Special Types of Concrete Application of waste/Recycled materials in concrete Foundry Sand ◦ By product of ferrous/Non-ferrous metal casting Fly Ash ◦ By product of coal Silica Fume ◦ By product of silicon/silicon alloy Slag ◦ Co-product of iron & steel making process Waste Rubber ◦ Waste tyres Waste Plastic/waste Glass Plastic Aggregate Waste Glass Aggregate Types Reinforced cement concrete (RCC) Ready mixed concrete (RMC) Fiber reinforced concrete ( FRC) Ferro-cement concrete(FCC) Light weight aggregate concrete (LAC) High density concrete (HDC) High performance concrete(HPC) Polymer concrete Radio active concrete(RAC) Foamed concrete Pavement quality concrete(PQC) RCC Definition= Concrete + Steel bars. Advantages high compressive strength Adequate tensile strength Fire and weather resistance More durable Economically mold into a nearly shapes. Low maintenance cost Less skill labour Disadvantages Tensile strength to comp. strength ratio High form cost Larger column section Shrinkage RAC Less specific gravity High water absorption Less bulk density Relatively less compressive strength Less modulus of elasticity Flexural strength (0.95-7.2 Mpa) Splitting tensile strength (0.3-3.1 Mpa) Advantages of RAC • Reduces the amount of material that would be delivered to a landfill • Reduces the need of virgin aggregates to be created • reduces the amount of CO2 in the atmosphere. • Highly heat insulating • Low weight and high compressive strength • Resistant to chemical and alkaline attack • Excellent thermal and sound resistant properties Disadvantages Decrease modulus and strength Greater moisture shrinkage Higher water absorption (3%-9%) Reduced workability Lower bulk specific gravity HSC High strength concrete has compressive strength of up to 100 MPa as against normal concrete of 50 Mpa. VHSC (100MPa-200MPa),UHSC(>200MPa) Methods of producing HSC ◦ Seeding ◦ Revibration ◦ High speed slurry mixing ◦ Use of admixtures ◦ Inhibition of cracks ◦ Sulphur Impregnation ◦ Use of cementatious aggregates Advantages Reduction in member size(i.e self weight reduction) Reduction in form work. Increases the stability to withstand heavy loads Supirior durability & long term performance Lower creep & shrinkage Higher resistance to crack & chemical attack Reduced maintenance cost. Applications Railway bridge, Highway bridge High-rise concrete buildings Steel concrete structures Railway sleepers RC Piles Machine foundations FRC ( concrete + Fibres ) Fibre reinforced concrete can be defined as a composite material consisting of mixtures of cement mortar or concrete and discontinuous, descrete, uniformly dispersed suitable fibres. Shape of Fibres Types of Fibres Steel Fibres ◦ Length-0.1-7.62cm ◦ Diameter-0.25-0.75mm ◦ Aspect Ratio-30-150 Advantages ◦ High strength ◦ Holds the cracks tightly, thus improves durability ◦ Less steel reinforcement required ◦ Improves ductility ◦ Improves impact & abrasion resistance Glass fibres (ɸ=9-15µm) Plastic fibres(ɸ=20-200µm) Carbon fibres(ɸ=9µm) Asbestos fibres Benefits of fibres (Role) To arrest the cracks Increase the ductility of concrete elements More resistance to impact load Lowers the permeability & bleeding of water Improved resistance to freezing & thawing Increases tensile strength & impact strength Advantages Reduction in shrinkage & cracking Improvement in bond strength Enhancement of fatigue strength & endurance limit Better toughness Lower permeability of concrete Disadvantages Greater reduction of workability. High cost of materials. Applications Polymer concrete Polymer concrete composites are produced by combined processing of polymeric materials with the ingredients of concrete. Types ◦ Polymer-imprignated concrete ◦ Resin concrete ◦ Polymer modified concrete Advantages Good bond with old concrete Improved durability, resistance to chemical attack & abrassion Reduction in water absorption upto 80-100% Reduces the permeability of concrete Compressive strength of concrete increased by 100%-150%. Applications Ferrocement defined as a composite material obtained by reinforcing the cement mortar with steel fibers in the form of a wire mesh. While the mortar provides the mass, steel fiber imparts tensile strength and ductility to the material. It can take almost any shape and is adaptable to almost any traditional design. Structures are thin and light. 30% reduction in dead weight on supporting structure, 15% saving in steel consumption and 10% in roof cost has been estimated. suitable for manufacturing the precast units which can be easily transported. The construction technique is simple and not required highly skilled labour. Elimination of formwork is possible. Damage repairable is easy. Where timber is scarce and expensive, ferrocement is a useful substitute. As a roofing material, ferrocement is a climatically and environmentally more appropriate and cheaper alternative, to galvanized iron and asbestos cement sheeting. Cheaper than normal concret, requires no formwork, is lighter, and has a ten times greater specific surface of reinforcement, achieving much higher crack resistance. Ferrocement is not attacked by biological agents, such as insects, vermin and fungus. Applications of FCC Marine Structures Tank construction Chimney Construction Bench Wall & Water tank Housing Application in Rural Energy Application in Industrial Structures Foamed Concrete Also known as cellular concrete, it contains more than 20% of air. W/c=0.6, Comp. Strength=1-25 MPa Advantages Aesthetic view is good Fire resistant Thermal insulator More durable Speedy construction Easy to transport Disadvantages Very sensitive with water content in the mixtures Mixing time is longer than conventional Less Compressive and flexural strengths Difficult to place and finish Applications Light weight blocks/precast panels In-situ wall construction Heat/sound insulation for floor & walls Floor construction SCC Self-consolidating concrete is a highly flowable type of concrete that spreads into the form without the need for mechanical vibration. Materials ◦ Cement ◦ CA/FA ◦ Water ◦ Mineral Admixtures/Chemical Admixtures ◦ Fibres Properties Filling ability Passing ability Segregation resistance Ease of placement Speed of placement Less noise Advantages Elimination of vibration problems Faster construction Greater freedom in design Less noise from vibrators Ease of placement results in reduction in cost Improves quality, durability & reliability Reduced wear & tear Reduced permeability Reduced equipment cost Applications Bridge/Precast units In congested reinforcements New type of elements which are not possible by normal concrete HPC It can produced by low W/C of 0.3-0.35, finer cements, more C3S. Strength 60-100 MPa. High performance concrete is used for concrete mixture possess high workability, high strength, high modulus, high density, high stability, low permeability. Advantages High strength High early strength High modulus of elasticity High abrasion resistance High durability in severe conditions Resistance to chemical attack Toughness/impact resistance Ease of placement Speedy construction Long term strength Applications Pavement quality concrete The concrete slab is generally of M40- M50 grade of concrete as per IS code and is called as paving quality concrete. Applications Airfield/Road pavements .