Full Form of RCC :
RCC Full Form is Reinforced Concrete. RCC contains embedded plates, fibers, or embedded steel bars to strengthen the material. Since RCC can carry heavy loads, it is vastly used in construction. It is also one of the most commonly used materials for construction. The concrete is made of reinforced materials in a way that the combination of the materials resists any kind of external force. The combined strength of the steel bar and concrete form a very strong bond which enables it to resist stress for a long time. Most often, plain concrete alone is not sufficient to withstand vibrations and stresses or forces. Since the cement paste inside the concrete hardens and blends with the surface of the steel, stresses are transmitted efficiently between the two. This, in turn, enhances the toughness of the RCC.
RCC Full Form – Additional Information
Reinforced Cement Concrete, also known as Reinforced Concrete, is essentially a combination of steel and concrete, which helps in countering the weak ductility and tensile strength of concrete. Through this combination, a higher ductility and tensile strength are reached. This reinforcement is generally attained with the help of steel reinforcing bars, which are passively embedded in the concrete prior to the settlement of concrete. These reinforcing schemes are usually designed to tackle tensile stresses in specific areas of the concrete, which may result in structural failure or unacceptable cracking.
Reinforced concrete can be permanently stressed for the purposes of improving the final structure’s behavior under working loads. In the United States of America, the most commonly used methods for production of reinforced Concrete are post-tensioning and pre-tensioning. Reinforced Cement Concrete, which will hereinafter be referred to as RCC, must possess high relative strength, strong bond, and high resistance to tensile strain, thermal compatibility, and high durability. Thus, RCC is highly helpful for the construction purposes and is, therefore, popularly used. There are various aspects of RCC that must be dealt with for proper appreciation. So, here are five points about RCC that everyone must know about:
History of RCC
Francois Coignet was the pioneer in the field of structural and reinforced concrete development. He is known for being the first person to use iron-reinforced concrete for the construction of building structures. In the year 1853, he developed the first ever structure constructed with iron reinforced concrete: a four-storey house situated in Paris. He, however, seemed to have no knowledge of tensile stresses. His successor in this field, William B. Wilkinson further improved techniques relating to reinforced concrete and demonstrated that he had knowledge on tensile stresses.
Joseph Monier, who was surprisingly a French gardener, invented reinforced flowerpots by blending a mortal shell and a wire mesh and was granted a patent for the same. In the year 1877, he obtained another patent for a much-advanced technique that pertained to the reinforcement of concrete columns with the help of iron rods established in a grid-like pattern. There is doubt, however, as to whether he knew about tensile stresses.
A major contribution to the development and improvement of reinforced concrete technique was made by Thaddeus Hyatt, who conducted various experiments on RCC. Use of steel came to limelight because of G.A. Wayss, who was a German engineer engaged in steel and iron concrete construction. In the year 1879, he purchased the German rights to the patents belonging to Monier and subsequently in the year 1884 began commercial use of RCC in his Wayss & Freytag firm. The firm is credited to have made many technological and financial inputs in the development of RCC.
Ernst L. Ransome was an English engineer who gave different styles to the RCC technique. He introduced the technique of twisting the steel bar with the concrete. His knowledge was immense and greatly acknowledged and subsequently, he went on to construct two of the first ever reinforced concrete bridges in the American continent. In the United States, the RCC was first used in the construction of a private house, which was William Ward’s design, in the year 1871. In the year 1904, the skyscraper Ingalls Building was constructed with the help of RCC.
Use in Construction
RCC has many utilities in the construction field. Different kinds of structures and components thereof can be constructed with RCC such as walls, slabs, foundations, columns, frames, and etc. RCC can be categorized into either precast or cast-in-place concrete. Former is manufactured in a reusable form later cured in a tamed environment, which is then transported to the site of construction. The Latter is simply a typical form of concrete.
An efficient floor system is integral in constructing optimal building structures. Minute changes in a floor system’s design can bring out palpable impacts on the construction schedule, material cost, operating costs, end use of a building, ultimate strength, and occupancy levels. RCC is extremely important in the construction of modern-day building structures. This is particularly due to several advantages attributed to RCC such as high resistance to strength, durability, stronger bonds, and others which have already been mentioned before.
