CONCRETE TECHNOLOGY

 Study on concrete technology

The concrete technology basically deals with the behaviour of concrete in various situation.

concrete is basically a mixture of cement, water, fine and coarse aggregate and in some cases, plasticisers are also used in concrete.

This is a huge topic to discuss, I am covering as much as possible. There are many factors of concrete. 

Let's learn from the basic-

A-WORKABILITY OF CONCRETE- 

Workability of concrete is the measure of concrete to designate it as 'workable'. 

A workable concrete is the one which exhibits very little internal friction between particle and particle OR which overcomes the frictional resistance offered by the formwork surface or reinforcement contained in the concrete with just the amount of compacting efforts forthcoming.

FACTORS THAT AFFECTS THE WORKABILITY ARE-

1. water content
2. mix proportions
3. size of the aggregate
4. shape of aggregate
5. the surface texture of aggregate
6. grading of aggregate
7. use of admixtures.

TEST TO DETERMINE WORKABILITY OF CONCRETE-

1. Slump test.
2. compacting factor test.
3. flow table test.
4. vee-bee test.
5. key ball test etc.

B-CREEP AND SHRINKAGE OF CONCRETE-

➤Creep of concrete- 

creep can be defined as time-dependent part of the strain resulting from stress. The stress-strain relationship of concrete is not a straight line but a curved one.

The gradual increase in a strain without an increase in stress with time is due to creep.
So creep can also be defined as the increase in strain under sustained stress.

➤Shrinkage of concrete- 

One of the most important factors that contribute to the cracks in the floor and pavements is that due to shrinkage.

 The term shrinkage is loosely used to describe the various aspects of volume changes in concrete due to loss of moisture at different stages due to different reasons.

 shrinkage can be classified in the following ways-

1. plastic shrinkage
2. drying shrinkage
3. autogenous shrinkage
4. carbonation shrinkage.

C-SEGREGATION AND BLEEDING OF CONCRETE-

segregation of 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.

If a sample of concrete exhibits a tendency for separation of a say coarse aggregate from the rest of the ingredients then that sample is said to be showing a tendency for segregation.

Such a concrete is not only going to be a weak lack of homogeneity is also going to induce all undesirable properties in the hardened concrete.

There are three types of segregation of concrete-

1. coarse aggregate separating out from the rest of the matrix,
2. water separating away from the coarse aggregate,
3. water separating out from the rest of the material is a material of a lowest specific gravity.

Bleeding of concrete- 

Bleeding is sometimes referred as water gain in concrete.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.

Due to bleeding water comes up and accumulates at the surface.
 sometimes along with this water, a certain quantity of cement also comes to the surface.
owing to the fact that the top surface has a higher content of water and is also devoid aggregate matter, it also develops higher shrinkage cracks. This could be avoided by removing the laitance fully before the next lift is poured.

some most asked Q&A-

WHAT IS CURING OF CONCRETE?

1. Curing is the process of keeping the set concrete continuously damped for some days in order to enable the concrete to gain more strength. during the process of concrete, the concrete absorbs the water necessary for the concrete chemical action to reach its required strength.

WHAT IS EFFLORESCENCE IN CONCRETE STRUCTURE?

It is a crystalline deposit on surfaces of concrete. 

The movement of groundwater(with salt)into building foundations and by capillary is often the cause of efflorescence.

3. WHAT IS POLYMER CONCRETE?

Polymer concrete is an aggregate bound with a polymer binder instead of Portland cement as in conventional concrete.
advantages- 

i.high compressive strength
ii.high resistance to chemical attack and abrasion
iii.reduced permeability
disadvantages-
i.material poorer than the OPC obtained,
ii.modest improvements of strength and durability.

 I Hope this will help you to know more about concrete technology.
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