Lecture12_concrete_testing_construction_and_deteroration

Lecture12_concrete_testing_construction_and_deteroration -...

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CE Materials, Portland Cement, Page 1 Testing of Concrete Properties of Concrete ± Fresh Concrete: ± Workability ± Air content ± Hardened Concrete: ± Destructive Tests: ± Compressive Strength ± Tensile Strength ± Flexural Strength ± Modulus of Elasticity ± Nondestructive Tests: ± Rebound Hardness ± Ultrasonic Pulse Velocity ± Impact-Echo Method Workability ± Workability: amount of mechanical work required to achieve full compaction of the concrete without segregation ± Factors affecting workability: ± Water content of the mix ± Influence of the aggregate ± Time and temperature ± Cement Characteristics ± Admixtures
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CE Materials, Portland Cement, Page 2 Slump Test ± Workability measured by slump test 12” slump 1. Layer 1: Fill 1/3 full. 25 stokes 2. Layer 2: Fill 2/3 full. 25 stokes 3. Layer 3: Fill full. 25 stokes 4. Lift cone and measure slump (typically 2-6 in.) 1 2 3 4 Slump Test ± Slump test: ± Normal (true) slump: general subsidence of the mass ± Shear slump: distinct shearing of the concrete from one side of the concrete ± Collapse slump: a lean or very wet mix Workability
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CE Materials, Portland Cement, Page 3 Air Content ± The pressure method: measures the total air content in concrete ± Measures the change in volume when subjected a pressure ± Add water through the petcocks ± Release pressure and measure air content Compressive Strength ± The most common test used for concrete: ± Empirically related to important properties of concrete ± Concrete is used primarily in a compressive mode Indirect / Splitting Tensile Test ± Specimen is loaded diametrically ± Tensile stresses develop perpendicular to loading axis Failure is not purely tensile failure
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CE Materials, Portland Cement, Page 4 Modulus of Rupture— Flexural Strength Head of testing machine Steel ball 25 mm min. Rigid base Specimen L/3 L/3 L/3 L/3 L/3 Span length, L Relation PCC Properties 5 . 0 ' t c f 5 . 6 f = 5 . 0 ' c c f 8 S = 5 . 0 ' c c f 57000 E = S c = flexural strength, psi (modulus of rupture) f t = tensile strength, psi f’ c = compressive strength, psi E c = modulus of elasticity Freezing and Thawing ± Subject concrete to repetitive freeze-thaw cycles ± Cooling cycles between 4.4 and - 17.8 o C in two to five hours ± Monitor weight loss, length change, and decrease in strength
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CE Materials, Portland Cement, Page 5 Schmidt Hammer ± Measures the rebound of a steel hammer impacted on the concrete ± Based on an Based on an empirical relationship ± Results may be affected by moisture content, surface finish, temperature, etc. Ultrasonic Test
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This note was uploaded on 06/22/2009 for the course CM 3400 taught by Professor Hassan during the Spring '09 term at LSU.

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Lecture12_concrete_testing_construction_and_deteroration -...

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