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Refractory Bricks – Properties and Types

Refractory bricks, also known as firebrick are ceramic materials used to line furnaces, kilns, fireboxes, and fireplaces. A refractory brick is designed to withstand high temperatures while still having poor thermal conductivity for increased energy efficiency. Refractory bricks are used in place of regular bricks, which always have a tendency to shatter at high temperatures. These bricks may also go by the titles ceramic bricks or fire bricks. Brick is one of the most popular construction materials used since ancient times. Regular bricks tend to crack at high temperatures and are not preferred for high-temperature areas. In such conditions, conventional bricks are often replaced by Refractory bricks.

This article is about refractory brick, their types, and their properties.

  1. What are refractory bricks?
  2. Properties of Refractory brick
  3. Types of Refractory bricks
    1. Acid refractory bricks
    2. Basic refractory bricks
    3. Neutral refractory bricks

What are refractory bricks?

Refractory brick is a type of brick that can resist high temperatures. It is also known as ceramic bricks or fire bricks. Generally, they are yellowish-white in colour. These bricks have good thermal resistance and good compressive strength. The chemical composition of fire bricks differs from regular bricks’ chemical composition. It mainly consists of 25 to 30% alumina, and 60 to 70% silica. Also, oxides of magnesium, calcium, potassium etc are present. The main application of fire bricks is in the construction of kilns, furnaces, etc. They are able to withstand temperatures above 2100 degrees Celsius. Thus the thermal capacity helps the structure to be stable at high temperatures. 


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Properties of Refractory brick

Following are the properties of Refractory brick.

  • Refractory brick should resist high temperatures.
  • They have good compressive strength. 
  • The weight of fire bricks is 150 lbs per cubic ft. 
  • The size of refractory brick is 9×4.5×2.5 inches or 9×2.7×2.25 inches. 
  • They also have good chemical resistance, Since they do not react with the furnace gases. 
  • The water absorption of refractory brick is 5 to 10%. 
  • They have a high fusion point. 

Types of Refractory bricks

Refractory bricks are available in various sizes and shapes. There mainly three types of refractory brick

  • Acid refractory bricks
  • Basic refractory Bricks
  • Neutral refractory Bricks

Acid refractory bricks

The acid refractory brick includes silica bricks and ganister bricks. Silica brick consists of 93% of Silicon dioxide. They possess good strength and fusion points. Also, they are hard and it is suitable for acid lining in furnaces. They can withstand temperatures up to 2000 degrees Celsius. Silica bricks are made from sandstone or quartzite. Ganister bricks consist of 85% of silica, 10% clay and 2% of lime. They are also hard and can withstand temperatures up to 2100 degrees Celsius. But acid bricks are not suitable to undergo rapid temperature. Since they tend to spall. 

Basic refractory bricks

Basic refractory bricks are basic in nature. They have good corrosion resistance and chemical resistance. They consist of Magnesite bricks, dolomite bricks and Bauxite bricks. Magnesite bricks contain 85% of magnesium oxide and 3 to 5% of iron oxide. They are suitable for the lining of the furnace. They can withstand temperatures up to 1800 to 2100 degrees Celsius. Dolomite bricks can withstand temperatures up to 1400 to 1600 degrees Celsius. It contains a high amount of dolomite. Bauxite bricks are a type of basic refractories that can withstand temperatures up to 1600 degrees Celsius and contains 85% of bauxite. 

Neutral refractory bricks

Neutral refractory bricks are suitable in places to separate the acid and basic lining in the furnace. They consist of chromite bricks, carborundum, spinal bricks and forsterite bricks. These bricks have a high percentage of chrome and magnesite. 

Components of staircase – Importance and functions

The components of the staircase must fulfil specific functional requirements. The main components of the staircase include Stringers, Treads, Risers, flights, Winders, Landing, Handrails Balusters etc. A staircase is one of the most important structural elements of a building. The primary function of a staircase is to facilitate movement from one floor to another. Staircases can be straight or curved and made of reinforced concrete, steel, wood, stones, and other materials. Staircases enhance the aesthetic appearance of the building in addition to providing access between floors.

It is necessary to understand the various components of the staircase as well as its functions when detailing it. This article discusses the components of a staircase and their functions.

