Compressive Strength of Concrete Testing

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Questions and Answers

What is the purpose of this session?

To determine the volume stability of concrete

To determine the impermeability of concrete

To determine the compressive strength of hardened concrete (correct)

To determine the durability of concrete

What is compression test used for?

To determine the ductility of materials

To determine the hardness of materials

To determine the behavior of materials under crushing loads (correct)

To determine the tensile strength of materials

What is compressive strength?

The stress a material can sustain under shear load

The stress a material can sustain under tension load

The minimum stress a material can sustain under crushing load

The maximum stress a material can sustain under crushing load (correct)

How is compressive strength calculated?

By dividing the maximum load by the original cross-sectional area of a specimen Signup and view all the answers

What is hardness?

A measure of a material’s resistance to localized plastic deformation Signup and view all the answers

Why is strength considered a valuable property of concrete?

Because it gives an overall picture of the quality of concrete Signup and view all the answers

What is the relationship between concrete strength and the structure of cement paste?

Concrete strength is directly related to the physical structure of cement paste Signup and view all the answers

What factors affect the strength of concrete?

The physical structure of cement paste and their relative volumetric proportions Signup and view all the answers

What is the significance of flaws, discontinuities, and pores in concrete?

They affect the strength of concrete and understanding their influence is important Signup and view all the answers

What is the limitation of destructive testing of concrete?

It requires specially made specimens and is relatively high cost Signup and view all the answers

What is the advantage of non-destructive testing (NDT) of concrete?

It permits re-testing at the same location and monitors changes with time Signup and view all the answers

What is the principle of the Schmidt Hammer test?

The hardness of the surface against which an elastic mass impinges Signup and view all the answers

Why are multiple readings necessary when using the Schmidt Hammer test?

To account for the presence of aggregate and voids immediately underneath the plunger Signup and view all the answers

What is the purpose of using a Vernier Caliper in compressive strength testing?

To determine the cross-sectional area of the concrete cube Signup and view all the answers

What is the drawback of using destructive testing for concrete?

Specially made specimens are required which may not represent the actual structure Signup and view all the answers

What is the term for testing methods that do not impair the performance and appearance of structures?

Non-destructive testing Signup and view all the answers

Study Notes

Overview of Compressive Strength of Concrete

The purpose of the session is to determine the compressive strength of concrete using British Standard (BS) and American Society for Testing and Materials (ASTM) procedures.

Key Terminology

Compression Test: determines the behavior of materials under crushing loads, recording deformation at various loads.
Compressive Strength: the maximum stress a material can sustain under a crushing load, calculated by dividing the maximum load by the original cross-sectional area.
Hardness: a measure of a material's resistance to localized plastic deformation, often reported as resistance to scratching or rebound of a projectile.

Background of Concrete Strength

Concrete strength is considered its most valuable property, but other characteristics like durability, impermeability, and volume stability are also important.
Strength depends on the physical structure of cement paste and the presence of flaws, discontinuities, and pores.
Understanding the mechanics of fracture of concrete under stress is crucial to understand the influence of flaws on strength.

Destructive Testing (DT) vs Non-Destructive Testing (NDT)

Destructive testing (DT) involves high cost, specially made specimens, and does not provide direct information about the concrete in actual structures.
Non-Destructive Testing (NDT) does not impair the performance and appearance of structures, allows re-testing, and monitors changes with time.
NDT measures other properties, and estimates strength by calibration.

Non-Destructive Testing (NDT) using Schmidt Hammer

The Schmidt Hammer test is based on the principle that rebound of an elastic mass depends on the hardness of the surface.
The test is sensitive to the presence of aggregate and voids underneath the plunger, requiring 10-12 readings over the area to be tested.

Equipment Needed

Compression Testing Machine with sufficient capacity
Vernier Caliper
Schmidt (Rebound) Hammer
Abrasive (Grinding) stone
Concrete cube samples

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Description

This quiz covers the methods for determining the compressive strength of hardened concrete according to British Standard (BS) and American Society for Testing and Materials (ASTM) using destructive and non-destructive testing procedures.