BT 1: Concrete and Admixtures

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BT 1: Concrete and Admixtures

  1. 1. Concrete and AdmixturesReported by: Morales, Zani Gamaliel F. Odiame, Yeoj C.Submitted to: Arch. Sylvester, Seño D. CONCRETE AND MIXTURES Morales, Zani Gamaliel F. / Odiame, Yeoj C. BUILDING TECHNOLOGY – 1 / 10:00 – 11:00
  2. 2. History / Origin of Concrete• Concrete comes from the Latin word "concretus" (meaning compact or condensed), the perfect passive participle of "concrescere", from "con-" (together) and "crescere" (to grow).• Modern tests show that opus cae-menticium had as much compressive strength as modern Portland-cement concrete (ca. 200 kg/cm2).Two important details: 1. Its mix consistency is fluid and homogeneous, allowing it to bepoured into forms rather than requiring hand-layering together with theplacement of aggregate. 2. Integral reinforcing steel gives modern concrete assemblies greatstrength in tension, whereas Roman concrete could depend only upon thestrength of the concrete bonding to resist tension. CONCRETE AND MIXTURES Morales, Zani Gamaliel F. / Odiame, Yeoj C. BUILDING TECHNOLOGY – 1 / 10:00 – 11:00
  3. 3. History / Origin of Concrete• The baths of Caracalla in Rome are just one example.• Some have stated that the secret of concrete was lost for 13 centuries until 1756, when the British engineer John Smeaton pioneered the use of hydraulic lime in concrete, using pebbles and powdered brick as aggeregate. CONCRETE AND MIXTURES Morales, Zani Gamaliel F. / Odiame, Yeoj C. BUILDING TECHNOLOGY – 1 / 10:00 – 11:00
  4. 4. Difference• Roman Conrete – Made of quicklime , pozzolana and an aggregate of pumice during the Roman Empire (old concrete used by the Romans, did not use any steel reinforcing bars) – Widespread use of concrete in Roman structures • Freed Roman construction from restrictions of stone and brick materials • Allowed for revolutionary new designs in terms of structural complexity and dimensions – Had much compressive strength as modern Portland cement – Tensile strength is lower without steel reinforcement – Mix consistency requires hand layering together with placement of aggregate that consisted of rubble – Depend upon the strength of concrete bonding to resist tension• Modern structural concrete - Mix consistency is fluid and homogenous - Could be poured into forms - Integral reinforcing steel gives modern concrete assemblies great strength in tension CONCRETE AND MIXTURES Morales, Zani Gamaliel F. / Odiame, Yeoj C. BUILDING TECHNOLOGY – 1 / 10:00 – 11:00
  5. 5. Chemical AdmixtureChemical Admixtures are materials in the form of powder or fluids thatare added to the concrete to give it certain characteristics notobtainable with plain concrete mixes. In normal use, admixturedosages are less than 5% by mass of cement and are added to theconcrete at the time of batching/mixing.Types of Admixtures• Accelerators - speed up the hydration (hardening) of the concrete.• Retarders – slow the hydration of concrete.• Plasticizers – increase the workability of plastic or fresh concrete.• Pigments – can be used to change the colour of concrete, for aesthetics.• Air-entraining agents - stop formation of air bubbles in concrete, used in freezing locations. CONCRETE AND MIXTURES Morales, Zani Gamaliel F. / Odiame, Yeoj C. BUILDING TECHNOLOGY – 1 / 10:00 – 11:00
