format an engineering report

This report is based on the four tests which were carried out on the laboratory to help gain concepts in Highway Engineering. Highway Engineering being a broad area of study involves the study of both foundation of the subbase and the design of the pavement surfaces. These two areas of study were involved in the laboratory experiments which were carried out. The experimental work involved tests on bitumen and tests involving the California Bearing Ratio. The test on bitumen are carried out prior the design of the pavements so as to know the important parameters affecting the pavement. Pavement are always exposed to adverse environmental condition among them being temperature. In the experiments carried out on bitumen; softening point, the needle penetration test and the viscosity of cutback bitumen test, it was observed that temperature and affected the softening point and also the fluidity of bitumen. On the soil test, various experiment were carried out on the sample soil among them being the compaction test, the % moisture content test, the swelling and the CBR test. The maximum dry density of the soil and its corresponding optimum moisture content were achieved. Through computations, the recorded penetrations and their corresponding forces in the CBR test helped in getting the CBR at 2,5 and 5.0 mm where the highest value were considered. The experiments carried out were compared to the expected results where no much discripancy were observed.

As a core importance in the study of Highway engineering, there is great need to understand all the engineering aspects in design of the pavements and their subbases. As a result four experiments were carried out on in order to correlate the theory with the practical application. The tests carried out were categorised into two broad areas. There were the bitumen tests and the CBR tests. The bitumen tests included the softening point test, the penetration test and the viscosity cutback of bitumen test. According to (Rogers, 2003), softening point and penetration tests are prominent in that they ensure binder has the correct properties. The penetration test involved a standard steel needle which was subjected to vertical load of 100g and the bitumen was maintained at a temperature of 250 C. For every sample, three tests were performed and the average determined. Penetrated length can be well explained from the difference in level of the needle with varying force subjected.

Figure 1.1 illustrates how penetration varied as the force increased. Gradual increase of the force resulted to an increased difference in levels. On the other hand, softening point test involved taking a bitumen sample and placing it in a 15 mm diameter metal ring inside a water bath. As the temperature increased, the sample sagged touching the bottom of the cylinder. This temperature is taken as the softening point of the sample. The viscosity of cutback bitumen involved recording the time taken by the fluid bitumen to reach a certain mark upon passing an orifice regulated with a valve. This test was performed using a standard tar viscometer which computed the time in seconds for the volume of binder to flow. The CBR test involved testing of sample soil where various parameters were analysed. The maximun dry density and the optimum moisture content were first computed using the compaction test method. Upon conducting the CBR test using the penetrating needle and the all the parameters revolving aroung the density and compaction of the soil were related and analysed in graphical manner. The CBR test aimed in achieving the bearing capacity of the soil that is used in the subgrade of the pavements.

The experiments were carried out in a procedural manner as indicated in the laboratory manual. Care was taken when carrying out the penetration test in order to maintain the required least distance of 10 mm from each area of penetration and the surface of the cylinder.

Figure 1.1 shows how the 10 mm distance was maintained in penetration test of bitumen. From the figure, K indicate that at least 10mm distance apart for the had to be maintained for the penetrated areas while S shows at least 10 mm distance from the area of penetration to the side surface. During the penetration test, maintaining this distance was necessary so as to avoid exaggerated penetration. The CBR test had some differences in the way it was handled. This is because it involved two other main tests which had not been included in the manual. To obtain the maximum dry density and the corresponding optimum moisture content, a compaction test was carried out using the proctor and the test samples dried to obtain the % loss in moisture. It should be noted that the samples were not oven dried as was required but open drying was adopted instead. In order to obtain a realistic dry density against % moisture content curve, five samples tests were performed. From the graphical results, the maximum dry density and the optimum % moisture content were used in successive CBR tests. Using the geometrical properties of the mould using in compaction test, the bulk and unit weights of the soil used in different blows were obtained.

Softening point is a very important parameter that is normally used in calculating the penetration index. Different parameters were taken before and after the experiment.

3.1 (a) 3.1 (b)

Table 3.1 (a) and (b) shows the temperature of the bitumen when the softening point was attained. This temperature was recorded using a thermometer immediately the bitumen touched the bottom of the jar. The two balls are provided to help in getting the mean of the two (D Jones, 2010). The mean was simply calculated from;

Equation 1

The penetration value as given by (The Constructor, 2015) , is a measure of hardness of bituminous material which is the vertical distance traversed by a point of standard needle.

