Tuesday, November 15, 2011

Applications Of Ferrocement

1.Widely used in domestic overhead tank.This tank is light, flexible, easy to transport and cheap.

2.Different types of inlet and outlet connections can be easily done with the help of adhesive using ferrocement.

3.It can be used as "gasholder" in "gobbar gas plant".
4.With slight modification ferrocement tanks can be used as grain silos in villages to keep grains

5.Can be used as septic tank.

6.Ferrocement is ideal for boat building.This kind of boat weighs 10% less if it is made of wood.


Ferrocement is a relatively new material consisting of mortar made with portland cement, water and aggregate with reinforcing mesh.
P.L. Nervi an Italian engineering and architecture developed this material in 1940.

Saturday, September 3, 2011

Advantages of Hydration

1.Because of hydration cement get adhesive property and bind fine and coars aggregate.

2.Helps in joining bricks.

3.Binds rids with concrete in R.C.C(Reinforced Concrete Cement).

4.Make the cement paste rigid.

Tuesday, August 30, 2011


Concrete is a rock like material, which is made by mixing cement, coarse aggregate and fine aggregate with water.

Thursday, August 18, 2011

Endogeneous or endogen timber

This kind of trees increase both longitudinally and diametrically.Its diameter increase by the addition of new fibre with the old. Endogens are mostly plants like paddy, sugarcane, jute etc.

Exogeneous or exogen timber

This kind of trees increase diametrically by annual formation of layer new wood between old wood and bark of the wood which consists all the living portion of the tree.

Types of Timber

Timber is of mainly two types.
1.Exogeneous or exogen
2.Endogeneous or endogen

Relation between water cement ratio to the strength of concrete

Water has three functions in concrete

1.Wets aggregate surface
2.Imparts workability
3.Binds aggregate with cement chemically by hydration

For a given degree of compaction with the increase
of percentage of water, percentage of hydration increases.
So sufficient amount of water is necessary for hydration as well
as for increase in strength.Water also imparts workability to
concrete.but excess water cause concrete to be porous.
Hence for a certain limit strength increase with the increase of
water cement ratio.But after that strength decreases with the
increase of water cement ratio.

Why fineness of cement is necessary for rapid development of strength

The surface area of cement particles increases with the increase of fineness modulus. Hydration takes place on the surface area of cement particles.For rapid hydration surface area of cement particles should be high.Strength develops on the concrete as hydration takes place. This is why for rapid development of strength high fineness of cement is necessary.

Placing concrete underwater

Sometimes concrete needs to be placed underwater.In this case bottom dump bucket or tremie pipe is used. In this case concrete is carried through the water in water tight box by bottom dump bucket and reaching the final position there is a mechanism to open the bottom of the bucket and dispose the concrete. This will not give satisfactory result as some concrete get washed away.

Sometimes dry cement and dry coars aggregate and fine aggregate are mixed in a cement bag and disposed under water. This also do not give satisfactory result as cement bag make voids in concrete.

Among the two tremie pipe method is preferable.

Process of determining the opening area and opening length of seive

Let us consider we have to determine the opening area and opening length of #100 sieve.
#100 sieve means 100*100 openings are present in 1 square inch or 25.4*25.4= 645.16 square mm.

Hence 1 opening is present in =645.16/(100*100)
                                           =0.065 square mm
sieve openings are surrounded by threads which take some areas.Hence sieves actually get areas of around 36 to 40 percent(can vary) of its opening.
Let us assume sieve opening is 36 percentage.
Then the actual are of sieve opening is =0.065*(36/100)
                                                        =0.0234 square mm
As sieve openings are square size
Then length of the each sieve opening =square root of 0.0234
                                                       =0.153 mm

