Que2.1. What’s amalgamation? Why is it used with concrete? Also give its types.
Answer amalgamation cocktails are accoutrements used to modify the parcels of fresh hardened concrete. ii. They’re classified as chemical and mineral cocktails. iii. Chemical cocktails are used in the construction assiduity for erecting strong, durable, and leakproof structures. Reason for using cocktails with Concrete Following are the purposes for which the cocktails could be used with concrete 1. To accelerate the original set of concrete, i.e., to speed up the rate of development of strength at early periods. 2. To slacken the original set of concrete, i.e., to keep concrete workable for a longer time for placement. 3. To enhance the plasticity. 4. To ameliorate the penetration( flowability) and pumpability of concrete. 5. To reduce the isolation in grout and concrete fusions. 6. To increase the strength of concrete by reducing the water content and by densification of concrete. 7. To drop the capillary inflow of water through concrete and to increase in impermeability to liquids. 8. To inhibit the erosion of underpinning in concrete. 9. To increase the resistance to chemical attack. 10. To increase the bond between old and new concrete shells. Types of cocktails Following are the types of cocktails 1. Accelerators. 2. Water reducing cocktails. 3. Retarders. 4. Air- enplaning agents.
Que2.2. Explain the accelerators with suitable illustration. Also give the functions of accelerators.
Answer Accelerator An amalgamation is use to speed up the original set of concrete is called accelerator. exemplifications Calcium chloride, sodium nitrate, calcium nitrate,etc. Functions Following are the functions of accelerators 1. These are added to concrete either To increase the rate of hydration of hydraulic cement, and hence to increase the rate of development to strength. ii. To dock the setting time. 2. An increase in the rate of early strength development may help in i. before junking of forms, ii. Reduction of required period of curing, and iii. before placement of structure in service. 3. Accelerating cocktails are also used when the concrete is to be placed at low temperatures. 4. The benefits of reduced time of setting may include Early finishing of face, ii. Reduction of pressure on forms or of period of time during which the forms are subordinated to hydraulic pressure, and iii. More effective plugging of leaks against hydraulic pressure. 5. With the vacuity of important accelerators, the under- water concreting, the basement waterproofing operations, the form work of the shorefront structures in the tidal zones have come easy.
Que2.3. Describe the accelerator effect on the concrete parcels.
Answer Following are the accelerator effect on the concrete parcels 1. The general action of accelerators is to beget a more rapid-fire dissolution of composites of cement, particularly tricalcium silicate, in water and hence grease more rapid-fire hydration of these composites. 2. The use of 2 calcium chloride by mass of cement can reduce the setting time by one- third and raise the one to seven day compressive strength by 3 to 8 MPa. 3. An increase in flexural strength of 40 to 80 of one day and up to 12 at 28 days in attained. 4. Large boluses of CaCl2 result in flash set of concrete and the ambient temperature. 5. Calcium formate( a fine greasepaint), which is kindlyless answerable than calcium chloride and is less effective doesn’t have the same adverse effect on erosion of bedded sword as CaCl2. It’s added in the same tablets.
Que2.4. Explain the part of cocktails in concrete technology.
Answer Following are the part of cocktails in concrete technology 1. To Modify Fresh Property Increase the plasticity without adding the water cement rate or drop the water content at the same plasticity. ii. Retard or accelerate the time of original setting. iii. Reduce or help the agreement or produce slight expansion. iv. Modify the rate or capacity of bleeding. 2. To Modify Harden Property Reduce the heat of elaboration. ii. Accelerate the rate of strength development at early stages. iii. Increase the continuity. iv. drop the permeability of concrete.
Que2.5. What’s air- detrained concrete? What are the air- enplaning agents? What are factors affecting the airentrainment in the concrete?
