AUS

NGN110R-12

Group 4

CVE Lab ReportFinding Compressive Strength of Concrete

Abdulwahab Sahyoun(47562)

Hakam AbdulQader(49431)

Jad Abdulsamad(47719)

Moath Abu Qaoud(48225)

Hassan Bassem Saleh(48302)

Instructors: Arshi Faridi/Riyad Temam

Date: 7/11/12

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Abstract

Civil engineering is the most common part of engineering departments all around the world, this

domain concentrates on the usage of CONCRETE (most used artificial material all over the

world) with infrastructure. Concrete is a mixture of cement, water and aggregate, were those

three substances are mixed together to form durable and strong concrete. Throughout the lab we

learned how to know if a slab of concrete is valid for usage in construction and learned how to

determine the breaking points (compressive strength or non-destructive test) of such slab by

using different kind of equipment such as Schmidt hammer and compressive testing machines.

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Table of Contents

Abstract...................................................................................... 2

Introduction................................................................................ 4

Theory ........................................................................................ 5

Setup and Procedure ..................................................................6-8

Results ........................................................................................ 9

Discussion of Results.................................................................. 10

Conclusion .................................................................................. 11

References ...................................................................................12

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Introduction

Concrete is a solid material used to support structures and buildings. Contrary to what people

think, cement is not the same as concrete, cement is in fact a component of concrete which is

basically used to strengthen the concrete itself. Concrete, however, is a substance consisting of

three main components: Cement, water, and aggregate. Cement comes in powder form and is

mixed with water and crushed stones all together to form a strong concrete mix. Certain

properties of concrete are sometimes desired depending on the purpose [1]. Concrete should be

strong and wear resistant, that is why it is required to test the concrete every now and then to

ensure that it is safe to use.

Concrete strength mainly depends on the reaction of cement with water, which is also known as

Hydration. If there isn't enough water, hydration could fail, hence only a few crystals will grow

leading to a weak concrete mix. Temperature is another factor that affects the strength of

concrete. concrete should never be too hot or cold and must always remain at a temperature of

50°F to 72°F (15° C- 22° C)[2]. In case such temperatures are hard to achieve in certain

locations, concrete admixtures can be used to create the ideal concrete mix. The consequences of

using weak concrete could be fatal, that is why it is extremely important to test concrete mixes

before using it in the building process.

The objectives of this experiment is to determine the compressive strength of concrete using two

different methods: Destructive procedure (BS) and Non-destructive procedure (ASTM). During

both tests, the compression load of the material is determined and any deformations or fractures

are recorded. In this experiment the concrete floor was tested using the non-destructive method,

while the concrete cube was tested using the destructive method.

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Theory

Compressive strength is the maximum stress a material can sustain under pushing, crushing

forces. The compressive strength of a material is determined by the shattering fracture of the

material under these forces. Compressive stress is calculated by dividing the maximum load by

original cross – sectional area of the sample. The SI unit of measurement is Newton per square

meter (Pa) but the common unit used is (MPa) Mega Pascal.

The material that does not shatter in compression is defined as “the amount of stress required to

distort the material, an arbitrary amount” [3]. The destructive test measures the compressive

strength by a machine that applies gradually increasing load applied on a sample usually in the

form of a cube, prism or cylinder. [4]

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Experiment Setup and Procedure

Equipment:

1. Schmidt hammer

2. Abrasive stone.

3. Concrete cube samples.

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4. Compression testing machine

Steps:

Destructive test: In this test we destroy a sample of concrete by a compression machine:

First measure the dimensions of the concrete cube using a vernier caliper

Then determine the cross sectional area by the multiplying the average width with the

average depth.

After that weigh the cube.

After these calculations put the cube in the machine and start applying the compressive load

until it cracks.

With the area and the maximum load known we can calculate the compressive strength by

dividing the maximum load over the area calculated.

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Non Destructive Test: It's an easy and short way for testing the strength and can be done

simply, since the application direction is vertical.

Press the Schmidt Hammer perpendicular against the concrete surface.

Record several numbers of bounds.

After recording the bounds take the average of them and finally convert it to compressive

strength by using calibration charts shown below.

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Results and Calculations

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Discussion of results

The first table discusses the usage of the Schmidt hammer. The Schmidt hammer is pointed

downward facing the floor and pressed ten times to give us ten values in which an average can be

calculated to eventually allow us to calculate an estimated compressive strength.

The second table discusses the measurements of the length and width of the concrete cube. These

measurements helped us derive further measurements such as the density, area, height and mass

of the cube. Then, using the destructive test we found the compression failure load value and

finally calculated the compressive strength.

Destructive and non-destructive tests both are good and helpful, but each one has advantages and

disadvantages which make each of them appropriate in different conditions.

Advantages are:

Destructive test Non-destructive test• It tests different mix designs to attain

required strength.• It saves time.• Testing can be repeated on the same structure.• Enable continuous monitoring of the performance of the structure.

Disadvantages are:

Destructive test Non-destructive test• Specimen do not actually represent actual structures.• Costly.• Time consuming.

• Strength properties are not measured directly, thus needs calibration.

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Conclusion

In the civil engineering lab, we were introduced to two types to measure the strength of the

concrete cube. The two ways are the British standard (destructive test) and the American

standard (non-destructive test). Both tests yielded in results that gave us estimated and/or

accurate results. The objective of this lab session was to determine the compressive strength of

concrete using two different methods: Destructive procedure (BS) and Non-destructive

procedure (ASTM), and the objectives were met by the end of the session.

The destructive test was more accurate and precise than the non-destructive test simply because

in the destructive test, the cube was set to real physical experiments, while the non-destructive

test depended on calculations only, thus the destructive test is more trustable and reliable.

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References

[1] The Concrete Network. (2012). What is Concrete: Concrete and Cement defined. Retrieved October 29, 2012, from Concrete Network: http://www.concretenetwork.com/concrete.html

[2] Henry W., (2008). What is the best temperature range when pouring concrete? [Web log comment] Retrieved October 29, 2012, from Yahoo Answers: http://answers.yahoo.com/question/index?qid=20080915213044AAH7nTM

[3] Instron. (2008). Compressive Strength. Retrieved fromhttp://www.instron.us/wa/glossary/CompressiveStrength.aspx?ref=http://www.google.com/url

[4] Civil Guy. (2010). Testing the Common Properties of materials. Retrieved fromhttp://www.civilcraftstructures.com/materials-testing/testing-the-common-properties-ofmaterials/

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