In this post we know about what’s concrete admixture and type of admixture, also know about natural admixtures, mineral admixture and manufactured admixture
● What is admixture of concrete and its types and uses.
● Admixture of concrete :- the extra material in the form of liquid ,powder or paste added to concrete before or during the mixing process is known as admixture. it may be natural ,manufactured chemical or semi synthetic chemical. It is act as retarder , accelator ,plasticizer ,fungicidal agent ,water resistant agent, corrosion preventing agent.
● commonly used admixture:-
Alum ,Aluminium Sulphate ,barium oxide ,Bitumen, calcium chloride ,coal ash, common salt, iron oxide, lime ,mineral oil,organic oil ,potassium chloride ,tar product ,zinc chloride, volcanic ashes and carbon etc.
● main function of admixture of concrete:-
1) It Act as water reducing agent
2) It Act as accelator
3) air entraining agent
4) waterproofing agent
5) gas forming agent
6) Air detraining agent
7) alkali aggregate expansion preventing agent
8) admixture adjusting the final setting time of concrete
9)admixture increase the higher early and ultimate strength
10) admixture make the concrete higher slump and self travelling
11) admixture increase the durability of concrete
12) it also reduced quantity of cement
13) it also reducing the permeability of concrete
● Main type of admixture- according to origin from which they are obtained admixture have following three types ● (1) natural admixtures
(2) mineral admixture
( 3) manufactured admixture
● (1)natural admixtures:- it is obtained from pure Natural sources from plant products, its increase the durability of concrete, its example is cellulose ,natural rubber, gum etc .it is added to the concrete before or during the mixing of concrete.
●(2) mineral admixture:- it is obtained from mineral sources like Mineral oil ,organic oil silica, lime coal ashes
● (3) manufactured admixture :- it is made in factories by the laboratory process, the mineral or natural product which is obtained from Natural Sources it is modify by human beings like that synthetic rubber obtained from natural rubber and making of Coal Tar from coal or bitumen etc.
● Main types of admixture :- according to its function admixture have following types ,it is mainly based on function of admixture.
● (1) Accelerating admixture:- this type of admixture reduce initial setting time of concrete and also speed of final setting and hardening of concrete. It is commonly used in low Temperature zone of world having cold climate condition .you know that in cold season setting of concrete taking long time that’s why accelerating type of admixture is added to concrete to reduce the setting time of concrete.
● example of accelerating admixtures:-
(1) calcium formate
● (2) air entraining concrete admixture:- it is new generation admixture used in today new technology in cold climate region of the world for final setting and hardening of concrete. It Increase durability of concrete under freezing condition, when added to the concrete it make millions of non -coalescing air bubbles which are make more counter interact between sand cement and aggregate and take long time for setting. And prevent from shrinkage and cracking concrete.
● example of air entraining admixture
( 1) resin
(2) vegetable fats
(3) animal fats
●(3) water reducing admixture:- it can minimise demand of water also known as plasticizer .plasticizer have few types like 1)mid range plasticizer 2) normal plasticizer and 3)superplasticizer. Normal plasticizer can minimise 10% of extra water and mid range plasticizer can minimise 15% of extra water and super plasticizer can minimise 30% of extra water.
● Example of water reducing admixture:-
(3)ammonium lignosulfonate (4)polycarboxylate
● (4) Retarding admixtures:- it can Slow Down The hydration of cement in initial stage and increase the initial setting time of concrete is also called as retarder. it can be used in high Temperature zone of world .you know that in high temperature setting time of concrete is decrease .to inhance and balance the concrete settling time retarder is used.
In absence of retarder the bond between cement sand and aggregate will be poor Bond and it can be tracking . So retarder is must used in high Temperature zone during the formation of concrete.
●Example of retarder:-
( 1)calcium sulphate
● (5) Pozzolanic admixture:- in new generation Technology it is used to prepare dense concrete and used for formation of water retaining structure like Dam ,Talab where it can reduce the hydration and thermal structure of RCC work by several alkali material which are present in water.
● Example of pozzolanic admixture:-
(1) fly ashes
● (6) water -proofing admixture:- it can make concrete impermeable to water and prevent from dampness on concrete.
● Example water proofing admixture:-
(1) Aluminium Sulphate
(3)silicate of soda
● (7) corrosion preventing admixture:- it can prevent concrete from corrosion of iron oxide .most commonly used admixture is sodium benzoate and sodium nitrate which prevent concrete from corrosion
● (8) anti wash-out admixture:- underwater condition like Dam and Talab it increases the cohesiveness of concrete. And prevent from wash out of concrete. Most commonly is used is cellulose.
●(9) bonding admixture:- this type of admixture is being used when we make new concrete surface on old concrete surface, when we apply new concrete material on old concrete surface bonding between old and new concrete is poor. To increase the bonding strength between old and new concrete we should use bonding type of admixture like natural rubber and PVC known as polyvinyl chloride.
(10) insecticidal admixture:- when fresh concrete comes in contact with water and moisture and air there is a so many types of germs and fungi and algae germinate on the surface of concrete. To prevent from germs and fungi we should use insecticidal type of admixture. Most commonly insecticidal admixture is poly halogenated phenol.
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