Lab Report Concrete-compressive Strength e3m38

FACULTY OF ENGINEERING AND TECHNOLOGY INFRASTRUCTURE BACHELOR IN CIVIL ENGINEERING

BEC205 - CONCRETE, FLUID & SOIL LAB CONCRETE LAB-COMPRESSIVE STRENGTH TEST GIVEN DATE DEADLINE SUBMISSION DATE

5th December 2016

LECTURER’S

Pn Siti Farah Ezdiani Miasin

NAME NAME & MATRIC

Noor Affendi bin Dikkir

152015122

Nur Syazwani bt Saidin

151014652

Ong Yen Ling

151014734

Nik Amir Imran bin Nik Marzukee Hidayat Ahmad Faiz

152015235 151914674 MARKS

Table of Contents

1.1 1.2 1.3 1.4 2.1 2.2 3.1 4.1 5.1 5.2 6.1 7.1

Introduction.....................................................................................................................2 Theory..............................................................................................................................2 Purpose.............................................................................................................................3 Objective..........................................................................................................................3 Apparatus........................................................................................................................3 Procedure.........................................................................................................................4 Data Collection and Recording......................................................................................4 Data Analysis...................................................................................................................5 Discussion.........................................................................................................................6 Conclusion........................................................................................................................6 References........................................................................................................................7 Appendices.......................................................................................................................7

1

1.1

Introduction Compressive strength is the capacity of a material to withstand axially directed pushing forces. When the limit of compressive strength is reached, materials are crushed. Concrete can be made to have high compressive strength, e.g. many concrete structures have compressive strengths in excess of 50 MPa, whereas a material such as soft sandstone may have a compressive strength as low as 5 or 10 MPa.

1.2

Theory By theory, the compressive strength of a material is the value of uniaxial compressive stress reached when the material fails completely. The compressive strength is usually obtained experimentally by means of a compressive test by applying load to the concrete cubes. Compressive strength of concrete depends on many factors such as watercement ratio, cement strength, quality of concrete material, quality control during production of concrete etc. The strength of concrete also increases with age.

Age

Strength per cent

1 day

16%

3 days

40%

7 days

65%

14 days

90%

28 days

99%

Grade of Concrete 15

Minimum compressive strength N/mm2 at 7 days 10

20

13.5

25

17

30

20

35

23.5

40

27

45

30

TABLE 1: the strength of concrete at different

TABLE 2: Compressive strength of

ages in comparison with the strength at

different grades of concrete at 7 days

28 days after casting.

2

1.3

Purpose To get general knowledge about all the characteristics of concrete. We also can judge whether the concrete is properly done or not.

1.4

Objective 1. To try to achieve 75% of the strength of concrete cubes cured for 7 days. 2. To determine the strength of concrete with different curing process

2.1

Apparatus 1. Compressive Strength Test Machine

FIGURE 1: Compressive Strength Test Machine

3

2.2

Procedure 1. Remove the concrete cube from water tank after 7 days of curing time and wipe out excess water from the surface. 2.

Clean the bearing surface of the testing machine

3.

Place the s concrete cube in the machine in such a manner that the load shall be applied to the opposite sides of the cube cast (smooth side up)

4. Align the cube centrally on the base plate of the machine. 5.

Rotate the movable portion gently by hand so that it touches the top surface of the concrete cube

6. Apply the load gradually without shock and continuously at steady rate until fails. 7. Record the maximum load and note any unusual features in the type of failure.

3.1

Data Collection and Recording Sample No

Sample Reference

1

WET

2

WET

Date Date Cast 23-11-16 Date Test 30-11-16 Testing Age 7 days Date Cast 23-11-16 Date Test 30-11-16 Testing Age 7 days

Load (P) (kN)

Types of failure

242.7

Satisfied

245.2

Satisfied

4

3

Date Cast 23-11-16 Date Test 30-11-16 Testing Age 7 days

DRY

Satisfied

242.9

TABLE 3: Data Collection from Compressive Strength Test Machine

4.1

Data Analysis Calculation (Grade) Target Strength

=

25 x 75%

Area (A) of Cube no 1 (WET), mm2 =

=

18.75 N/ mm2

LxW

=

148.4mm x 149.2mm

=

22141.28 mm2

Area (A) of Cube no 2 (WET), mm2 =

LxW

=

149.1 mm x 149.9 mm

=

22350.09 mm2

Area (A) of Cube no 3 (DRY), mm2 =

LxW

=

150.6 mm x 149.4 mm

=

22499.64 mm2

Compressive Strength (N/ mm2)

=

P A

x 1000

Cube no 1 (N/ mm2) =

242.7 22141.28

x 1000 =

10.78 N/ mm2

Cube no 2 (N/ mm2) =

245.2 22350.09

x 1000 =

10.90 N/ mm2

5

Cube no 3 (N/ mm2) =

242.9 22499.64

x 1000 =

10.80 N/ mm2

Results Area, mm2

Load (P) (kN)

Compressive Strength at 7 days (N/ mm2)

22141.28

242.7

10.78

22350.09

245.2

10.90

22499.64 242.9 10.80 TABLE 4: Tabulated Results from Data Analysis Average compressive strength of the concrete cube = 10.83 N/ mm2 (7 days) If strength of any specimen varies by more than 15 per cent of average strength from target strength, results of such concrete cubes should be rejected. Percentage difference =

100% - (10.83/18.75) x 100% = 42% difference,

Therefore, the concrete cubes are rejected.

5.1

Discussion 1.

What are the factors affecting concrete strength? Concrete strength is effected by many factors, such as quality of raw materials, water/cement ratio, coarse/fine aggregate ratio, age of concrete, compaction of concrete, temperature, relative humidity and curing of concrete.

5.2

Conclusion After finish conducting this experiment, we conclude that the concrete cubes do not meet the desirable target strength of concrete. This is due to many factors such as many air void, poor workmanship such as improper mixing of fresh concrete, improper compacting, exposed to weather and environment.

However, from our test, although 6

the difference is bare, well-cured concrete in water can sustain more load compared to normal cured concrete.

6.1

References 1.

Internet a) http://theconstructor.org/concrete/factors-affecting-strength-of-concrete/6220/ b) http://theconstructor.org/concrete/compressive-strength-of-concrete-cubes/1561/

7.1

Appendices

APPENDIX 1: Concrete Cubes (from left: Dry cube, wet cube and wet cube

APPENDIX II: Compressive Strength Test Machine

APPENDIX IV: The concrete achieve satisfaction for types of failure APPENDIX III: Inserting Concrete cube in the machine

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APPENDIX V: Failure pattern of cubes

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