Special concrete

This presentation covers the types of special concrete

1. CE6002 CONCRETE TECHNOLOGY Module 5 SPECIAL CONCRETE

2. SPECIAL CONCRETE Frequently, CONCRETE may be used for some special purpose for which special properties are more important than normal concrete In order to achieve a special concrete, suitable proportions of chemical and mineral admixtures are used. This concrete is called as special concrete. 3/5/2018 Dr.V.Kannan 2

3. SPECIAL CONCRETE (Cont) USES OF SPECIAL CONCRETE Special concrete is used in extreme weather. It has been used in large structures Good cohesiveness or sticky in mixes with very high binder content Comparable flexural strength and elastic modulus Better drying shrinkage and significantly lower creep Good protection to steel reinforcement in high chloride environment Excellent durability in aggressive sulphate environments Lower heat characteristics Low resistance to de-icing salt scaling PC pipes with good resistance to chemical attack 3/5/2018 Dr.V.Kannan 3

4. SPECIAL CONCRETE (Cont) Types of Special concrete: Depending upon the special properties of concrete, it can be classified into ten types as follows; Lightweight concrete High strength concrete Fibre reinforced concrete Ferrocement Ready mix concrete SIFCON Shotcrete Polymer concrete High performance concrete Geo polymer concrete 3/5/2018 Dr.V.Kannan 4

5. 1. LIGHTWEIGHT CONCRETE (LWC) 3/5/2018 Dr.V.Kannan 5 Think about Density of Concrete How?

6. 1. LIGHTWEIGHT CONCRETE (LWC) Lightweight concrete is a concrete whose density varies from 300 to 1850 kg/m 3 . This type of concrete mainly used to reduce the dead weight of the concrete with same load carrying capacity like normal concrete. It is achieved by using light weight aggregate or by introducing air bubbles in mortar or by omitting fines (fine aggregate). [Density of normal concrete varies from 2200 to 2600 kg/m 3 ] Type of lightweight concrete: Lightweight aggregate concrete Aerator or Cellular or Foamed concrete No-fine lightweight concrete 3/5/2018 Dr.V.Kannan 6

7. 1. LIGHTWEIGHT CONCRETE (cont) Types of Lightweight Concrete: 1. Lightweight aggregate concrete: In this concrete, lightweight aggregates are used to reduce the density of concrete. Varieties of light weight aggregates are available in natural or artificial source as follows; 3/5/2018 Dr.V.Kannan 7 Natural lightweight aggregate Artificial lightweight aggregate Pumice Diatomite Scoria Volcanic cinder Sawdust Rice husk Artificial cinder Coke breeze Foamed slag Bloated clay Expanded shales and slate Sintered fly ash Expanded perlite

8. 1. LIGHTWEIGHT CONCRETE (cont) 2. Aerator or Cellular or Foamed concrete: This concrete is achieved by introducing of air or gas into mortar so that when the mix sets and hardens, a uniform cellular structure is formed. Due to this cellular structure, the overall weight of the concrete is much reduced. Aluminium powders, Zinc are used to produce hydrogen gas. 3. No-fine lightweight concrete In this no-fine concrete, omit the fines from the conventional concrete. Its means in this concrete the fine aggregate is completely omitted and made only by coarse aggregate. The main aim is to produce large voids inside the concrete. and suitable for pavement construction 3/5/2018 Dr.V.Kannan 8

9. 1. LIGHTWEIGHT CONCRETE (cont) Advantages of Lightweight Concrete: Reduced dead load of the concrete allows longer span. This saves both labor and time. Screeds and walls where timber has to be attached by nailing. Casting structural steel to protect it against fire and corrosion or as a covering for architectural purposes. Gives heat insulation on roofs. Used in insulation of water pipes. Construction of partition walls and panel walls in frame structures. Fixing bricks to receive nails from joinery, mainly in domestic or domestic type construction. General insulation of walls. It is also being used for reinforced concrete. 3/5/2018 Dr.V.Kannan 9

10. 2.HIGH STRENGTH CONCRETE High strength concrete can be defined by compressive strength of concrete at 28 days of water curing. When the grade of concrete exceeds M35, then the concrete may be called as high strength concrete. In general, producing of HSC is difficult with the use of conventional materials like cement, aggregate and water alone and it can be achieved by using of chemical and mineral admixtures or any one of the following methods. (a) Seeding (b) Re vibration (c) High speed slurry mixing (d) Use of admixtures (e) Inhibition of cracks (f) Suphur Impregnation (g) Use of cementitious aggregates 3/5/2018 Dr.V.Kannan 10

