CE6401 PART A 1. What are the geological classification of rocks? a) Igneous rocks b) Sedimentary rocks c) Metamorphic rocks 2. What ere the physical classification of rocks? a) Stratified rocks b) Unstratified rocks c) Foliated or laminated rocks 3. What are the classification of bricks? a) b) c) d) e)

First class bricks Second class bricks Third class bricks Over burnt or Jhama bricks Under burnt or pilla bricks

4. What is meant by pugging or tempering of clay? Pugging or tempering of clay means breaking up of prepared clay , watering and kneading till the earth becomes a homogeneous mass. 5. What are the ingredients of a good brick earth? A good brick earth mainly consists of silica (sand), alumina (clay), lime, oxide of iron and magnesia. 6. What is meant by slaking.? Quick lime has very large affinity for moisture. Adding water in sufficient quantity to quick lime is known as slaking. When water is added to quick lime, it swells and cracks. Lot of heat is also generated during slaking and quick lime gets converted into hydrated lime or calcium hydrate.

7. What are the classification of lime. ? a) Fat lime b) Hydraulic lime

c) Poor lime

8. What is known as clinker.? Artificial cement is manufactured by burning approximately proportioned mixture of calcareous and argillaceous materials at a very high temperature and then grinding the resuling burnt mixture to a fine powder. The burnt mixture of calcareous and argillaceous matter is known as clinker.

9. What are the constituents of ordinary cement.? Alumina or clay, silica, lime, iron oxide, magnesia, sulphur trioxide, alkalies, calcium sulphate (gypsum). 10. What are the types of cement.? a) b) c) d)

Ordinary portland cement, rapid hardening cement, low heat cement, blast furnace slag

11. Define mortar. The mortar is a paste like substance prepared by adding required amount of water to a dry mixture of sand or fine aggregate with some binding material like clay, lime or cement.. I 12. What is meant by grading of aggragates? Grading of aggregate means particle size distribution of the aggregate. If all the particle of an aggregate were of one size, more voids will be left on the aggregate mass.properly graded aggregate produces dense concrete and needs smaller quantities of fine aggregate and cement. Grading determines the workability of the mix, which controls segregation, bleeding, water-cement ratio, handling, placing, and other characteristics of the mix.

13. Define Seggregation. The tendancy of separation of coarse aggregate grains from the concrete mass is called segregation.

14. Define workability. Workability is that property of concrete which determines the amount of internal work necessary to produce full compaction. It is a measure with which concrete can be handled from the mixer stage to its final fully compacted stage.

15. What are the factors affecting proportioning of concrete mixes. 1. Water cement ratio 2. Cement content 3. Temperature 4. Age of concrete 5. Size, shape and grading of aggregate 6. Curing 16. Define curing of concrete. Curing is the operation by which moist conditions are maintained on finished concrete surface, to promote continued hydration of cement . 17. Define seasoning of timber? A freshly felled tree contains lot of moisture which is usually in form of sap. The excess of moisture have to be removed, before timber can be used for any structural purposes. The process of removing excess surplus moisture from freshly converted timber is known as seasoning of timber. 18. What are the methods of seasoning of timber. 1. Natural seasoning 2. Artificial seasoning 3. Water seasoning, 4. boiling seasoning, 5. kiln seasoning, 6. chemical seasoning, 7. electrical seasoning 19. What is meant by distempering. It is a process of applying wash or coating like white-washing or colour washing on the surface. 20. What are the constituents of oil paints? A base, an inert extender or filler, a vehicle or carrier, a drier, a solvent or thinner, a colouring pigment.

21. Define glazing. It is a process of covering the earthen ware, stone ware and porcelain products with an impervious film of glaze. It is a glassy coat of about 0.1 to 0.2 mm thickness, applied on the surface and then fused into the product by burning at high temperature.

22. Name some of the clay products used in building construction. Bricks, tiles, terra-cotta, stoneware, earthen ware, porcelains Etc. 23. What are the different types of geosynthetics? 1. Geotextiles 2. Geogrid 3. Geonets 4. Geomembranes 5. Geosynthetic clay liner 6. Geocells 7. Geofoam 8. Geocomposites 24. What are the applications of geosynthetics?  

Use of Geosynthetics in Earth Retention Techniques - Retaining Walls For heavy loads or for greater slopes, concrete walls are placed along with the use of geosynthetic.

PART B 1. a) What are the criteria for selection of building stones? Parameters considered in selection of a good construction stone are being cheap, hard, durable and naturally good looking. Stones are often used in construction but keeping in view the variable properties of stones of different types, there must be some criteria for the selection of stones for construction. The criteria is based upon the following parameters.

1. 2. 3. 4. 5. 6. 7.

Chemical composition of stone: Strongness and hardness: Durability: Resistance to fire: Bio-Deterioration: Appearance: Susceptibility to being quarried in large sizes:

1. Chemical composition of stones: Using/selecting a stone for construction, its chemical properties and composition must be tested and verified because different elements and compounds in stones have different properties. For instance, Magnesium in Limestone causes it to be more stronger and is called Dolomite. Feldspar, in large quantities in stone is a source of weakness because CO2 dissolves Potassium, Sodium, and even Calcium in the Feldspar leaving pure white clay behind. Presence of Mica, even less than 2-3% makes stone unsuitable for building purposes. Stones with silicates as cementing materials are resistant to weathering.

2. Strongness and hardness: The more compact grained and heavier a stone, the more stronger it is. A crystalline stone is superior to a non-crystalline texture. The specific gravity of good stone should be above 2.7. Stones used for road metal, paving blocks, floor slabs and railway ballast have to withstand mainly abrasion or wear and tear. Stone wall subjected to vibrations of machinery and moving loads should necessarily possess toughness. Strongness and hardness itself depend on some factors:

Factors affecting strength, hardness and toughness a) b) c) d) e) f) g)

Hardness or softness of the components Proportions of the hard and soft minerals Size and shape of the minerals Cohesion Porosity Density Cementing material

a) Hardness or softness of the components: The composition of the compounds determines its hardness or softness. Stones containing Si, Na, K are poor while that containing Mg, Ca, and Fe are good, as they are harder. If the stone is composed of soft and unhardened materials it will result in a soft materials and vice versa.

b) Proportion of hard and soft materials:

The amount of soft and hard material in a specific sample of stone also matters. Greater the amount of hard materials more will be the resistence to weathering.

c) Size and shape of the minerals is stones: Crystalline solids are hard and compact, thus superioir to non-crystalline. Finer the crystals, stronger the stones and vice versa, This property i.e fineness reduces the pores in the stone.

d) Cohesion: It is the property of atoms or particles to attract each other. The fine grains have more cohesive power than the coarser grains. Greater the cohesion in stone causes increase in the hardness, strongness and toughness of stones. The property of compactness also depends deeply on cohesion.

e) Porosity: Stones in wet conditions and having pores in them allow a lower crushing strength than normal. Porosity can reduce the strength upto 30 - 40% e.g limestone and sandstone are affected by this property. Porosity is the property of a substance in which it contains pores i it. It also reduces the resistence to a concentrated (point) load.

f) Density: If a stone is compact, dense, it would also be non-porous and strong , thus toughness also depends upon density.

g) Cementing material: Stones with silicates as cementing material will be resistant to weathering than those with calcareous or ferruginous binding material. So, cementing material also affects the choice of stone selection.

