Hello, friends in this article i am going to tell about “Types of concrete” so, to get full knowledge read it line by line without skipping.
What is the Concrete?
The concrete is a mixture of cement, sand, crushed rock, water, which, when placed in the skeleton of forms and allowed to cure, becomes hard like a stone.
A cement concrete has attained the status of major building material in all branches of modern construction because of the following reasons. It can be readily moulded into durable structure items of various size and shapes at practically no considerable labour expenditure.
- Able to done check the properties of cement concrete within a wide range by using appropriate ingredients and by applying special processing techniques, mechanical, chemical, and physical.
- This is possible to mechanise completely it’s preparation and placing process.
- It possesses adequate plasticity for mechanical working.
Following are the properties of concrete,
- It is a high compressive strength.
- It is free from corrosion and there is a no appreciable effect of atmospheric agents on it.
- Make become harder with age and the process of hardening continues for a long time after the concrete has attained sufficient strength. It has this property of concrete which gives a distinct place among the building materials.
- This is proved to be more economical than steel. It is due to the fact that sand and crushed rock, forming the bulk of concrete, to the extent about 80 to 90%, are usually available at a moderate cost.
- This binds rapidly with steel and as it is weak in tension, the steel-reinforced is placed in Concrete at a suitable place to take up the tensile stresses. It is term as the reinforced cement concrete.
- It has a tendency to shrinks when there is initial shrinkage of concrete which is mainly due to loss of water through forms, absorption by surface of forms etc.
- It is tendency to be porous. It is due to the presence of voids which are formed during and after it’s placing.
- It forms a hard surface, capacity of resisting abrasion.
- This, it remembered hat apart from other materials, concrete comes to the site in the form of raw material only.its final strength and quality depend upon the person who handles it.
Following are the material required for making different types of concrete.
Different Type of concrete are given below,
- Waterproofing cement concrete.
- Coloured concrete.
- Lightweight concrete.
- No fines concrete.
- Pre-cast concrete.
- Ready-mix concrete.
- Transit-mix concrete.
1) Waterproofing concrete:- For certain types of works like water storage tanks, reservoir, basement wall, roofs, swimming pool, sewage units etc, the impermeability of concrete is absolutely essential. Normal, it can be stated that if the concrete is made dense and free from cracks, this is watertight.
2) Coloured concrete:-
Coloured concrete can be made by following way,
- By the addition of suitable colouring pigments to the extent of about 8 to 10% of the weight of the cement.
- By using coloured Cement for the preparation of concrete.
- By selecting aggregates possessing the required coloured.
3) Lightweight concrete:- The bulk density of ordinary concrete is about 23KN/m3. The concrete having a bulk density between 5 to 18 KN/m3 is called the lightweight concrete.
4) No fines concrete:- A no-fines concrete consists of cement, coarse aggregate and water. Therefore, fine aggregates or sand is eliminated and such concrete has been adopted for the cast-in-situ external load-bearing wall of the single and multi-storey house, small retaining wall, damp roofing sub-base material etc.
5) Pre-cast concrete:- The main difference between this concrete and cast-in-situ concrete is that the former is a factory-made product while the latter is prepared at the site of work. It is possible to prepare a well made precast product by keeping high standards of finishing. The precast products very simple structure such as fencing posts, pipes, paving slabs etc.
6) Ready-mix concrete:- Ready-mix concrete is a type of concrete that is manufactured is a factory or batching plant, according to set recipe, and then delivered to a worksite, by truck mounted transit mixers. Within of a transits mixer uses a simple Archimedes drew to mix and lift the concrete to the delivery chute.
7) Transit-mix concrete:- The concrete that is mixed, either wet or dry, en route to a job site is known as Transit-mix concrete. A Transit-mix truck carries a mixer and a water tank from which the driver can, at the proper time, introduce the required amount of water into the mix.
How to prepare different types of concrete?
Proportioning of concrete:- A process of selection of relative proportion of cement, sand, coarse aggregate and water , so as to obtain a concrete of desired quality is called the proportioning of concrete.
It is observed that if a vessel, is taken a filled with stone, of equal size, the voids to the extent of about 45 per cent are formed. This result is independent of the size of the stone. It is interesting to note that if sand is taken in place of stones, the same result will be proportioning concrete obtained.
A result can be verified by pouring water in the vessel till it is full . Volume of water added in the vessel present the amount of voids. The theory of the formation of concrete is based on this phenomenon of formation of the void. When coarse aggregate is placed, such voids are formed. When fine aggregate I,e, sand , is added , it occupies these void.
Further, when finely powdered cement is added, it occupies the voids of sand particles. Finally, when water is added, it occupies very fine voids between the cement particles. During the process of setting, a chemical reaction takes place between water and cement. This result is an absolutely solid substance, called concrete.
Following are the different method of proportioning of concrete;
1) Arbitrary method:- In the method of Arbitrary volumetric proportion, the proportion of cement, sand and coarse aggregate are fixed arbitrarily such as 1:2:4 or 1:3:6 etc. Depending on the nature of work for which concrete is required.
Usually, the fine coarse ratio is 1:2, on the assumption that must of the coarse aggregate have voids to the extent about 50 per cent. Another ratio may be used. Thus the general expression for the proportion of cement, sand and coarse aggregate is 1:n:2n by volume.
2) Fineness modulus method:- In the Fineness modulus method, the Fineness modulus of sand and aggregate is determined by the standard test. The term Fineness modulus is used to indicate an index number which is roughly proportional to the average size of the particle in the entire quantity of Aggregate.
3) Minimum void method:- In this method, the voids of coarse aggregate and fine aggregate are determined separately, and to get the dense concrete, it is so arranged that is;
– The quantity of fine aggregate completely fills the void of the coarse aggregate.
– The quantity of cement completely fills the voids of fine aggregate; and
– Sufficient water is added to mix the cement fine Aggregate and coarse aggregate to make the mix workable.
4) Maximum density method:- This method is based on the principle that the densest concrete is achieved by proportioning it’s aggregate in such a manner that the heaviest weight of concrete for same volume is obtained. A box is filled with varying proportion a Fine and Coarse Aggregate. The proportion which gives the heaviest weight in then adopted.
5) Water-cement ratio:- According to the Water-cement ratio law given by Abram as the result of many experiments, the strength of well-compacted concrete with good work ability is a development only on the Water-cement ratio.
It is to be noted that to apply this law, the concrete is assume to be fully compacted. The lower water content produce stiff paste having greater binding property and hence the lowering if water-cement ratio within certain limit results in the increased strength.
So, friends, I hope this article on “Types of concrete” remains helpfull for you.