11. 2.HIGH STRENGTH CONCRETE (Cont.) (a) Seeding: In this method, small percentage of finely ground, fully hydrated Portland cement is added to fresh concrete mix. (b) Re vibration: Mixing water to concrete mix creates continuous capillary channels, bleeding and accumulates of water at some selected places. All these reduce the strength of concrete. Hence controlled re-vibration is given after suitable time and it is increasing the strength of concrete. (c) High speed slurry mixing: This process involves advanced preparation of cement water mixture which is then blended with aggregate to produce HSC. 3/5/2018 Dr.V.Kannan 11

12. 2.HIGH STRENGTH CONCRETE (Cont.) (d) Use of admixtures: The high strength can be achieved by adding chemical admixtures such as super plasticizer and mineral admixtures such as fly ash, silica fume etc... (e) Inhibition of cracks: Inhibition or arresting of crack is needed to improve the strength of concrete. Normally, it is achieved by replacing 2-3% of fine aggregate (polythene of 0.025 mm thick and 3 to 4 mm in diameter). The polythene is act as a crack arrester. By this method the strength is much improved up to 105 MPa 3/5/2018 Dr.V.Kannan 12

13. 2.HIGH STRENGTH CONCRETE (Cont.) (f) Suphur Impregnation: Satisfactory high strength concrete has been produced by impregnating low strength porous concrete by sulphur . The process consists of the harden concrete (drying them at 120° C for 24 hours), immersing in molten sulphur under vacuum for 2 hours. By this method the strength is improved up to 58 MPa . (g) Use of cementitious aggregates: Some kind of clinkers are used as aggregate in concrete and is called cementitious aggregate ( Eg . ALAG). It gives high strength to the concrete up to 125 MPa with very low water cement ratio of 0.32. 3/5/2018 Dr.V.Kannan 13

14. 3. FIBRE REINFORCED CONCRETE 3/5/2018 Dr.V.Kannan 14

15. 3. FIBRE REINFORCED CONCRETE Fiber Reinforced Concrete can be defined as a composite material consisting of mixtures of cement, aggregate and uniformly dispersed fibers. Fiber is a small piece of reinforcing material possessing certain characteristics properties. The fiber is often described by a convenient parameter called “aspect ratio”. The aspect ratio of the fiber is the ratio of its length to its diameter. Typical aspect ratio ranges from 30 to 150. 3/5/2018 Dr.V.Kannan 15

16. 3. FIBRE REINFORCED CONCRETE Types of fibre : Following are the different type of fibers generally used in the construction industries. Steel Fiber Polypropylene Fiber GFRC Glass Fiber Asbestos Fibers Carbon Fibers Organic Fibers Natural fibre (Coir fibre , Cotton fibre , Sisal fibre , Jute fibre and Wool fibre ) 3/5/2018 Dr.V.Kannan 16

17. 3. FIBRE REINFORCED CONCRETE Necessity of Fiber Reinforced Concrete: It increases the tensile strength of the concrete. It reduces the air voids and water voids the inherent porosity of gel. It increases the durability of the concrete. Fibres such as graphite and glass have excellent resistance to creep. Deferential deformation is minimized It has been recognized that the addition of small, closely spaced and uniformly dispersed fibers to concrete would act as crack arrester It substantially improves its static and dynamic properties. 3/5/2018 Dr.V.Kannan 17

18. 3. FIBRE REINFORCED CONCRETE Factors Affecting Properties of Fiber Reinforced Concrete Relative Fiber Matrix Stiffness Volume of Fibers Aspect Ratio of the Fiber Orientation of Fibers Workability and Compaction of Concrete Size of Coarse Aggregate Mixing 3/5/2018 Dr.V.Kannan 18

19. 4.FERROCEMENT 3/5/2018 Dr.V.Kannan 19

20. 4.FERROCEMENT (Cont) “Ferro cement is a type of thin wall reinforced concrete, commonly constructed of hydraulic cement mortar, reinforced with closely spaced layers of continuous and relatively small size wire mesh. The mesh may be made of metallic or other suitable materials.” Materials for ferrocement Cement mortar mix Skeleton steel Steel mesh reinforcement 3/5/2018 Dr.V.Kannan 20

21. 4.FERROCEMENT (Cont) Advantages of ferrocement It is highly versatile and can be formed into almost any shape for a wide range of uses 20% savings on materials and cost Suitability for pre-casting Flexibility in cutting, drilling and jointing Very appropriate for developing countries; labor intensive Good fire resistance Good impermeability Low maintenance costs Reduction in self weight & Its simple techniques require a minimum of skilled labor Reduction in expensive form work so economy & speed can be achieved Only a few simple hand tools are needed to build any structures Structures are highly waterproof & Higher strength to weight ratio than R.C.C 3/5/2018 Dr.V.Kannan 21

