In the text below I've tried my best and devote most of my efforts to make a document that may help other students even without any prior understanding of the subject to comprehend the very important subject concrete with extensive understanding of the concrete. The text gives the routine knowledge of the smaller important concepts and has been written to depth for important and useful concepts. I've tried to make a document that will be used to give lectures and cover the difference between a teacher with comprehensive knowledge of the topic and students who have just been created to the subject.
I am also thankful to my professors and friends for his or her support in concluding this work. I am hoping the document operates as a function of information rather than being a jigsaw puzzle and gratify all the requirements for the formal distribution.
Introduction: - Civil anatomist is the oldest and the most basic streams of anatomist. When we think of civil engineering the initial thing that involves mind is concrete and construction, when we come down to the greater uses of civil executive we think of cement. Concrete is not such a simple thing as it might look right down to a non development related person, it is due to the fact it has so many practical uses, more than any structure materials that it has a specialization of its. So the review of concrete is very useful or may be looked at the most necessary studies for a civil engineer. Nowadays the analysis of concrete is considered as the backbone of the construction industry. This subject has its own specializations designed for research is such a huge subject matter that for a development industry or company the success is decided by its concrete technicians. The modern industry of the todays world depends completely on the engineering of concrete buildings. Cement has experienced this great variety of use because of its marvelous properties that completely distinguish it from the rest of construction materials. The annals of structure traces back to the times of Assyrians and Babylonians who first made the use of clay as a cementing material. The traditional forts and military buildings, the protection structures have witnessed a broad use of the cement manufactured from aggregates and lime as a binder. Engineering of the pyramids in Egypt has also proved the use of lime and gypsum as a binder in the concrete works. The visible experts of the concrete research are Vitruvius who is thought to have the data of chemistry of the cementitious lime. Among the remarkable historic works is the pantheon, which involves a dome spanning 43. 43m and is manufactured entirely of cement. The Romans also used appropriate cements manufactured from suitable limestone burned up in kiln or were mixtures of lime and puzzolanic materials (volcanic, ash, tuff) incorporating into a hard concrete. Vitruviuss work was followed by the researches created by M. Vicat of France. Joseph Aspedin of Yorkshire (U. K. ) was the first ever to introduce Portland concrete in 1824 developed by heating a mixture of limestone and finely divided clay in a furnace to a temperature high enough to drive off the carbonic acid gas. In 1845, Issac C. Johnson invented the cement by increasing the heat range of which the combination of limestone and clay were burned up to create clinker. This concrete was the prototype of the modern Portland cement. From then onwards, a progressive improvement in the properties and features of cement has been made possible by experts in U. S. A. , U. K. , France and Germany.
What exactly is concrete: - Concrete is a composite man-made material hottest building material in the engineering industry. It includes a rationally chosen mixture of binding material such as lime or concrete, well graded fine and coarse aggregates, water and admixtures (to create cement with special properties). Within a concrete mix, concrete and water form a paste or matrix which in addition to filling the voids of the fine aggregate, coats the surface of fine and coarse aggregates and binds them collectively. The matrix is usually 22-34% of the total volume. Freshly combined concrete before set is known as wet or renewable concrete whereas after setting and hardening it is recognized as set or hardened cement. The moulded concrete blend after sufficient healing becomes hard like stone credited to chemical action between your drinking water and binding materials. It would be impossible to discuss all the areas of this materials in few pages and the dialogue is limited to the overall characteristics and quality exams essential for its use by civil technical engineers and architects.
Most of the traditional set ups and historical properties had been constructed with lime concrete. With all the advent of cement, the use of lime concrete has been limited to making bases for concrete foundations and roof terracing. The major factors accountable for wide use of cement-concrete are mouldability, early on hardening, high early compressive strength, development of desired properties with admixtures to be used in negative situations, suitability for guniting, pumpability and longevity. The simple reason for its extensive utilization in the construction of almost all civil executive works is usually that the properties can be manipulated within a wide range by using appropriate ingredients and by special mechanised, physical and chemical control techniques Buildings"from solitary storey to multistorey, bridges, piers, dams, weirs, keeping walls, liquid keeping constructions, reservoirs chimneys, bins, silos, runways, pavements, shells, arches, railway sleepers are but a few types of cement cement applications.
Concept of high strength concrete: - Concrete because of its versatile properties can be used for many heavy and medium or low cost constructions. Therefore the concrete used in these works is not entirely same. Thus to get more important and demanding works a cement with higher strength is needed. This concrete can be given extra strength by various methods. Usually any concrete which comes in a class over M65 is known as or called high strength concrete. This M65 indicates a compressive durability of 65N/mm2 after 28 days.