3) Resistence to heat: Resistence to heat means that the stone must have a very low amount of expansion due to large increase in temperature. Silicious materials are good at areas where resistence to fire is required.

4) Bio-deterioration: Certain trees and creepers thrust theri roots in the joints of stones and have both mechanical and chemical adverse effects. Special microbes can grow on the surface and in minute fissures, their by-products cause flaking and discoloration.

5) Appearance: The aesthetic aspect that is color, appearance and show of stones must also be considered when being used in a project. Appearance depends on the color and the ease with which the stone can be dressed, rubbed or polished.

1. b) Explain the test on stones. Building stones are to be tested for their properties. Following are the tests conducted on stones: i) Acid Test: Here, a sample of stone weighing about 50 to 100 gm is taken. It is placed in a solution of hydrophobic acid having strength of one percent and is kept there for seven days. Solution is agitated at intervals. A good building stone maintains its sharp edges and keeps its surface free from powder at the end of this period. If the edges are broken and powder is formed on the surface, it indicates the presence of calcium carbonate and such a stone will have poor weathering quality. This test is usually carried out on sandstones. ii) Attrition Test: This test is done to find out the rate of wear of stones, which are used in road construction. The results of the test indicates the resisting power of stones against the grinding action under traffic. The following procedure is adopted: i. Samples of stones is broken into pieces about 60mm size.

ii. Such pieces, weighing 5kg are put in both the cylinders of Devil’s attrition test machine. Diameter and length of cylinder are respectively 20cm and 34 cm. iii. Cylinders are closed. Their axes make an angle of 30 degree with the horizontal. iv. Cylinders are rotated about the horizontal axis for 5 hours at the rate of 30 rpm. v. After this period, the contents are taken out from the cylinders and they are passed through a sieve of 1.5mm mesh. vi. Quality of material which is retained on the sieve is weighed. vii. Percentage wear worked out as follows: Percentage wear = iii) Crushing Test: Samples of stone is cut into cubes of size 40x40x40 mm. sizes of cubes are finely dressed and finished. Maximum number of specimen to be tested is three. Such specimen should be placed in water for about 72 hours prior to test and therefore tested in saturated condition. Load bearing surface is then covered with plaster of paris of about 5mm thick plywood. Load is applied axially on the cube in a crushing test machine. Rate of loading is 140 kg/sq.cm per minute. Crushing strength of the stone per unit area is the maximum load at which the sample crushes or fails divided by the area of the bearing face of the specimen. iv) Crystalline Test: At least four cubes of stone with side as 40mm are taken. They are dried for 72 hrs and weighed. They are then immersed in 14% solution of Na2SO4 for 2 hours. They are dried at 100 degree C and weighed. Difference in weight is noted. This procedure of drying, weighing, immersion and reweighing is repeated atleast 5 times. Each time, change in weight is noted and it is expressed as a percentage of original weight. Crystallization of CaSO4 in pores of stone causes decay of stone due to weathering. But as CaSO4 has low solubility in water, it is not adopted in this test. v) Freezing and thawing test:

Stone specimen is kept immersed in water for 24 hours. It is then placed in a freezing machine at -12 degC for 24 hours. Then it is thawed or warmed at atmospheric temperature. This should be done in shade to prevent any effect due to wind, sun rays, rain etc. this procedure is repeated several times and the behaviour of stone is carefully observed. vi) Hardness Test: For determining the hardness of a stone, the test is carried out as follows: i. A cylinder of diameter 25mm and height 25mm is taken out from the sample of stone. ii. It is weighed. iii. The sample is placed in Dorry’s testing machine and it is subjected to a pressure of 1250 gm. iv. Annular steel disc machine is then rotated at a speed of 28 rpm. v. During the rotation of the disc, coarse sand of standard specification is sprinkled on the top of disc. vi. After 1000 revolutions, specimen is taken out and weighed. vii. The coefficient of hardness is found out from the following equation: Coefficient of hardness = vii) Impact Test: For determining the toughness of stone, it is subjected to impact test in a Page Impact Test Machine as followed: i. A cylinder of diameter 25mm and height 25mm is taken out from the sample of stones. ii. It is then placed on cast iron anvil of machine. iii. A steel hammer of weight 2kg is allowed to fall axially in a vertical direction over the specimen. iv. Height of first blow is 1 cm, that of second blow is 2cm, that of third blow is 3 cm and so on.

v. Blow at which specimen breaks is noted. If it is nth blow, ‘n’ represents the toughness index of stone.

1. a) Explain the wet process technology in cement manufacturing prosess The manufacture of cement is a very carefully regulated process comprising the following stages: Quarrying - a mixture of limestone and clay. Grinding - the limestone and clay with water to form a slurry. Burning - the slurry to a very high temperature in a kiln, to produce clinker. Grinding - the clinker with about 5% gypsum to make cement. Raw Materials Extraction The limestone and clay occur together in our quarries at Cape Foulwind. It is necessary to drill and blast these materials before they are loaded in 70t capacity trucks. The quarry trucks deliver the raw materials to the crusher where the rock is crushed to smaller than 100mm (4 inches). The raw materials are then stored ready for use. Raw Materials Preparation About 80% limestone and 20% clay are ground in ball mills with water, producing very fine, thin, paste called slurry. The chemical composition of the slurry is very carefully controlled by adjusting the relative amount of limestone and clay being used. The slurry is stored in large basins ready for use. Clinker Burning The slurry is fed into the upper end of a rotary kiln, while at the lower end of the kiln, a very intense flame is maintained by blowing in finely ground coal. The slurry slowly moves down the kiln and is dried and heated until it reaches a temperature of almost 1500 degrees Celsius producing "clinker". This temperature completely changes the limestone and clay to produce new minerals which have the property of reacting with water to form a cementitious binder. The hot clinker is used to preheat the air for burning the coal, and the cooled clinker is stored ready for use. Cement Milling The clinker is finely ground with about 5% gypsum in another ball mill, producing cement. (The gypsum regulates the early setting characteristic of cement). The finished cement is stored in silos then carted to our wharf or packing plant facilities.

2. 2. b) Explain the various test on cement. Checking of materials is an essential part of civil engineering as the life of structure is dependent on the quality of material used.Following are the tests to be conducted to judge the quality of cement.

1. Fineness 2. Soundness 3. Consistency 4. Initial And Final Setting Time Of Cement

FINENESS So we need to determine the fineness of cement by dry sieving as per IS: 4031 (Part 1) – 1996.The principle of this is that we determine the proportion of cement whose grain size is larger then specified mesh size. The apparatus used are 90µm IS Sieve, Balance capable of weighing 10g to the nearest 10mg, A nylon or pure bristle brush, preferably with 25 to 40mm, bristle, for cleaning the sieve. Sieve shown in pic below is not the actual 90µm seive.Its just for reference.

Procedure to determine fineness of cement i) Weigh approximately 10g of cement to the nearest 0.01g and place it on the sieve. ii) Agitate the sieve by swirling, planetary and linear movements, until no more fine material passes through it. iii) Weigh the residue and express its mass as a percentage R1,of the quantity first placed on the sieve to the nearest 0.1 percent. iv) Gently brush all the fine material off the base of the sieve. v) Repeat the whole procedure using a fresh 10g sample to obtain R2. Then calculate R as the mean of R1 and R2 as a percentage, expressed to the nearest 0.1 percent. When the results differ by more than 1 percent absolute, carry out a third sieving and calculate the mean of the three values. Reporting of Results Report the value of R, to the nearest 0.1 percent, as the residue on the 90µm sieve.

