Advances in Concrete TechnologyDocument Transcript
Advances in Concrete Technology By, M. Mayur, Siddharth Institute of Engineering and Technology, Puttur.Abstract: Workability. Cement is main and most important material in Concrete. It is aConcrete is the only binding material which mixture of Calcareous Materials andis used from ages till now. But we did not Argillaceous Materials. These materials canfind any kind of material which replaces it. be mixed in presence of water and also inSince it is a mixture of Cement, Aggregates absence of water. Wet Process meansand Water in a required or calculated ratio. mixing of raw materials used for cement inBut advances in concrete technology presence of Water and Dry Process meansincludes the properties of concrete such as mixing them even in presence of water butWorkability, Strength, Durability and so on. not as much as Wet Process. AfterBut this present scenario describes about completion of all above processes, we getAdvances in Concrete Technology such as Cement in a bag of 50 kgs.Admixtures, Plasticizers, Super plasticizers,Retarders. The usage of these materials hasbecome a lift for Structural Engineers tobring down big constructions in usage in asmaller time. But in general, Advances inConcrete Technology deals with increase inStrength and Durability of Concrete andincreasing Workability to required time. So,the present paper deals with Advances inConcrete Technology and their impacts onstructures building by using them. An aggregate includes Fine Aggregates and Coarsed Aggregates. Fine Aggregates includes Sand and Coarsed AggregatesIntroduction: includes Gravels.Concrete is a mixture of Cement,Aggregates and Water. Cement is mostimportant material in Concrete. Anaggregate consumes about 70% - 80% ofvolume of Concrete. Water is used to bindthe above materials and to give some
Fresh Concrete is such concrete in which Concrete is in plastic state. Hardened Concrete is next to Fresh type of Concrete means it gains 90% more strength than Fresh Concrete. Each of the above concrete’s has their own uses and their own applications and their properties unique to them.The above diagram shows different types ofAggregates such as Rounded, Flaky and Advances in CT:Irregular Shapes of Aggregates. Aggregatesalso have some strength. The main advances in CT deals with action of :Properties: Plasticizers,The main properties of Concrete areWorkability, Strength, Durability, Elasticity, Super plasticizers,Creep and Shrinkage. The advances in Retarders,Concrete Technology mean increase inStrength, Workability and Durability of Accelerators,Concrete. Air – entraining admixtures,Types of Concrete: Puzzolanic Admixtures,There are different types of Concrete. Someof them are: Damp – proofing Admixtures, Fresh Concrete Gas forming Admixtures, Hardened Concrete Workability Admixtures, Special Concrete Bonding Admixtures, Light – Weight Concrete Colouring Admixtures and Fibre Reinforced Concrete Corrosion Inhibiting Admixtures. Reinforced Cement Concrete Not only these, but these also includes Construction Chemicals such as: High Density Concrete • Concrete Curing Compounds, Self Compacting Concrete(SCC) • Mould Releasing Agents, • Non – shrink high Strength Grout, • Surface Retarders, • Ready to use Plaster, • Guniting Aid and
• Protective Coatings. 1. These are Water Reducers.The above mentioned Compounds are useful 2. In general, the water – cement ratioin not only increasing Strength, Durability of concrete is 0.40, but when theseand Workability of Concrete but they are are used they reduce w/c ratio to 5%also useful in giving protection to concrete, to 15%.creates bonds between the materials ofconcrete, and gives attractive colours to 3. The reduction of w/c ratio naturallyconcrete and also they reduce water to a increases Strength of Concrete.great extent which is a severe crisis in now – 4. These are composition ofa – days. lignosulphonates, salts of In past times, while construction of sulphonates hydrocarbons.bridges, they construct piers to support 5. They contain nonionic surfactantsbridges which are to be constructed in a such as polyglycol esters, acid ofdeep way below the water level in Sea or hydroxylated carboxylic acids.River. That was a serious problem at thosetimes. Since, some of problems such as: 6. Efficient Plasticizer is one which does not cause air – entrainment in At such great depths, temperature concrete more than 1% - 2%. will be high and concrete can loose moisture at those depths, and it sets 7. Dispersion Effect and Retarding from that point. Effects are main actions of Plasticizers. Transportation of Concrete to such great depths is also a problem with help of pulleys etc… Not only in depths, but when tallest buildings are constructed concrete is to be transported to top most floor of building which has to take place with in 5 minutes, since the initial setting time of OPC is 5 min.From that point of view, some of expertsobserved the properties of Concrete, and Action of Super plasticizers:they gave some formulae for initial and finalsetting time of concrete, from which 1) These are High Range Waterconcrete can be made to gain early strength Reducers.and also at the same time to gain strength 2) Their use was developed in Japaneven after 30 min. So, this can be said as and Germany in 1960 and 1970.ADVANCES IN CONCRETETECHNOLOGY. 3) Usage of Super plasticizers reduces the w/c ratio upto 30% withoutExplanation of Compounds: reducing workability.Action of Plasticizers:
