Welcome to Crack-Je-Civil with a new blog post!
SSC-JE | RRB-JE | GATE | ESE
The conventional cements and cement concretes as studied before are commonly used for structures in normal environmental conditions. With the advancements of technology and pressing demands of better mechanical properties and durability than the conventional ones as well as improvements in selected properties of interest has lead to the development of special cements and cement concretes.
The following describes some of the important and widely used special cements and cement concretes in the constructions industry.
1. Fibre Reinforced Concrete
Conventional Concrete modified by random dispersal of short discrete fine fibres of asbestos, steel, sisal, glass, carbon, poly-propylene, nylon etc. is known as Fibre Reinforced Concrete (FRC).
Asbestos cement fibres so far have proved to be commercially successful.
The development in structural overall performance relies upon at the strength characteristic, volume spacing, dispersion and orientation, form and their aspect ratio (ratio of length to diameter) of fibres.
A fibre reinforced concrete requires a considerably greater amount of fine aggregate than that for conventional concrete for convenient handling.
Advantages:
Strength of concrete will have a significant result which increases compared to normally reinforced cement concrete.
Fibres helps to reduce cracking and permit the use of thin concrete sections.
Mix turns into cohesive and possibilities of segregation are reduced.
Ductility, impact resistance, tensile and bending strength are improved.
Disadvantages:
Fibres reduce the workability of a mix and may cause the entertainment of air.
Steel fibres tend to intermesh with each other and form balls during mixing of concrete which may result in voids during concreting work.
Applications:
Fibre reinforced concrete is useful in hydraulic structures, airfield pavements, highways, bridge decks heavy duty floors, and tunnel linings.
2. Ferro-cement
Ferro-cement is a composite material in which the filler material (called matrix), cement mortar, is reinforced with fibre, usually steel mesh dispersed throughout the composite, which results in better structural performances than individual ones. The fibres imparts tensile strength to the mass.
Advantages:
Easy equality of raw materials.
Reduction in weight consequent of thin section.
Moulding can be done without any formwork.
No machinery or sophistication is required in construction.
3. Ready Mix Concrete (RMC) :
Ready Mix Concrete (RMC) is a concrete, delivered at site or into the purchaser’s Vehicle, in plastic condition i.e during the initial setting time of the concrete (may or may not use admixtures) and requires no further treatment before being placed in a position in which it is to set and harden.
Advantages:
Enhanced quality and durability resulting in lower maintenance costs and increased speed of construction.
Ready mix concrete is consistently of the same quality and provides a high quality of construction material, construction time is also reduced.
It reduces congestion at the site and prevents traffic jams.
It hastens infrastructure development and thus provides more employment opportunities.
It is an environmentally safer alternative.
4. Shotcrete :
It is a concrete conveyed through a hose and pneumatically projected at a higher velocity on a surface. It is similar to gunite (mortar) but with coarse aggregates.
The regular specs with respect to cement, aggregate and water additionally apply to shotcrete however the coarse combination used ought to be harder to account for attrition and of small size.
The W/C ratio is kept at its minimum.
Consolidation of shotcrete is achieved by the impact of the high velocity jet impinging on the surface.
Properties:
The strength and other properties of shotcrete are same as that for high quality concrete.
Normal shotcrete mixes are capable of strength above 35 N/mm2.
Shotcrete is highly durable.
Applications:
Shotcrete find its applications in tunneling, repairing of old concrete and thin sections.
Conclusion
The remaining types of Special Cements and Cement Concretes are to be discussed further in the coming blogs and here we discussed the most widely used in the present construction industry.
If you find the blog interesting please do like the post and leave a comment. And subscribe to Crack-Je-Civil for latest updates related to civil engineering and other interesting topics which are to be covered in the future.
Comments