structural materials lab report(1)

8/12/2019 Structural Materials LAB REPORT(1)

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TITLE: EXPERIMENTAL STUDY ON THE DETERMINATION OF

STRENGTH OF MASONRY WALLS USING VARIOUS MORTAR

MIX RATION AND RED MURRAM SOIL

ABSTRACT

Mortar is the bonding agent that ties masonry units into a strong, well-knit, weather tight

structure. Cement sand mortar in the ratio of 1:3 is perfect because of its high compressive

strength and produces a strong bond. The alternative use of this is however limited because of its

low research and a set mind of most people that a mortar is to comprise of sand and cement inorder to give a perfect bond between masonry units. This research is therefore aimed at finding

an alternative ways of producing mortar which is cheaper to complement the conventional

cement sand mortar using red muram soil as an alternative as well as varying the mix ratio of

cement sand to ratio of 1:7 to find out if the same can be used as a binder. The methodologyadopted will utilize recycled masonry units from a demolished house, red muram soil, river sand

and cement in the production of the model masonry walls to be tested. There were 3 models in

total. Model one used the normal mortar mix of cement- sand ratio 1:3, second model red muramratio 1:3 and the third model is varying the cement to sand ratio at 1:7. the recycled masonry

quary blocks were tested and found to have an average crushing strength of 5.1N/mm2

Compression test was carried out on the three models onto the testing frame at the Jomo

Kenyatta University of Agriculture and Technology structures laboratory to determine whether

the three types of mortars were adequate as a bond for masonry units. The first wall with a

mortar mix ratio of 1:3 (cement to sand), Initial cracking was observed at the application of

68.16kN loading. The second wall with a mortar mix ratio of 1:3 (cement to Redmuram soil ),

Initial cracking was observed at the application of 68.8kN loading. And the second wall with a

mortar mix ratio of 1:7 (cement to sand), Initial cracking was observed at the application of

53.28kN loading.\The research has shown that a mortar mix of cement to red muram at a ratio of

1:3 is good enough to provide a strong bond between masonry units or even enhance some of the

engineering properties of the mortar since cracks started at 68.8kN loading as opposed to 68.2kN

loading of the conventional cement sand mortar. However for alternative use, the red muraam

should be used with strong masonry stone of above 7.0 N/mm2 to further increase its strength,

because during the test, it was the stones that failed first due to their low crushing strength. Themortar can thus be used as a bidder to masonry unit. The mortar with cement sand ration 1:7

appeared weak and not recommended for a structural wall but can do for infill walls.


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MAIN OBJECTIVE

To assess the effect on strength of masonry block and the structural behavior of wall panels

under compressive load, given different types of materials for mortar and varied mix

rations.

SPECIFIC OBJECTIVES

-To design and fabricate the model

-To set up the testing system

-To conduct experiments

-To analyze and discuss the report

INTRODUCTION

The project will involve material sampling and testing, construction of the models and testing of the models.

INDENTIFICATION OF MATERIALS

The main raw materials are:

1. Sand2. Coarse aggregates (Sand)3. Cement (Portland pozzolana cement locally known as Nguvu cement)4. Red murram soil5. Masonry quarry stoneCOLLECTION OF MATERIALS

All the above materials were procured through the administration of the structures laboratory Jomo Kenyatta

university of Agriculture and Technology.


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MATERIAL TESTING

Stones

Three quarry stones were selected by visual inspection from the group and their crushingstrength obtained as shown on the figure 1below.

Figure1. Testing of the masonry stones

Stone one----crushed at a load of 42tonnes

Therefore crushing strength =F/A = (42x10000)/200x400= 5.2N/mm2

Stone two----470000/200x400=5.8N/mm2

Stone three----350000/(200x400)= 4.3N/mm2

Average crushing strength-----(4.3+5.2+5.8)/3 =5.1N/mm2

Sand and course aggregates

The test values for the course and fine aggregates were by visual inspection and large impuritieswere removed through sievingSieve Analysis of Fine & Coarse Aggregates (ASTM C136-01)Moisture Content (ASTM D146185).


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CONSTRUCTION OF THE TEST MASONRY WALLS MODELSThe three test walls were built assisted by a professional mason using recycled bricks. The bricks

were obtained from demolished buildings and cleaned for use in the tests. The mortar mixes wereas follows;

A weak mortar mix ratio of 1:7 (cement to sand)

A mix ratio of 1: 3 (cement to sand)A mix ratio of 1: 3 (cement to red murram soil)

Figure2. Construction of the models

Each test wall measured 1250 mm long 1850 mm tall 200 mm thick

The weakest stones in the group were selected to build the ratio 1:3 (cement to sand) model

while the stronger ones built the other two models.The walls were built one leave thick in the common bond pattern, on a pre-constructed timber

plat forms in the structures laboratory strong floor as shown above.