4) They reduce w/c ratio to 0.25 or even a. Accelerators are also mixed with more. plasticizers. 5) They can produce more workable b. They are added to concrete to concrete at same w/c ratio. increase the rate of early strength development. 6) For same workability, they produce usage of lower w/c ratio. c. They permit early removal of formwork. 7) It also permits reduction on Cement Content too… d. They reduce required period of curing. e. They advance the time that a structure can be placed in service. f. They are used in emergency repair work.Action of Retarders: Action of Air – entraining a) They are also called as Retarding Admixtures: Plasticizers. I. One of the most important b) Retarders are mixed with plasticizers advancements made in concrete to form Retarding Plasticizers for technology was the discovery of commercial purposes. air entrained concrete. c) These are used in RMC for retaining II. Air entraining agents are the slump loss during high considered as FIFTH temperature, long transportation, to INGREDIENT in concrete avoid construction or cold joints. making. III. They occupy 85% of concrete manufactured in America contains one or other type of air entraining agent. IV. Entrained air and Entrapped air are different groups in Air entraining admixtures.Action of Accelerators:
V. Natural wood resins, animal and a. A gas forming agent is a chemical vegetable oils, alkali salts, resin admixture such as aluminium acids, sodium salts of petroleum powder. sulphonic acids are types of air entraining admixtures. b. It reacts with the hydroxide produced in hydration of cement to produceAction of Mineral Admixtures: minute bubbles of hydrogen gas. i. These are also called as Puzzolanic c. Action of Aluminium powder causes materials. a slight expansion in plastic concrete or mortar and this reduces ii. Puzzolona addition in concrete settlement. improves increases the water tightness, reduce the alkali Action of Workability Agents: aggregate reaction, and improves extensibility, workability and lower 1. Workability is most important costs. characteristic of concrete. iii. Puzzolanic materials are siliceous or 2. Finely divided materials, siliceous and aluminous materials plasticizers, super plasticizers, air with out cementitious values. entraining agents are used as workability agents. iv. Clay and Shales, Opalinc Cherts are Natural Puzzolonas. 3. The property of concrete which is placed and compacted 100% v. Fly ashes, Rice Husk ash, Surkhi without air voids is called are Artificial Puzzolonas. Workability.Action of DP and WP Admixtures: A. Important requirement of concrete is that it should be impervious to water when subjected to pressure of water on one side and B. Absorption of surface water by capillary action. Action of Bonding Agents: C. Vegetable oils, fats, waxes are some 1. These are water emulsions of kind of water proofing admixtures. several organic materials that are D. Calcium or Ammonium stearate or used to grout for application to an oleate will mainly act as water old concrete surface just prior to repelling materials. patching. E. Butyl Stearate is superior to soap as 2. Natural Rubber, Synthetic Rubber,, water repellent material in concrete. Poly vinyl Chloride are Bonding Agents.Action of Gas Forming Agents:
3. They are added to 5 to 20% of 2. Sodium Benzoate was used as weight of cement. Corrosion Inhibiting Agents. 3. 2% of Sodium Benzoate is used in water. 4. Calcium Lignosulphate decreased rate of corrosion of steel in concrete.Action of Colouring Admixtures: I. The requirements of suitable admixtures include : 1. Colour fastness when exposed to sunlight, Effect of Compounds on Properties of 2. Chemical stability in presence Concrete: of alkalinity produced in set Workability: cement, Generally, concrete is to have more 3. No adverse effect on setting workability, if water content in time and strength. concrete is reduced, usually its II. They are used to give attractive workability is lost which is not colours and even pleasant good colours. So, in such cases, we use III. They are used in RMC to arrest plasticizer which not only reduces possible cracks and craziness in water content in w/c ratio up to floor. 15% of original content but also increases workability even with that less quantity of water. Super plasticizers, they even reduce water content up to 30%, which is double of plasticizers. So, it is mostly used in many constructions where water scarcity is a big problem. OPC sets at a time of even 5Action of Corrosion Inhibiting Agents: minutes, which is not wanted in many number of constructions. So 1. The problem of corrosion of to retard the initial setting time, reinforcement is universal problem. some of compounds such as Retarders are used. The main use
