Topic 14 concrete testing

What is the primary strength consideration for concrete?

Compressive Strength

How does the water-to-cement (w/c) ratio affect concrete strength?

Increased w/c leads to decreased strength.

What effect does age have on the strength of concrete?

Increased age results in increased strength.

What is the impact of uniformity on concrete strength?

Increased segregation leads to decreased strength.

How does the degree of consolidation affect concrete strength?

Voids in the concrete lead to decreased strength.

What type of load has a greater strength in concrete?

Compressive strength is greater than tensile and flexural strength.

What curing conditions improve concrete strength?

A wet environment leads to better curing and increased strength.

What is the purpose of a fog room in concrete testing?

To create a controlled environment for test batches and quality control.

What is ASTM C39?

The standard test method for compressive strength of cylindrical concrete specimens.

What are the two main problems in compressive strength testing?

Flat surface vs. non-flat surfaces and Poisson's ratio.

What solutions are used to address the problems in compressive strength testing?

Use end caps made of sulfur or neoprene and maintain a proper aspect ratio.

What happens to stress as the distance from the plates increases in concrete testing?

The stress in the X and Y directions decreases.

What is the Interfacial Transition Zone (ITZ) in concrete?

The area around large particles in the concrete matrix that is weaker due to a higher w/c ratio.

How does the elastic modulus (E) change with the water-to-cement ratio?

E decreases as w/c increases.

What is the typical assumption for tensile strength in design?

Tensile strength is assumed to be zero.

What is the relationship between tensile and compressive strength in concrete?

Tensile strength is commonly about 10% of compressive strength (f'c).

What does flexural beam testing assess in concrete?

It assesses the modulus of rupture, which represents tensile strength in bending.

What is the purpose of splitting tensile testing?

To determine the splitting tensile strength from indirect loadings.

What is the general relationship for modulus of rupture (fr) in concrete?

fr is generally less than or equal to 12 times the compressive strength (f'c).

What is the general relationship for splitting tensile strength (fsp) in concrete?

fsp is generally less than or equal to 8 times the compressive strength (f'c).