Advantages of Timber

1.Timber can be easily worked with tools of any size and can take a good polish.
2.It is comparatively stronger than any other materials in proportion to weight. That is other materials of such light weight as timber are not stronger than timber.
3.It is economic in the sense that any small piece of timber can be utilized.
4.Its use for making furniture, sports goods and decorative articles of artistic design are accepted universally without doubt.
5.Its low thermal conductivity, high resistance(electricity) and sound proofing property make it as an important building material.
6.timber structures are comparatively durable if properly treated and carefully protected from direct contact with weather and alternate change in wetting and drying.
7.Various types of timber products such as plywood, laminated board. hard board etc are nowadays used because of low weight and beauty.
8.It can be used both load bearing and non-load bearing members in structures and structural connections.
9.Its another importance is great resale value. The discard timber can be used as fuel.Even saw dust can be used by reconstructing partex board, hard boards, laminated boards etc.

Definition of Timber

Any wood which is used in engineering works is termed as timber.Although some of its usages are given up to steel, concrete and other products its usages in construction and other commercial purposes are still of great importance.

Tuesday, June 7, 2011

French Polish

It is made by dissolving shellac in spirit.It is mainly used in brightening surface of furniture. It is made by

Methylated spirit-3 gallons
Shellac-3 pounds
Copal-0.5 pounds

Procedure of Slump test

It is widely used in site works. The apparatus used in this method is a metallic mould of frustum cone structure having dimension as follows

Top diameter-10cm
Bottom diameter-20cm

1.First mould is placed on a smooth horizontal and rigid surface.
2.Then mould is filled with concrete by rodding in four layer.
3.After rodding top layer the top surface is smoothen by trowel.
4.Then the mould is removed vertically up.
5.After total removal of mould concrete will subside. The amount of subside is the slump of that concrete.

Various Methods of Determining Workability of Cement

1.Slump test
2.Compacting factor test
3.Flow test
4.Kelly ball test
5.Vee Bee test

Wednesday, April 27, 2011

Estimation of Wastage if Timber

In conversion of timber there is a great wastage.When a log is sawn only 50 to 65 percent can be useful other is waste.Following are the approximate estimation of wastage

Side slabs and trimmings--18%
Saw dust--12%
Loss of moisture--5%

Pressure Process of Applying Preservative

Pressure process is one of the most efficient process in applying preservative. It is of two kinds.

1.Full cell process:In this process cells of wood tissues are desired to practically completely filled with preservative.Woods are loaded on a special kind of trolly and then put in autoclave machine.The vacuum is applied inside the autoclave to remove air from wood as much as possible.Then heated(generally 210 degree Fahrenheit) preservative is pumped in the autoclave with 125 to 200 psi pressure.

2.Empty cell process:In this process preservative forms merely a thin layer on wood cells.All the process is same with full cell process, except that before applying preservative 50 to 75 psi pressure is created to fill wood cells with air and then preservatives are added with about 200 psi pressure.

Different Types of Mortar

1.Lime Mortar- Lime+sand+water
2.Surki(broken brick) mortar- Lime+broken brick+water
3.Lime surki mortar- Lime+sand+broken brick+ware
4.Cement mortar- Cement+sand+water
5.Mud mortar- Mud+water+saw dust(or rice husk or cow dung).


Mortar is the paste obtained from mixing water with cementing or binding material(cement or lime) and an inert material(sand or broken brick or stone).

Functions of Various Ingredients of Cement

1.Lime:It is very important in cement.It forms about 63 percent of cement. The nature of cement depends on it.Defeciency in lime reduces the strength of cement and cause it to set quickly. Again excess cause cement unsound and cause disintegration and expantion.

2.Silica:It is another important compound. It imparts strength to concrete.

3.Alumina:It imparts quick setting property of cement. Clinkering temperature is lowered by adding of alumina.

4.Magnesia:It should not present in cement more than 2 percent.Excess reduce strength.

5.Iron oxide:It imparts the color of cement. At high temperature it goes to a chemical reaction with calcium and aluminium and forms tetracalcium aluminofferrite which imparts hardness and strength.