Key characteristics of RCC
There are three physical characteristics of RCC that are responsible for its specialty and have been mentioned below:
- The RCC’s coefficient of thermal expansion, which eliminates internal stresses because of differences in thermal contraction or expansion.
- When the cement paste used in the concrete becomes hard, this settles on the surface details of the steel and permits any internal stress to be efficiently transmitted among different materials. Generally, the steel bars used are made rough for the purposes of improving the cohesion between the steel and the concrete.
- The alkaline environment that the alkali reserve (comprising NaOH and KOH) provides and the portlandite (which is essentially calcium hydroxide) contained in the cement paste results in the formation of a passivating film on the surface of the steel. This makes it more tolerant to corrosion in an alkaline
As a rule, the steel used is protected at a pH value above ~11 but begins to corrode below ~10, though much of it depends on the properties of the steel and physicochemical conditions when carbonation of concrete occurs. Two of the primary reasons for the failure of RCCs are the carbonation of concrete as well chloride ingress.
The cross-sectional area of the steel is generally small and varies from 1 percent for many slabs and beams to about 6 percent for a few columns. The reinforcing bars are generally round in the cross-sectional area and vary in their diameters. These bars may often come with hollow cores for regulating and controlling humidity and moisture. It is also to be noted that the distribution of the strength of concrete is not homogenous and depends on many factors. All of it shows quite clearly that RCC is invested with many great characteristics, though a few issues are there.
Common failures in RCC
On the whole, RCC is advantageous however, there are several modes which cause its failure.
- Mechanical failure: It is often impossible to prevent cracking of the concrete. Nevertheless, the damage done by the cracks can be controlled by introduction of apt reinforced control joints, concrete mix design, and curing methodology. Cracking is an issue because it facilitates moisture to penetrate in the concrete, which results in corrosion of the reinforcement. This is called a serviceability failure. Cracking occurs because an improper amount of rebar is used or the rebar is placed at a great distance. Due to this, concrete will crack under pressure from excess loading or thermal shrinkages, etc. Ultimate failure happens when compressive stresses exceed the strength of concrete.
- Carbonation: Also known as neutralization, it is a chemical reaction between calcium hydroxide, calcium silicate in the concrete and carbon dioxide present in the air. Carbonation results in durability issues when there are sufficient oxygen and moisture to result in electro-potential corrosion of the rebar.
One of the ways to determine carbonation is drilling a fresh hole on the surface and then treating the drilled surface with a solution of phenolphthalein indicator. The color of the solution will change to pink when it comes in contact with alkaline concrete. This helps in examining the depth of carbonation.
- Chlorides, which includes Sodium Chloride, has the ability to promote corrosion of steel rebar if it is present in high concentration. Chloride anions have the tendency to cause localized corrosion—also known as pitting corrosion—as well as generalized corrosion. It is, for this reason, it is advised that fresh water is used while mixing the concrete for ensuring that the fine and coarse aggregates do not have any remains of chlorides.
- Alkali-Silica reaction: This is a reaction between amorphous silica and hydroxyl ions. The former is present in the aggregates whereas the latter is present in cement pore solution. The dissolution of poorly crystallized silica occurs, which disassociates at the pH value between 12.5-13.5 in alkaline solution. This dissolved silica acid then causes a reaction with portlandite found in the cement paste forming calcium silicate hydrate. This reaction can cause cracking or tensile stress. This entire phenomenon is often referred to as concrete cancer.
- There are other modes which can cause failure in RCCs such as sulphates, conversion of high alumina cement, etc.
The reinforcement process has to undergo the strain that the concrete goes through for prevent of discontinuity, separation of these two materials under pressure, etc. For the maintenance of composite action, there is a transfer between the steel and the concrete required in which the direct stress is transferred to the bar from the concrete for the purposes of changing the tensile stress. This transfer is attained with the help of anchorage and is subjected to a continuous stress field, which develops around the interface between the concrete and steel.
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