability.
   • Negative Aspect: Very high clay content may lead to a reduction in strength and durability, as excessive amounts of clay can disrupt the formation of a well-structured matrix.

4. Durability:

   • Positive Aspect: Properly proportioned clay content can improve the durability of lime-based materials, making them more resistant to weathering and environmental factors.
   • Negative Aspect: Excessive clay content can lead to poor durability, as it may result in shrinkage, cracking, and reduced resistance to freeze-thaw cycles.

5. Compatibility:

   • Positive Aspect: Clay can improve the compatibility of lime with certain aggregates, providing a more cohesive mix.
   • Negative Aspect: Incompatibility issues may arise if the clay content is too high, leading to segregation or poor adhesion with other materials.

In summary, the presence of clay in lime can have both positive and negative effects on properties depending on the proportion and the specific application. It requires careful consideration and proper mixing to achieve the desired balance between workability, strength, and durability. Engineers and builders often conduct tests and evaluations to determine the optimal clay content for a given lime-based material in order to achieve the desired performance.

 

Contact of Lime and Hardened Concrete:

When lime comes into contact with hardened concrete, it can lead to a phenomenon known as delayed ettringite formation (DEF). Ettringite is a crystalline compound that forms as part of the cement hydration process. However, when lime is introduced to hardened concrete under certain conditions, it can react with existing constituents and cause DEF. Here's an explanation of the process and its potential negative effects on hardened concrete:

Delayed Ettringite Formation (DEF):

1. Reaction Mechanism:

   • In the presence of moisture and elevated temperatures, lime can react with tricalcium aluminate (C3A) in the cementitious matrix.
   • This reaction forms ettringite crystals, which expand as they grow.

2. Negative Effects on Hardened Concrete:

   • Expansion and Cracking: The formation of ettringite crystals can lead to the expansion of concrete. This expansion, if significant, may cause internal stresses and cracking within the concrete. Cracking is a critical concern as it can compromise the structural integrity and durability of the concrete.

   • Reduced Strength and Durability: The expansion associated with delayed ettringite formation can result in a decrease in the compressive strength of the concrete. Additionally, the cracking induced by the expansion may allow harmful substances such as water, chlorides, and other aggressive agents to penetrate the concrete, reducing its long-term durability.

   • Aesthetic Issues: Cracking and expansion due to DEF can also lead to aesthetic concerns, impacting the appearance of the concrete surface.

   • Structural Concerns: In severe cases, the internal stresses and cracking caused by delayed ettringite formation may compromise the overall structural performance of the concrete.

3. Conditions Favoring DEF:

   • DEF is more likely to occur under specific conditions, including high temperatures during the curing period, elevated moisture levels, and the presence of reactive aggregates.
   • The use of high-lime-content materials or the introduction of lime after concrete has hardened can contribute to the risk of DEF.

4. Prevention and Mitigation:

   • To minimize the risk of DEF, it's essential to control the mix design, curing conditions, and the quality of materials used in concrete construction.
   • The careful selection of cement types, aggregates, and admixtures can help mitigate the potential negative effects of lime on hardened concrete.

In summary, the interaction of lime with hardened concrete leading to delayed ettringite formation poses challenges in terms of expansion, cracking, and potential reductions in strength and durability. As such, it is crucial to follow good concrete practices, consider material compatibility, and carefully control mix proportions to minimize the risk of DEF and its associated negative effects.

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Civil engineering - Building Materials - mortar and Lime

 Mortar and lime

Building material Civil engineering

Mortar

Mortar is defined as the mixture containing a binding agent Like lime or cement,water and fine aggregate.

On the basis of Binding agent mortar is classified into following types

1 lime mortar

It does not set quickly

Lime mortar generally made with hydraulic Lime

Its provide better resistance against rain penetration 

It is unliable to crack when compared with cement mortar

2.Cement Mortar

It is most suitable for construction work in Water Logged area

Gives shrinkage crack

3.Gauge Mortar

It is also called as composite mortar or cement lime mortar

with proportion of 1:1:6 to 1:1:8

After addition of cement It should be used with 1 to 2 hr

4 Light weight Mortar

It is Prepared by adding the material 

like as Wood - Powder , saw-dust, etc to lime/cement mortar

5. Surkhi Mortar

Surkhi is a pozzolanic material and it is very fine in size 

and it must be pass from a 4.75 mm sieve

surkhi is added to lime mortar to give hydraulically ability to set in presence of water

Lime-Cement Mortar:

Also known as Gauged mortar.

It is made from cement and lime.

The advantages of lime-cement mortar are 

increased Water retentivity, 

workability,

 bonding properties 

and frost resistance.

This mortar gives good and smooth plaster finish and is used in buildings.

