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See more. Civil Engineering Basics. Education Apps For Students. Civil Engineer app explains that general thing of Civil Engineer for freshers. Basic Civil Engineering Notes The specimen is then sieved through 2. The recommended impact values for various works are: This test is normally carried out on sand stones to check the presence of calcium carbonate, which weakens the weather resisting quality.
In this test, a sample of stone weighing about 50 to gm is taken and kept in a solution of one per cent hydrochloric acid for seven days. The solution is agitated at intervals. A good building stone maintains its sharp edges and keeps its surface intact. If edges are broken and powder is formed on the surface, it indicates the presence of calcium carbonate. Such stones will have poor weather resistance.
Polished marbles and granite are commonly used for face works. When mixed with tar they form finishing coat. Their qualities and uses are explained below: The structure is medium to fine grained and compact.
Their colour varies from dark gray to black. Fractures and joints are common. These are igneous rocks. They are used as road metals, aggregates for concrete. They are also used for rubble masonry works for bridge piers, river walls and dams. They are used as pavement. Granites are also igneous rocks.
The colour varies from light gray to pink. The structure is crystalline, fine to coarse grained. They take polish well. They are hard durable.
Specific gravity is from 2. They are used primarily for bridge piers, river walls, and for dams. They are used as kerbs and pedestals.
The use of granite for monumental and institutional buildings is common. Polished granites are used as table tops, cladding for columns and wall. They are used as coarse aggregates in concrete. These are sedimentary rocks, and hence stratified. They consist of quartz and feldspar. They are found in various colours like white, grey, red, buff, brown, yellow and even dark gray. The specific gravity varies from 1.
Its porosity varies from 5 to 25 per cent. Weathering of rocks renders it unsuitable as building stone. It is desirable to use sand stones with silica cement for heavy structures, if necessary. They are used for masonry work, for dams, bridge piers and river walls. These are metamorphic rocks. They are composed of quartz, mica and clay minerals.
The structure is fine grained. They split along the planes of original bedding easily. The colour varies from dark gray, greenish gray, purple gray to black.
The specific gravity is 2. They are used as roofing tiles, slabs, pavements etc. It is a metamorphic rock. It is having porous and sponges structure. It contains high percentage of iron oxide. Its colour may be brownish, red, yellow, brown and grey. Its specific gravity is 1.
It can be easily quarried in blocks. With seasoning it gains strength. When used as building stone, its outer surface should be plastered. This is a metamorphic rock. It can take good polish. It is available in different pleasing colours like white and pink.
Its specific gravity is 2. It is used for facing and ornamental works. It is used for columns, flooring, steps etc. It is having fine to coarse grains. Alternative dark and white bands are common.
Light grey, pink, purple, greenish gray and dark grey coloured varieties are available. These stones are not preferred because of deleterious constituents present in it. They may be used in minor constructions. However hard varieties may be used for buildings. The specific gravity varies from 2. Quartzites are metamorphic rocks. The structure is fine to coarse grained and often granular and branded. They are available in different colours like white, gray, yellowish. Quartz is the chief constituent with feldspar and mica in small quantities.
They are used as building blocks and slabs. They are also used as aggregates for concrete. This is the oldest building block to replace stone. Manufacture of brick started with hand moulding, sun drying and burning in clamps. These bricks are used for the construction of walls. These are vitrified bricks and are used as pavers. These bricks are specially made to withstand furnace temperature. Silica bricks belong to this category.
These bricks are different from the commonly used building bricks with respect to their shape and the purpose for which they are made. Some of such bricks are listed below: Bricks of special shapes are manufactured to meet the requirements of different situations.
Some of them are shown in Fig. These bricks are used in the outer face of masonry. Once these bricks are provided, plastering is not required. These bricks are manufactured with area of perforation of 30 to 45 per cent.
The area of each perforation should not exceed mm2. The perforation should be uniformly distributed over the surface. Figure 1. They are light in weight. They are used for the construction of partition walls. They provide good thermal insulation to buildings.