SOUNDNESS Soundness of cement is determined by Le-Chatelier method as per IS: 4031 (Part 3) – 1988. Apparatus – The apparatus for conducting the Le-Chatelier test should conform to IS: 5514 – 1969 Balance, whose permissible variation at a load of 1000g should be +1.0g and Water bath. Procedure to determine soundness of cement i) Place the mould on a glass sheet and fill it with the cement paste formed by gauging cement with 0.78 times the water required to give a paste of standard consistency. ii) Cover the mould with another piece of glass sheet, place a small weight on this covering glass sheet and immediately submerge the whole assembly in water at a temperature of 27 ± 2oC and keep it there for 24hrs. iii) Measure the distance separating the indicator points to the nearest 0.5mm (say d1 ). iv) Submerge the mould again in water at the temperature prescribed above. Bring the water to boiling point in 25 to 30 minutes and keep it boiling for 3hrs. v) Remove the mould from the water, allow it to cool and measure the distance between the indicator points (say d2 ). vi) (d2 – d1 ) represents the expansion of cement.

Procedure to determine soundness of cement i) Place the mould on a glass sheet and fill it with the cement paste formed by gauging cement with 0.78 times the water required to give a paste of standard consistency. ii) Cover the mould with another piece of glass sheet, place a small weight on this covering glass sheet and immediately submerge the whole assembly in water at a temperature of 27 ± 2oC and keep it there for 24hrs. iii) Measure the distance separating the indicator points to the nearest 0.5mm (say d1 ). iv) Submerge the mould again in water at the temperature prescribed above. Bring the water to boiling point in 25 to 30 minutes and keep it boiling for 3hrs. v) Remove the mould from the water, allow it to cool and measure the distance between the indicator points (say d2 ). vi) (d2 – d1 ) represents the expansion of cement. Procedure to determine consistency of cement i) Weigh approximately 400g of cement and mix it with a weighed quantity of water. The time of gauging should be between 3 to 5 minutes. ii) Fill the Vicat mould with paste and level it with a trowel. iii) Lower the plunger gently till it touches the cement surface. iv) Release the plunger allowing it to sink into the paste. v) Note the reading on the gauge.

vi) Repeat the above procedure taking fresh samples of cement and different quantities of water until the reading on the gauge is 5 to 7mm. Reporting of Results Express the amount of water as a percentage of the weight of dry cement to the first place of decimal.

INITIAL AND FINAL SETTING TIME We need to calculate the initial and final setting time as per IS: 4031 (Part 5) – 1988. To do so we need Vicat apparatus conforming to IS: 5513 – 1976, Balance, whose permissible variation at a load of 1000g should be +1.0g, Gauging trowel conforming to IS: 10086 – 1982. Procedure to determine initial and final setting time of cement i) Prepare a cement paste by gauging the cement with 0.85 times the water required to give a paste of standard consistency. ii) Start a stop-watch, the moment water is added to the cement. iii) Fill the Vicat mould completely with the cement paste gauged as above, the mould resting on a non-porous plate and smooth off the surface of the paste making it level with the top of the mould. The cement block thus prepared in the mould is the test block. A) INITIAL SETTING TIME Place the test block under the rod bearing the needle. Lower the needle gently in order to make contact with the surface of the cement paste and release quickly, allowing it to penetrate the test block. Repeat the procedure till the needle fails to pierce the test block to a point 5.0 ± 0.5mm measured from the bottom of the mould.The time period elapsing between the time, water is added to the cement and the time, the needle fails to pierce the test block by 5.0 ± 0.5mm measured from the bottom of the mould, is the initial setting time. B) FINAL SETTING TIME Replace the above needle by the one with an annular attachment. The cement should be considered as finally set when, upon applying the needle gently to the surface of the test block, the needle makes an impression therein, while the attachment fails to do so. The period elapsing between the time, water is added to the cement and the time, the needle makes an impression on the surface of the test block, while the attachment fails to do so, is the final setting time.

3. a) what are the classification of bricks?

Classification of Bricks The classification of bricks is as follows: (i) unburnt or sun-dried bricks; and (ii) burnt bricks. The unburnt or sun-dried bricks are those bricks which are dried with the help of heat that is received from sun after the process of moulding. The unburnt bricks can only be used in the construction of simple temporary and cheap structures. Unburnt bricks should not be used at places exposed to heavy rains. The bricks used in construction works are burnt bricks and they are classified into the followingfour categories: (1) First class bricks (2) Second class bricks (3) Third class bricks (4) Fourth class bricks. (1) First class bricks: These first class bricks are table moulded and of uniform shape and they are burnt in kilns. The surfaces and edges of the bricks are sharp, square, smooth and straight. They comply with all the qualities of good bricks. These bricks are used for important work of permanent nature. (2) Second class bricks: The second class bricks are ground moulded and they are burnt in kilns. The surface of the second class bricks is slightly rough and shape is also slightly regular. These bricks may have hair cracks and their edges may not be sharp and uniform. These bricks are commonly used at places where brickwork is to be provided with a coat of plaster. (3) Third class bricks: These bricks are ground-moulded and they are burnt in clamps. These bricks are not very hard and they have rough surfaces with irregular and blunt edges. These bricks give dull sound when they are struck together. They are used for unimportant works, temporary structures and at places where rainfall is not heavy. (4) Fourth class bricks: These are overburnt bricks with irregular shape and dark colour. These bricks are used as aggregate for concrete in foundations, brick floors, surkhi, roads, etc. because of the fact that the overburnt bricks have a compact structure and hence they are sometimes found to be stronger than even the first class bricks. It is thus seen that the above classification of bricks is based on the of manufacturing or preparing bricks.

3. b) Explain the tests on bricks. Tests for the acceptance of bricks for building construction a) Dimension and tolerance test b) Compressive strength test c) Water absorption test d) Efflorescence test a) Dimension and Tolerance Test Take 20 bricks out of given sample. The dimensions of 20 bricks should be within the following limits.

b. Compressive Strength Test: The compressive strength of a common brick should be 50 kg/sq.cm c. Water Absorption Test: If the water absorption capacity of a brick is more, its strength will be comparatively low.

For first class bricks, the water absorption capacity should not be more than 20% by weight. d. Efflorescence Test This test is performed to know the presence of of any alkaline matter in the bricks.

4. a) Explain the properties of fresh concrete Fresh Concrete Fresh concrete is that stage of concrete in which concrete can be moulded and it is in plastic state. This is also called "Green Concrete". Another term used to describe the state of fresh concrete is consistence, which is the ease with which concrete will flow.

a) b) c) d) e) f) g)

Following are the important properties of fresh concrete Setting Workability Bleeding and Segregation Bleeding Segregation Hydration Air Entrainment

a. Setting of Concrete The hardening of concrete before its hydration is known as setting of concrete. The hardening of concrete before it gains strength. OR The transition process of changing of concrete from plastic state to hardened state. Setting of concrete is based or related to the setting of cement paste. Thus cement properties greatly affect the setting time. Factors affecting setting: Following are the factors that affect the setting of concrete.        

