Modulus of Elasticity and Strength

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Modulus of Elasticity and Strength

  1. 1. 2.2.3. Modulus of Elasticity and Strength11/20/99 Author: Tomas U. Ganiron Jr 1
  2. 2. The Modulus of the elasticity is the ratio of stress to corresponding strain below the proportional limit. • For granites and limestone the modulus of elasticity in compression is in the range 2,000,000 – 7,000,000 psi. • Sandstone has lower value modulus, which may range from 1,000,000 – 5,000,000 psi. • The modulus of elasticity of concrete increases with increase in the modulus of aggregate used in its manufacture. • Creep and shrinkage of concrete are also affected by the modulus of elasticity of the aggregate11/20/99 Author: Tomas U. Ganiron Jr 2
  3. 3. Compressive strengths of aggregates depend on the compressive strengths of original rocks. The strength of an aggregate affects the strength of the building material made with it when the two strength values are close to each other.11/20/99 Author: Tomas U. Ganiron Jr 3
  4. 4. GRADATION The particle size or grain-size distribution, of an aggregate is one of the most influential aggregate characteristics in determining how it will perform as a pavement material. Gradation helps determine almost every important property including stiffness, stability, durability, permeability, workability, fatigue resistance, frictional resistance and resistance to moisture damage . Gradation helps determine durability, porosity, workability, cement and water requirements, strength, and shrinkage.11/20/99 Author: Tomas U. Ganiron Jr 4
  5. 5. The process that determine the GRADING particle-size distribution of a representative sample of the aggregate. BLENDING The process of combining aggregates of various size to obtain a specified gradation11/20/99 Author: Tomas U. Ganiron Jr 5
  6. 6. Typical Gradations Dense or well-graded. Refers to a gradation that is near maximum density. The most common HMA mix designs Gap graded. Refers to a gradation that contains only a small percentage of aggregate particles in the mid-size range. The curve is flat in the mid-size range. These mixes can be prone to segregation during placement.11/20/99 Author: Tomas U. Ganiron Jr 6
  7. 7. Open graded. Refers to a gradation that contains only a small percentage of aggregate particles in the small range. This results in more air voids because there are not enough small particles to fill in the voids between the larger particles. The curve is flat and near-zero in the small-size range. Uniformly graded. Refers to a gradation that contains most of the particles in a very narrow size range. In essence, all the particles are the same size. The curve is steep and only occupies the narrow size range specified.11/20/99 Author: Tomas U. Ganiron Jr 7
  8. 8. 11/20/99 Author: Tomas U. Ganiron Jr 8
  9. 9. Other Gradation Terms•Fine aggregate (sometimes just referred to as"fines"). Defined as natural or crushed sand passing theNo. 10 sieve and mineral particles passing the No. 200sieve.•Coarse aggregate. Hard, durable particles or fragmentsof stone, gravel or slag retained on the No. 10 sieve.•Fine gradation. A gradation that, when plotted on the0.45 power gradation graph, falls mostly above the 0.45power maximum density line.•Coarse gradation. A gradation that, when plotted on the0.45 power gradation graph, falls mostly below the 0.45power maximum density line. The term generally appliesto dense graded aggregate.•Mineral filler. Defined as a finely divided mineral productat least 65 percent of which will pass through a No. 200sieve.11/20/99 Author: Tomas U. Ganiron Jr 9
  10. 10. Gradation is determined using sieve analysis in which arepresentative sample of the aggregate is passedthrough a series of sieves and the weight retained ineach sieve SIEVES - is an apparatus with square openings. - A utensil of wire mesh or closely perforated metal, used for straining, sifting, or puréeing.11/20/99 Author: Tomas U. Ganiron Jr 10
  11. 11. STANDARD COARSE AGGREGATE SIEVES are No.4, 1/8 in., ½ in., ¾ in., 1 in., 1 ½ in., 2 in., 2 ½ in. STANDARD FINE AGGREGATE SIEVES are No. 100, No. 50, No. 30, No. 16, No. 8, No. 4,11/20/99 Author: Tomas U. Ganiron Jr 11
  12. 12. Sieve designation Normal Opening in. mm. in. mm. Type 2 50 2 50 H 1½ 37.5 1.5 37.5 F 1 25 1 25 H ¼ 19 0.75 19 F ½ 12.5 0.5 12.5 H ⅛ 9.5 0.375 9.5 F No. 4 4.74 0.187 4.74 F No. 8 2.36 0.0937 2.36 F No. 16 1.18 0.0469 1.18 F No. 30 600 ųm 0.0234 0.6 F No. 50 300 ųm 0.0117 0.3 FNo. 100 150 ųm 0.0059 0.15 FNo. 200 11/20/99 75 ųm 0.003 Author: Tomas U. Ganiron Jr 0.075 F 12H = half sieve F = full sieve
  13. 13. Other Properties Other important aggregate physical properties are: •Toughness and abrasion resistance. Aggregates should be hard and tough enough to resist crushing, degradation and disintegration from activities such as manufacturing stockpiling, production, placing and compaction •Durability and soundness. Aggregates must be resistant to breakdown and disintegration from weathering (wetting/drying) or else they may break apart and cause premature pavement distress. •Particle shape and surface texture. Particle shape and surface texture are important for proper compaction, load resistance and workability. Generally, cubic angular- shaped particles with a roughU.surface texture are best. 1311/20/99 Author: Tomas Ganiron Jr
  14. 14. •Cleanliness and deleterious materials. Aggregates must be relatively clean when used in HMA. Vegetation, soft particles, clay lumps, excess dust and vegetable matter may affect performance by quickly degrading, which causes a loss of structural support and/or prevents binder-aggregate bonding. •Specific gravity. Aggregate specific gravity is useful in making weight-volume conversions and in calculating the void content in compacted HMA (Roberts et al., 1996).11/20/99 Author: Tomas U. Ganiron Jr 14
  15. 15. Find the volume of Voids in a 3-yd³ coarse aggregate of bulk density equal to 102 pcf. The specific gravity of the particle is 2.65 Solution: SG x W – B Void = X 100 SG x WSpecific gravity, SG = 2.65 Density of water, Bulk density, B = 102 pcf W = 62.4 pcf 2.65(62.4) - 102 Void = X 100 2.65(62.4) 27 Volume of voids = 38.3(3) x 11/20/99 = 31 ft³ 15 100 Author: Tomas U. Ganiron Jr

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