As we known Concrete is produced in a variety of compositions, finishes and performance characteristics to meet a wide range of needs.
Types Of Concrete:- Depending Upon the composition, Finishes and performance Concretes are:
1. Regular Concrete 2. High Strength Concrete 3. Stamped Concrete
4. High Performance Concrete 5. Vacuum Concrete 6. ShotCrete
7. Pervious Concrete 8. Cellular Concrete 9. Cork Cement Coposite
10. Roller Compacted Concrete 11. Glass Concrete/Asphalt Concrete 12. Rapid Strength Concrete
13. Rubberised Concrete 14. Polymer Concrete 15. Geopolymer/Green Concrete
16. Limecrete 17. Refractory Cement 18. Concrete Cloth
19. Gypsum Concrete
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1. Regular Concrete:- Also known as Modern Concrete is the lay term for concrete that is produced by following the mixing instructions that are commonly published on packets of cement, typically using sand or other common material as the aggregate, and often mixed in improvised containers. The ingredients in any particular mix depends on the nature of the application. Regular concrete can typically withstand a pressure from about 10 MPa to 40 MPa , with lighter duty uses such as blinding concrete having a much lower MPa rating than structural concrete. Many types of pre-mixed concrete are available which include powdered cement mixed with an aggregate, needing only water.
2. High Strength Concrete :- It has a compressive strength greater than 40 MPa. High-strength concrete is made by lowering the water-cement (W/C) ratio to 0.35 or lower. Often silica fume is added to prevent the formation of free calcium hydroxide crystals in the cement matrix, which might reduce the strength at the cement-aggregate bond.
Low W/C ratios and the use of silica fume make concrete mixes significantly less workable, which is particularly likely to be a problem in high-strength concrete applications where dense rebar cages are likely to be used. To compensate for the reduced work ability, superplasticizers are commonly added to high-strength mixtures. Aggregate must be selected carefully for high-strength mixes, as weaker aggregates may not be strong enough to resist the loads imposed on the concrete and cause failure to start in the aggregate rather than in the matrix or at a void, as normally occurs in regular concrete
3. Stamped Concrete :- It is an architectural concrete that has a superior surface finish. After a concrete floor has been laid, floor hardeners (can be pigmented) are impregnated on the surface and a mold that may be textured to replicate a stone / brick or even wood is stamped on to give an attractive textured surface finish. After sufficient hardening, the surface is cleaned and generally sealed to provide protection. The wear resistance of stamped concrete is generally excellent and hence found in applications like parking lots, pavements, walkways etc.
4. High Performance Concrete :- High-performance concrete (HPC) is a relatively new term for concrete that conforms to a set of standards above those of the most common applications, but not limited to strength. While all high-strength concrete is also high-performance, not all high-performance concrete is high-strength. Some examples of such standards currently used in relation to HPC are:
- Heat of hydration
- Ease of placement
- Compaction without segregation
- Early age strength
- Long-term mechanical properties
- Permeability
- Density
- Toughness
- Volume stability
- Long life in severe environments
- Depending on its implementation, environmental
The final strength of concrete is increased by about 25%. Vacuum concrete stiffens very rapidly so that the form-works can be removed within 30 minutes of casting even on columns of 20 ft. high. This is of considerable economic value, particularly in a precast factory as the forms can be reused at frequent intervals. The bond strength of vacuum concrete is about 20% higher. The surface of vacuum concrete is entirely free from pitting and the uppermost 1/16 inch is highly resistant to abrasion. These characteristics are of special importance in the construction of concrete structures which are to be in contact with flowing water at a high velocity. It bonds well to old concrete and can, therefore, be used for resurfacing road slabs and other repair work.
6. ShotCrete :- Shotcrete which is also known by Gunite uses compressed air to shoot concrete onto (or into) a frame or structure. The greatest advantage of the process is that shotcrete can be applied overhead or on vertical surfaces without form-work. It is often used for concrete repairs or placement on bridges, dams, pools, and on other applications where forming is costly or material handling and installation is difficult. Shotcrete is frequently used against vertical soil or rock surfaces, as it eliminates the need for form-work. It is sometimes used for rock support, especially in tunneling. Shotcrete is also used for applications where seepage is an issue to limit the amount of water entering a construction site due to a high water table or other subterranean sources. This type of concrete is often used as a quick fix for weathering for loose soil types in construction zones.
Application Method of Shotcrete :- There are Two Methods of Application of shotcrete
1. Dry Mix:- The dry mixture of cement and aggregates is filled into the machine and conveyed with compressed air through the hoses. The water needed for the hydration is added at the nozzle
2. Wet Mix:- The mixes are prepared with all necessary water for hydration. The mixes are pumped through the hoses. At the nozzle compressed air is added for spraying.