  1. Components of Staircase
    1. Tread – Horizontal Components of the staircase step
    2. Rise – Vertical components of the staircase step
    3. Step – Combination of vertical and horizontal components of the staircase
    4. Curtail step
    5. Nosing
    6. Flight
    7. Landing – Crucial components of the staircase
    8. Going
    9. Winders
    10. Railing
    11. Baluster
    12. Run
    13. Soffit
    14. Stringer
    15. Waist

Components of Staircase

The staircase is made of several components and each component is associated with specific functional requirements. Following are the components of a staircase.

  • Tread
  • Rise
  • Steps
  • Curtail step
  • Nosing
  • Flight
  • Landing
  • Going
  • Winders
  • Railing
  • Baluster
  • Run
  • Soffit
  • Stringer
  • Waist
Components of Staircase
Components of Staircase

Tread – Horizontal Components of the staircase step

A tread is a major horizontal component of the staircase where we put our feet. The depth of tread is the distance between the staircase’s inner and outer edges. The tread width is the distance along the width of the steps. Generally, the tread of the staircase should be 270 mm in residential buildings and 300 mm in public buildings.

Rise – Vertical components of the staircase step

A rise in a staircase is the vertical component of the staircase step. It serves as a support for the treads. The vertical distance between successive treads is referred to as the rise. Generally, the riser should be 150 mm for public buildings and 190 mm for residential buildings.

Step – Combination of vertical and horizontal components of the staircase

Steps are the combination of treads and risers. Similarly, a pair of risers and tread makes a step. Basically, it is the functional unit of a staircase. 

Curtail step

The curtail step is the first step in the staircase. The width of the curtail step can be more than the normal steps. The curtail step is another major components of the staircase which acts as a base for the staircase. 


The edge of a stair tread that projects out horizontally is known as the nosing. In general, nosing has a rounded edge. However, the length of the nosing should not exceed 1.5″. Basically, nosing enhances the appearance of the staircase. The line of nosing is the imaginary line that connects the nosing. This line runs parallel to the stairwell’s incline.


Flight is a component of the staircase that consists of a series of steps. Basically, it is the total steps between the two landings. Generally, flights consist of 8 to 10 steps. 

Landing – Crucial components of the staircase

Landing is the horizontal space between two flights. It acts as a space to change the direction of the staircase. Generally, the minimum height of the landing should be 7 feet. The width of a landing is the distance between one end to the other end, which is normally equal to the width of the step. 



Going is the distance measured from the nosing of successive treads. It is the horizontal distance between the consecutive risers. 


Winders are tapering steps. That is one end of the step is narrower than the other. Likewise, It is a type of step which helps in changing the direction of the staircase. Basically, it acts as a landing. However, Spiral staircases consist of a series of winders. 

Compounds of staircase - Winder stair
Winder stair


The railing is a components of staircase which is used for holding hands. Generally, it is inclined and parallel to the slope of the staircase. Similarly, they act as protective bars. Generally, they are made using timber. 


The baluster is the vertical component of the handrail. Basically, balusters act as a support for the railing. 


The total length of the series of flights including the length of landing is the run of a staircase


The bottom part of the staircase component is the soffit. Basically, this place is suitable as a storage area.


The components in the staircase which support the risers and treads are the stringer. There are two types of stringers,

  • Cut or type stringers
  • Closed or Housed type stringers

They are parallel to the slope of the staircase.


The staircase is rest on a thick RCC slab. This RCC slab is known as the waist slab. It is perpendicular to the soffit of the staircase. 

Segregation and bleeding in concrete – Types, Causes and remedies

Segregation is the separation of concrete ingredients from one another. Concrete is one of the most used construction materials. It consists of coarse aggregate, fine aggregate, cement and water. There are many reasons for the cause of segregation. This article is about segregation and bleeding and their types, causes and remedies.

  1. What is Segregation in Concrete?
    1. Causes of Segregation in Concrete
    2. Types of Segregation
  2. Bleeding
    1. Causes of bleeding in concrete
    2. How to reduce bleeding in concrete?

What is Segregation in Concrete?

Workability is an important property of concrete that reflects how easily we can place a particular concrete mix . Good concrete should be uniformly mixed and easily placeable without segregation or bleeding.

What is segregation in concrete ?