The thickness of any shell should not be less than 11 mm and that of any web not less than 8 mm. WEBS 8 mm minimum thick Fig. Hollow bricks e Sewer Bricks: These bricks are used for the construction of sewage lines. They are manufactured from surface clay, fire clay shale or with the combination of these.
The average strength of these bricks should be a minimum of The water absorption should not be more than 10 per cent. These bricks are used for floorings likely to be subjected to acid attacks, lining of chambers in chemical plants, lining of sewers carrying industrial wastes etc. These bricks are made of clay or shale of suitable composition with low lime and iron content, flint or sand and vitrified at high temperature in a ceramic kiln.
Colour should be uniform and bright. Bricks should have plane faces. They should have sharp and true right angled corners. Bricks should be of standard sizes as prescribed by codes. They should possess fine, dense and uniform texture. They should not possess fissures, cavities, loose grit and unburnt lime.
When struck with hammer or with another brick, it should produce metallic sound. Finger scratching should not produce any impression on the brick. Crushing strength of brick should not be less than 3. A field test for strength is that when dropped from a height of 0. After immercing the brick in water for 24 hours, water absorption should not be more than 20 per cent by weight.
For class-I works this limit is 15 per cent. Bricks should not show white patches when soaked in water for 24 hours and then allowed to dry in shade. White patches are due to the presence of sulphate of calcium, magnesium and potassium.
They keep the masonry permanently in damp and wet conditions. Bricks should have low thermal conductivity, so that buildings built with them are cool in summer and warm in winter. Heavier bricks are poor insulators of sound while light weight and hollow bricks provide good sound insulation.
Fire resistance of bricks is usually good. In fact bricks are used to encase steel columns to protect them from fire. The brick specimen are immersed in water for 24 hours. The frog of the brick is filled flush with 1: The specimen is placed in compression testing machine with 6 mm plywood on top and bottom of it to get uniform load on the specimen.
Then the crushing strength is the ratio of crushing load to the area of brick loaded. Average of five specimen is taken as the crushing strength.
Brick specimen are weighed dry. Then they are immersed in water for a period of 24 hours. The specimen are taken out and wiped with cloth. The weight of each specimen in wet condition is determined. The difference in weight indicate the water absorbed. Then the percentage absorption is the ratio of water absorbed to dry weight multiplied by The average of five specimen is taken. This value should not exceed 20 per cent.
Bricks should be of standard size and edges should be truely rectangular with sharp edges. To check it, 20 bricks are selected at random and they are stacked along the length, along the width and then along the height.
IS code permits the following limits: The following field tests help in acertaining the good quality bricks: A good brick should have rectangular plane surface and uniform in size.
This check is made in the field by observation. A good brick will be having uniform colour throughout. This observation may be made before downloading the brick. A few bricks may be broken in the field and their cross-section observed. The section should be homogeneous, compact and free from defects such as holes and lumps. If two bricks are struck with each other they should produce clear ringing sound. The sound should not be dull. For this a simple field test is scratch the brick with nail.
If no impression is marked on the surface, the brick is sufficiently hard vi Efflorescense: The presence of alkalies in brick is not desirable because they form patches of gray powder by absorbing moisture.
Hence to determine the presence of alkalies this test is performed as explained below: Place the brick specimen in a glass dish containing water to a depth of 25 mm in a well ventilated room. After all the water is absorbed or evaporated again add water for a depth of 25 mm. No patches b Slight: More than 50 per cent area covered with deposits but unaccompanied by flaking of the surface.
Heavy deposits of salt accompanied by flaking of the surface. These bricks are of standard shape and size. They are burnt in kilns. They fulfill all desirable properties of bricks. These bricks are ground moulded and burnt in kilns. The edges may not be sharp and uniform. The surface may be some what rough. Such bricks are commonly used for the construction of walls which are going to be plastered.
