Compressive Strength Test (Cube Crushed Test)

 

This test was done by using a Cube crushed machine named ELE Compact 1500 machine designed for measure compressive strength of materials. Maximum applied load was 2000kN. Samples were taken from the concrete mixture which was used for the construction by making cubes (150mm×150mm×150mm), normally six cubes were made from one sample and it was compacted by using a hammer having 1.8Kg weight when it was making. Three Cubes were tested for strength after 7 days and others in 28 days from particular construction date. For that test a cube was put on the machine which consist a hydraulic jack and then oil valve was closed to take the pressure on jack. After placing the cube, the top screw has to be tightened to touch the upper plate on the specimen. Then adjust the manual display for the test and start the machine for compressed the specimen. When the loading was applying cracks were visible in the cube. When that specimen has reached its maximum load it displayed on the display. The description of the concrete mixture was mentioned on the top face of the each & every cube. All cubes were kept in a tank which was fully saturated by water. According to the testing order cubes were merged in the water in an array.

ELE compact 1500 machine

Bitumen Extraction Test

 

After taken samples from the asphalt plant, this test was used to find out the bitumen content of the asphalt concrete, to make sure the correct content of bitumen has been used in the actual mix.

PROCEDURE OF BITUMENN EXTRUCTION TEST

Sample was selected from dump truck which is in the site and then it was put in to the oven. Sample size was depended on maximum aggregate size of the mixture and capacity of the Extraction equipment. About 1250g sample was collected as capacity of the bitumen extraction equipment. That was put into the bowl of the machine and some petrol also added.(About 5l of petrol had to use for complete extraction) Then the bowl was covered by using a special filter paper, which was oven dried nearly 140 ⁰C and had weighted (12.7g) and the system was closed by steel cover and tied.

After some time, the machine was “on” (it is rotating while discharging bitumen mixed with petrol) and the discharge of petrol and bitumen mixture was collected from the outlet at bellow. Continuously petrol was put into the system through the top hole of the machine until the bottom outlet gives pure petrol.

Then the retained sample was collected and put into the oven and the filter paper also put. After that both are weighted. Using calculation, we can obtain the bitumen content of the sample having bitumen content 3.9%. Then the retained sample was analyzed from sieves having mesh sizes from 25mm-0.075mm as per the lab sheet.

Bitumen Extractor Machine

Flakiness Index Test

 

The flakiness index of aggregates is determined by the percentage of flaky particles contained in it. For base course, and construction of asphalt and cement concrete types the presence of flaky particles is considered undesirable as it may cause inherent weakness with possibilities of braking down under heavy loads. Therefore, in pavement construction the flaky particles are to avoid particularly is surface course.

Thickness gauge

The test apparatus consists of a standard thickness gauge (6.30 – 63.0 mm) is used for this test. The flakiness index test (FI) is not applicable passing 6.30 mm or retaining 63.0 mm test sieve.

Testing procedure

The dried aggregates sample is allowed to passing and retained on a set of sieve.

The weight of retained aggregate on each sieve is measured and determined the percentage of retained.

Each of the particles fractions of aggregate is tried to passing through the slot of the thickness gauge.

The weight of aggregates passing on each gauge is measured.

Discarded the fraction of aggregate if it has the percentage of retained is less than or equal to 5 percent.

Then, the FI is the total weight of the material passing the various thickness gauges expressed as a percentage of the total weight of the sample gauged. The flakiness index value of the aggregate should be below 35 % that recommended for the road construction.

Calculation

Field Density Test

 

The sand cone method is used for field density test in our highway construction. In the field, the dry density test is carried out for check the compaction of layers.

Compaction is most useful for the preparation of sub base grade and other pavement layers and in construction of embankment in order to increase the stability and to decrease settlement. In field compaction, the compacting moisture content is first controlled at optimum moisture content and the adequacy of rolling or compaction is controlled by checking the dry density achieved and comparing with the maximum dry density.

Base layer-98%

Sub base layer-98%

Type 1 layer-95%

ABC layer-100%

Road shoulder- 98%

Field density test

Testing procedure:

The weight of empty sand cone is measured and then filled with dry sand and weighted.

The soil excavated from the hole is collected and weighted.

After weighting, a specimen of soil is taken to determine it water content.

The sand cone is placed on the test hole with the help of the base plate and sand is allowed to run by opening the control value.