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Figure3. Construction in progress of the models

Figure3b. Models ready for testing

Figure3c. Models being transported to the loading frame


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TEST SETUP FOR THE MODELS

Figure 4 shows the test setup. The test walls were built directly on the timber platform. A layerof strong cement/sand mortar was spread on the platform before laying the first course of the

wall, to provide adequate bonding with the timber platform, which was used to lift the model

onto the testing frame. A loading system was incorporated into the test setup to provide axialloads.

Figure4. Test Setup

Vertical load was simulated using an external stressing tendon, centrally placed onto a UDL plat

which distributes the load uniformly along the wall. The tendon was anchored to testing frame asshown. The required stressing force was applied to the top of the tendons by a hydraulic jack.

INSTRUMENTATION

The following instrumentation was used:

Load cellsA load cell were used to monitor axial forces in the stressing tendons during the test.Portal Transducers: Portal transducers were used to measure displacements in the test walls.

Top lateral displacement was measured by connecting a portal transducer between the end faceof a wall and a stiff frame. In-plane wall displacements were determined by mounting portal

transducers on one face of a test wall.

Data Acquisition: Test data was acquired by an electronic data logger.


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TESTING PROCEDUREAxial load was applied to the test walls.

Cracks appearing on the wall were being monitored as load was increase.A maximum superimposed axial load of 159.2 kN (Max) was applied to be the walls. This

corresponds to the superimposed axial loads on the URM walls in the lowest storey of a 5-storey

building with RC floors.After stressing the tendons to the required level of force, an initial load cell reading was taken.All loading cycles were displacement-controlled, with two cycles at each displacement level to

obtain a stabilized crack pattern. A test wall was initially pushed to 0.5 mm. The test was paused

at this displacement level to inspect the wall for any damage/de-bonding. The displacement wasthen released to bring the wall back to the original position. After this, the wall was pulled to

0.5 mm and the procedure were repeated. The displacement increment was maintained at

0.5 mm up to a displacement of 2 mm. For displacements greater than 2 mm, the increment

was increased to 1 mm. The complete displacement cycle is shown in Figure 5. The test wasstopped after a definite failure mode was established.

Figure5a. Failure mode1


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Figure5b. Failure mode2

Figure5c. Failure mode3


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Figure5d. Failed wall after testing (1:7 ratio)

RESULTS, ANALYSIS AND DISCUSSIONS

PRELIMINARY TEST RESULTSAs-built Wall: The as-built wall deformed by rocking and show of cracks. For the wall with a

mortar mix ratio of 1:3 (cement to sand), Initial cracking was observed at a displacement ofapprox2 mm. The first crack appeared at the second stone from the right edge of the wall,

second course. The corresponding force was 68.16kN. Another crack appeared on the lower last

course on the first stone at the right edge. As load was increased to 79.84kN an upper crackappeared on the first course and these cracks did not join but the wall started to rock at the three

courses. Failure mainly was due to the weak recycled quarry stones(4.3N/mm2). The load was85.2kN when the test was stopped as the wall had completely failed as shown above. figure5a.

The second wall with a mortar mix ratio of 1:7 (cement to sand), Initial cracking was observed atthe application of 53.28kN loading.

With increasing displacements, the crack propagated towards the other edge of the wall.

Another crack appeared on the lower last course. As load was increased to 71.52kN an upper

crack appeared on the first course and both cracks joined and the wall started to rock at the threecourses. The load was 77.76kN when the test was stopped as the wall had completely failed as

shown above. figure 5b.The third wall with a mortar mix ratio of 1:3 (cement to red murram), Initial cracking was

observed at the application of68.8kN loading at the left edge on the second course.As load was increased to 80.62kN an upper crack appeared on the first course at the second stone

from left. At 129.6kN the wall was still stable with cracks on other stone but not on the mortar

joints. The wall started to rock at 143.52kN loading and fully failed at159.2kN when the test wasstopped, with major failure on the stones as shown above. figure 5c.


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Conclusions and Recommendations

Mortar mix ratio 1:3(cement to Sand) shown excellent performance bearing in mind the weakest

of the recycled stones were used for this test (4.3N/mm2).

1:3 ratio of cement to red murram proved good too so long as strong stones of above 6.0N/mm2are used. As seen in the discussion, during testing the stones failed before the mortar.

The mix ratio 1:7 (cement to sand) both the mortar joint and the stone failed.

In conclusion therefore, a mix ratio of 1:3 (cement to red murram) can be effective on quarry

stone masonry work just as it is with 1:3 of (cement to sand) having failed at159.2kN

which was the maximum design load.

However, ratio 1:7 (cement to sand) appeared weak as it failed at quite a low loading of

77.76kN.therefore may not be adequate for structural walls but can br used for infill

walls.

References

-Structural design of masonry: By Andrew Orton

-Internet

structural materials lab report(1)

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