LECTURE - 5

LIGHT WEIGHT CONSTRUCTION MATERIALSThe Northcap University, Gurgaon1UNIT-1LECTURE - 7Brig. S.K. Sharma (Retd.) Pro Vice Chancellor and Professor Department of Civil Engineering, The Northcap University, Gurgaon

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INDEXThe Northcap University, Gurgaon2WASTE MATERIAL BASED CONCRETEINDUSTRIAL WASTES

INDUSTRIAL WASTES

Some of the industrial by-product wastes can be profitably used in the concrete construction industry which requires large quantities of low cost raw materials. This utilization offers triple benefits, namely, conservation of fast-declining natural resources, planned gainful exploitation of waste materials and release of valuable land for more profitable use. The most influential factor that dictates the utilization of industrial by-products is the economic cost in comparison to the conventional materials that would have been otherwise used. 3The Northcap University, Gurgaon

BLAST-FURNACE SLAG: Large quantities of slag are generated during the production of iron and steel. Granulated or foamed or dense blast-furnace slag can be produced depending on the rate and manner of cooling the molten slag. The granulated slag can be used in the manufacture of slag cements. Blast-furnace slag cements contain slag up to 60 per cent, hence there is considerable reduction in the rate of heat evolution and a significant increase in the resistance to chemical attack. For the same reasons, these cements can be advantageously used in mass concrete, and for high chemical resistance in marine structures. The dense air-cooled slag aggregate may be used as a replacement of natural aggregate in concrete. On the other hand, foamed blast-furnace slag, a lightweight aggregate, is mainly used for block making and insulating roofs and floor screeds and is suitable for structural reinforced concrete. 4The Northcap University, Gurgaon

COAL ASH FROM POWER STATIONS: The main by-product is fly ash or pulverized fuel ash which is the fine dust carried upward by combustion gases and collected in wet scrubbers and electrostatic precipitators. The bulk ash which is greyish in color becomes darker with increasing proportions of unburnt carbon. It is used as a cement replacement. The contribution of fly ash to the strength of concrete has been attributed to: Direct water reduction.Increase in the effective volume of paste in the mixPozzolanic reactionHowever, fly ash reduces the rate of development of strength and increases drying shrinkage. Since the early strength of fly ash concrete is less than that of Portland cement, its proportion is generally limited to 30 per cent in the situations where early strength is important. The low rate of heat evolution makes fly ash useful in mass concrete. 5The Northcap University, Gurgaon

SILICA-FUME CONCRETE: Silica-fume is a by-product of the reduction of high purity quartz with coal in electric arc furnaces in the production of ferro-silicon metal. Because of its extreme fineness and high glass content, Silica-fume is a very efficient pozzolanic material i.e., it is able to react efficiently with the hydration products of Portland cement in concrete.6The Northcap University, Gurgaon

Silica-fume in concrete can be used for the following purposes:To conserve cementTo produce ultra high strength concreteTo control alkali-silica reactionTo reduce chloride associated corrosion and sulfate attackTo increase early age strength of fly ash/slagconcrete.7The Northcap University, Gurgaon

SHOTCRETE OR GUNITING Shotcrete is mortar or very fine concrete deposited by jetting it with high velocity (pneumatically projected or sprayed) on to a prepared surface. The system has different proprietory names in different countries such as Blastcrete, Blowcrete, Guncrete, Jet-crete, Nucrete, Plneukrete, Spraycrete, Torkrete, etc.Shotcrete has wide applications in different constructions, such as thin over-head vertical or horizontal surfaces, particularly the curved or folded sections; canal, reservoir and tunnel lining; swimming pools and other water-retaining structures and prestressed tanks. Shotcrete is very useful for the restoration and repair of concrete structures, fire damaged structures and waterproofing of walls.8The Northcap University, Gurgaon

Shotcrete has also been successfully used in the stabilization of rock slopes and temporary protection of freshly excavated rock surfaces. Its utility has been proved for protection against long-term corrosion of piling, coal bunkers, oil tanks, steel building frames and other structures as well as in encasing structural steel for fireproofing. 9The Northcap University, Gurgaon

TYPES OF SHOTCRETINGDRY MIX PROCESS: In the dry mix process, the mixture of cement and damp sand is conveyed through a delivery hose pipe to a special mechanical feeder or gun called delivery equipment. The mixture is metered into the delivery hose by a feed wheel or distributor. This material is carried by compressed air through the delivery hose to a special nozzle. The nozzle is fitted with a perforated main fold through which water is introduced under pressure and intimately mixed with other ingredients. The mortar is jetted from the nozzle at high velocity on to the surface to be shot crated. The water-cement ratio should be between 0.33 and 0.50.Video: C&D Waste (Construction & Demolition) Recycling Process - 3:51 minConstruction waste crusher, construction waste disposal equipment 4:10 minInground swimming pool building process - step by step 31:21 minBridge Repair, Gunite, Shotcrete, Concrete Repair, Cyclone Gunite Machine Demonstration 7:36 min

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The Northcap University, Gurgaon11

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