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The definition of the strength of Hohhottra bending processing!

2019-06-20 16:57:21

  Hohhottra Bend Factory: The bending strength refers to the maximum stress that can be withstood by the bending material used to reach the limit state or damage when it is under static load.

  Strength failure: 1 Sliding or relative displacement along a sliding surface due to excessive shear stress (such as slippage of roadbed and admixture of asphalt surface layer); 2 excessive tensile stress or bending stress ( For example, a sudden drop in temperature or a heavy load on the wheel.

  First, the shear strength

  Shear strength—the ultimate or maximum stress at which the material is sheared.

  According to the (Mohr-Coulomb) strength theory:

  c, the value is determined:

  (1) Direct shear test (2) Triaxial test (3) Calculation of compressive strength σc and tensile strength σt

  Factors affecting the shear strength of soil and granular materials: particle size and shape, mineral composition and gradation, compactness and water content, stress conditions, etc.

  Factors affecting the shear strength of asphalt mixture: the gradation composition, shape and surface properties of the mineral material are also related to the adhesion and dosage of the asphalt.

  Asphalt mixture adhesion depends on factors:

  (1) The viscosity of asphalt is high and the viscosity is high.

  (2) The optimum amount of asphalt is the most suitable for asphalt.

  (3) Temperature and shear rate increase in temperature, shear rate decreases, and adhesion decreases

  (4) Fine material Increased fine material (mineral powder), increased aggregate (edge), good adsorption

  Second, the tensile strength

  It can be measured by direct tensile test or indirect tensile test.

  (1) Direct tensile test

  The mixture was made into a cylindrical test piece, and the two ends of the test piece were adhered to the metal cap with epoxy resin, and stretched at a certain loading rate. The deformation under load stress was measured by a deformation sensor placed on the test piece. (Strain) value, the maximum stress value in the stress-strain curve is the tensile strength.

  (2) Indirect tensile test (crack test)

  Cylindrical specimens (diameter d, height t) are usually used, and the diameter of the specimen is tested along the diameter of the specimen. The pressure is applied at a constant rate through the gaskets on both sides of the specimen (see Figure 4-4) until the specimen is cracked. .

  The tensile strength of the pavement material is mainly provided by the bonding force of the binder in the mixture.

  (1) Influencing factors of tensile strength of asphalt mixture: asphalt content, application rate, needle humanity, temperature, compactness

  (2) Influencing factors of tensile strength of hydraulic materials: aggregate (or soil) composition, binder content and activity (or water-cement ratio), as well as mixing uniformity and compaction degree, age.

  Third, the bending strength

  The bending strength (also known as the flexural strength) of pavement materials is mostly determined by the indoor simple beam test.

  (1) 5cm × 5cm × 24 cm span 15cm lime (or cement) stabilized soil, tar sand

  (2) 10cm × 10cm × 40cm span 30cm Dmax2.5 stable material, medium and fine granular asphalt mixture

  (3) 15cm × 15cm × 55 cm Span 45cm Dmax3.5 of stable materials, coarse-grained asphalt mixture, cement concrete is usually loaded with three points.