These bricks are ground moulded and burnt in clamps. Their edges are somewhat distorted. They produce dull sound when struck together. They are used for temporary and unimportant structures. These are the over burnt bricks. They are dark in colour.
The shape is irregular. They are used as aggregates for concrete in foundations, floors and roads. 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. It is composed of 95 percentage of calcium oxide. When water is added, it slakes 1 vigorously and its volume increases to 2 to 2 times. It is white in colour. Its properties are: It contains clay and ferrous oxide. Depending upon the percentage of clay present, the hydraulic lime is divided into the following three types: Its colour is muddy. It has poor binding property.
The mortar made with such lime is used for inferior works. 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. 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. 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. 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: 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. The cement is obtained by burning a mixture of calcarious calcium and argillaceous clay material at a very high temperature and then grinding the clinker so produced to a fine powder.
It was first produced by a mason Joseph Aspdin in England in He patented it as portland cement. Important varieties are briefly explained below: The cement when made free from colouring oxides of iron, maganese and chlorium results into white cement. In the manufacture of this cement, the oil fuel is used instead of coal for burning.
White cement is used for the floor finishes, plastering, ornamental works etc. In swimming pools white cement is used to replace glazed tiles. It is used for fixing marbles and glazed tiles. The cements of desired colours are produced by intimately mixing pigments with ordinary cement. The chlorium oxide gives green colour. Cobalt produce blue colour. Iron oxide with different proportion produce brown, red or yellow colour.
Addition of manganese dioxide gives black or brown coloured cement. These cements are used for giving finishing touches to floors, walls, window sills, roofs etc. Quick setting cement is produced by reducing the percentage of gypsum and adding a small amount of aluminium sulphate during the manufacture of cement.
Finer grinding also adds to quick setting property. This cement starts setting within 5 minutes after adding water and becomes hard mass within 30 minutes. This cement is used to lay concrete under static or slowly running water.
This cement can be produced by increasing lime content and burning at high temperature while manufacturing cement. Grinding to very fine is also necessary. Though the initial and final setting time of this cement is the same as that of portland cement, it gains strength in early days.
This property helps in earlier removal of form works and speed in construction activity. In mass concrete works like construction of dams, heat produced due to hydration of cement will not get dispersed easily. This may give rise to cracks. Hence in such constructions it is preferable to use low heat cement. Pozzulana is a volcanic power found in Italy.
It can be processed from shales and certain types of clay also. In this cement pozzulana material is 10 to 30 per cent. It can resist action of sulphate. It releases less heat during setting.
It imparts higher degree of water tightness. Its tensile strength is high but compressive strength is low. It is used for mass concrete works. It is also used in sewage line works. This cement expands as it sets. This property is achieved by adding expanding medium like sulpho aluminate and a stabilizing agent to ordinary cement. This is used for filling the cracks in concrete structures. It is manufactured by calcining a mixture of lime and bauxite. It is more resistant to sulphate and acid attack.
It develops almost full strength within 24 hours of adding water. It is used for under water works. In the manufacture of pig iron, slag comes out as a waste product. By grinding clinkers of cement with about 60 to 65 per cent of slag, this cement is produced. The properties of this cement are more or less same as ordinary cement, but it is cheap, since it utilise waste product.
This cement is durable but it gains the strength slowly and hence needs longer period of curing. This cement is produced by adding acid resistant aggregated such as quartz, quartzite, sodium silicate or soluble glass. This cement has good resistance to action of acid and water.
It is commonly used in the construction of chemical factories. By keeping the percentage of tricalcium aluminate C3A below five per cent in ordinary cement this cement is produced.
It is used in the construction of structures which are likely to be damaged by alkaline conditions. Examples of such structures are canals, culverts etc. Fly ash is a byproduct in thermal stations. The particles of fly ash are very minute and they fly in the air, creating air pollution problems. Thermal power stations have to spend lot of money to arrest fly ash and dispose safely. It is found that one of the best way to dispose fly ash is to mix it with cement in controlled condition and derive some of the beneficiary effects on cement.
