compressive and flexural strength test of hydraulic cement mortar

Technological University of the PhilippinesAyala Boulevard, Ermita, Manila

College of EngineeringDepartment of Civil Engineering

CE 49L 4AConstruction Materials and Testing, Lab.

Experiment No. 4

COMPRESSIVE AND FLEXURAL STRENGTH TESTOF HYDRAULIC CEMENT MORTAR

Fesalbon, Mayson R.10-205-041

Date of Submission: September 19, 2013

Engr. Reynaldo O. BaardeInstructor

EXPERIMENT NO. 4

COMPRESSIVE AND FLEXURAL STRENGTH TEST OF HYDRAULIC CEMENT MORTAR

I.OBJECTIVE

To determine the compressive and flexural strength of hydraulic cement mortar

II.MAIN PRINCIPLE

Strength of cement usually gives an overall picture of the quality of the resulting concrete. The strength of concrete structure is directly related to the strength of hardened cement paste. Strength gain in concrete is the result of hardening of the cement paste. Direct compressive test of mortar specimen is a form of evaluation to determine the quality of cement.

Flexural stress is expressed in terms of the modulus od rupture that corresponds to the maximum tensile strength at peak flexural load. Prior to this, a mortar mix is prepared and then molded to form beam specimens. These specimens are then cured for different ages. After the specimens attained the specimen age, they are then subjected to flexural strength test. The ages are usually 24 hours, 3 days, 7 days and 28 days.

III. APPARATUS NEEDED

1. Universal Testing Machine (UTM) and accessories2. Upper spherical block and fixed lower seat block3. Mechaelis Flexure tester4. Weighing Scale

IV. PREPARATION

1. Proper accessories of UTM should be attached (upper spherical seat, lower fixed seat block) prior to zero calibration of the machine.2. All test specimens shall be tested within the permissible tolerance.

Test AgeTolerance (hr.)

24 Hours+ 0.5

3 Days+ 1.0

7 Days+ 3.0

28 Days+ 12.0

3. All surfaces of the specimen where the load will be applied must be flat and smooth.4. The operator of the UTM must have thorough knowledge of the machine.

V. TEST PROCEDURE

A. Preparation of UTM1. Attach the accessories. Warm-up the machine for at least 5 minutes in order to ensure smooth circulation of oil in the hydraulic system.2. Calibrate to zero the UTM as follows:a. Move the lower crosshead by pressing the UP/DOWN crosshead button to a significant clearance from the table (preferably not less than 5cm)b. Adjust the load control knob to OPEN position to raise the UTM table to a height of about 2cm, and then put knob in HOLD position.c. Set the zero knob at the bottom of the dynamometer such that the pointer will be in zero position.d. It is preferably to keep the UTM table in this raised position and the load control knob in HOLD position.pB. Compression Test Using the UTM1. Position the specimen between the raised table and lower crosshead. There should be enough clearance of about 2 to 3mm between the specimen and the lower crosshead. It is very important to prevent sudden contact between the crossheads or the lower crosshead and specimen for this will result in a gear lock-up.2. Load is applied by raising the UTM table gradually. This is done by adjusting the load control knob beyond LOAD markto raise the table. As soon as the lower crosshead touches the specimen, the load control knob should be returned to LOAD mark. Initial loading is indicated by the movement of the auxiliary pointer to the center.3. Adjust the loading rate by turning the load control knob. See to it that the desired loading rate is attained immediately while the specimen is still at its elastic stage. Make no more adjustment in the load control when the specimen is already yielding. If a load pacer is available, the loading rate at the elastic range should be in accordance to the movement of the pacer.4. As the pointer goes back to zero, return also the control knob to zero. This is an indication that the specimen had already failed. Record the reading indicated by the maximum load pointer. The load is divided by the area will give the strength in force per unit area units.5. The report shall include the following:a. Specimen identification, age, diameter, length and cross-sectional areab. Maximum loadc. Compressive strengthd. Remarks