Water Cement ratio Suitable Temperature Cement content Type of Cement Fineness of Cement Relative Humidity Admixtures Type and amount of Aggregate

Workability is often referred to as the ease with which a concrete can be transported, placed and consolidated without excessive bleeding or segregation. The internal work done required to overcome the frictional forces between concrete ingredients for full compaction. It is obvious that no single test can evaluate all these factors. In fact, most of these cannot be easily assessed even though some standard tests have been established to evaluate them under specific conditions. In the case of concrete, consistence is sometimes taken to mean the degree of wetness; within limits, wet concretes are more workable than dry concrete, but concrete of same consistence may vary in workability. Because the strength of concrete is adversely and significantly affected by the presence of voids in the compacted mass, it is vital to achieve a maximum possible density. This requires sufficient workability for virtually full compaction to be possible using a reasonable amount of work under the given conditions. Presence of voids in concrete reduces the density and greatly reduces the strength: 5% of voids can lower the strength by as much as 30%.

Slump Test can be used to find out the workability of concrete. View Procedure of Slump Test Factors affecting concrete workability:        

Water-Cement ratio Amount and type of Aggregate Amount and type of Cement Weather conditions Temperature Wind Chemical Admixtures Sand to Aggregate ratio

i. Water content or Water Cement Ratio More the water cement ratio more will be workability of concrete. Since by simply adding water the inter particle lubrication is increased. High water content results in a higher fluidity and greater workability. Increased water content also results in bleeding. another effect of increased water content can also be that cement slurry will escape through joints of formwork. High water content results in a higher fluidity and greater workability. Increased water content also results in bleeding. another effect of increased water content can also be that cement slurry will escape through joints of formwork. ii. Amount and type of Aggregate Since larger Aggregate sizes have relatively smaller surface areas (for the cement paste to coat) and since less water means less cement, it is often said that one should use the largest practicable Aggregate size and the stiffest practical mix. Most building elements are constructed with a maximum Aggregate size of 3/4" to 1", larger sizes being prohibited by the closeness of the reinforcing bars. Because concrete is continuously shrinking for years after it is initially placed, it is generally accepted that under thermal loading it will never expand to it's originally-placed volume. More the amount of aggregate less will be workability. Using smooth and round aggregate increases the workability. Workability reduces if angular and rough aggregate is used. Greater size of Aggregate- less water is required to lubricate it, the extra water is available for workability

Angular aggregates increases flakiness or elongation thus reduces workability. Round smooth aggregates require less water and less lubricationand gretaer workability in a given w/c ratio Porous aggregates require more water compared to non absorbent aggregates for achieving sam degree of workability. iii. Aggregate Cement ratio More ratio, less workability. Since less cement mean less water, so the paste is stiff. iv. Weather Conditions 1. Temperature If temperature is high, evaporation increases, thus workability decreases. 2. Wind: If wind is moving with greater velocity, the rate of evaporation also increase reduces the amount of water and ultimately reducing workability. v. Admixtures Chemical admixtures can be used to increase workability. Use of air entraining agent produces air bubbles which acts as a sort of ball bearing between particles and increases mobility, workability and decreases bleeding, segregation. The use of fine pozzolanic materials also have better lubricating effect and more workability. vi. Sand to Aggregate ratio If the amount of sand is more the workability will reduce because sand has more surface area and more contact area causing more resistance. The ingredients of concrete can be proportioned by weight or volume. the goal is to provide the desired strength and workability at minimum expense. A low water-cement ratio is used to achieve a stronger concrete. It would seem therefore that by keeping the cement content high one could use enough for god workability and still have a low w/c ratio. the problem is that cement is the most costly of the basic ingredients. the dilema is easily seen in the graphs below. 3(a). Concrete Bleeding Bleeding in concrete is sometimes referred as water gain. It is a particular form of segregation, in which some of the water from the concrete comes out to the surface of the concrete, being of the lowest specific gravity among all the ingredients of concrete. Bleeding is

predominantly observed in a highly wet mix, badly proportioned and insufficiently mixed concrete. In thin members like roof slab or road slabs and when concrete is placed in sunny weather show excessive bleeding. Due to bleeding, water comes up and accumulates at the surface. Sometimes, along with this water, certain quantity of cement also comes to the surface. When the surface is worked up with the trowel, the aggregate goes down and the cement and water come up to the top surface. This formation of cement paste at the surface is known as “Laitance”. In such a case, the top surface of slabs and pavements will not have good wearing quality. This laitance formed on roads produces dust in summer and mud in rainy season. Water while traversing from bottom to top, makes continuous channels. If the water cement ratio used is more than 0.7, the bleeding channels will remain continuous and un segmented. These continuous bleeding channels are often responsible for causing permeability of the concrete structures. While the mixing water is in the process of coming up, it may be intercepted by aggregates. The bleeding water is likely to accumulate below the aggregate. This accumulation of water creates water voids and reduces the bond between the aggregates and the paste. The above aspect is more pronounced in the case of flaky aggregate. Similarly, the water that accumulates below the reinforcing bars reduces the bond between the reinforcement and the concrete. The poor bond between the aggregate and the paste or the reinforcement and the paste due to bleeding can be remedied by re vibration of concrete. The formation of laitance and the consequent bad effect can be reduced by delayed finishing operations. Bleeding rate increases with time up to about one hour or so and thereafter the rate decreases but continues more or less till the final setting time of cement.

Prevention of Bleeding in concrete Bleeding can be reduced by proper proportioning and uniform and complete mixing. Use of finely divided pozzolanic materials reduces bleeding by creating a longer path for the water to traverse. Air-entraining agent is very effective in reducing the bleeding. Bleeding can be reduced by the use of finer cement or cement with low alkali content. Rich mixes are less susceptible to bleeding than lean mixes. The bleeding is not completely harmful if the rate of evaporation of water from the surface is equal to the rate of bleeding. Removal of water, after it had played its role in providing workability, from the body of concrete by way of bleeding will do good to the concrete.

Early bleeding when the concrete mass is fully plastic, may not cause much harm, because concrete being in a fully plastic condition at that stage, will get subsided and compacted. It is the delayed bleeding, when the concrete has lost its plasticity, which causes undue harm to the concrete. Controlled re vibration may be adopted to overcome the bad effect of bleeding.

Segregation in concrete Segregation can be defined as the separation of the constituent materials of concrete. A good concrete is one in which all the ingredients are properly distributed to make a homogeneous mixture. There are considerable differences in the sizes and specific gravities of the constituent ingredients of concrete. Therefore, it is natural that the materials show a tendency to fall apart. Segregation may be of three types a) Coarse aggregate separating out or settling down from the rest of the matrix. b) Paste separating away from coarse aggregate. c) Water separating out from the rest of the material being a material of lowest specific gravity. A well made concrete, taking into consideration various parameters such as grading, size, shape and surface texture of aggregate with optimum quantity of waters makes a cohesive mix. Such concrete will not exhibit any tendency for segregation. The cohesive and fatty characteristics of matrix do not allow the aggregate to fall apart, at the same time; the matrix itself is sufficiently contained by the aggregate. Similarly, water also does not find it easy to move out freely from the rest of the ingredients.