6.Salphur tri oxide:It should not present more than 2 percent.Excess cause cement to be unsound.

7.Calcium sulphate:It is present in cement in the form of gypsum.It retards the setting of cement.

8.Alkalies: It should not present more than 1 percent.Excess cause efflorescence.

Differences Between Thermoplastic and Thermosettingplastic

     Thermoplastic                                      Thermosettingplastic
1.These are plastics which can          1.These are plastics which harden permanently.
be softened after once hardened        can not be reshaped once hardened.
and again can be hardened
2.Retains almost all the original         2.Properties especially chemical properties changes
properties remelting and then            after remelting
3.e.g.Nylon, poly vinyl chloride,          3.e.g. Phenol formaldehyde, urea
cellulose acetate etc.                         formaldehyde etc

Differences Between Sapwood and Heartwood

       Sapwood                                                Heartwood
1.It is the living element of           1.It is the dead element of tree.
2.It is comparatively weak.           2.It is comparatively strong.
3.It is more in young trees.          3.It is more in old trees.
4.Contains higher moisture.        4.Contains less moisture.
5.Lighter in color                         5.Darker in color.
6.Has weaker cell wall.                6.Has weaker cell wall.
7.Attracts fungus and insects      7.Does not attract fungus and insects.

Saturday, April 23, 2011

The Essential Properties of Preservatives of Wood

1.It should be safe in handling and use.
2.Non injurious to wood tissues and do not react with them.
3.Should not get washed away and permanently preserve.
4.Should be such that decorative and ornamental paints could be applied on wood.
5.Should be non flamable.
6.Penetrate thorough timber.

Market Forms of Timber

The followings are the various types of market forms of timber.
1.Log     2.Lumber     3.Bilk     4.Deal     5.Batten     6.Plank     7.Board     8.Scantline     9.Pole

Conversion of Timber

The preparation of timber from felled tree by cutting off branches, removing bark., cutting and sawing to convert it to marketable form is termed as conversion of timber.

Ply wood

Plywood consists of number of thin sheets of wood(veneer) which are pressed and bonded together by some bonding materials like glue or synthetic adhesive under temperature of 350 degree Fahrenheit to 500 degree Fahrenheit.The grains of each sheet are bonded right angles to each other to uniform strength in both direction and reduce shrinkage.Plywood is relatively lighter then other plank of same strength. Sometimes plywood is covered with plastic sheet for attractive appearance, zero water absorbance, reduction of decay etc. Plywood is specially used where some amount of bending is necessary. Generally not less then three sheets of woods are used for plywood.


Veneers are thin layers of wood of 1/16 to 1/ 4 inches..It is used when lightness, stiffness, durability, no-shrinkability, non-splitting and decorative properties are desired, Veneers are generally obtained from those woods which have well shaped grans and pleasing appearance. Veneers are used in mainly manufacturing plywood, batten boards, decorative facings and laminating boards.

Bulking of Aggregate

The increase of volume of given weight of aggregate due to the presence of moisture is called bulking of aggregates.5 to 8 percent of moisture of aggregate weight cause 20 to 30 percent volume increase. This because of the creation of thin film of water inside aggregates which cause interlocking air.This air tries to get out and cause volume to increase.by adding of water in dry aggregates the volume increase up to adding of 8 percent of water of aggregate weight.Further adding of water cause water to move into the void of aggregate particle. This cause volume to decrease.When aggregates are saturated its volume is same as the dry condition.Fine aggregates increase volume more than coarse aggregates.

The bulking is determined by following expression
                    bulking, b=(Vm/Vd)*100
Where Vm is the volume with moisture and Vd is the dry or fully saturated volume and b is the bulking percentage.