This test involved preparation of three samples where each was penetrated thrice and the reading recorded. Table 3.2 shows these results for the samples and the mean value of the results. From the results above the first values are taken and their average determined

Equation 2

Viscosity can be said to be the inverse of fluidity. The degree of fluidity of bituminous material is greatly influenced by the temperature where it is able to spread and penetrate into voids coating the aggregate. This test aimed in determining the viscosity of cutback bitumen.

Table 3.3 shows the data collected after the valve of the orifice was released. The time recorded was in seconds. The second test result was neglected for it was far from the rest

Hence the mean value was given as

The CBR test is the ratio of the force per unit are which is required to penetrate in a soil mass with a circular plunger of 50 mm in diameter at a rate of 1.25mm/min (Rogers, 2003). The test objectives were full filled by first carrying tests on;

Compaction of the soil sample

Determining the % moisture content and

Dry density tests

As accordance to the British Standard, a compaction test was conducted in order to determine the density of the soil sample. A container of 1000 cm3 capacity was used. The rammer used had a mass of 2.5 and was raised to a height of 300 mm where three layers were compacted. The masses of the fully compacted soil were taken. In the computation, the masses of the container were excluded so as to obtain the densities of the soil (Catch Themes, 2015).

Table 3.4 shows the data collected regarding the compaction data of the soil sample. The following equations were used in coming up with the above results;

When obtaining the densities of the soil at different moisture contents, soil samples were taken from each test and the %s of the moistures determined. The collected samples were weighed and then dried in an oven. The samples were then weighed their dry weights.

Table 3.5 shows all the data collected and the computation that was done regarding to the % moisture content of the soil. Using this data and the compaction data, a graph was plotted to help determine the maximum dry density and the optimum moisture content.

Table 3.6 shows the data calculated for the compaction and moisture content tests. Using this experimental result a graph showing the variation of density with increasing moisture content was plotted.

Figure 3.1 above shows the density % moisture variation curve. From the graph, the maximum density attained in compaction was 2.214 g/cc and the optimum % moisture content attained was 9.2 %

This test involved compaction of the soil sample in a CBR mould. The compaction was done in three ways. First 10 blows were used, followed by 30 blows and finally 65 blows per each compaction. The procedure given in the manual was used in carrying out this test.

10 blows test

Table 3.7 shows the data collected and calculated for the 10 blows compaction. The piston used had a plunger of 50 mm and thus its cross-section as computed gave an area of 0.00196m2. The stress was computed from; Pressure = Force / Area

Test Report

10

Data known from the compaction test

Maximum Dry Density= 2.214 g/cc

Optimum Moisture Content = 9.2 %

Dry density and the CBR DATA for the 10 blows

Sample container = A10

Weight of container = 90.4g

Weight of cont. + wet soil = 883.5 g

Weight of cont. + Dry soil = 827.3g

*100= 7.63%

Moisture %

Dry density

Weight of the mould = 7384g

Weight of mould + compacted soil = 11846g

Volume of the mould (cm³) = 2110

= 2.1147

Bulk unit weight (g/cc) =

Dry unit weight=

= 1.96

Figure 3.2 shows the variation of penetration with loading. From the curve, the value for 2.5 and 5.0 mm penetration are obtained and the CBR calculated.

CBR at 2.5 mm = (2.1/13.2)*100= 16.66%

CBR at 5.0 mm = (2.75/20)*100= 20.83%

The greater of the two is taken i.e. CBR = 20.83

30 blows test

Table 3.8 shows the data collected and calculated for the 30 blows compaction.

A Laboratory Report on Bitumen and CBR Tests

A Laboratory Report on Bitumen and CBR Tests

Test Report

11

Dry density test data for the 30 blows

Sample container = A30

Weight of the container= 92.4g

Weight of the cont. + moist soil = 857.4g

Weight of the cont. + dry soil = 809.2 g

*100= 7.625%

Moisture %

Dry density

Weight of the mould = 7387g = 7387g

Weight of mould + soil = 12054g

Volume of the mould = 2100 cm3

Bulk unit weight (g/cc) =

Dry unit weight=

Figure 3.3 shows the variation of penetration with loading. From the curve, the value for 2.5 and 5.0 mm penetration are obtained and the CBR calculated. CBR at 2.5 mm = (8.0/13.2)*100= 60.6% and the CBR at 5.0 mm = (13.8/20)*100= 69% where > of the 2 is taken i.e. CBR = 69%

65 blows test

Table 3.9 shows the data collected and calculated for the 65 blows compaction.