Now-a-days cement factories produce the fly ash in their own thermal stations or borrow it from other thermal stations and further process it to make it suitable to blend with cement. Fly ash blended cements have superior quality of resistance to weathering action.
The ultimate strength gained is the same as that with ordinary portland cement. However strength gained in the initial stage is slow. Birla plus, Birla star, A. Suraksha are some of the brand mame of blended cement. Portland cement consists of the following chemical compounds: When water is added to cement, C3A is the first to react and cause initial set.
It generates great amount of heat. C3S hydrates early and develops strength in the first 28 days. It also generates heat. C2S is the next to hydrate. It hydrates slowly and is responsible for increase in ultimate strength. C4AF is comparatively inactive compound. The following physical properties should be checked before selecting a portland cement for the civil engineering works. IS — specifies the method of testing and prescribes the limits: It is measured in terms of percentage of weight retained after sieving the cement through 90 micron sieve or by surface area of cement in square centimeters per gramme of cement.
According to IS code specification weight retained on the sieve should not be more than 10 per cent. A period of 30 minutes as minimum setting time for initial setting and a maximum period of minutes as maximum setting time is specified by IS code, provided the tests are conducted as per the procedure prescribed by IS Once the concrete has hardened it is necessary to ensure that no volumetric changes takes place.
The cement is said to be unsound, if it exhibits volumetric instability after hardening. IS code recommends test with Le Chatelier mould for testing this property. At the end of the test, the indicator of Le Chatelier mould should not expand by more than 10 mm. For this mortar cubes are made with standard sand and tested in compression testing machine as per the specification of IS code.
It is conducted by sieve analysis. Residue on the sieve is weighed. This should not exceed 10 per cent by weight of sample taken. Initial setting time and final setting time are the two important physical properties of cement. Initial setting time is the time taken by the cement from adding of water to the starting of losing its plasticity. Final setting time is the time lapsed from adding of the water to complete loss of plasticity. Vicat apparatus is used for finding the setting times [Ref.
Vicat apparatus consists of a movable rod to which any one of the three needles shown in figure can be attached. An indicator is attached to the movable rod. A vicat mould is associated with this apparatus which is in the form of split cylinder. The plunger is attached to the movable rod of vicat apparatus and gently lowered to touch the paste in the mould. Then the plunger is allowed to move freely.
If the penetration is 5 mm to 7 mm from the bottom of the mould, then cement is having standard consistency. If not, experiment is repeated with different proportion of water fill water required for standard consistency is found. Then the tests for initial and final setting times can be carried out as explained below: Initial Setting Time: Then it is freely allowed to penetrate.
In the beginning the needle penetrates the paste completely. As time lapses the paste start losing its plasticity and offers resistance to penetration. When needle can penetrate up to 5 to 7 mm above bottom of the paste experiment is stopped and time lapsed between the addition of water and end if the experiment is noted as initial setting time. Final Setting Time. The square needle is replaced with annular collar. Experiment is continued by allowing this needle to freely move after gently touching the surface of the paste.
Time lapsed between the addition of water and the mark of needle but not of annular ring is found on the paste. This time is noted as final setting time. This test is conducted to find free lime in cement, which is not desirable. Le Chatelier apparatus shown in Fig. It consists of a split brass mould of diameter 30 mm and height 30 mm. On either side of the split, there are two indicators, with pointed ends. The ends of indicators are mm from the centre of the mould. Glass plate 30 mm Glass plate Elevation Brass mould Thickness 0.
Then the whole assembly is kept under water for 24 hours. Note the distance between the indicator. Then place the mould again in the water and heat the assembly such that water reaches the boiling point in 30 minutes. Boil the water for one hour. The mould is removed from water and allowed to cool. The distance between the two pointers is measured. The difference between the two readings indicate the expansion of the cement due to the presence of unburnt lime.