Thursday, March 10, 2011

Process of Hydration

The process of hydration is mainly the formation of minute crystals of calcium and gels fom the solution of cement and water.The hydration process of portland cement is as follows-

Tricalcium silicate hydrates as follows
3(3CaO.SiO2)+6H2O=3CaO.2SiO2.3H2O  + 3Ca(OH)2
                                          Calcium Silicate          LIme

This can be written as -
3C3S+6H2O= C3S2H3+3Ca(OH)2

Dicalcium silicate hydrates as follows

This can be written as

The reaction of triclcium aluminate (C3A) with water very fast and immediately cause stiffening of cement paste which is termed as flash setting.This can be reduced by mixing gypsum(CaSo4.2H2O)
with cement clinker during grinding.Gypsum and C3A reacts to form calcium sulphoaluminate which eventually form calcium sulphoaluminate which eventually form calcium aluminate(hydrate).
 This retards the action of the starting of initial setting.     

Gypsum not only reacts with C3A.These accelerate the hydration of calcium silicate.Gypsum is added very carefully to cement because excess will cause expansion and disintegration of  cement paste and also slower the initial setting.


Anhydrous cement does not bind fine and coars aggregate.The cement acquires binding property after mixing with water.The chemical reaction that take place in cement after mixing of water is termed as hydration

Tuesday, March 8, 2011

Differences Between False Settingand Flash Setting

     False setting                                            Flash setting

1.No heat evolves                           1.Appreciable amount of heat evolves

2.Remixing of cement without          2.Remixing of cement without adding
adding of water regain plasticity.       of water do not regain plasticity.


Setting refers to the change of cement paste from fluid to rigid.It differs from hardening. Hardening refers to gain of strength after setting. Although cement paste acquire some strength in setting

Aluminium Paint

This consists of very finely grounded aluminum suspended in the medium of slow drying oil or spirit varnish. It is an expensive white paint.It can resist heat to a great extent.

1.Mainly decorative purpose
2.Also protects steel and iron
3.Used for painting marine pipes, oil tanks, gas tanks,water pipes etc.


Distemper is a kind of water paint containing water and oil as thinner agents and glue,starch are used for base and different color pigments for desired color.It is used for interior decoration


A resin is an amorphous,vitreous,semi liquid organic matter which is soluble in organic liquid and drying oil but non soluble in water.When it is heated it gives a product which is soluble in drying oils.

Preparation of Concrete Surface for Painting

1.Cement and concrete should be treated with benzene to remove grease and oil.

2.Then zinc sulphate should be applied to neutralize lime present in the concrete.

Preparation of Plastered Surface for Painting

1.Plastered surface should be brushed with zinc sulphate before painting.

2.Prior to repainting benzene should be applied to remove grease

Pigments Used in Luminescent Coating

Generally there are two types of pigments used in luminescent coating.

1.Fluorescent Pigments:These are synthetic dyes zinc sulphide or mixture of zinc and cadmium sulphide.

2.Phosphorescent Pigments: These are mainly calcium sulphide or strontium sulphide.

Constituents of Cement

Constituents of cement are mainly two types
1.Mineral constituents , 2.Acid and Alkaline constituents.

Mineral Constituents

       Name                   Oxide compositions   Abbreviation    Percentage(%)

Tricalcium Silicate ~     3CaO.SiO2(*1) ~            C3S(*1) ~              45~55
Dicalcium Silicate ~      2CaO.SiO2(*1) ~            C2S(*1) ~              20~30
Tricalcim Aluminate ~    3CaO.Al2O3 ~                      C3A ~                        9~13
Aluminoferrite ~              4CaO.Al2O3.Fe2O3~             C4AF  ~                 8~20
Calcium Sulphate~          CaSo4  ~                                  ----------        ~            2~6
Other Compounds~        ----------   ~                               ---------   ~                  2~8       

Acid and Alkaline Constituents
        Name               Composition                Range of percentage

