Basic Concrete Tests Plastic Concrete Basic Tests Cylinder - - PowerPoint PPT Presentation

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Basic Concrete Tests Plastic Concrete Basic Tests Cylinder - - PowerPoint PPT Presentation

Aug 17, 2022 333 likes •733 views

Basic Concrete Tests Plastic Concrete Basic Tests Cylinder Compression Splitting Tension Beam Flexure Elastic Modulus Slump Unit Weight and Yield Air Content CIVL 3137 2 Slump The concrete slump test measures the workability of fresh

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Basic Concrete Tests

Plastic Concrete

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CIVL 3137 2

Basic Tests

Cylinder Compression Splitting Tension Beam Flexure Elastic Modulus Slump Unit Weight and Yield Air Content

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Slump

The concrete slump test measures the workability of fresh concrete by indirectly assessing the shearing resistance of the plastic concrete under its own weight. The test specification (ASTM C143) dates all the way back to 1922!

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CIVL 3137 4

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Slump

To perform the test, a conical metal mold called a slump cone is filled with fresh concrete. The slump cone is 12" tall and has a diameter of 4" at the top and 8" at the bottom. As with the dry-rodded unit weight test for aggregate, the mold is filled in three lifts of equal volume and each lift is rodded 25 times with a tamping rod to eliminate any voids in the specimen.

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Slump Cone

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12" 4" 8"

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Slump

The concrete is then struck off level with the top of the mold and the mold is carefully lifted vertically upwards, allowing the now-unsupported concrete to subside (slump). The test measurement is the change in the height of the concrete from the supported to the unsupported

  • condition. This is called the slump, and is measured

to the nearest ¼ inch.

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Slump Test

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http://cemsolutions.org/concrete-slump-test/

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Slump

The slump test is an index test. The higher the slump the more fluid is the concrete. Thus, it can tell you something about the consistency of the concrete. The shape of the slumped concrete can also tell you something about the cohesion of the concrete. A shear slump indicates a lack of cohesion and possible

  • segregation. A collapse slump suggests a mix that is

too wet or has too little cement and may be harsh.

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CIVL 3137 13

Slump Types

“True” slump Good cohesion Good consistency Collapse Slump Too lean or too wet May be harsh Shear Slump Lacks cohesion May segregate

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CIVL 3137 14

Basic Tests

Cylinder Compression Splitting Tension Beam Flexure Elastic Modulus Slump Unit Weight and Yield Air Content

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Unit Weight

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http://www.dot.state.oh.us

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Unit Weight

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  • D = unit weight (density) of concrete (lb/ft3)

Mc = mass of unit weight measure filled with concrete (lb) Mm = mass of unit weight measure empty (lb) Vm = volume of unit weight measure (ft3)

Typical values are 140 lb/ft3 to 150 lb/ft3!

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Yield

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Y = yield (volume of concrete produced per batch) (yd3) M = total mass of ingredients in each batch (lb) D = unit weight of concrete (lb/ft3)

Yield is used for quality control purposes

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Relative Yield

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  • Ry = relative yield (dimensionless)

Y = yield (volume of concrete produced) (yd3) Yd = volume of concrete intended (yd3)

Sometimes expressed as ft3 per yd3 since mix designs are typically done for 1 yd3

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Cement Content

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  • C = cement content (lb/yd3)

Cb = mass of cement in the batch (lb or kg) Y = yield (volume of concrete produced) (yd3 or m3)

Sometimes divided by 94 lb per sack of cement to get cement content in “bags” (e.g., a 7-bag mix)

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Gravimetric Air Content

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A = air content (% by volume) D = actual density of the concrete (lb/ft3) T = theoretical air-free density of the concrete (lb/ft3)

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Gravimetric Air Content

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A = air content (% by volume) D = actual density of the concrete (lb/ft3) T = theoretical air-free density of the concrete (lb/ft3)

This is the same calculation we did for |the void content of aggregate!

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Theoretical Air-Free Density

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T = theoretical air-free density of the concrete (lb/ft3) M = total mass of batched ingredients (lb) V = total absolute volume of batched ingredients (ft3)

𝑊 𝑁 𝑆𝐸 𝛿

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Example

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Assume a 10-yd3 batch of concrete requires 3200 lb of water (RD = 1.00) 5800 lb of cement (RD = 3.15) 19,400 lb of gravel (RD = 2.68) 11,100 lb of sand (RD = 2.65)

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Example (cont.)

𝑊 3200 1.00 62.4 51.3 ft 𝑊 5800 3.15 62.4 29.5 ft 𝑊 19,400 2.68 62.4 116.0 ft 𝑊 11,100 2.65 62.4 67.1 ft 𝑊 263.9 ft Wwater 3,200 lb Wcement 5,800 lb Wgravel 19,400 lb Wsand 11,100 lb M 39,500 lb

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Example (cont.)

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  • T = theoretical air-free density of the concrete (lb/ft3)

M = total mass of batched ingredients (lb) V = total absolute volume of batched ingredients (ft3)

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Example (cont.)

Vm = 0.251 ft3 Mm = 8.3 lb Mc = 45.0 lb

Vm should be measured to 3 significant digits Masses should be measured to nearest 0.1 lb

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Example (cont.)

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  • Mc = mass of unit weight measure filled with concrete (lb)

Mm = mass of unit weight measure empty (lb) Vm = volume of unit weight measure (ft3) D = unit weight (density) of concrete (lb/ft3)

Typical values are 140 lb/ft3 to 150 lb/ft3!

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Example (cont.)

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  • M = total mass of ingredients in each concrete batch (lb)

D = unit weight of concrete (lb/ft3) Y = yield (volume of concrete produced per batch) (yd3)

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Relative Yield

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  • Y = yield (volume of concrete actually produced per batch) (yd3)

Yd = volume of concrete batch was designed to produce (yd3) Ry = relative yield (dimensionless)

A value less than 1.00 indicates the batch produced is “short” of its design volume

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Cement Content

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  • Cb = mass of cement in the batch (lb or kg)

Y = yield (volume of concrete actually produced per batch) (yd3 or m3) C = cement content (lb/yd3)

C =

⁄ ⁄

= 6.2 bags per cubic yard

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Gravimetric Air Content

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  • 2.7%

A = air content (% by volume) D = actual density of the concrete (lb/ft3) T = theoretical air-free density of the concrete (lb/ft3)

This is the same calculation we did for |the void content of aggregate!

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CIVL 3137 35

Basic Tests

Cylinder Compression Split Tension Beam Flexure Elastic Modulus Slump Unit Weight and Yield Air Content

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Volumetric Method

The measuring bowl is filled with concrete, the device is assembled, and water is added to reach the zero mark in the neck. As the device is agitated (“rolled”), the air in the concrete is replaced by water from the top section and the water level in the neck drops in proportion to the air content.

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Volumetric Method

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“roller meter”

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Pressure Method (Type A)

The bowl is filled with concrete, the device is assembled, and water is added to reach the zero mark in the neck. As the unit is pressurized, the air bubbles compress, the concrete surface falls and the water level drops in proportion to the change in air volume.

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Type A Pressuremeter

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Pressure Method (Type B)

The bowl is filled with concrete, the device is assembled, and the air chamber is pressurized. When the air pressure is released into the bowl, the air bubbles compress, the concrete surface falls and the chamber pressure drops in proportion to the change in air volume.

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Type B Pressuremeter

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