The conditions favorable for segregation are:    

Badly proportioned mix where sufficient matrix is not there to bind and contain the aggregates Insufficiently mixed concrete with excess water content Dropping of concrete from heights as in the case of placing concrete in column concreting When concrete is discharged from a badly designed mixer, or from a mixer with worn out blades

Conveyance of concrete by conveyor belts, wheel barrow, long distance haul by dumper, long lift by skip and hoist are the other situations promoting segregation of concrete Vibration of concrete is one of the important methods of compaction. It should be remembered that only comparatively dry mix should be vibrated. It too wet a mix is excessively vibrated; it is likely that the concrete gets segregated. It should also be remembered that vibration is continued just for required time for optimum results. If the vibration is continued for a long

time, particularly, in too wet a mix, it is likely to result in segregation of concrete due to settlement of coarse aggregate in matrix.

4. Hydration in concrete Concrete derives its strength by the hydration of cement particles. The hydration of cement is not a momentary action but a process continuing for long time. Of course, the rate of hydration is fast to start with, but continues over a very long time at a decreasing rate In the field and in actual work, even a higher water/cement ratio is used, since the concrete is open to atmosphere, the water used in the concrete evaporates and the water available in the concrete will not be sufficient for effective hydration to take place particularly in the top layer. If the hydration is to continue, extra water must be added to refill the loss of water on account of absorption and evaporation. Therefore, the curing can be considered as creation of a favorable environment during the early period for uninterrupted hydration. The desirable conditions are, a suitable temperature and ample moisture. Concrete, while hydrating, releases high heat of hydration. This heat is harmful from the point of view of volume stability. Jeat of hydration of concrete may also shrinkage in concrete, thus producing cracks. If the heat generated is removed by some means, the adverse effect due to the generation of heat can be reduced. This can be done by a thorough water curing. 5. Air Entrainment Air entrainment reduces the density of concrete and consequently reduces the strength. Air entrainment is used to produce a number of effects in both the plastic and the hardened concrete. These include: Resistance to freeze–thaw action in the hardened concrete. Increased cohesion, reducing the tendency to bleed and segregation in the plastic concrete. Compaction of low workability mixes including semi-dry concrete. Stability of extruded concrete. Cohesion and handling properties in bedding mortars. 1. Explain the properties of hardened concrete Following are the properties of hardened concrete:

Strength of concrete Concrete Creep Shrinkage Modulus Of Elasticity Water tightness (impermeability) Rate of Strength gain of Concrete

1. Strength: The strength of concrete is basically referred to compressive strength and it depends upon three factors. 1- Paste Strength 2- Interfacial Bonding 3- Aggregate Strength 1. Paste strength: It is mainly due to the binding properties of cement that the ingredients are compacted together. If the paste has higher binding strength, higher will be strength of concrete. 2. Interfacial bonding: Interfacial bonding is very necessary regarding the strength. Clay hampers the bonding between paste and aggregate. The aggregate should be washed for a better bonding between paste and aggregate. 3. Aggregate strength: It is mainly the aggregate that provide strength to concrete especially coarse aggregates which act just like bones in the body. Rough and angular aggregate provides better bonding and high strength.

Factors affecting Strength of concrete:

Following are the factors that affect the strength of concrete: 1. Water-Cement ratio 2. Type of cementing material 3. Amount of cementing material 4. Type of aggregate 5. Air content 6. Admixtures 1. Water-Cement ratio: It is water cement ratio that basically governs the property of strength. Lesser the water cement ratio, greater will be strength. 2. Type of cement: Type of cement affect the hydration process and therefore strength of concrete. Amount of cementing material: it is the paste that holds or binds all the ingredients. Thus greater amount of cementing material greater will be strength. 3. Type of Aggregate: Rough and angular aggregates is preferable as they provide greater bonding. 4. Admixtures: Chemical admixtures like plasticizers reduce the water cement ratio and increase the strength of concrete at same water cement ratio. Mineral admixtures affect the strength at later stage and increase the strength by increasing the amount of cementing material. 4. b) Explain the various tests on concrete i) SAMPLING The first step is to take a test sample from the large batch of concrete. This should be done as soon as discharge of the concrete commences. The sample should be representative of the concrete supplied. The sample is taken in one of two ways:

For purposes of accepting or rejecting the load: Sampling after 0.2 m3 of the load has been poured. For routine quality checks: Sampling from three places in the load. a) Concrete Slump Test This test is performed to check the consistency of freshly made concrete. The slump test is done to make sure a concrete mix is workable. The measured slump must be within a set range, or tolerance, from the target slump. Workability of concrete is mainly affected by consistency i.e. wetter mixes will be more workable than drier mixes, but concrete of the same consistency may vary in workability. It can also be defined as the relative plasticity of freshly mixed concrete as indicative of its workability. Tools and apparatus used for slump test (equipment): 1. Standard slump cone (100 mm top diameter x 200 mm bottom diameter x 300 mm high) 2. Small scoop 3. Bullet-nosed rod (600 mm long x 16 mm diameter) 4. Rule Slump plate (500 mm x 500 mm) Procedure of slump test for concrete: 1. Clean the cone. Dampen with water and place on the slump plate. The slump plate should be clean, firm, level and non-absorbent. Collect a sample of concrete to perform the slum test. 2. Stand firmly on the footpieces and fill 1/3 the volume of the cone with the sample. Compact the concrete by 'rodding' 25 times. Rodding means to push a steel rod in and out of the concrete to compact it into the cylinder, or slump cone. Always rod in a definite pattern, working from outside into the middle. 3. Now fill to 2/3 and again rod 25 times, just into the top of the first layer. 4. Fill to overflowing, rodding again this time just into the top of the second layer. Top up the cone till it overflows. 5. Level off the surface with the steel rod using a rolling action. Clean any concrete from around the base and top of the cone, push down on the handles and step off the footpieces. 6. Carefully lift the cone straight up making sure not to move the sample. 7. Turn the cone upside down and place the rod across the up-turned cone. 8. Take several measurements and report the average distance to the top of the sample.If the sample fails by being outside the tolerance (ie the slump is too high or too low), another must be taken. If this also fails the remainder of the batch should be rejected.

b) The Compression Test The compression test shows the compressive strength of hardened concrete. The compression test shows the best possible strength concrete can reach in perfect conditions. The compression test measures concrete strength in the hardened state. Testing should always be done carefully. Wrong test results can be costly. The testing is done in a laboratory off-site. The only work done on-site is to make a concrete cylinder for the compression test. The strength is measured in Megapascals (MPa) and is commonly specified as a characteristic strength of concrete measured at 28 days after mixing. The compressive strength is a measure of the concrete’s ability to resist loads which tend to crush it. Apparatus for compression test 1. Cylinders (100 mm diameter x 200 mm high or 150 mm diameter x 300 mm high) (The small cylinders are normally used for most testing due to their lighter weight) 2. Small scoop 3. Bullet-nosed rod (600 mm x 16 mm) 4. Steel float 5. Steel plate Procedure for compression test of concrete 1. Clean the cylinder mould and coat the inside lightly with form oil, then place on a clean, level and firm surface, ie the steel plate. Collect a sample. 2. Fill 1/2 the volume of the mould with concrete then compact by rodding 25 times. Cylinders may also be compacted by vibrating using a vibrating table. 3. Fill the cone to overflowing and rod 25 times into the top of the first layer, then top up the mould till overflowing. 4. Level off the top with the steel float and clean any concrete from around the mould. 5. Cap, clearly tag the cylinder and put it in a cool dry place to set for at least 24 hours. 6. After the mould is removed the cylinder is sent to the laboratory where it is cured and crushed to test compressive strength COMPACTING FACTOR Compacting factor of fresh concrete is done to determine the workability of fresh concrete by compacting factor test as per IS: 1199 – 1959. The apparatus used is Compacting factor apparatus.