Calcium oxide     ~     CaO               ~               60~67
Magnesium oxide~     MgO               ~               0.1~4
Silica                    ~     SiO2                  ~                  17~25
Alumina               ~     Al2O3                ~                   3~8
Iron oxide             ~     Fe2O3               ~                  0.5~6
Sulphur trioxide   ~     SO3                    ~                  1~3
Potassium oxide   ~     K2O                   ~                   0.3~1
Sodium oxide       ~      Na2O                ~                   0.4~1.3
Loss on Ignition   ~      --------            ~              1.8~2
Insoluble Resedue ~     --------           ~              0.3~0.5

Monday, March 7, 2011

Harmful Consituents of Brick

The followings are the harmful constituents of brick.

1.Iron pyrites
It causes crystallization and disintegration of brick particles on drying.

These are mainly chlorides and sulphates of calcium,magnesium,sodium and potassium causing dark greenish hue on brick surface on drying.It also cause brick to twist,fuse and warp.It absorb moisture which cause efflorescence.

3.Stone particles
It prevents mixing of clay thoroughly and uniformly.It makes brick porous and weak.

4.Vegetation and Organic Matter
These leave pores in brick on burning.

Excess lime cause brick to fuse and hence shape is lost.Lime in the form of lime stone and Kankar nodule very harmful.Because limestone(CaCO3) leaves CO2 in burning and in contact with water it gets hydrated and swells and cause the brick to lose shape.Kankar also cause similar type of damage to brick.but lime is very important in brick.So proper amount of lime should present in brick.

Chemical Composition and It's Function of Brick Clay

The chemical composition of brick clay is as follows-

                                              Silica - 55%

                                              Alumina - 30%

                                              Iron oxide - 8%

                                              Magnesia - 5%

                                               Lime - 1%

                                              Alkali and organic matter-1%
Silica is present in brick clay as the chemical composition of alumina and forming silicate of alumina.Sometimes silica is present in pure form termed as flint.
Silica prevents shrinking,cracking and warping of brick clay.High amount cause uniform texture.Too much presence of silica cause brick to be brittle and weak.

Alumina imparts plasticity to brick clay which is very important in molding.It also imparts density.Excess alumina cause brick to crack and warp during drying and very hard when heated.

Iron oxide:
The presence of iron oxide increases impermeability and durability of brick.The color of brick depend upon iron oxide and color changes from light yellow to orange and red as iron oxide goes up to 8%.

Presence of small quantity of magnesia decreases shrinkage and gives yellowish tint.

Lime melts silica in burning and binds the particles of brick together.It also reduces the shrinkage of brick during drying.
Excess of lime cause the brick to fuse and shape will be lost.

Alkali and Organic Matter:
Small quantity assist burning of brick clay.It also reduces the fusion point.If excess amount is present and not burned properly the brick would be porous.

Sunday, March 6, 2011

Differences Between Mortar and Plaster

                        Mortar                                          Plaster
1.Mortar is the paste made              1.Plaster is thin coat of various
of mixing cementing and inert        composition of mortar which is                                             
 material with water.                       applied both external and internal
                                                          surfaces of walls, ceiling, clolumns
2.Mortar is the ingredient                2.Plaster is the applied work of mortar.
 of plaster                                                                                          

Friday, March 4, 2011

Function of Sand in Mortar

1.Sand s mainly used as a inert material to give volume in mortar for economy.

2.It subdivides cementing material into a thin film which is the principle of using all cementing material.

3.It offers requisite surface area for film of cementing material to adhere and spread.

4.Prevents shrinkage and cracking of mortar.

5.Well graded sand provide density.

6.It allows CO2 to enter in some depth in case fat lime mortar and increase setting power.

7.Some chemical reaction take place between silica of sand grain and other cementing material.


Sand is a very important material in concrete.It plays a vital role in engineering construction. Sand is a form of silica and may be argillaceous(clay like), silicious(silica type) or calcarious(calcium type) according to its composition.