For both methods additives such as accelerators and fiber reinforcement may be used.
7. Pervious Concrete :- It used in permeable paving, contains a network of holes or voids, to allow air or water to move through the concrete
This allows water to drain naturally through it, and can both remove the normal surface-water drainage infrastructure, and allow replenishment of groundwater when conventional concrete does not.
It is formed by leaving out some or all of the fine aggregate (fines). The remaining large aggregate then is bound by a relatively small amount of Portland cement. When set, typically between 15% and 25% of the concrete volume is voids, allowing water to drain through the concrete.
8. Cellular Concrete :- This type of concrete is produced by an addition of air en-training agent to the concrete like Foam concrete.
9. Cork Cement Composite :- These are obtained during production of bottle stoppers from the treated bark of Cork oak. These granules have a density of about 300 kg/m3, lower than most lightweight aggregates used for making lightweight concrete. Cork granules do not significantly influence cement hydration, but cork dust may. Cork cement composites have several advantages over standard concrete, such as lower thermal conductivity, lower densities and good energy absorption characteristics. These composites can be made of density from 400 to 1500 kg/m3, compressive strength from 1 to 26 MPa, and flexural strength from 0.5 to 4.0 MPa.10. Roller Compacted Concrete :- sometimes also called rollcrete, is a low-cement-content stiff concrete placed using techniques borrowed from earth moving and paving work. The concrete is placed on the surface to be covered, and is compacted in place using large heavy rollers typically used in earthwork. The concrete mix achieves a high density and cures over time into a strong monolithic block. Roller-compacted concrete is typically used for concrete pavement, but has also been used to build concrete dams, as the low cement content causes less heat to be generated while curing than typical for conventionally placed massive concrete pours
11. Glass Concrete :- The use of recycled glass as aggregate in concrete has become popular in modern times, as the Research says. This greatly enhances the aesthetic appeal of the concrete. Recent research findings have shown that concrete made with recycled glass aggregates have shown better long-term strength and better thermal insulation due to its better thermal properties of the glass aggregates.
12. Rapid Strength Concrete :- This type of concrete is able to develop high resistance within few hours after being manufactured. This feature has advantages such as removing the form work early and to move forward in the building process very quickly, repaired road surfaces that become fully operational in just a few hours. Ultimate strength and durability can vary from that of standard concrete, depending on compositional details.
13. Rubberised Concrete :- This type of concrete is still undergoing experimental test.
14. Polymer Concrete :- It is a concrete which uses polymers to bind the aggregate. Polymer concrete can gain a lot of strength in a short amount of time. For example, a polymer mix may reach 5000 psi in only four hours. Polymer concrete is generally more expensive than conventional concretes.
15. Geopolymer/Green Concrete :- It is an alternative to ordinary Portland cement and is used to produce Geopolymer concrete by adding regular aggregates to a geopolymer cement slurry. It is made from inorganic aluminosilicate (Al-Si) polymer compounds that can utilise recycled industrial waste (e.g. fly ash, blast furnace slag) as the manufacturing inputs resulting in up to 80% lower carbon dioxide emissions. Greater chemical and thermal resistance, and better mechanical properties, are said to be achieved for geopolymer concrete at both atmospheric and extreme conditions.
16. Limecrete :- In limecrete, lime concrete the cement is replaced by Lime One successful formula was developed in the mid-1800s. Lime has been used since Roman Times either as mass foundation concretes or as lightweight concretes using a variety of aggregates combined with a wide range of pozzolans (fired materials) that help to achieve increased strength and speed of set. Lime concrete was used to build monumental architecture during and after the roman concrete revolution as well as a wide variety of applications such as floors, vaults or domes. Over the last decade, there has been a renewed interest in using lime for these applications again.
17. Refractory Cement :- At High-temperature applications, such as masonry ovens and the like, generally require the use of a refractory cement; concretes based on Portland cement can be damaged or destroyed by elevated temperatures, but refractory concretes are better able to withstand such conditions. Materials may include calcium aluminate cements, fire clay, ganister and minerals high in aluminum.
18. Concrete Cloth :- Concrete cloth is a Innovative Material composed of flexible aluminate cement powder-Impermagnated fabric that rapidly hardens upon hydration to form a thin layer durable, waterproof, and fire resistant concrete layer.
19. Gypsum Concrete:- It is a Mixture of Gypsum, Portland Cement and sand. These are used in sound reduction, floor leveling, fire resistance etc.
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