Segregation of concrete is the separation of ingredients in concrete. Since concrete is a non-homogeneous material, improper mixing is the main reason for the segregation. It occurs during transporting, handling and placing of concrete. Also, it affects the concrete properties. The strength of concrete decreases and leads to cracking. Therefore it should be properly mixed before use in construction. 


Causes of Segregation in Concrete

A good quality concrete mix is prepared by considering factors like the size of aggregate, water-cement ratio, compaction, etc. They are many reasons for the causes of segregation. They are

Prevention of segregation is very important as it adversely affects the properties of concrete. 

Types of Segregation

Segregation occurs in three types such as

  1. Separation of water and cement from other ingredients
  2. Segregation of coarse aggregate
  3. Separation of water content

Segregation is hard to measure since there is no particular test for determining it. However, the Flow table test measures the segregation. Also, the slump test of concrete can give an idea about segregation. Coarse aggregate in concrete tends to settle down from other ingredients. Usually, It occurs when the concrete mix is dry. While segregation by separation of water content occurs due to an insufficient amount of fine aggregates or due to the use of an excess amount of water content.

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What is bleeding in concrete?

Segregation occurs when the principal ingredients in a concrete mix – in other words, gravel aggregate, cement, and water – separate prior to and during the curing process. Moreover, Segregation causes excessive amounts of water to rise to the surface. This process is know as bleeding. Bleeding is also similar to segregation in which the water in the concrete rises to the surface of the concrete. As a result, the concrete becomes porous and weak.

Bleeding affects its strength and its durability of concrete . Likewise, It breaks the bond between the concrete and steel reinforcement. However, a proper proportion of concrete ingredients and controlled vibration can reduce bleeding. Moreover, air entraining admixtures can also be used for reduce bleeding. 

Bleeding of concrete
Bleeding of concrete

Causes of bleeding in concrete

The main causes of bleeding in concrete mix is as follows

  • Segregation is the main cause of bleeding in concrete
  • High water cement ratio causes bleeding.
  • Type of cement used and quantity of fine aggregate
  • Over vibration

How to reduce bleeding in concrete?

By adapting the following methods bleeding can be reduced

  • Minimum water cement ratio should be maintained.
  • A proper design mix
  • Use mineral admixtures like fly ash
  • Use air entrapping admixtures
  • Maintain fine aggregate ratio

Types of Cement in Construction

Cement is an integral part of all types of construction ranging from huge skyscrapers, bridges, tunnels, etc to small residential buildings. It is one of the oldest and most used binding materials and an integral ingredient used in the construction sector. There are different types of cement available in the market. Each type of cement has its application depending on its properties. 

Types of cement

  • Ordinary Portland cement
  • Portland pozzolona cement
  • Rapid hardening cement
  • Slag cement
  • Hydrophobic Portland cement
  • Low heat Portland cement
  • Suphates resisting Portland cement
  • Quick setting Cement
  • High alumina cement
  • Masonry cement
  • White cement
  • Coloured cement
  • Expansive cement
  • Air-entraining Portland cement

Ordinary Portland cement  – Types of cement

Ordinary Portland cement or OPC is one of the most commonly used cement types in construction. OPC cement forms and integral part of for high strength concrete and is more economical. OPC consists of calcareous material, argillaceous material and gypsum. This type of cement has good resistance to cracks, shrinkage and chemical attacks. OPC cement is used in a wide range of applications in civil construction. 

Ordinary Portland Cement
Ordinary Portland Cement

Also read : Best cement of India

Portland pozzolana cement – Types of cement

Portland Pozzolana cement or PPC cement is a type of cement consisting of 15% to 35% of pozzolanic materials, gypsum and clinker. PPC cement is a combination of OPC and pozzolanic materials. The initial setting time of PPC is 30 minutes and the final setting time of PPC is 600 minutes. It is suitable for hydraulic, marine structures. Since PPC has good resistance to sulphate attack. 

Rapid hardening cement – Types of cement

It is a type of cement that can achieve high strength within less time. It has high resistance to chemical attacks. RHC needs less curing time. So it is suitable for formworks, pavements etc. It has more application than OPC because of its early hardening property. Rapid hardening cement is expensive. 