This strength apart from other methods can be come to by REINFORCING the cement with other materials of higher power. Reinforcing means the combining the concrete blend with other materials. The materials mostly used are steel, bamboo, line mesh, sticks etc. These materials provide those properties to the cement that the concrete itself lacks. The concrete so reinforced becomes so strong that no other materials can be in comparison to it. Also the power to cost proportion of the is very less when compared with any other materials available for sale.
RCC and concrete: - RCC and cement are the same thing but for the actual fact that RCC has some reinforcement provided to the mixture and the simple concrete is just a variety of cement sand and water along with aggregates. The reinforcement is placed where the framework must be built and concrete is later placed on it and both these bond together to form a high power concrete. The most frequent reinforcing material used is material in the form of steel pubs and wire mesh. So the line mesh or the metallic bars are easy to put and the primary work then lies in properly setting up the concrete combination. So we will now research the preparation of the concrete combine.
Preparation of cement: - The concrete is rather easy to produce. The prep of concrete is a stepwise process. Its prep involves safe-keeping of materials specifically sand aggregate, concrete, water. After that uses batching of materials which is a process of way of measuring of materials by different, convenient methods. Then falls the process of mixing which really is a vital process; the almost all of properties rely upon the mixing conditions and the type of mixing done. Blending is the process of mixing the materials, batched before and getting ready the final concrete mixture or paste. The concrete so prepared is now must be transferred to the site of use. This is done by using pans, wheel pub rows, transit mixers, chutes, bell conveyers, pumps, tower crane and hoists etc. Now that the cement has been taken to the site it needs to be placed so that it gains maximum durability as easily as is feasible. So the inserting is also an extremely vital procedure for the concreting operation. Now that the cement has been positioned we now have to be sure that no voids are remaining in the located blend. Compacting the concrete combination makes sure that the concrete increases fullest of its strength. Then remains finishing of the concrete work done to make certain that it looks good aesthetically. Then your concrete needs to be cured to check the development of breaks and control the heat of hydration.
Storing of materials: - Storing of materials is managed so the materials don't get deteriorated. The materials stored on sites are cement, aggregate, sand, water, steel and another admixtures. The concrete should be stored very carefully as the cement is the second most costly materials after material which is utilized in lesser amounts; cement easily allures any dampness in the air and hardens and gets worthless for the construction purpose. The concrete should be stored in air small rooms free of moisture content and rodents. The hand bags of cement should be put at least 30 cm in addition to the walls with least 20 cm above the floor level this is performed by making a temporary program of hardwood or other cheap materials. The cement handbags should be put one over other to a maximum elevation of 1 1. 5m. The cement bags should be used on the first in first out basis. These handbags should be maintained covered at all times with a suitable clear plastic cover.
Then comes the aggregates, the aggregates should be so stored that these are distinguishly stored relating with their size. These should either be held completely moist or completely dried out this helps to raised understand the water cement ratio and a tight control over this essential ratio.
Then comes fine sand, sand does not need much special attention while storing but fine sand so stored should be checked regularly for increase in the moisture content and hence bulking.
The water used for increasing the concrete or cement is usually potable drinking water and this particular should be placed clean and free of any vegetation and any sort of visible materials and sand etc.
Batching: - The batching of materials is a simple process of measuring the amount of the materials to be used for the concrete mix. That is done by two methods specifically by weight and by size. The materials while blending have to be proportioned properly so that the desired strength and properties can be achieved. This must be done strictly to guarantee the desired properties. Within the former category every one of the ingredients are assessed by weight. But this technique has a disadvantage that the wetness content alters the weight of the materials and this has to be adjusted after experiments and mathematical computations.
The later uses the measuring the materials by quantity and it is less better the above mentioned method. That is because the fine sand content varies greatly in amount by the water content. This variant is harder to take into account accurate measurement.
Mixing: - The procedure of mixing of varied ingredients of concrete in specified percentage is referred to as mixing of concrete. Objectives of blending: the quality and strength of concrete will depend on upon proper blending. The object of mixing is to coating the surface all aggregate particles with concrete paste and to obtain concrete of standard color and required steadiness.
Hand mixing up: - the procedure of mixing the materials of cement by manual labor is called hand mixing. It is implemented for small and unimportant and where level of cement used is small. Hands blending method requires more cement (10%) than machine combining for acquiring the same power of cement.
Machine mixing up: - The procedure of combining the ingredients of concrete by the machine is called machine mixing.
In circumstance where a huge quantity of concrete is to be produced, hand combining becomes costly even if the labor is cheap. The machine maxing becomes essential. The concrete can thus be produced at a faster rate and at minimal cost. The grade of concrete by machine mixing up is also better.
Transportation of concrete: - The process of carrying concrete combine from the area of mixing to the final position of deposition is called transportation of cement. Transportation of concrete mixture is very important because in transportation, time factor is involved. The mix must be transported at the earliest opportunity.