Selection of Mortar

Selection of Mortar

No	work	Proportion cement:sand
1.	Normal Brick work	1:6
2.	Plaster work	1:3 to 1:4 1:2 (lime:mortar)
3.	Pointing in m2	1:1 to 1:2
4.	Damp Proof Work	1:2
5.	Grouting	1:1.5
6.	Guniting	1:3

Note - Addition of 5% to 6% of moisture content by weight increase

the volume of dry sand from 13% to 18%

Lime

CaCO3 = CaO + CO2 

CaO + H2O = Ca(OH)2

Chart for lime reactions

no	Name	Chemical formula
1.	Limestone	CaCO3
2.	Quick lime or Lump lime	CaO
3.	Ca(OH)2	Hydrated lime or slaked lime
4.	H2o	water

When the water is added to quick lime in sufficient quantity then a Chemical

reaction take place due to which quicklime Swell, Crack and Finally we get

Hydrated lime

Types of lime

No	Type	Description
1.	Fat lime	Also known as  Pure lime, Rich lime,  White lime etc. It contains impurity less than 5% hence  It has High Calcium Oxide content It is obtained from Sea shell, Coral Reefs etc It can be used in white washing and Plastering.
2.	Hydraulic Lime	This is called water lime because it can set under water. It contain Silica, Alumina and Iron Oxide in small quantity. It can be suitable for making mortar and using in masonry construction
3.	Poor lime	It is also called Impure lime or Weak lime, lean lime It contains 30% Impurities as compared to pure Lime
4.	Milk of Lime	A thin pour able suspension of slake lime in water is called milk of lime.
5.	Note	slaked lime is utilized in painting and decorative work Hydraulic lime is obtained from Kankar Non hydraulic lime from calcined dolomite stones. Burning of limestone in presence of Oxygen is known as Calcination.

Bulking of Sand

• The increase in moisture of sand increases the volume of sand and is known as bulking of sand.
• The volume of dry sand increases due to absorption of moisture. These volume increase of dry sand is known as bulking of sand. When dry sand comes in contact with moisture, a thin film is formed around the particles, which causes them to get apart from each other. This results in increasing the volume of sand. Addition of 5% and 6% of moisture content by weight increases the volume of dry sand from 18% to 38%.

Reason for the bulking of sand

• The reason is that moisture causes the film of water around sand particles which results in the increase of the volume of sand
• Bulking structure in sand is due to capillary action.
• For a moisture content percentage of 5 to 8, there will be an increase in volume up to 20 to 40 percent depending upon the sand
• If the sand is finer there will be more increase in volume

Graphical representation of bulking of sand is shown below:

Terracotta

• It is refractory clay brick and used in ornamental parts of buildings.
• The clay used for its manufacture should be of superior quality 
• and should have sufficient iron and alkaline matters. 
• It is burnt in special furnace known as Muffle furnace.

Water needed for complete Hydration of Cement

Approximately 23% water by weight is required for hydration and 15% water is entrapped in between the voids of cement. So, the total water required for complete hydration and workability is 38% by weight.

Segregation

• As per clause 13.2 of IS 456: 2000, the maximum permissible free fall of concrete to avoid segregation may be taken as 1.5 m or 150 cm.

• Segregation can be defined as the separation of the constituent materials of concrete.

• Insufficiently mixed concrete with excess water content shows a higher tendency for segregation.

• Dropping of concrete from heights as in the case of placing concrete in column concreting will result in segregation.

Slump and compaction Factor

Consistency	Slump	Compaction Factor
Moist earth	0	0.65-0.7
Very Dry	0-25	0.7-0.8
Dry	25-50	0.8-0.85
Plastic	50-100	0.85-.95
Semi-fluid	100-175	0.95-1

Plastic asphalt 

• It is a mixture of cement and asphalt. Mechanical properties, resilient modulus, temperature susceptibility, water damage, creep and permanent deformation resistance are all improved by the mixing of cement and asphalt altogether.

• It is used for filling patches and cracks of flexible pavements. The temperature sensitiveness of the asphalt is overcome by the application of cement to it. Thus, it is primarily used for repair or reconstruction purpose.

Types of lime:

1. Fat lime: 

It slacks rapidly and its volume is increased by 2 to 2.5 times of its original volume hence, it is referred as fat lime. It is also known as pure lime, rich lime, high calcium lime. It has more than 95% purity.

Properties- Slow setting, High plasticity, Soluble in water, Vigorous slaking, Perfectly white colour

Application- White wash & Plastering

Source- Sea shells

2. Hydraulic lime: 

It is also known as water lime as it is capable of setting in water and damp condition. It has 70% to 90% purity.

Properties- Insoluble in water, Low plasticity, Less slaking, Off white colour, High hydraulicity

Application- Brick masonry or Stone masonry

Source- burning of Kankar

3. Poor lime: 

It is also known as Impure or lean lime. It has less than 70% purity.

Properties- Muddy Colour

Application- Used in brick work around foundation

Floats are used to press mortar and spread it uniformly.

A trowel is a small hand tool used for digging, applying, smoothing, or moving small amounts of viscous or particulate material. Aluminium rod is used to strike off excess mortar.

A brush is used to clean the mortar. Floats are used to press mortar and spread it uniformly.

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Building Material

The calcination of pure lime result in:-

• quick lime
• hydraulic lime
• hydrated lime
• fat lime

Quick Lime ; Calcination or calcining is a thermal treatment process to bring about a thermal decomposition. The process takes place below the melting point of the product. The name calcination is derived from the Latin word ‘Calcinare’ which mean to burn lime. CaCO3→heatCaO+CO2(Limestone)→(Lime)+(Carbondioxide)CaCO3→heat⁡CaO+CO2(Limestone)→(Lime)+(Carbondioxide) The lime which is obtained by the calcination of comparatively pure limestone is known as quick lime or caustic lime. It's chemical composition is (CaO) oxide of calcium and it has great affinity for moisture. The quick lime as it comes out from kiln is also known as lump limes.

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