Slag cement -Types of cement

This type of cement is made from granulated blast furnace slag (GGBFS). It has good compressive strength. It is applicable in the construction of residential, commercial and industrial buildings. Also, it is resistant to alkali-silica reactions. chloride and sulphate attacks. 

Hydrophobic Portland cement

It is most suitable for water-resistant structures. It consists of admixtures such as acid naphthene soap, oxidized petrolatum, etc which reduces the melting of cement grains. The strength of hydrophobic cement is similar to OPC after 28 days. This type of cement is expensive. 

Low heat Portland cement 

Low heat cement is preferable for the construction of dams, large raft foundations etc. Because the heat of hydration of this type of cement is 20% less than normal cement. It consists of 5% of tricalcium aluminate and 46% of dicalcium silicate. Therefore it produces low heat of hydration. It has excellent wear, impact resistance and workability. 

Sulphate resisting Portland cement 

Sulphate resisting portland cement consists of Tricalcium aluminate which is less than 5% and Calcium aluminoferrite which is less than 25%. It is applicable in structures that are subjected to a high amount of sulphate. It helps in reducing the corrosion of reinforcement. Sulphate resisting cement can improve later age concrete strength. 

Quick setting Cement

It is a special type of cement manufactured by adding aluminium sulphate and reducing the amount of gypsum. It is applicable for underwater concreting and grouting. The setting time of this cement is less because aluminium sulphate is an accelerating admixture. It is also preferable for concrete repair works, tunnelling etc.

High alumina cement

High alumina concrete attains strength within 24 hours. It can withstand high temperatures and fire. It is applicable in refractory concrete. The initial setting time of high alumina cement is 4 to5 hours and the final setting time is 30 minutes. Also, it is highly resistant to sulphate attacks. 

Masonry cement

The main application of masonry cement is for ordinary masonry, plastering mortar, etc. Since it has low strength it is not suitable for structural applications. The cost of masonry cement is less. It is manufactured by combining portland cement with non-pozzolanic materials such as limestone. Also, they have high water retentivity and workability. 

White cement

White cement is manufactured by using limestone, clay, oil and gypsum. It consists of less amount of Iron oxide and manganese oxide. Thus they have white colour. It is applicable for decorative purposes. But they are expensive compared to normal cement. 

Coloured cement

Coloured cement consists of colour pigments like chromium, cobalt, ton oxide, manganese oxide etc. which gives them colour. It is preferable for floor finishing, window sills stair treads, and other external surfaces. The number of colouring pigments should about be 5 to 10 percentage. 


Expansive cement

Expansive cement is a special type of cement that can increase its volume after setting. It consists of expansive compounds like calcium sulphate. Based on the expansive compounds, there are three types of expansive cement. 

  • K type expansive cement
  • M type expansive cement
  • S type expansive cement

The use of expansive cement is in water retaining structures, concrete repairing, large floor slabs, etc. 

Air-entraining Portland cement

Air entraining Portland cement is a special type of cement that produces air content. These air bubbles act as a space for the freezing and thawing process. This reduces the crack formation. Air entraining agents like aluminium powder, hydrogen peroxide is added to the cement. 

Areas of building | Built-up area | Carpet area | Super built-up area

Reading the floor plan is an important skill that a civil engineer should possess. There are different types of areas in the floor plan of a building. In this article, we will see about the different types of areas.

Different types of areas in Building Construction

Before planning to purchase a home we should be familiar with the following areas adopted in building construction.

1. Plot area

2. Built-up area or Plinth area

3. Carpet area

4. Setback area

5. Super built-up area

Before getting into these terms first we have to know what is RERA 

Real Estate Regulation and Development Act, 2016, (RERA)

The Real Estate Regulation and Development Act, 2016, (RERA) is an act established by the Indian parliament. The main objective of RERA is to give prompt information between the buyers and sellers. This increases transparency and reduces the chance of cheating.

There are three different ways to calculate the area of the property. 

1. In terms of the Carpet area

2. In terms of Built-up area

3. In terms of Super built-up area

While buying a property buyer should pay for the area which is usable. RERA provides safety of money, buyer protection and balanced agreement.

Areas of building

Plot area (Areas of building)

The plot area includes the complete area which you own. This area comes under the fencing.


Carpet area (Areas of building)

Carpet area is a term which the real estate agent uses the most. It is the area of the building which can be covered by using carpet. It is also called a net usable floor area. 