of them is to retard the Initial used in Constructions as they give Setting Time of concrete. good strength. Accelerators are also used to The better the workability of accelerate Initial and also Final concrete, the better the strength of Setting Time of Concrete. concrete, so workability agents play role in improving strength of Air entraining admixtures are very concrete. important in concrete, so, they are considered as Fifth Ingredient in Without proper bond between the Concrete components of concrete, the concrete cannot with stand loads, Workability agents are mainly to give more strength Bonding useful to give better workability for Agents are necessary to be used. concretes. Colouring admixtures does not Bonding agents are mainly used to give any strength to concrete but bring a good bond between they can give pleasant colours to components of concrete. concrete. Colouring and Corrosion Inhibiting Corrosion inhibiting agents are Admixtures are mainly useful to useful in preventing corrosion to give pleasant colours and also to reinforcements in concrete. reduce corrosion effects on Reinforcements in Concrete.On Strength: On Durability: Plasticizers not only reduces w/c As strength increases, durability ratio but also gives good strength. also increases. So all the above discussed compounds have good Super plasticizers are not only high durability as far as they are used in range water reducers they also give a limited and in calculated manner. more strength than general w/c ratio concrete. Though, plasticizers affect PVC coatings, but not so much, but Accelerators are mainly used to get these play a vital role in improving Early Strength of Concrete. strength, durability and workability of concrete. Retarders are also useful to gain strength but in late time. Uses: Air entraining admixtures are While constructing bridges, piers mainly considered as Fifth supporting bridges must be strong Ingredient in Concrete, so it also enough to support and carry loads gives good strength to concrete. coming on to it. Mineral admixtures are Puzzolanic So, to have better workability and materials which includes Fly ash, strength, we use some of Rice Husk which are presently
compounds such as Plasticizers, To give pleasant Colour to Super plasticizers, Accelerators, concrete, we add colouring agents. Retarders. To give good strength, Piers are to constructed inside reinforcements should not be water. If any concrete structure is corroded. To prevent that, we use placed in water, it collapses. corrosion inhibiting agents. To prevent such collapses, we use To have better workability, we use ACCELERATORS, which are workability agents which are used wonderful invention in Civil in many cases such as construction Engineering. of underground works, piers. Accelerators, they accelerate the Concrete Curing Compounds, initial setting time of concrete to 1 to 1.5 minutes. So, as if pour Mould Releasing Agents, Non – concrete inside piers, the concrete shrink high Strength Grout, Surface starts to set inside the hollow Retarders, columns and pier is constructed Ready to use Plaster, Guniting Aid inside water. are Protective Coatings are many types If the construction is done at a of construction chemicals which are business site, it is almost used at construction site which give impossible to mix concrete at site better workability and also prevent itself. cracks and problems coming in future. So, we have to transport concrete from manufacturing industries. As they travel from industries to site, the concrete may set. So to retard the setting time of concrete, Retarders are used. Not only in such cases, when concrete is to be sent at very lower depths, at about, 600 – 700 feet below, they due to heat evolving there, concrete may loose water and they may set. To prevent Initial Setting time, we use Retarders. To have a good bond between components of concrete, we use Bonding Agents.
Conclusion: There is no particular conclusion for Advances in Concrete Technology, since technology is increasing day by day. But as Civil Engineers we have to concentrate on Economy and Durability of Structures. Since: WE ARE THE ONLY HOPES OF TOMMORROW’S WONDERFUL CONSTRUCTIONS.These are some of constructionsbuilt by using above mentionedcompounds.