22. 5. READY MIX CONCRETE 3/5/2018 Dr.V.Kannan 22

23. 5. READY MIX CONCRETE (cont) “Ready mix concrete is concrete mixed away from the construction site and then it is delivered to the construction site by the truck in a ready-to-use-condition is called ready mix concrete.” Advantages of Ready Mixed Concrete: Concrete is produced under controlled conditions using consistent quality of raw material. Speed of construction can be very fast in case RMC is used. Reduction in cement consumption by 10 – 12 % due to better handling and proper mixing. The mix design of the concrete can be tailor made to suit the placing methods of the contractor. 3/5/2018 Dr.V.Kannan 23

24. 5. READY MIX CONCRETE (cont) Since ready mixed concrete (RMC) uses bulk cement instead of bagged cement, dust pollution will be reduced Conservation of energy and resources because of saving of cement. Environment pollution is reduced due to less production of cement. Better durability of structure Minimizing human error and reduction in dependency on labour . Timely deliveries in large as well as small pours. No need for space for storing the materials. Reduced noise and air pollution; less consumption of petrol and diesel and less time loss to business. 3/5/2018 Dr.V.Kannan 24

25. 6.SIFCON SIFCON is a abbreviation for Slurry Infiltrated Fibrous Concrete. SIFCON is a high-strength, high-performance material containing a relatively high volume percentage of steel fibres and gives ductility. The cement slurry is introduced over the steel fibre and coarse aggregate is omitted. 3/5/2018 Dr.V.Kannan 25

26. 6.SIFCON (Cont) Advantages: The tensile strength of SIFCON is higher than ordinary FRC In FRC there is a risk of clustering. The fiber content is limited to 2 – 5% in FRC The SIFCON possess high flow ability and passing ability. SIFCON possess excellent durability, energy absorption capacity, impact and abrasion resistance and toughness. Modulus of elasticity (E) values for SIFCON specimens is more compared with plain concrete. SIFCON exhibits high ductility. Deflection for SIFCON will be very less compared to conventional and will act as rigid body. 3/5/2018 Dr.V.Kannan 26

27. 6.SIFCON (Cont) Usage /Application Area: Pavement rehabilitation and pre cast concrete products. Overlays, bridge decks and protective revetments. Seismic and explosive resistant structures. Security concrete applications. Refractory applications. Sea protective works. Military applications such as anti-missile hangers, under ground shelters. Aerospace launching platforms. Repair, rehabilitation and strengthening of structures. Concrete mega structures like offshore and long span structures, solar towers. 3/5/2018 Dr.V.Kannan 27

28. 7.SHOTCRETE or GUNITE Process of conveying dry (or damp) sand and cement by means of compressed air through material hose to a nozzle where water is added before the material is sprayed on the construction surface is called shotcrete or Gunite . Methods: Dry mix - In this dry mix the cement and sand is mixed thoroughly in dry state Wet mix - Concrete is mixed with water before conveying through delivery pipe and not suitable like dry mix 3/5/2018 Dr.V.Kannan 28

29. 7.SHOTCRETE or GUNITE (CONT) 3/5/2018 Dr.V.Kannan 29

30. 7.SHOTCRETE or GUNITE (CONT) Procedure of shotcrete on surface: Thoroughly clean all surfaces to receive shotcrete by removing loose materials and dust, pressure washing and dampen the surface to a saturated surface dry condition. Fix wire mesh to the concrete surface. The steel wire mesh has to be placed in position keeping the mesh within 10-15 mm from the surface. Suitable fixing pins are to be inserted to keep the mesh in proper position and to ensure that the weld mesh is not disturbed during shotcreting . Prepare a cement-sand / water mix and pour this mix into Pump hose for lubrication before starting to pump the production mixture When the pumped mixture reaches the nozzle, turn on compressed air. Apply shotcrete evenly to targeted surfaces. Built-up the desired thickness of shotcrete in layers of about 30 mm thick each. The presence of voids can be found by hollow hammering sound after the shotcrete has attained strength after around 3 days. 3/5/2018 Dr.V.Kannan 30

31. 7.SHOTCRETE or GUNITE (CONT) Application of Shotcrete : Shotcrete can be used to repair the damaged surface of concrete Shotcrete repair can be used for bridge deck rehabilitation repair of fire and earthquake damage and deterioration, strengthening walls. To marine structures can result from deterioration of the concrete and of the reinforcement. Shotcrete is used in underground excavations in rock used for temporary protection of exposed rock surfaces that will deteriorate when exposed to air to construct concrete swimming pools. Shotcrete floors in tanks and pools on well compacted sub-base 3/5/2018 Dr.V.Kannan 31