This value should not exceed 10 mm. For this gm of cement is mixed with gm of standard sand confirming to IS — They are 4 mixed with trowel for 3 to 4 minutes to get uniform mixture. The mix is placed in a cube mould of A hopper is secured at the top and the remaining mortar is filled.
The mould is vibrated for two minutes and hopper removed. The top is finished with a knife or with a trowel and levelled. After specified period cubes are tested in compression testing machine, keeping the specimen on its level edges. Average of three cubes is reported as crushing strength. The compressive strength at the end of 3 days should not be less than Some of them are listed below: This form of timber is known as rough timber.
By sawing, rough timber is converted into various commercial sizes like planks, battens, posts, beams etc. Such form of timber is known as converted timber. Many ancient temples, palaces and bridges built with timber can be seen even today. The following are the important basis: On the basis of mode of growth trees are classified as a Exogeneous and b Endogeneous a Exogeneous Trees: These trees grow outward by adding distinct consecutive ring every year.
These rings are known as annual rings. Hence it is possible to find the age of timber by counting these annual rings. These trees may be further divided into 1 coniferrous and 2 deciduous.
Coniferrous trees are having cone shaped leaves and fruits. The leaves do not fall till new ones are grown. They yield soft wood. Deciduous trees are having broad leaves.
These leaves fall in autumn and new ones appear in springs. They yield strong wood and hence they are commonly used in building construction. The classification as soft wood and hard wood have commercial importance. The difference between soft wood and hard wood is given below: In soft wood annual rings are seen distinctly whereas in hard wood they are indistinct.
The colour of soft wood is light whereas the colour of hard wood is dark. Soft woods have lesser strength in compression and shear compared to hard woods. Soft woods are light and hard woods are heavy. Fire resistance of soft wood is poor compared to that of hard wood. The structure of soft wood is resinous while structure of hard wood is close grained. The cross-section of a exogeneous tree is as shown in the Fig. The following components are visible to the naked eye: It is the inner most part of the tree and hence the oldest part of exogeneous tree when the plant becomes old, the pith dies and becomes fibrous and dark.
It varies in size and shape. Heart Wood: This is the portion surrounding pith.
It is dark in colour and strong. This portion is useful for various engineering purpose. This is the dead part of wood. It consists of several annular rings. Sap Wood: It is the layer next to heart wood. It denotes recent growth and contains sap. It takes active part in the growth of trees by allowing sap to move in upward direction. The annual rings of sap wood are less sharply divided and are light in colour.
The sap wood is also known as alburnum. Cambium Layer: It is a thin layer of fresh sap lying between sap wood and the inner bark. It contains sap which is not yet converted into sap wood.
If the bark is removed and cambium layer is exposed to atmosphere, cells cease to be active and tree dies. Inner Bark: It is a inner skin of tree protecting the cambium layer. It gives protection to cambium layer. Outer Bark: It is the outer skin of the tree and consists of wood fibres. Sometimes it contains fissures and cracks.
Medullary Rags: These are thin radial fibres extending from pith to cambium layer. They hold annular rings together. In some of trees they are broken and some other they may not be prominent. These trees grow inwards. Fresh fibrous mass is in the inner most portion. Examples of endogenous trees are bamboo and cane. They are not useful for structural works. On this basis timber is classified as: Group A: Durability tests are conducted by the forest research establishment.
Then timbers are classified as: High durability: If average life is more than 10 years. Moderate durability: Average life between 5 to 10 years. Low durability: Average life less than 5 years. IS classifies the structural timber into three grades-select grade, grade I and grade II. The classification is based on permissible stresses, defects etc.
Forest departments classify timbers based on the availability as X—Most common. Less than m3 per year. It should be uniform. It should be pleasant when cut freshly. A clear ringing sound when struck indicates the timber is good. Texture of good timber is fine and even. In good timber grains are close. Higher the density stronger is the timber.