  6. 6. Concrete mixture and proportionsMixture Class Proportion Cement in Bag Sand Gravel Cement : 40 kg 50 kg Cubic Meter Cubic Meter Sand : Gravel Class AA 1:1½:3 12 9.5 0.5 1.0 Class A 1:2:4 9.0 7.0 0.5 1.0 Class B 1:2½:5 7.5 6.0 0.5 1.0 Class C 1:3:6 6.0 5.0 0.5 0.1Compressive Strength (pounds per sq. inch) of Mixture and their Application /Usage a. Class AA - - 4000 PSI (retaining walls, concrete under water) b. Class A - 3500 PSI (beams, slabs, footings, columns) c. Class B - 3000 PSI d. Class C - 2500 PSI (planboxes, non-critical areas) CONCRETE AND MIXTURES Morales, Zani Gamaliel F. / Odiame, Yeoj C. BUILDING TECHNOLOGY – 1 / 10:00 – 11:00
  7. 7. Concrete mixture and proportionsNote: Commercially-available Portland cement bags come in 40kg and 50kg quantitiesMixture Class Proportion Cement in Bag Sand Gravel Cement : 40 kg 50 kg Cubic Meter Cubic Meter Sand : Gravel Class AA 1:1½:3 12 9.5 0.5 1.0 Class A 1:2:4 9.0 7.0 0.5 1.0 Class B 1:2½:5 7.5 6.0 0.5 1.0 Class C 1:3:6 6.0 5.0 0.5 0.1Meaning: Class AA concrete Meaning: Class AA concrete using 40 kg Portlandhas 1 part Cement, 1.5 parts cement bag (bought from hardware), will beSand and 3 parts Gravel in equivalent to 12 bags of 40-kg Portland cement +terms of proportion. 0.5 cubic meters (m3) of sand + 1.0 cubic meter (m3) of gravel in terms of quantity
  8. 8. How to compute for the mixture proportion1. Determine the length, width and depth of the space you’d like to fill with concrete, in inches.2. Multiply the length, width and depth.3. Divide the result by 12 to determine the cubic feet for concrete needed.4. Divide number of cubic feet by 0.45 if you plan on using 60 pound bags of concrete mix. If you’re using 80 pound bags of concrete mix, divide by 0.6. CONCRETE AND MIXTURES Morales, Zani Gamaliel F. / Odiame, Yeoj C. BUILDING TECHNOLOGY – 1 / 10:00 – 11:00
  9. 9. How to compute for the mixture proportionAnother method:1. Measure the length and width in feet of the space to be filled with a tape measure. Multiply these measurements to arrive at the square footage of the space.2. Measure the depth in feet of the space to be filled. Multiply this measurement by the square footage number. This will give you the number of cubic feet of concrete you will need to buy.3. Divide the number of cubic feet by three to arrive at the number of cubic yards of concrete to be mixed and poured. Some companies will sell concrete by the cubic foot; you can buy it without the extra step.4. Add a cubic foot or yard to the number before purchasing to allow for errors. Because pouring concrete is a permanent form of construction and difficult to fix once its done, it is usually better to have a little too much concrete than not enough. CONCRETE AND MIXTURES Morales, Zani Gamaliel F. / Odiame, Yeoj C. BUILDING TECHNOLOGY – 1 / 10:00 – 11:00
  10. 10. DifferentiationConcrete – is a composite construction materialcomposed primarily of aggregate, cement and sand. It isalso widely used for making architectural structures,foundations, pavements etc.Cement – is a binder, a substance that sets and hardensindependently, and can bind other materials together.Therefore, cement and concrete can be differentiated insuch a way that cement is just one of the 3 mainingredients to create a concrete. CONCRETE AND MIXTURES Morales, Zani Gamaliel F. / Odiame, Yeoj C. BUILDING TECHNOLOGY – 1 / 10:00 – 11:00
  11. 11. DifferentiationGrout – is generally composed of a mixture of water,cement, sand, often colour tint, and sometimes finegravel.Plaster (cement) – is a mixture of suitable plaster, sand,Portland cement, and water which is normally applied tomasonry interiors and exteriors to achieve a smoothsurface.Therefore Grout is used in flooring in between whilePlaster (cement) is used in exterior / interior wall to havea smooth surface. CONCRETE AND MIXTURES Odiame, Yeoj C. / Morales, Zam BUILDING TECHNOLOGY – 1 / 10:00 – 11:00

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