Carpet Area = Total floor area – Area of internal/external walls

But as per RERA Carpet area = Total Floor area – Area of external walls


According to RERA flats should be sold on the basis of carpet area. The carpet area as per RERA is the area of usable spaces such as bedrooms, kitchen, bathroom, toilet etc. It also includes an area covered by internal partition walls. It excludes areas such as Balcony, utility areas, external walls area, open terrace area, lift, lobby, staircase etc. Mostly carpet area is 70% of its built-up area.

Plinth area

The plinth area is also known as the Built-up area. It is the total area of the building within the plot area. It is mostly 30% of the total plot area. 

Built-up Area = carpet area + Area of walls


It includes living room, bedrooms, utility, bathroom, wall thickness, kitchen, balcony closed staircases etc. and excludes open terrace area, lift, open staircase, swimming pool etc. It is 10 to 15 % more than the carpet area.

Super built-up area

Super built-up area was used to measure the area of property before the RERA act came into existence. Because the super built-up area lowers the rate per square foot. Saleable area is another name of super built-up area.

Super Built-Up Area = Setback area + Built-up Area+20% of common area 

Super built-up area includes common areas like swimming pool, clubhouses, lobby, staircase, Lift, etc. and the built-up area of the flat.

Set back area

Set back area is the space between the boundary and the building. It is the minimum open space necessary around the building. As per the municipal regulation a specific margin should be provided between building and road. 


Setback area = Built-up Area – Plot area

This provides sufficient ventilation, ease in vehicle movement and protection from other entities.

Admixture types | Mineral and Chemical Admixture

Types of admixture to be used in concrete depend on the structure’s intended use, design strength, pouring conditions, and other factors. The most commonly used material in construction is concrete. Admixture is a material that is added to concrete along with cement, sand, water, and aggregates to modify or enhance the properties of the concrete and make it more suitable for a specific environment.

Concrete is used in many applications and is exposed to extreme environmental conditions that can lead to severe performance and quality issues. Admixture and their types are important ingredients in today’s high-performance, long-lasting, durable, and beautiful concrete. Admixtures are broadly classified into chemical admixtures and Mineral Admixtures. This article discusses the most common types of admixture used in concrete.

Definition of Admixture and its types used in concrete

Admixtures are materials that enhance performance and alter the properties of concrete. Concrete admixtures are natural or manufactured chemicals or additives added during concrete mixing to enhance specific properties of the fresh or hardened concrete, such as workability, durability, or early and final strength and make it desirable for a certain condition. Also, Admixture reduces construction costs and makes the concrete more economical.

Types of Admixture
Types of admixture used in concrete

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Functions of different types of admixture

There are many applications for different types of admixture, including but not limited to the following ones:

  • Reduces the water-cement ratio.
  • Increases the strength and durability of concrete.
  • Improves the workability of concrete.
  • Provides particular properties to concrete to make it suitable under different weather conditions 
  • Limits the shrinkage cracks.
  • Avoids bleeding and segregation of concrete
  • Accelerates or retards the setting time of concrete 
  • Reduces corrosion of reinforcement in concrete or improves Resistance to chemical attack.
  • Decreases the heat of hydration.
  • Strengthens the bond between old and new concrete surfaces.

Types of Admixture

There are mainly two types of admixture 

  1. Mineral admixtures
  2. Chemical admixtures

Types of Mineral Admixture

Mineral admixtures are siliceous and insoluble materials other than cement and aggregate that are added to concrete in concentrations ranging from 20 to 70% by mass of cement. These are fine materials that have an impact on concrete via hydraulic and pozzolanic activity. Natural materials, processed natural materials, and artificial materials are all examples of mineral admixtures. The following are some types of mineral admixture commonly used in concrete.