Different Types of Shrinkage Of Concrete

1.Plastic Shrinkage: While the cement is in plastic condition shrinkage occurs during the period of hydration. It is believed that evaporation of water in air of water by aggregate or sub grade cause this shrinkage.

2.Drying Shrinkage: Withdrawal of water from concrete in saturated air cause drying shrinkage, The loss of water contained in hardened concrete does not cause shrinkage. The loss of water from gel pores cause drying shrinkage.

3.Carbonation shrinkage: Carbon-di-oxide(Co2) present in the atmosphere reacts with hydrated cement. As a result calcium hydroxide [Ca(OH)2] decomposes and forms calcium carbonate [CaCO3] and some other compounds of hydrated cement also decomposes.This reaction takes place even at low pressure of CO2 in atmosphere.This reaction is called carbonation. It accompanies with increase of weight and shrinkage of concrete. The shrinkage is due to the production of CaCo3 in the place of Ca(OH)2, where the volume of CaCO3 is less than the volume of of Ca(OH)2.

Problems Of Using Salt Contaminated Sand

Salt contaminated sand absorb moisture from atmosphere causing permanent dampness and efflorescence and work gradually disintegrates. It also contain shells and organic matter which decompose in the body of mortar.Hence strength and life of mortar reduces.

Propertise of Good Sand

Good sand should be pure silica.It should be free from clay, salt,silt and organic matters.It is better wash sand before construction work.

Bulking of Aggregates

The increase of volume of given weight of aggregates due to the presence of moisture is called bulking of aggregates. 5 to 8 percent of moisture of aggregate weight cause 20 to 30 percent volume increase. This because of the creation of thin film of water inside aggregates which cause interlocking air. This are tries to get out and cause volume increase. By adding of water in dry aggregates the volume in crease up to adding of 8 percent of water of aggregate weight. Further adding of water cause water move into the void of aggregates particle. This cause volume to decrease. When aggregates are saturated its volume is same as the dry condition. Five aggregates increase volume more than coarse aggregates.
The bulking is determined by following expression
Bulking, b = Vm/Vd x100
Where Vm is the volume with moist and Vd is the dry or fully saturated volume and b is the bulking percentage.

Thursday, March 3, 2011

Alkali Aggregate Reaction

For a long time aggregates are considered to be inert.But now it is proven that they are not inert totally. Some aggregates contain reactive silica which reacts with alkalies,i.e, sodium or potassium present in cement.
The reaction starts by attacking on silicous mineral by alkaline hydroxide derived from alkali. Hence silicate gel of unlimited swelling form inside concrete. This swelling cause pattern of cracks and eventual failure of concrete structure.

Soundness of Aggregates

Soundness of aggregates is the ability of aggregates to resist change of volume due to change of physical condition. These physical conditions include freezing and thawing,temperature change, alternative change of drying and wetting in normal condition and alternative change of drying and wetting in salt water.The aggregates which are weak, porous and containing undesirable materials undergo large volume change in change of those physical conditions.

Importance of Aggregates

As at least three quarters of concrete is occupied by aggregates it is of great importance.

1.Cheaper than cement.Hence it reduces the cost of concrete.

2.Increases the binding capacity of cement.Cement alone can not be strong.

3.The chemical and thermal properties of aggregates effect the properties of concrete.

4.Durability of concrete depends on the characteristics of concrete.


The inert materials which are used in concrete is called aggregates.Such as sand,pebbles,cinder, gravel etc.But aggregates are not always inert. Recent study shows that the chemical and thermal properties of aggregates influence the quality of concrete.

Kinds of aggregates

Two kinds.

1.Fine aggregates:The aggregates which are smaller than 3/16 inch or 4.76 mm is called fine aggregates. Sand is the common fine aggregate.

2.Coarse aggregates:The aggregate which are bigger than 3/16 inch or 4.76 mm is called coarse aggregate. Broken brick,pebbles,gravel etc are coarse aggregates.