Procedure to determine workability of fresh concrete by compacting factor test. i) The sample of concrete is placed in the upper hopper up to the brim. ii) The trap-door is opened so that the concrete falls into the lower hopper. iii) The trap-door of the lower hopper is opened and the concrete is allowed to fall into the cylinder. iv) The excess concrete remaining above the top level of the cylinder is then cut off with the help of plane blades. v) The concrete in the cylinder is weighed. This is known as weight of partially compacted concrete. vi) The cylinder is filled with a fresh sample of concrete and vibrated to obtain full compaction. The concrete in the cylinder is weighed again. This weight is known as the weight of fully compacted concrete. Compacting factor = (Weight of partially compacted concrete)/(Weight of fully compacted concrete) VEE-BEE TEST To determine the workability of fresh concrete by using a Vee-Bee consistometer as per IS: 1199 – 1959. The apparatus used is Vee-Bee consistometer. Procedure to determine workability of fresh concrete by Vee-Bee consistometer. i) A conventional slump test is performed, placing the slump cone inside the cylindrical part of the consistometer. ii) The glass disc attached to the swivel arm is turned and placed on the top of the concrete in the pot. iii) The electrical vibrator is switched on and a stop-watch is started, simultaneously. iv) Vibration is continued till the conical shape of the concrete disappears and the concrete assumes a cylindrical shape. v) When the concrete fully assumes a cylindrical shape, the stop-watch is switched off immediately. The time is noted.The consistency of the concrete should be expressed in VB-degrees, which is equal to the time in seconds recorded above. REBOUND HAMMER

Rebound hammer test is done to find out the compressive strength of concrete by using rebound hammer as per IS: 13311 (Part 2) – 1992. The underlying principle of the rebound hammer test is The rebound of an elastic mass depends on the hardness of the surface against which its mass strikes. When the plunger of the rebound hammer is pressed against the surface of the concrete, the pring-controlled mass rebounds and the extent of such a rebound depends upon the surface hardness of the concrete. The surface hardness and therefore the rebound is taken to be related to the compressive strength of the concrete. The rebound value is read from a graduated scale and is designated as the rebound number or rebound index. The compressive strength can be read directly from the graph provided on the body of the hammer. Procedure to determine strength of hardened concrete by rebound hammer. i) Before commencement of a test, the rebound hammer should be tested against the test anvil, to get reliable results, for which the manufacturer of the rebound hammer indicates the range of readings on the anvil suitable for different types of rebound hammer. ii) Apply light pressure on the plunger – it will release it from the locked position and allow it to extend to the ready position for the test. iii) Press the plunger against the surface of the concrete, keeping the instrument perpendicular to the test surface. Apply a gradual increase in pressure until the hammer impacts. (Do not touch the button while depressing the plunger. Press the button after impact, in case it is not convenient to note the rebound reading in that position.) iv) Take the average of about 15 readings.

ULTRASONIC PULSE VELOCITY This test is done to assess the quality of concrete by ultrasonic pulse velocity method as per IS: 13311 (Part 1) – 1992. The underlying principle of this test is – The method consists of measuring the time of travel of an ultrasonic pulse passing through the concrete being tested. Comparatively higher velocity is obtained when concrete quality is good in terms of density, uniformity, homogeneity etc. Procedure to determine strength of hardened concrete by Ultrasonic Pulse Velocity. i) Preparing for use: Before switching on the ‘V’ meter, the transducers should be connected to the sockets marked “TRAN” and ” REC”.

The ‘V’ meter may be operated with either: a) the internal battery, b) an external battery or c) the A.C line. ii) Set reference: A reference bar is provided to check the instrument zero. The pulse time for the bar is engraved on it. Apply a smear of grease to the transducer faces before placing it on the opposite ends of the bar. Adjust the ‘SET REF’ control until the reference bar transit time is obtained on the instrument read-out. iii) Range selection: For maximum accuracy, it is recommended that the 0.1 microsecond range be selected for path length upto 400mm. iv) Pulse velocity: Having determined the most suitable test points on the material to be tested, make careful measurement of the path length ‘L’. Apply couplant to the surfaces of the transducers and press it hard onto the surface of the material. Do not move the transducers while a reading is being taken, as this can generate noise signals and errors in measurements. Continue holding the transducers onto the surface of the material until a consistent reading appears on the display, which is the time in microsecond for the ultrasonic pulse to travel the distance ‘L’. The mean value of the display readings should be taken when the units digit hunts between two values. Pulse velocity=(Path length/Travel time) v) Separation of transducer leads: It is advisable to prevent the two transducer leads from coming into close contact with each other when the transit time measurements are being taken. If this is not done, the receiver lead might pick-up unwanted signals from the transmitter lead and this would result in an incorrect display of the transit time.

5. a) Explain the Different types of wood treatment. There are numerous benefits in maintaining the quality of wooden structures or furniture that are an integral part of your home décor. Not only does the material conjure a natural and warming impression to the eye, creating a soothing and fresh atmosphere for guests and visitors but its low-key effect means you can adapt your own interior design style around any fittings or household items you might have. Unfortunately in Britain wet weather is a guarantee, which means outdoor timber is going to get soaked from time to time, and indoor wooden fittings perhaps damp at the very least. Different methods for timber treatment

Luckily, timber treatment is a simple and efficient technique by which you can extend the life of your wooden structures and increase their durability against insects, bacteria, rot and various forms of wooden fungi that can all cause softening, splintering and loss of strength in the material. There are a number of chemical or natural processes widely common that can be used for both residential or community buildings, and for a variety of different purposes; from garden posts, poles or fencing, wooden decking or framing or even your more precious wooden furniture – all can be protected against daily weathering and bugs with timber treatment. There are three primary methods to choose from – one of them will surely suit your personal home-improvement needs.

Water-borne treatment: This method is popular due to its low cost and high availability; preservatives and insecticides are usually mixed with a water-based solvent and applied in a vacuum or pressure treatment facility to create a strong, protective layer on the surface of the timber, making it less susceptible to exterior damage. The treatment can, however, result in swelling, which increases the risks of internal twisting and splitting in the wood – a greater problem if you’re looking to make your decking or furniture that little extra-sturdy. Oil-borne treatment: A substantial layer of Linseed or Tung oil mixed with preservatives usually penetrates deeper into the wood than water-borne treatment, making for a longer-lasting and glossier finish to your timber structures, as well as acting as a drying agent and repelling water to prevent damp. Many oils do, however, give off strong, unpleasant odours – so make sure you shop around and aren’t hosting any parties or gatherings too soon after you have the fittings treated. Light Organic Solvent Preservative (LOSP’s): This method basically involves the use of white spirit as the solvent carrier and uses a mixture of insecticides and water-repellent chemicals that form a protective coating over the wooden product. This specialised treatment takes place in professional plants and is therefore a longer, more expensive choice than water or oil-based alternatives. LOSP is also unsuitable for wooden garden fittings that are going to come into contact with soil, although it usually results in a nice, dry finish to your timber. Cost of timber treatment Before you start the treatment you could even hire an independent surveyor, who will help you judge the amount of work that needs to be done and figure out an estimate – a significant portion of timber treatment can cost as much as £3000-4000, but this will depend on the processes you choose and how quickly you want it completed. Timber treatment comes with a variety of polishes, varnishes and finishes to choose from – leaving the rest of your home ready to be styled and redesigned in the fashion that best suits you. 5. b) Write short notes in a.Paints b.Varnishes c.Distempers d.Bitumens