C. Flexural Test Using the Mechaelis Flexure Tester1. Place the Mechaelis flexure tester flat on a rigid spot.2. Each part of the tester must be cleaned and checked.3. Remove the beam specimen from the curing tank within the permissible tolerance time for the given test age.4. Wipe the specimen with damp cloth to remove the dirt.5. Weigh each specimen.6. Detach the bucket and upper roller from the main unit so that the specimen can be positioned to the specimen attachment. In positioning the specimen, the observing hole should be in line with the central line of the specimen. Note that the specimen should be turn to its side with respect to its position as molded.7. Adjust the balance weight so that the lever where the bucket is attached would be horizontal. After balancing the lever, do not re-adjust the balance weight until the test for that particular specimen is finished.8. Insert the upper roller to its position.9. Attach the bucket to the main unit. Balance the adjusting handle so that the lead shots will directly fall in the bucket during the loading operation.10. To start loading, the loading lever should be pulled up and quickly released. Immediately after the loading lever is pulled, the lead shots will start to fall to the bucket.11. When the specimen breaks the bucket drops to the bucket receiver causing the time gate to close and stops the loading. Weigh the bucket together with the lead shots. The resulting weight multiplied by 11.71875 would give the flexural strength of the specimen.12.

VI.CALCULATIONS

Compressive Strength

Where: = Compressive strength (kg/cm2)P= Maximum applied force (kg)A = Cross-sectional area of the specimen (cm2)

Flexural Strength

Where:f= Flexural strength (kg/cm2)W= Weight of bucket and and the lead shotsb,h=Dimensions of the cross-sectional area of the beam (cm)

VII.DATA AND RESULTS

For Compressive Strength

Weight(kg)Length(cm)D1(cm)D2(cm)Dave(cm)Area(cm2)UTM Reading (kgf)Compressive Strength(kgf/cm2)

Cylinder 10.4380810.205.205.205.2021.237181085.228

Cylinder 20.4360010.305.105.205.1520.831146070.089

Weight(kg)Sides(cm)Area(cm2)UTMReading(kgf)CompressiveStrength(kgf/cm2)

Cube0.290705.2027.042900107.249

For Flexural Strength

Weight(kg)Length(cm)Width(cm)Depth(cm)W(kg)FlexuralStrength(kgf/cm2)

Beam 10.5520016.304.104.103.18534.659

Beam 20.5563916.254.204.102.99531.816

Beam 30.5540816.304.104.102.97032.320

VIII.SAMPLE COMPUTATIONS

For Compressive Strength

Cylinder 1Cylinder 2Cube

For Compressive Strength

Beam 1Beam 2Beam 3

IX.DISCUSSION AND OBSERVATION

A. Discussion

Compressive Strength Test. The test comprises of the determination of the maximum applied force by the Universal Testing Machine (UTM) which causes failure on the specimen. As exhibited in real-life scenario, mortar acts as a binder so that materials will be intact. Consider a wall which is applied by a compressive force. The force was transmitted to the hollow blocks that makes up the wall and then transmitted to mortar. Failure for the mortar to resist the load means a failure in the whole structure. But this test cannot assure the real strength of a mortar. It is just only one of the many parameters that can measure how strong a mortar is.

Flexural Strength Test. This test accounts for the resistance of beam to bending. In real-life scenario, structures must also resist applied moments acted on them. Since these moments are also transmitted to the joints of the structure, the flexural strength of the mortar must be determined. This can be determined using the Mechaelis flexure test where the total weight of the lead shots material that causes the beam to break serves as the moment applied on both ends of the beam.

B. Observations

During the experiment, the following was observed:

1. The mode of failure of the cubic and cylindrical specimen is cracking at its surface at about equal to its height 2. Lead shots in the Mechaelis flexure test are very small and cannot be magnetized.3. The mode of failure of beams in Mechaelis flexure test is breaking at about the midspan of the beam.4. Compression Test in the UTM takes more time than the flexural test using the Mechaelis flexure test.

X.CONCLUSION

The compressive strength is determined as the maximum applied force per unit area of the that cause the specimen to crack.

Where: = Compressive strength (kg/cm2)P= Maximum applied force (kg)A = Cross-sectional area of the specimen (cm2)The flexural strength is determined as the maximum applied moment that causes rupture of the beam in the Mechaelis flexure apparatus

Where:f= Flexural strength (kg/cm2)W= Weight of bucket and and the lead shotsb,h=Dimensions of the cross-sectional area of the beam (cm)