Precautions in transport: - concrete should be transferred as fast as possible to the formwork within the initial environment time of cement.
Efforts should be produced to avoid segregation.
Transportation cost should be as low as possible.
The concrete mix should be safeguarded from drying in hot weather and from rainwater during travelling.
No normal water should be lost from the combination during transport.
Pans- in this technique concrete is transferred in flat iron pans manually.
Wheel barrows- metal wheel barrows with 70L capacity with pneumatic wheels are being used for moderate ranges.
Truck mixers or tipping lorries- this can be used for longer distances of travel. In this particular a pickup truck or lorry having a mixer included in it can be used to carry cement.
Formwork: - The non permanent development used as a mould for the composition for the framework in which the concrete is located and in which it hardens is named formwork or shuttering.
It includes all the surfaces in touch with concrete and everything necessary supporting associates. The part of formwork which contains sheeting and its own immediate helping or stiffening members is called form. The part of formwork which facilitates the varieties usually for a huge structure is named false work. It is yet another important process for concreting.
Compaction: - Compaction of concrete is a process of reducing the entrapped air in concrete and attaining maximum density. The significance should not be under estimated. The effectiveness of cement is reduced by about 40% by occurrence of only 5% voids. The compaction reduces voids to a minimum. The compaction is done by doing exterior work on the cement.
Finishing: - finishing may be defined as the process followed for finding a true, homogeneous concrete surface. The importance of finishing is inescapable. It really is to keep carefully the concrete surfaces free from undulations. The vibrating or palm tamping of your cement leaves a slightly abrasive surface. Finishing of concrete surface is therefore important. The choice of concrete finishing is based upon the best use of the aspect and desired cosmetic effect.
Curing: - The process off keeping the concrete moist to permit it to get strength is named curing. It really is name given to method used for prompting the hydration of concrete. The concrete hardens because of hydration i. e. the chemical reaction between normal water and cement. This reaction is determined by the occurrence of water. Although there is enough water during mixing yet it is necessary to ensure that the is maintained to allow the chemical reaction to continue.
Methods of healing: - The many methods of treating are
Shading of concrete work.
Covering the concrete surface with gunny bags or hessians.
Sprinkling of drinking water.
Of these, ponding covering of concrete surface with gunny carriers or hessians are the most commonly and incredibly widely used.
Proportioning of concrete mixes: - Proportioning of any concrete mixture means deciding the relative amounts of materials necessary for batches of concrete of required strength. This process is normally called as design of combine.
In proportioning a concrete blend, one has to choose suitable proportions of all the ingredients of concrete i. e. concrete, aggregate and normal water in order to give cement its desired properties both on the clear plastic as well as in hardened stage with the utmost economy.
Compressive Strength (N/mm2)
High power concrete
Concretes of compressive strength reduced than 20MPa can be utilized for trim concrete bases and simple foundations for masonry wall space.
Grades lower than M20 shouldn't be used in reinforced concrete works.
Grades less than M30 shouldn't be found in post tensioned prestressed cement.
Grades lower than M40 shouldn't be used in pre tensioned prestressed cement.
Ordinary cement (normal mix cement)
Controlled cement (design mix cement)
Ordinary concrete (normal mix cement): - The cement where the proportions of concrete, aggregates and drinking water are determined by adopting nominal concrete mixes no preliminary assessments are performed is called ordinary cement. It is only used when it's not possible to work with controlled concrete. It might be used for marks M20 or lower if designed mix concrete can't be used for some reasons. The proportions of the ingredients are specified by the engineer usually without examining the materials. There is no guarantee a M20 nominal mix with adopted proportions (say 1:4:8) will have a 28 days cube strength of 20N/mm2.
Grade of concrete
Total level of dried up aggregate per 50 kg of concrete (kg)
Proportions of fine aggregate to coarse aggregate by wt.
Maximum level of water per 50kg of concrete (liters)
Generally 1:2 but upper
Limit is 1:1. 5 and lower
Limit is 1:1. 25
Controlled cement (design mix concrete): - The cement where the proportions of concrete, aggregate and normal water are dependant on conducting preliminary checks for the design of mix is called controlled concrete. A design mixture concrete is preferred over a nominal mix concrete for durability, strength and economy.
Reinforced cement cement: - RCC or strengthened concrete cement is another kind of high strength cement. As described when reinforcing materials of higher power are added to the cement it becomes strengthened cement concrete.
The main feature of adding this reinforcement is the fact it makes the concrete very strong even in stress; otherwise in which concrete is very weak. This happens because of the bonding between reinforcing materials and the concrete blend.