Paint Paint is any liquid, liquefiable, or mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture to objects. Paint can be made or purchased in many colors—and in many different types, such as watercolor, artificial, etc. Paint is typically stored, sold, and applied as a liquid, but dries into a solid. Varnish Vanish is a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials. Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent. Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss sheens by the addition of "flatting" agents. Varnish has little or no color, is transparent, and has no added pigment, as opposed to paints or wood stains, which contain pigment and generally range from opaque to translucent. Varnishes are also applied over wood stains as a final step to achieve a film for gloss and protection. Some products are marketed as a combined stain and varnish. After being applied, the film-forming substances in varnishes either harden directly, as soon as the solvent has fully evaporated, or harden after evaporation of the solvent through certain curing processes, primarily chemical reaction between oils and oxygen from the air (autoxidation) and chemical reactions between components of the varnish. Resin varnishes "dry" by evaporation of the solvent and harden almost immediately upon drying. Acrylic and waterborne varnishes "dry" upon evaporation of the water but experience an extended curing period. Oil, polyurethane, and epoxy varnishes remain liquid even after evaporation of the solvent but quickly begin to cure, undergoing successive stages from liquid or syrupy, to tacky or sticky, to dry gummy, to "dry to the touch", to hard. Environmental factors such as heat and humidity play a very large role in the drying and curing times of varnishes. In classic varnish the cure rate depends on the type of oil used and, to some extent, on the ratio of oil to resin. The drying and curing time of all varnishes may be sped up by exposure to an energy source such as sunlight, ultraviolet light, or heat.

Distemper Distemper is a term with a variety of meanings for paints used in decorating and as a historical medium for painting pictures, and contrasted with tempera. The binding element may be some form of glue or oil; these are known in decorating respectively as soft distemper and oil bound distemper. Bitumen

Bitumen is an oil based substance. It is a semi-solid hydrocarbon product produced by removing the lighter fractions (such as liquid petroleum gas, petrol and diesel) from heavy crude oil during the refining process. As such, it is correctly known as refined bitumen. In North America, bitumen is commonly known as “asphalt cement” or “asphalt”. While elsewhere, “asphalt” is the term used for a mixture of small stones, sand, filler and bitumen, which is used as a road paving material. The asphalt mixture contains approximately 5% bitumen. At ambient temperatures bitumen is a stable, semi-solid substance.

6. a) Write short notes on fibre glass reinforced plastic Fibre-reinforced plastic (FRP) (also fibre-reinforced polymer) is a composite material made of a polymer matrix reinforced with fibres. The fibres are usually glass, carbon, basalt or aramid, although other fibres such as paper or wood or asbestos have been sometimes used. The polymer is usually an epoxy, vinylester or polyester thermosetting plastic, and phenol formaldehyde resins are still in use. FRPs are commonly used in the aerospace, automotive, marine, construction industries and ballistic armor. Forming processes A rigid structure is usually used to establish the shape of FRP components. Parts can be laid up on a flat surface referred to as a "caul plate" or on a cylindrical structure referred to as a "mandrel". However most fibre-reinforced plastic parts are created with a mold or "tool." Molds can be concave female molds, male molds, or the mold can completely enclose the part with a top and bottom mold. The moulding processes of FRP plastics begins by placing the fibre preform on or in the mold. The fibre preform can be dry fibre, or fibre that already contains a measured amount of resin called "prepreg". Dry fibres are "wetted" with resin either by hand or the resin is injected into a closed mold. The part is then cured, leaving the matrix and fibres in the shape created by the mold. Heat and/or pressure are sometimes used to cure the resin and improve the quality of the final part. The different methods of forming are listed below.

Bladder moulding Individual sheets of prepreg material are laid up and placed in a female-style mould along with a balloon-like bladder. The mould is closed and placed in a heated press. Finally, the bladder is pressurized forcing the layers of material against the mould walls.

Compression moulding[edit]

When the raw material (plastic block,rubber block, plastic sheet, or granules) contains reinforcing fibres, a compression molded part qualifies as a fibre-reinforced plastic. More typically the plastic preform used in compression molding does not contain reinforcing fibres. In compression molding, A "preform" or "charge", of SMC, BMC is placed into mould cavity. The mould is closed and the material is formed & cured inside by pressure and heat. Compression moulding offers excellent detailing for geometric shapes ranging from pattern and relief detailing to complex curves and creative forms, to precision engineering all within a maximum curing time of 20 minutes.

Autoclave / vacuum bag Individual sheets of prepreg material are laid-up and placed in an open mold. The material is covered with release film, bleeder/breather material and a vacuum bag. A vacuum is pulled on part and the entire mould is placed into an autoclave (heated pressure vessel). The part is cured with a continuous vacuum to extract entrapped gasses from laminate. This is a very common process in the aerospace industry because it affords precise control over moulding due to a long, slow cure cycle that is anywhere from one to several hours.[17] This precise control creates the exact laminate geometric forms needed to ensure strength and safety in the aerospace industry, but it is also slow and labour-intensive, meaning costs often confine it to the aerospace industry.[16]

Mandrel wrapping Sheets of prepreg material are wrapped around a steel or aluminium mandrel. The prepreg material is compacted by nylon or polypropylene cello tape. Parts are typically batch cured by vacuum bagging and hanging in an oven. After cure the cello and mandrel are removed leaving a hollow carbon tube. This process creates strong and robust hollow carbon tubes.

Wet layup Wet layup forming combines fibre reinforcement and the matrix as they are placed on the forming tool.[2] Reinforcing Fibre layers are placed in an open mould and then saturated with a wet [resin] by pouring it over the fabric and working it into the fabric. The mould is then left so that the resin will cure, usually at room temperature, though heat is sometimes used to ensure a proper cure. Sometimes a vacuum bag is used to compress a wet layup. Glass fibres are most commonly used for this process, the results are widely known as fibreglass, and is used to make common products like skis, canoes, kayaks and surf boards.[16]

Chopper gun Continuous strands of fibreglass are pushed through a hand-held gun that both chops the strands and combines them with a catalysed resin such as polyester. The impregnated chopped glass is shot onto the mould surface in whatever thickness the design and human operator think is appropriate. This process is good for large production runs at economical cost, but produces geometric shapes with less strength than other moulding processes and has poor dimensional tolerance.

Filament winding Machines pull fibre bundles through a wet bath of resin and wound over a rotating steel mandrel in specific orientations Parts are cured either room temperature or elevated temperatures. Mandrel is extracted, leaving a final geometric shape but can be left in some cases.

Pultrusion Fibre bundles and slit fabrics are pulled through a wet bath of resin and formed into the rough part shape. Saturated material is extruded from a heated closed die curing while being continuously pulled through die. Some of the end products of pultrusion are structural shapes, i.e. I beam, angle, channel and flat sheet. These materials can be used to create all sorts of fibreglass structures such as ladders, platforms, handrail systems tank, pipe and pump supports.

