Concrete Technology Assignment


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Concrete Technology Assignment

  1. 1. AggregatesAggregate is a broad category of coarse particulate material used in construction, including sand, gravel,crushed stone, slag, and recycled concrete. Aggregates are a component of composite materials such asconcrete and asphalt concrete; the aggregate serves as reinforcement to add strength to the overallcomposite material. Various construction aggregate products, which, by their individual design, are suitable for specificconstruction purposes including specific types of coarse and fine aggregate designed for such uses asadditives to asphalt and concrete mixes, as well as other construction uses. Figure 1 : 10 mm graded crushed rock or aggregate, for use in concrete. Figure 2 : 20 mm graded aggregateSources for these basic materials can be grouped into three main areas: Mining of mineral aggregatedeposits, including sand, gravel, and stone; use of waste slag from the manufacture of iron and steel;
  2. 2. and recycling of concrete, which is itself chiefly manufactured from mineral aggregates.The costs of different grades of aggregates are as follows:Description Price per tonneMacadam 3/8" (5-10 mm) Rs 338.00Macadam 1/2" (10-14 mm) Rs 338.00Macadam 3/4" (14-20 mm) Rs 324.00Macadam 1/2" & 3/4" (10-20 mm) Rs 324.00Crusher Run 0-20 mm Rs 386.00Crusher Run 0-31.5 mm Rs 369.00
  3. 3. Concrete and Other Cement-based MaterialsConcrete is a mixture of cement, water, sand, and gravel. By volume, 10 to 15% of concrete is cement.As concrete hardens, the mixture becomes stronger. The hardening process can take years. Concretehas the ability to withstand the pressure of heavy loads because it has high compression strength. It canalso be molded into any shape, can be made porous or watertight, and is a relatively cheap material foruse in construction projects.Cement is powder and is one of the main ingredients in concrete. Modern cement is made of limestone,silicon, calcium, and often aluminum and iron.The type of cement used in almost all concrete is Portland cement. Portland cement has been aroundsince 1824. The name Portland does not refer to a brand name, as many might think. The originalinventor, Joseph Aspdin, was a British bricklayer and named his new invention “Portland” because itscolor reminded him of the color of the natural limestone on the Isle of Portland which is a peninsula inthe English Channel. Figure 3 : Portland cementThe price of Portland cement is Rs 182 per 50kg bagsAlthough Portland cement is the main cement used in concrete, there are other types of cement. Thethree types that are often mentioned are Portland, blended, and hydraulic. All Portland and blendedcements are actually hydraulic cement. Hydraulic cement is actually the generic term in the construction
  4. 4. industry. It refers to any cement that will set and harden after it is combined with water. Most modernconstruction cements are hydraulic. There are six different types of hydraulic cement:Type GU: General UseType HE: High Early StrengthType MS: Moderate Sulfate ResistanceType HS: High Sulfate ResistanceType MH: Moderate Heat of HydrationType LH: Low Heat of HydrationPortland cement is a particular type of hydraulic cement. Portland cement contains hydraulic calciumsilicates.The reason that there are different types of cements is not only required because of the different usesof the cement, but also because of the type of materials available differ by location. Many of the typesdescribed above actually cross-over between the different categories. This allows for flexibility inparticular construction projects.Concrete is a composite construction material composed primarily of aggregate, cement and water.Various chemical admixtures are also added to achieve varied properties. Water is then mixed with thisdry composite which enables it to be shaped (typically poured) and then solidified and hardened intorock-hard strength through a chemical process known as hydration. The water reacts with the cementwhich bonds the other components together, eventually creating a robust stone-like material. Concretehas relatively high compressive strength, but much lower tensile strength. For this reason it is usuallyreinforced with materials that are strong in tension (often steel). Concrete can be damaged by manyprocesses, such as the freezing of trapped water. Figure 4 : Installing reinforcements in a floor slab during a concrete pour
  5. 5. Mineral admixtures are fine-grained materials that are added to the concrete mix to improve theproperties of concrete, or as a replacement for Portland cement (blended cements). Examples are:Fly ash: A by-product of coal-fired electric generating plants; it is used to partially replace Portlandcement (by up to 60% by mass). The properties of fly ash depend on the type of coal burnt.Ground granulated blast furnace slag (GGBFS or GGBS): A by-product of steel production is used topartially replace Portland cement (by up to 80% by mass). It has latent hydraulic properties.Silica fume: A by-product of the production of silicon and ferrosilicon alloys. Silica fume is similar to flyash, but has a particle size 100 times smaller. This results in a higher surface to volume ratio.High reactivity Metakaolin (HRM): Metakaolin produces concrete with strength and durability similar toconcrete made with silica fume. While silica fume is usually dark gray or black in color, high-reactivitymetakaolin is usually bright white in color, making it the preferred choice for architectural concretewhere appearance is important.The prices for concrete are as follows:Description Price per m3Premix Concrete Grade 15 Rs 2977.00Premix Concrete Grade 20 Rs 3085.00Premix Concrete Grade 25 Rs 3215.00Premix Concrete Grade 30 Rs 3347.00Premix Concrete Grade 35 Rs 3470.00Premix Concrete Grade 40 Rs 3485.00Lightweight Concrete Rs 6478.00