The concrete so prepared is used for many purposes such as piers, bridges, flyovers, dams, slabs, arches etc. The effectiveness of same proportions of materials of concrete when reinforced produces more than twice the power as it would otherwise.
Steel bars can be purchased in the market in a variety of sizes which will be the way of measuring the diameter of the bar. These sizes range from 6 mm to 24 mm for general purpose. Other much larger and specialized sizes are also designed for special constructions. These pubs are cast of metallic created by addition of about 1% of carbon content to iron while its manufacturing. This steel is very hard and is very ductile. Traces of other materials are also added to this steel to modify suited properties.
TMT- thermo mechanically treated bars
Sal- ordinary ribbed bars.
TMT: - this is a product of the modern and has advanced because of this of scientific research through the years in the fields of metallurgy and other related field such as metallurgy and the properties of metals. These pubs as the name suggests are mechanically cured to make better. These are first warmed to a temp of 1400C (red hot) and then cooled all of a sudden which makes it more powerful. Then these bars are also ribbed which makes them stronger at bonding. These pubs can be purchased in the market and are preferred on the other basic or ribbed or SAL bars.
SAL: - these are the traditional pubs which were first tested by creating corrugations or ribs. The ribs on these are helical in form. They are less strong than the other styles of bars (TMT). These bars are produced from metallic with 0. 8-1. 2% of carbon content in flat iron. These pubs are brittle and less ductile. So these are nowadays moving out of market. They are not used in any of the engineering works. The cost of these is not significantly significantly less than the TMT pubs. These bars are available in sizes ranging from 8mm to 26mm. these bars make a weaker relationship than TMT and really should not be utilized for just about any important works.
Design of RCC: - RCC constructions need a great deal of mathematical evaluation to be achieved before the beliefs of final engineering are received. The utmost amount of metallic that can be added to the structures is 4% of the cross sectional area. The slabs and beams designed of RCC are classified into two parts- singly reinforced set ups and doubly reinforced structures.
Singly reinforced constructions are those where the metal reinforcement is put into the lower area of the beam or the slab that bears stress.
Doubly reinforced structures are those in which the metallic reinforcement is put into both- higher and lower part of the framework for conditions of variable tension and compression worth; or extra durability is necessary for higher weight beliefs or when the measurements of the member to be solid are limited credited to some reason or other. These sorts of things make the RCC structures backbone of the engineering industry. These RCC structures with metallic are also very safe for shear and torsional pushes too.
Alterations of properties of concrete (Admixtures): - The concrete has its certain properties that sometimes are would have to be changed, because of this reasons other materials other than the basic ingredients are put into the concrete while combining. These materials are called admixtures.
Some common examples of admixtures are fly ashes, silica fume, grain husk ash, metakaolin.
Now information on these kinds of admixtures
Increase the rate of hydration and hence to increase the rate of strength development.
Reduce the environment time.
E. g. of accelerators- calcium mineral chloride, triethenolamine etc.
Retarding admixtures (Retarders): - Retarders will be the chemicals used to delay the environment and hardening of cement. Retarders decelerate the chemical process of hydration so that concrete remains clear plastic and workable for a longer time than a concrete without retarder. E. g. of retarders are sweets, calcium sulphate, skimmed milk, ammonium chloride, calcium mineral borate, calcium tartarate, mucic acid solution etc.
Increase the workability of newly mixed cement without increasing water cement percentage.
Maintain workability with reduced water cement ratio.
Sugar in addition to acting as a retarder, improves the workability of cement also. Glucose and organic acids are other types of water lowering admixtures.
Air entraining agents: - Air-entraining admixtures are being used to entrain air in form of really small disconnected air bubbles in concrete. The air bubbles (approximately. 01 to. 25mm dia) act as adaptable ball bearings and adjust the properties of clear plastic concrete. It also modifies the properties of solidified concrete.
Plasticizers: - Plasticizing admixture is a element which imparts high workability with a big decrease in normal water content (at least 20%) for confirmed workability. It also permits the use of lower drinking water cement proportion for the same workability.
Anionic chemicals such as lignosulphonates.
Nonionic surfactants such as hydroxylated carboxylic acidity.
Other products such as carbohydrates.
Calcium, sodium, and ammonium lignosulphonates are typically used as plasticizers.
Plasticizers are used in the quantity of 0. 1 to 4% by weight of concrete.
Increase the 28 days compressive strength by 30% with 20% decrease in water cement percentage.
Increase slump from 25 to 100mm.
Require 15% less concrete.
Column and beam junctions.
Pumping of concrete.
Thin wall surfaces of water keeping structures with raised percentage of steel reinforcement.
This was it about the research study of high power concrete. I have tried my best to supply the best procedure possible to every aspect of any notion. Still humans will keep making mistakes in order to learn from them. Thanks a lot.
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