32. 8.POLYMER CONCRETE Polymer concrete is nothing but impregnations of monomer into the pores of harden concrete and then getting it polymerized by thermal process is called polymer concrete. By this polymerization, the strength of the concrete is much improved. Types of polymer concrete: Polymer Impregnated concrete Polymer cement concrete Polymer concrete Partially impregnated and surface coated polymer concrete 3/5/2018 Dr.V.Kannan 32

33. 8.POLYMER CONCRETE (Cont) Types of monomer: Methylmethacrylate Styrene Acrylontrile T-butyl styrene Thermoplastic monomer 3/5/2018 Dr.V.Kannan 33

34. 8.POLYMER CONCRETE (Cont) Advantages of polymer concrete: It has high impact resistance and high compressive strength. Polymer concrete is highly resistant to freezing and thawing. Highly resistant to chemical attack and abrasion. Permeability is lower than other conventional concrete. 3/5/2018 Dr.V.Kannan 34

35. 8.POLYMER CONCRETE (Cont) Application of polymer concrete: Nuclear power plants. Kerbstones . Prefabricated structural element. Precast slabs for bridge decks. Roads. Marine Works. Prestressed concrete. Irrigation works. Sewage works. Waterproofing of buildings. Food processing buildings etc. 3/5/2018 Dr.V.Kannan 35

36. 9. HIGH PERFORMANCE CONCRETE High performance concrete is a type of special concrete and it has high workability, high strength, and high modulus of elasticity, high density, low permeability and resistance to chemical attack. Normally this concrete is achieved by the following materials; Cement Fine Aggregate Coarse aggregate Water Chemical admixture ( Superplasticizer ) Mineral Admixture (Fly ash and Silica fume) Fibre etc… 3/5/2018 Dr.V.Kannan 36

37. 9. HIGH PERFORMANCE CONCRETE (Cont) Characteristic or properties of high performance concrete: High strength, High early strength High modulus of elasticity,High abrasion resistance High durability and long life in severe environments Low permeability and diffusion Resistance to chemical attack High resistance to frost and deicer scaling damage Toughness and impact resistance Volume stability Ease of placement Compaction without segregation Inhibition of bacterial and mold growth 3/5/2018 Dr.V.Kannan 37

38. 10.GEOPOLYMER CONCRETE Geopolymer concrete is an innovative and eco-friendly construction material and an alternative to Portland cement concrete. Use of geo polymer reduces the demand of Portland cement which is responsible for high CO 2  emission. Geopolymer cement concrete is made from utilization of waste materials such as fly ash and ground granulated blast furnace slag (GGBS). 3/5/2018 Dr.V.Kannan 38

39. 10.GEOPOLYMER CONCRETE (Cont ) Manufacturing of Geopolymer concrete: Both fly ash and GGBS are processed by appropriate technology and used for concrete works in the form of geopolymer concrete. The use of this concrete helps to reduce the stock of wastes and also reduces carbon emission by reducing Portland cement demand. The main constituent of geopolymers source of silicon and aluminium which are provided by thermally activated natural materials (e.g. kaolinite ) or industrial byproducts (e.g. fly ash or slab) and an alkaline activating solution which polymerizes these materials into molecular chains and networks to create hardened binder. It is also called as alkali-activated cement or inorganic polymer cement. 3/5/2018 Dr.V.Kannan 39

40. 10.GEOPOLYMER CONCRETE (Cont ) Following materials are required to produce this concrete: Fly ash – A byproduct of thermal power plant GGBS – A byproduct of steel plant Fine aggregates and coarse aggregates as required for normal concrete. Alkaline activator solution for GGBS. [Catalytic liquid system is used as alkaline activator solution. It is a combination of solutions of alkali silicates and hydroxides, besides distilled water. The role of alkaline activator solution is to activate the geopolymeric source materials containing silica (Si) and Alumina (Al) such as fly ash and GGBS.] 3/5/2018 Dr.V.Kannan 40

41. 10.GEOPOLYMER CONCRETE (Cont ) Properties of geopolymer concrete: The drying shrinkage of is much less compared to cement concrete. This makes it well suited for thick and heavily restrained concrete structural members. It has low heat of hydration in comparison with cement concrete. The fire resistance is considerably better than OPC based concrete. This concrete is chloride permeability rating of ‘low’ to ‘very low’ as per ASTM 1202C. It offers better protection to reinforcement steel from corrosion as compared to traditional cement concrete. This concrete is found to possess very high acid resistance when tested under exposure to 2% and 10% sulphuric acids. It gives better resistance to sulphate attack than normal concrete Since this concrete produces less CO 2 emission, geopolymer concrete consider as eco friendly concrete 3/5/2018 Dr.V.Kannan 41

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