  6. 6. Wood and wood productsEngineered wood products, glued building products "engineered" for application-specific performancerequirements, are often used in construction and industrial applications. Glued engineered woodproducts are manufactured by bonding together wood strands, veneers, lumber or other forms of woodfiber with glue to form a larger, more efficient composite structural unit. These products include gluedlaminated timber (glulam), wood structural panels (including plywood, oriented strand board andcomposite panels), laminated veneer lumber (LVL) and other structural composite lumber (SCL)products, parallel strand lumber, and I-joists.Engineered wood products display highly predictable and reliable performance characteristics andprovide enhanced design flexibility: on one hand, these products allow the use of smaller pieces, and onthe other hand, they allow for bigger spans. They may also be selected for specific projects such aspublic swimming pools or ice rinks where the wood will not deteriorate in the presence of certainchemicals, and are less susceptible to the humidity changes commonly found in these environments.Engineered wood products prove to be more environmentally friendly and, if used appropriately, areoften less expensive than building materials such as steel or concrete. These products are extremelyresource-efficient because they use more of the available resource with minimal waste. In most cases,engineered wood products are produced using faster growing and often underutilized wood speciesfrom managed forests and tree farms.Wood unsuitable for construction in its native form may be broken down mechanically (into fibers orchips) or chemically (into cellulose) and used as a raw material for other building materials, such asengineered wood, as well as chipboard, hardboard, and medium-density fiberboard (MDF). Such woodderivatives are widely used: wood fibers are an important component of most paper, and cellulose isused as a component of some synthetic materials. Wood derivatives can also be used for kinds offlooring, for example laminate flooring.Description Price per m2Plywood for fairface formwork Rs 265.00Plywood for rough formwork Rs 133.00
  7. 7. Bituminous Materials and MixturesPitch is the name for any of a number of viscoelastic, solid polymers. Pitch can be made from petroleumproducts or plants. Petroleum-derived pitch is also called bitumen. Pitch produced from plants is alsoknown as resin.Tar pitch is a viscoelastic polymer. This means that even though it seems to be solid at roomtemperature and can be shattered with a hard impact, it is actually fluid and will flow over time, butextremely slowly. The heating (dry distilling) of wood causes tar and pitch to drip away from the woodand leave behind charcoal. The terms tar and pitch are often used interchangeably. However, pitch isconsidered more solid while tar is more liquid.Asphalt, also known as bitumen, is used in road construction, where it is used as the glue or bindermixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminouswaterproofing products, including production of roofing felt and for sealing flat roofs. Figure 5 : Refined asphaltDescription Price per m2Asphalt concrete base (binder) course, 80mm thick Rs 992.00Asphalt concrete wearing course, 50mm thick Rs 646.00
  8. 8. SteelStructural steel is steel construction material, a profile, formed with a specific shape or cross section andcertain standards of chemical composition and mechanical properties. Structural steel shape, size,composition, strength, storage, etc., is regulated in most industrialized countries.A rebar is a common steel bar, and is commonly used as a tensioning device in reinforced concrete andreinforced masonry structures holding the concrete in compression. It is usually formed from carbonsteel, and is given ridges for better mechanical anchoring into the concrete.Figure 6 : A tied rebar beam cage. This will be embedded inside cast concrete to increase the tensile strength of the concrete.Steel has an expansion coefficient nearly equal to that of modern concrete. If this were not so, it wouldcause problems through additional longitudinal and perpendicular stresses at temperatures differentthan the temperature of the setting. Although rebar has ribs that bind it mechanically to the concrete, itcan still be pulled out of the concrete under high stresses, an occurrence that often precedes a larger-scale collapse of the structure. To prevent such a failure, rebar is either deeply embedded into adjacent
  9. 9. structural members (40-60 times the diameter), or bent and hooked at the ends to lock it around theconcrete and other rebar. This first approach increases the friction locking the bar into place, while thesecond makes use of the high compressive strength of concrete.Welded wire mesh is a steel reinforcement material in concrete. The mesh is used for replacing thetraditional "cut & bend" and placing of steel thermo-mechanical treated bars. The mesh is an electricfusion welded prefabricated reinforcement consisting of a series of parallel longitudinal wires withaccurate spacing welded to cross wires at the required spacing. Machines are used to produce the meshwith precise dimensional control. The product results in considerable savings in time, labour and money.In wet and cold climates, reinforced concrete for roads, bridges, parking structures and other structuresthat may be exposed to deicing salt may benefit from use of epoxy-coated, hot dip galvanized orstainless steel rebar, although good design and a well-chosen cement mix may provide sufficientprotection for many applications. Epoxy coated rebar can easily be identified by the light green color ofits epoxy coating. Hot dip galvanized rebar may be bright or dull grey depending on length of exposure,and stainless rebar exhibits a typical white metallic sheen that is readily distinguishable from carbonsteel reinforcing bar.Description Price6mm, 5.5m Rs 41.408mm, 9m Rs 122.7710mm, 9m Rs 191.6612mm, 9m Rs 276.0016mm, 9m Rs 492.8620mm, 9m Rs 766.6725mm, 9m Rs 1189.65
  10. 10. PlasticsIn building construction, plastics abound in plumbing fixtures, siding, flooring, insulation,panels, doors, windows, glazing, bathroom units, gratings, railings and a growing list of bothstructural and interior or decorative uses.For pipes, valves and fittings, plastics offer superior corrosion resistance and are lighter, easier toinstall, and more cost effective than their alternatives. Impervious to chemicals and sulfur-bearing compounds, plastic piping safely transports everything from fresh water to salt water,and from crude oil to laboratory waste.These qualities also have combined with plastics high strength-to-weight ratio to producematerials for bridge construction, including tough reinforcement rods, nonskid surfacing andquickly installed replacement decking.For commercial buildings that contain sensitive electronic equipment, plastics can provide highlyprotective housing that does not interfere with radio frequency or magnetic waves.Description Price per mPolystyrene, 25mm thick Rs 40.00PVC pipe, 160mm diameter Rs 256.67PVC pipe, 110mm diameter Rs 82.50PVC pipe, 75mm diameter Rs 47.50PVC pipe, 63mm diameter Rs 44.17
  11. 11. ReferencingNational Schedule of Rates by Construction Industry Development Board from Quicaillerie Bon Marché, Phoenix