Que1.12. What’s meant by total? Compactly describe their bracket.
Answer total These are inert accoutrements which are mixed with binding material similar as cement or lime for manufacturing of mortar or concrete. Aggregate are used as padding in mortar and concrete and also to reduce their cost. Bracket of Aggregate 1. According to Geological Origin Natural Aggregate 1. These summations are generally attained from natural deposits of beach and gravels or from chases by cutting jewels. 2. The cheapest among them are the natural beach and clay which have been reduced to their present size by natural agents, similar as water, wind and snow,etc. 3. The swash deposits are the most common and are good quality. ii. Artificial Aggregate 1. The most extensively used artificial total are clean broken bricks and air cooled fresh blast- furnace- sediment. 2. The broken bricks of good quality give a satisfactory total for the mass concrete and aren’t suitable for corroborated concrete work if the crushing strength of slipup is lower than 30 to 35 MPa. 3. The bricks should be free from lime mortar and lime sulphate cataplasm. 4. The bricks total isn’t suitable for leakproof construction. 5. It has poor resistance to wear and hence isn’t used in concrete for the road work. 2. According to Size Fine Aggregate 1. The total which passes through4.75 mm sieve and retained on 75 micron sieve are known as fine total. ii. Coarse Aggregate 1. The total retained on4.75 mm sieve are known as coarse total. iii. each- by- Aggregate 1. It’s the combination of both coarse and fine total. 3. According to Shape Rounded Shape a. The total with rounded patches( swash or shore clay) has minimal voids ranging 32 to 33. b. The only disadvantage is that interlocking between its patches is less and hence the development of bond is poor, making it infelicitous for high strength concrete and pavement. ii. Irregular Aggregate a. The total having incompletely rounded patches( hole beach and clay) has advanced of voids ranging from 35 to 38. b. It needed further cement paste for a given plasticity. iii. Angular Aggregate The total with sharp, angular and rough patches( crushed jewels) has a outside of voids ranging from 38 to 40. The interlocking between the patches is good. iv. short Aggregate a. An total is nominated short when its least dimension( consistence) is lower than three- fifth of its mean dimension. b. The presence of these patches should be confined to 10 to 15. 4. According to Unit Weight Normal Weight Aggregate The generally used total, i.e., beach and gravels; crushed jewels similar as determinedness, basalt quartz, sandstone and limestone; and slipup cargo,etc., which have specific earnestness between2.5 and2.7 yield concrete with unit weight ranging 23 to 26 kN/ m3 and crushing strength at 28 days between 15 to 40 MPa are nominated normal weight concrete. ii. Heavy Weight or High- viscosity Aggregate Concrete having unit weight of about 30, 31, 35, 38, 40, 47 and 57 kN/ m3 can be produced by using typical goethite, limonite, baryte, magnetite, hematite, ferrophosphorus and scrap iron, independently. iii. Light Weight Aggregate The light weight total having unit weight up to12 kN/ m3 are used to manufacture the structural concrete masonry blocks for reduction of the tone weight of the structure.
Que1.13. bandy the characteristics of good summations.
Answer Following are the characteristics of good total 1. It should rather be boxy or globular in shape and of limiting porosity. 2. It should be chemically inert and not be soft and pervious. 3. It shouldn’t absorb water further than 5. 4. It should have rough face. 5. It shouldn’t reply with cement after mixing. 6. It should be durable and strong. 7. It must be clean i.e., it should be free from lumps, organic accoutrements etc.
Que1.14. Compactly describe the physical mechanical and thermal parcels of summations in concrete.
Answer Physical parcels of Aggregate 1. Grading It’s the flyspeck- size distribution of an total as determined by a sieve analysis using line mesh sieves with square openings. 2. Fineness Modulus The result of aggregate sieve analysis is expressed by a number called fineness modulus. 3. Flakiness Index It’s the chance by weight of patches in it whose least dimension is lower than three- fifth of their mean dimension. 4. extension indicator It’s the chance of weight of patches whose topmost dimension is lesser than1.8 times their mean dimension. Mechanical Assets of Aggregate 1. Aggregate Crushing Value It gives a relative measure of the resistance of an total to crushing under a gradationally applied compressive cargo. 2. Aggregate Impact Value It gives a relative measure of the resistance of an total to unforeseen shock or impact. 3. Aggregate Bruise Value It gives a relative measure of resistance of an total to wear when it’s rotated in a cylinder along with some abrasive charge. Thermal parcels of Aggregate Following are the thermal parcels of aggregate 1. Measure of Thermal Expansion The measure of thermal expansion of the concrete increase with the measure of thermal expansion of total. The measure of expansion of the aggregate depends on the parent gemstone 2. Specific Heat It’s a measure of its heat capacity. 3. Thermal Conductivity It’s the capability of the total to conduct the heat.
Que1.15. Explain the bulking and soundness of summations.
Answer Bulking of Fine Aggregate
1. The increase in the volume of a given mass of fine total caused by the presence of water is known as bulking. Cement product & summations 1 – 18 D( CE- Sem- 5) 2. The bulking of fine total is caused by the flicks of water which push the patches piecemeal.
3. The extent of bulking depends upon the chance of humidity present in the beach and its fineness.
4. It’s seen that bulking increases gradationally with humidity content up to a certain point and also begins to drop with farther addition of water due to the coupling of flicks, until when the beach is submersed.
5. With ordinary beach the bulking generally varies between 15- 30. 6. In extremely fine beach the bulking may be of the order of 40 at a humidity content of 10 but similar beach is infelicitous for concrete. Soundness of Aggregate 1. The soundness indicates the capability of the total to repel inordinate changes in volume due to changes in environmental conditions,e.g. freezing and thawing, thermal changes, and interspersing wetting and drying.
2. The total is said to be unsound when volume changes result in the deterioration of concrete.
3. This may appear in the form of original scaling to expansive face cracking or to decomposition over a considerable depth, and therefore vary from an disabled appearance to a structurally dangerous situation.
4. IS 2386( Part- V)- 1963 describes a system to determine the resistance to decomposition of summations by impregnated result of sodium sulphate Na2SO4) or magnesium sulphate( MgSO4).
5. According to IS383-1970 the average loss of weight after ten cycles should not exceed 12 and 18 when tested with sodium sulphate and magnesium sulphate, independently. Que1.16. What are the goods of the shape and texture of total on the strength and plasticity of concrete? Answer Effect of Shape
1. Rounded summations are suitable to use in concrete because short and elongated patches reduce plasticity, increase water demand and reduce strength.
2. In the case of angular patches, the bond between aggregate patches is advanced due to interlocking but due to advanced face area, angular patches increase water demand and thus reduce plasticity. Effect of Texture
1. This affects the bond to the cement paste and also influences the water demand of the admixture.
2. Smooth It improves plasticity but bond between cement paste and total is weak. 3. Rough It reduce plasticity but bond between cement paste and total is strong.
4. face texture isn’t a veritably important property from compressive strength point of view but total having rough face texture perform better under flexural and tensile stresses.