  • Cementitious
  • Pozzolanic
  • Blast Furnace Slag
  • Flash
  • Silica Fume
  • Rice Husk
Type of Mineral Admixture - Blast furnace slag
Type of mineral Admixture – blast furnace slag

Types of Chemical Admixture

Chemical admixtures are chemical additives blended with concrete to modify their properties. It imparts special properties to concrete. The most common types of chemical admixture are listed below

  • Plasticizers
  • Super Plasticizers
  • Accelerators
  • Set Retarders

Types of concrete admixture based on applications

Admixture is classified into various types based on various applications

  • Water-reducing admixture
  • Retarding admixture
  • Accelerating admixture
  • Air entraining admixture
  • Pozzolanic admixture
  • Damp-proofing admixture
  • Gas forming admixture
  • Air detraining admixture
  • Anti-washout admixture
  • Corrosion inhibiting admixture
  • Bonding admixture

Water-reducing admixtures

Plasticizers are another name for water-reducing admixtures. Basically, by lowering the water-cement ratio, they assist in reducing the water content of the concrete mix by 5 to 20%, resulting in high-strength concrete. Workability is increased by water-reducing admixtures because they can even maintain a high slump without adding more water. Examples include polycarboxylates, multicarbovyl ethers, and acrylic polymers. etc.

Retarding admixtures/Retarders

Retarding admixtures or retarders decreases the setting rate of concrete. They are suitable in hot weather conditions where the high temperature drastically increases the setting rate of concrete. However, the fast setting rate of concrete affects its strength and durability. Generally, retarding admixtures are widely used to overcome this problem. Some examples of retarders are Starch, cellulose products, common sugar, acid salts, etc.

Accelerating admixture/Accelerators

Accelerating admixture decreases the initial hardening time of concrete. As a result the rate of hydration of cement increases. There are two types of accelerating admixtures.

  • Set accelerating admixture
  • Hardening accelerators

Accelerating admixture improves the concrete strength by increasing the rate of hydration. This type of admixture is suitable for early formwork removal, emergency repairs, buildings in low-temperature regions, etc. Some examples of accelerators are triethanolamine, calcium formate, active silica, calcium chloride, finely divided silica gel, etc.

Air entraining admixtures

During the mixing of concrete air bubbles are formed.

Air-entraining admixtures facilitate the development of a stable air-void system within the concrete that increases durability, workability of the concrete and cohesion. Similarly, these admixtures impart air entrainment that results in:

  • Increased resistance to deterioration from cyclic freezing and thawing 
  • Improved workability and cohesiveness of concrete placement
  • Reduced segregation and bleeding

Pozzolanic admixtures

These admixtures are suitable for hydraulic structures such as dams, reservoirs, etc. Pozzolana is a cementitious material that helps in preparing high-dense concrete mixes. Accordingly, It increases the strength, and reduces the cost of concrete and thermal shrinkage. Some examples of pozzolanic admixtures are fly ash, silica fume, rice husk ash, metakaolin, etc.

Damp proofing admixtures

Dampproofing admixtures make the concrete impervious and durable. It also helps in attaining the early stage of concrete hardening. Some examples of dam-proofing admixtures are hot bitumen, mastic asphalt, bituminous felt, etc.

Gas forming admixtures

During the hydration process of cement, we get hydroxide. The gas-forming admixture reacts with the hydroxides and forms hydrogen gas bubbles. This bubble helps in avoiding settlement and bleeding of concrete. Some examples of gas-forming admixtures are Aluminum powder, activated carbon, hydrogen peroxide, etc. 

Air detraining admixture

During the mixing of concrete, the air gets entrapped in the concrete. Furthermore, this air reduces the strength of the concrete. So to avoid this air content we use air-detraining admixtures. Some examples of this type of admixture are tributyl phosphate, silicones, water-insoluble alcohols, etc.

Anti-washout admixture

Generally, the main application of anti-wash-out admixtures is in underwater construction. Some examples are natural or synthetic rubbers, thickeners based on cellulose, etc. Similarly, It makes the concrete more cohesive and avoids washing out of concrete mixes underwater. 

Corrosion inhibiting admixture

Corrosion of reinforcement is one of the common problems in construction. So to decrease the corrosion this type of admixture is used. Basically, corrosion-inhibiting admixtures help in decreasing the corrosion rate and delaying the corrosion. Some examples of corrosion-inhibiting admixtures are sodium benzoate, sodium nitrate, sodium nitrite, etc.

Bonding admixture

This type of admixture helps to the bond between the new and old concrete surface. Basically, It is commonly used in floor overlays, screed over roofing, repair work, etc. Some examples of bonding admixtures are natural rubber, synthetic rubbers, and polymers such as polyvinyl chloride, polyvinyl acetate, etc.