RTM & VARTM Also called resin infusion. Fabrics are placed into a mould which wet resin is then injected into. Resin is typically pressurized and forced into a cavity which is under vacuum in RTM (Resin Transfer Molding). Resin is entirely pulled into cavity under vacuum in VARTM (Vacuum-Assisted Resin Transfer Molding). This moulding process allows precise tolerances and detailed shaping but can sometimes fail to fully saturate the fabric leading to weak spots in the final shape.

Advantages and limitations FRP allows the alignment of the glass fibres of thermoplastics to suit specific design programs. Specifying the orientation of reinforcing fibres can increase the strength and resistance

to deformation of the polymer. Glass reinforced polymers are strongest and most resistive to deforming forces when the polymers fibres are parallel to the force being exerted, and are weakest when the fibres are perpendicular. Thus this ability is at once both an advantage or a limitation depending on the context of use. Weak spots of perpendicular fibres can be used for natural hinges and connections, but can also lead to material failure when production processes fail to properly orient the fibres parallel to expected forces. When forces are exerted perpendicular to the orientation of fibres the strength and elasticity of the polymer is less than the matrix alone. In cast resin components made of glass reinforced polymers such as UP and EP, the orientation of fibres can be oriented in two-dimensional and three-dimensional weaves. This means that when forces are possibly perpendicular to one orientation, they are parallel to another orientation; this eliminates the potential for weak spots in the polymer.

Applications of fibre-reinforced plastic Glass-aramid-hybrid Fabric (for high tension and compression) Fibre-reinforced plastics are best suited for any design program that demands weight savings, precision engineering, finite tolerances, and the simplification of parts in both production and operation. A moulded polymer artefact is cheaper, faster, and easier to manufacture than cast aluminium or steel artefact, and maintains similar and sometimes better tolerances and material strengths.

6. b) Write short notes on geo textiles & geo membranes GEOTEXTILES AND GEOMEMBRANES BASIC FUNCTIONS a) b) c) d)

Drainage Filtration Separation Reinforcement

a) Drainage: Collecting and redirecting seepage water within a soil mass or adjacent to retaining walls culverts and tunnel linings . Ex - Non-woven fabrics or composits have sufficient inflow capacity to fulfill this function.

b) Filtration Geotextiles acts as a filter if it allows seepage from a water bearing layer while preventing most soil particles from being carried away by the water flow. c) Separation It is achieved if the fabric prevents mixing of adjacent dissimilar soils which may occur during construction or may be caused by repeated external loading of a soil layer system Most fabrics can act as separators provided they have adequate strength.

d) Reinforcement Means the inclusion of the fabric to provide tensile strength, redistribution of stresses and / or confinement, thereby increasing the stability of a soil mass, reducing earth pressures, or decreasing deformation or susceptibility to cracking. Fabrics are used to provide containment if they are used to form soil or concrete filled bags, tubes, or mattresses. Fabrics are used to act as a tensioned membrane if it supports loads across a gap or plastic zone of soft soil Fabrics may be required to provide cushioning against localized stresses which may cause puncturing or abrasion If placed on the surface of a slope the geotextile may prevent erosion and dispersion of soil due to wind, surface runoff or wave action.

Applications Major applications 1. Embankments over very soft soils 2. Unpaved road supports 3. Retaining walls 4. Slope stabilization 1. Embankments Embankment can fail in a multitude of ways involving excessive settlement and lateral spreading, with or without single or multiple failure surfaces and surface bulging becoming apparent. Geotextiles provides restraint against lateral deformation and assist in load distribution on the soft subsoil. Stability analysis of a reinforced embankment will have to take the following modes of failure (a) Block sliding on the geotextiles: A vertical crack or other type of failure through the embankment isolates a block of soil which slides outward on geotextiles .

A simple analysis would assume horizontal active earth pressures pushing outward and soil fabric friction resisting the process.

Figure 20.1

Rail Roads: Geotextiles installed in the track bed are submitted to extreme conditions of cyclic stress and seepage flow. Geotextiles directly contact with coarse ballast without protective layers above and below, are subjected to significant abrasion and puncturing which affects their filtration and reinforcement capacity Laboratory tests and field observations confirm that heavy nonwovens better than lighter nonwovens. 

Geotextiles are successful in solving difficult track foundation

perform



Economic gains and better long term track performance could be achieved by protective layer above /or below the installed fabric

With particular reference to road and embankment construction proper management of a geotextile reinforced soil project requires the followling actions. 

Site preparation :- Level site and remove obstructions such as sharp tree stumps and boulders, minimize disturbance of the subgrade where soil structure, roots in the ground and light vegetation may provide additional bearing strength.



Equipment selection:- use low ground pressure and small dump trucks for initial stage of construction pay attention to ground disturbance caused by turning equipment and dumping procedures.



Fabric placement :-Roll rather than drag geotextile into place giving attention to the isotropic properties of the fabric (i.e. warp direction parallel to road alignment). Eliminate wrinkles, tension fabric and provide edge anchorage for increased membrane action in cures, cutting and sewing of or overlapping may be necessary.

7. a) Explain reinforcement of earth using Geomembranes and Geotextiles When used in applications such as retaining walls and earth embankments, geogrids must have a resistance to "creep". Unlike traffic loading, the forces that act upon a geogrid in an earth retention structure are constant. Polypropylene geogrids subjected to similar conditions will continue to stretch or "creep", making the structure unsafe. Soil Reinforcement Geogrids are made with materials and processes that minimize creep making them well suited to such applications. Most Soil Reinforcement Geogrids are Uniaxial, meaning that they are considerably stronger in one direction versus the other. It is important, when using a Uniaxial Geogrid to properly position the material so the higher strength direction is in line with the direction of the highest anticipated load. GSI offers a wide variety of Soil Reinforcement Geogrids for a variety of applications

7. b) Write short notes on structural composites These are special class of composites, usually consists of both homogeneous and composite materials. Properties of these composites depend not only on the properties of the constituents but also on geometrical design of various structural elements. Two classes of these composites widely used are: laminar composites and sandwich structures. Laminar composites: there are composed of two-dimensional sheets/layers that have a preferred strength direction. These layers are stacked and cemented together according to the

requirement. Materials used in their fabrication include: metal sheets, cotton, paper, woven glass fibers embedded in plastic matrix, etc. Examples: thin coatings, thicker protective coatings, claddings, bimetallics, laminates. Many laminar composites are designed to increase corrosion resistance while retaining low cost, high strength or light weight.

Sandwich structures: these consist of thin layers of a facing material joined to a light weight filler material. Neither the filler material nor the facing material is strong or rigid, but the composite possesses both properties. Example: corrugated cardboard. The faces bear most of the in-plane loading and also any transverse bending stresses. Typical face materials include Al-alloys, fiber-reinforced plastics, titanium, steel and plywood. The core serves two functions – it separates the faces and resists deformations perpendicular to the face plane; provides a certain degree of shear rigidity along planes that are perpendicular to the faces. Typical materials for core are: foamed polymers, synthetic rubbers, inorganic cements, balsa wood. Sandwich structures are found in many applications like roofs, floors, walls of buildings, and in aircraft for wings, fuselage and tailplane skins.