Answer Air- Entrained Concrete 1. Air- entrainment is the internal creation of bitsy air bubbles in concrete. A concrete maker introduces the bubbles by adding to the blend an air enplaning agent. The air bubbles are created during mixing of the plastic concrete and utmost of them survive to be part of the hardened concrete. 2. It contains billions of bitsy air cells per boxy bottom. These air pockets relieve internal pressure on the concrete by furnishing bitsy chambers for water to expand into when it freezes. 3. It’s produced using air- enplaning Portland cement, or by the preface of air- enplaning agents, under careful engineering supervision, as the concrete is mixed on the job. 4. The quantum of detrained air is generally between four to seven percent of the volume of the concrete. Air- enplaning Agents Following are the air- entrainment agent used in the concrete 1. Natural wood resins. 2. Beast and vegetable fats and canvases similar as tallow, olive oil painting and their adipose acids similar as stearic and oleic acids. 3. colorful wetting down agents similar as alkali mariners or sulphonated organic composites. 4. Water answerable detergents of resins acid. 5. eclectic accoutrements similar as sodium mariners of petroleum sulphonic acids, hydrogen peroxide and aluminium greasepaint,etc. Factor Affecting Air Entrainment Following are the factor affect the air entrainment 1. Type and volume of air enplaning agents used. 2. Water cement rate of blend. 3. Type and grading of summations. 4. Mixing time. 5. Temperature. 6. Type of cement. 7. Influence of contraction. 8. cocktails other than air enplaning agents used.
Que2.6. What are the goods of air entrainment amalgamation on the parcels of concrete?
Answer Effect of Air Entrainment on Concrete parcels Following are the effect of air entrainment on concrete parcels 1. Reduction in strength. 2. enhancement in plasticity. 3. Increased resistance to freezing and thawing. 4. Reduces the tendencies of isolation. 5. Reduces the bleeding and laitance. 6. Decreases the permeability. 7. Increases the resistance to chemical attack. 8. Permits reduction in beach content, water content, cost and heat of hydration. 9. Reduces unit weight, alkali aggregate response and modulus of pliantness. 10. Enhance the continuity of concrete against cycles of climatic freezing and thawing and against the goods ofde-icing mariners.
Que2.7. What are the different types of superplasticizers?
Answer Types of Superplasticizers Different types of superplasticizers are as follows 1. Lignosulphonates These are deduced from neutralization, rush, and turmoil processes of the waste liquor attained during product of paper- making pulp from wood 2. Sulphonated Melamine Formaldehyde( SMF) It’s manufactured by normal resinification of melamine- formaldehyde. 3. Sulphonated Napthalene Formaldehyde( SNF) Produced from naphthalene by oleum or SO3 sulphonation; posterior response with formaldehyde leads to polymerization and the sulphonic acid is annulled with sodium hydroxide or lime. 4. Polycarboxylic Ether( PCE) Free radical medium using peroxide inaugurators is used for polymerization process in these systems.
Que2.8. bandy the part of plasticizers when used as an amalgamation for concrete.
Answer part of Plasticizers cocktails are used for following purposes 1. To achieve a advanced strength by dwindling the water cement rate at the same plasticity. 2. To achieve the same plasticity by dwindling the cement content so as to reduce the heat of hydration in mass concrete. 3. Water reduction further than 5 but lower than 12. 4. To increase the plasticity so as to ease placing inapproachable locales.
Que2.9. Describe the effect of superplasticizer on the parcels of fresh and toughened concrete.
Answer Effect on Fresh Concrete 1. Superplasticizers enhance plasticity. The effect depends on type, lozenge, and time of addition( stylish with mixing water). Water demand is reduced by 15 to 30. Performing concrete has advanced strength and lower permeability. 2. Superplasticizers produce advanced than normal plasticity for 30- 60 min and there will be rapid-fire loss of plasticity. 3. Generally bleeding is dropped( less water). still, If flowing concrete ismade.precautions are demanded not to induce bleeding and isolation. Effect on Hardened Concrete 1. Water reduction allows producing high- strength concrete. 2. loss of superplasticized concrete is similar to or lower than normal concrete. 3. Creep of superplasticized concrete is analogous to that of a reference concrete. 4. The use of superplasticizers allows advancements in the bond between concrete and buttressing sword. Effect on Durability 1. Lower water/ cement rate leads to lower permeability and enhanced strength and continuity. 2. In normal concrete, the critical distance between air bubbles is 200m. In superplasticized concrete, that value is exceeded. Better snap- thaw continuity can be anticipated for air detrained superplasticized concrete. 3. continuity to sulphate attack depends on the particular medium of sulphate attack and exposure type. For expansion, lower permeability ( lower face penetration) can lead to better continuity. 4. Lower water/ cement rate leads to lower permeability and bettered resistance to chloride penetration and erosion of sword. 5. Lower water/ cement rate leads to lower humidity penetration, which could enhance resistance to alkali expansion.