Harder timbers are strong and durable. Good timber do not warp under changing environmental conditions. Timber should be capable of resisting shock loads. Good timber do not deteriorate due to wear. This property should be looked into, if timber is to be used for flooring. Timber should have high strength in bending, shear and direct compression.
Modulus of Elasticity: Timber with higher modulus of elasticity are preferred in construction. Fire resistance: A good timber should have high resistance to fire. Good timber has low water permeability. Timber should be easily workable. It should not clog the saw. Good timber is one which is capable of resisting the action of fungi and insects attack Defects: Good timber is free from defects like dead knots, shakes and cracks. By doing so the durability of timber is increased.
The various methods of seasoning used may be classified into: It may be air seasoning or water seasoning. Air seasoning is carried out in a shed with a platform. On about mm high platform timber balks are stacked as shown in Fig.
Care is taken to see that there is proper air circulation around each timber balk. Over a period, in a natural process moisture content reduces. This is a slow but a good process of seasoning. Water seasoning is carried out on the banks of rivers. The thicker end of the timber is kept pointing upstream side.
After a period of 2 to 4 weeks the timber is taken out. During this period sap contained in the timber is washed out to a great extent. Then timber is stalked in a shed with free air circulation. Air seasoning ii Artificial Seasoning: In this method timber is seasoned in a chamber with regulated heat, controlled humidity and proper air circulation.
Seasoning can be completed in 4 to 5 days only. The different methods of seasoning are: In this method timber is immersed in water and then water is boiled for 3 to 4 hours. Then it is dried slowly. Instead of boiling water hot steam may be circulated on timber. The process of seasoning is fast, but costly. Kiln is an airtight chamber. Timber to be seasoned is placed inside it. The heat gradually reaches inside timber. Then relative humidity is gradually reduced and temperature is increased, and maintained till desired degree of moisture content is achieved.
The kiln used may be stationary or progressive. In progressive kiln the carriages carrying timber travel from one end of kiln to other end gradually. The hot air is supplied from the discharging end so that temperature increase is gradual from charging end to discharging end.
This method is used for seasoning on a larger scale. In this method, the timber is immersed in a solution of suitable salt. Then the timber is dried in a kiln. The preliminary treatment by chemical seasoning ensures uniform seasoning of outer and inner parts of timber. In this method high frequency alternate electric current is passed through timber. Resistance to electric current is low when moisture content in timber is high.
As moisture content reduces the resistance reduces. Measure of resistance can be used to stop seasoning at appropriate level. This technique has been tried in some plywood industries but not in seasoning of timber on mass scale. The following defects are caused by natural forces: When a tree grows, many of its branches fall and the stump of these branches in the trunk is covered.
In the sawn pieces of timber the stump of fallen branches appear as knots. Knots are dark and hard pieces. Grains are distorted in this portion. If the knot is intact with surrounding wood, it is called live knot. If it is not held firmly it is dead knot. Live knot Decayed knots Fig. Knots b Shakes: The shakes are cracks in the timber which appear due to excessive heat, frost or twisting due to wind during the growth of a tree.
Depending upon the shape and the positions shakes can be classified as star shake, cup shake, ring shakes and heart shakes [Ref. These are the cracks on the outside of a log due to the shrinkage of the exterior surface. They appear as shown in Fig. Wind cracks Fig. Wind cracks d Upsets: This type of defect is due to excessive compression in the tree when it was young.
Upset is an injury by crushing. This is also known as rupture. Upset ii Defects due to Defective Seasoning and Conversion: If seasoning is not uniform, the converted timber may warp and twist in various directions.
Sometimes honey combining and even cracks appear. This type of defects are more susceptible in case of kiln seasoning. In the process of converting timber to commercial sizes and shapes the following types of defects are likely to airse: Fungi are minute microscopic plant organism.
Due to fungi attack rotting of wood, takes place. Wood becomes weak and stains appear on it.