When the sand stops running, the valve is closed and the cone is weighted with the remaining sand.

Then the dry density of soil can be calculated and the present of compaction of otherwise the compaction is failure. Then, the compacted place to be re-compacted and re-test.

Calculation:

• Weight of used sand: 16000mg
• Remain sand weight: 4286mg
• Density of sand: 1.349mg/cm3
• Weight of ABC: 15632.42mg
• Volume of cone: 2274cm3
• Volume of hole: 8683.47cm3
• Density of ABC: 2.48mg/cm
• Moisture content: 4.5%
• Dry density: 2.33mg/cm3
• Degree of compaction: 98%

Plastic Limit Test (Pl)

 

Plastic limit is defined as the minimum moisture content at which the soil remains in a plastic state. Plasticity index (PI) is defined as the numerical difference between the liquid limit and plastic limit. Plastic index thus indicates the range of moisture content over which the soil is in a plastic condition. Plastic limit is the moisture content at which a soil when rolled in to thread of smallest diameter possible starts crumbling and has a diameter of 3 mm.

Testing procedure

The dry soil that passing 0.425 mm test sieve is mixed with distilled water until it becomes sufficiently plastic to be mould into a ball.

Part of the soil sample is formed into a thread, about 6 mm in diameter between the first finger and thumb of each hand.

The thread is then rolled on a glass plate until its diameter is reduced to about 3 mm.

The thread is then folded and rolled repeatedly until the 3 mm thread begins to crumble.

All threads are collected into the container and placed on the oven for drying.

The dry samples are weighed for the moisture content of soil.

Then percentage of the moisture content is determined from the above reading. Similarly, the moisture content to another sample is determined and calculated the average value of percent of the moisture content, which is defined as plastic limit.

Calculation

Liquid Limit Test (Ll)

 

Liquid limit is defined as minimum water content at which the soil flow under the application of a very small shearing force. The LL is usually determined in the laboratory using a mechanical device. Liquid limit is moisture content at which 25 blows in standard liquid limit apparatus will just close a groove of standardized dimensions cut in the sample by the grooving tool by specified amount.

Liquid limit tests

Testing procedure

The dry soil sample that passing 0.425 mm test sieve is mixed with distilled water to a thick paste.

Some of the soil paste is placed in the cup, leveled off horizontally and divided by cutting a groove.

The two halves of the soil gradually flow together as the cup is raised and repeatedly dropped on to the base at the rate of 2 drops per second.

The number of blows required to close the bottom of the groove is calculated.

This test is repeated after adding more water.

All test samples are collected and placed on the oven for 24 hours.

The dry samples are weighed for the moisture content of soil.

From the above reading, the percent of moisture content of the soil is determined and plot the number of blows-moisture content % graph. According to the graph, the LL is defined as the moisture content at which 25 blows.

Proctor Compaction Test

Soil compaction is a mechanical process by which the soil particles are constrained to be packed more closely together by reducing the air voids. Soil compaction causes decreases in air voids and consequently an increase in dry density. This may result in increase in shearing strength. Increase the dry density of a soil due to compaction.

Compaction depends on following three factors

• The nature of soil
• The compacting moisture content
• The amount of compaction or compactive effort

At the laboratory, the dynamic compaction test call proctor compactions test is tested for determining the moisture-density relationship of soils. This relationship indicates that under a given compaction effort every soil has optimum moisture content at which the soil attains maximum dry density.

Through the compaction test, the maximum dry density (MDD) and optimum moisture content (OMC) of the soil found for the selected type and amount of compaction. The OMC of the soil indicates the particular moisture content at which the soil should be compacted to achieve MDD. The MDD in the proctor compaction test lower value indicating weaker soil.

Proctor compaction test

Testing procedure:

The soil to be used in the test is first air dried and passed through a 20m test sieve.

It is mixed thoroughly with a small amount of water and compacted into the mould 5 equal layers.

Each layers being compacted by 27 blows of the 4.5Kg hammer dropped through a height of 450mm above the soil surface.

The soil is trimmed to the tope of the mould and weighted to determine it is dry density.

The test is repeated five times with gradually increasing water contents until the whale of the relevant range of water content has been covered.

Then, the moisture content and the dry density are determined and plot the dry density-moisture content graph. From this graph, the maximum dry density and optimum moisture content are read out the graph curve comes similar to following graph.

Calculation

a Dry density Vs moisture content