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LESSON 8

THE PROPERTIES OF CONCRETE : SPECIMENS FOR TESTING

-Paragraf 1 :

The standard cylinder, 300 mm high by 150 mm in diameter, is the basic specimen

used for testing concrete in Australia.

LESSON 9

THE PROPERTIES OF CONCRETE : CONCRETE COMPRESSIVE STRENGTH

-Paragraf 1 :

The compressive strength of a standard concrete cylinder, prepared and cured for

28 day in accordance with AS 1020, is used as the prime means of determining the quality

of a given batch of concrete.

-Paragraf 2 :

The inevitable variability of test results means that statistical methods must be

applied in order to obtain a measure of the concrete strength for design purposes.

LESSON 10

THE PROPERTIES OF CONCRETE : TENSILE TEST FOR CONRETE

- Paragraf 1 :For certain aspects of design it is necessary to obtain the measure of the tensile

strength of concrete.

-Paragraf 2 :

The modulus of rupture test is carried out on a standard small beam of cross-section

150 x 150 mm and length 700 mm, which is supported over a span of 600 mm (Fig. 1.5a).

-Paragraf 3 :

The cylinder-splitting test is so-called because a concrentrated line load is applied

to the sylindrical specimen laid on edge, producing a tensile stress across the vertical

diameter of the specimen (Fig. 1.5b).

LESSON 11

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THE PROPERTIES OF CONCRETE : SHEAR, ELASTICITY, AND CONCRETE

DENSITY

11. 1 Pure shear strength

Pure shear strength is encountered only when beding is not present of is very small.

Such as in keyways and on boding planes between surfaces.

11. 2 Modulus of elasticity (Ec)

Strictly speaking, concrete does not have an elastic modulus; this is because, as

for any elastoplastic materials, stress is not proportional to strain over a large part of the

stress range obtained in tests.

11. 4 Poissons ratio (v)

Poissons is the ratio of transverse to longitudinal strain, under axial load or stress,

within the elastic range.

11. 5 Modular ratio (n)

The modular ratio, designated by n, is the ratio of the elastic modulus for steel to

the modulus adopted for a particular grade of concrete.

11. 6 Concrete density

Concrete density, utilizing normal weight aggregates, varies from 2300 to 2500

kg/m3 when reinforced, and an average figure of 2400 kg/m3 is often adopted.

LESSON 12

TIME-DEPENDENT CHANGES IN CONCRETE VOLUME : SHRINKAGE

Shirinkage occurs of the concrete is allowed to dry in the atmosphere.

LESSON 13

TIME-DEPENDENT CHANGES IN CONCRETE VOLUME : CREEP

-Paragraf 1 :

Creep is the term applied to a reduction in concrete volume due to the application ef

external forces over a period of time, and may be present in a structure for a considerable

time (3 - 6 year).