A Laboratory Report on Bitumen and CBR Tests

A Laboratory Report on Bitumen and CBR Tests

Test Report

13

Dry density and the CBR DATA for the 65 blows

Sample container = A65

Weight of container = 92.7g

Weight of cont. + wet soil = 859.6 g

Weight of cont. + Dry soil = 805.3g

*100= 7.61996%

Moisture %

Dry density

Weight of the mould = 7387g

Weight of mould + compacted soil = 12452g

Volume of the mould (cm³) = 2110

= 2.4004

Bulk unit weight (g/cc) =

Dry unit weight=

= 2.218

Figure 3.4 shows the variation of penetration with loading. From the curve, the value for 2.5 and 5.0 mm penetration are obtained and the CBR calculated. CBR at 2.5 mm = (10.2/13.2)*100= 77.2% and the CBR at 5.0 mm = (17.0/20)*100= 85% where > of the 2 is taken i.e. CBR = 85%

Using the results from the three tests, a relationship between the compaction and the CBR can be analyzed graphically.

Table 3.0 gives a combination of the data for the three blow methods used. The % compaction were computed from the MDD value calculated in section 3.4.2 above i.e. MDD = 2.214

Equation 3

Figure 3.5 shows a graphical relationship of the % CBR and % compaction for different number of blows as used in the laboratory. It is shown that the soil became denser with increasing CBR.

Figure 3.6 shows a graphical relationship of the % CBR and the dry density for different number of blows as used in this experiment. As the soil matrix became denser, the % CBR increased

From the two areas of the experiments, i.e. the bitumen tests and the CBR, various inferences can be observed.

In the softening point test, the grade of bitumen that was used to perform this test was Grade 60/70. This grade has its softening temperature falling within 45 to 550C. As 480C falls between the 450C and 550C, the value obtained was ok.

In the test carried out on penetration, the minimum and the maximum values attained were compared to get their differences. In the standards, the value with a penetration ranging from 50 to 149 should have a difference of maximum of 4. This is as accordance to the result attained in this test of;

Equation 4

The results on softening point and penetration test are used to come up with the penetration Index which is an important parameter in the pavement design. The equation below gives the penetration index of the bitumen.

Equation 5

Using the values computed above for the SP and the pen value;

Equation 6

According to the standards, the value of PI should be;

Equation 7

For Highly susceptible to lowly susceptible bitumen. Hence the bitumen used in the test experiment was highly susceptible.

The test on viscosity of cutback bitumen gave a value of 17 seconds. This range was ok.

The results from the CBR test gave different data which helped into achieving the expected result. Through the use of the plotted graphs, the values of loading at 2.5and 5.0 mm penetration were used to coming up with the CBRs for the soil sample. The result from the compaction and the % moisture content were very crucial in that all the other test on the CBR revolved around them. The MDD and the OMC helped in computing the final %s of the CBR (Geotechnical Engineering Office, 2001).

As a means of practical application of whatever that has been taught in theory work, these practical experiments on bitumen and CBR test helped a lot in broadening the knowledge on highway design. All the test were carried out in accordance to the manual given. The graphs and computations as carried out using excel sheets gave a clear understanding on the factors that affects the highways. Temperature being an environmental factor which is inevitable was found from the test to affect the softening, penetration and the viscosity of bitumen. As a result care has to be taken in ensuring that bituminous material remains effective throughout the design life of the highway surface. Age of the bitumen might have affected the results of the experiments conducted. It’s known that as bituminous material ages, the penetration value increases (Eurocode, 1999). Such effect affect the whole design of the pavement as the PI depends on the penetration value. From the values obtained in the CBR tests, graphs were drawn from the line on best fit. More analytical methods such as the regression methods has to be adopted if more realistic values are to be obtained. The moisture content obtained may have affected the result as 100 % drying of the samples could not have been obtained. Studies have shown that the soaking of the samples affects the CBR with soils varying differently to the duration of soaking. This duration should be considered for specific soils for more accurate results (Al-Gurah, 2009). For any construction projects on roads, the expected values has to be computed prior the project to ensure that the results falls within a certain limit.

A density/% Moisture content curve

4.8 6.9333299999999998 9.1999999999999993 11.36666 16.16667 2.1800000000000002 2.2040000000000002 2.214 2.2080000000000002 2.1989999999999998

% MOISTURE CONTENT OF THE SOIL

DENSITY OF THE SOIL

CBR TEST for 10 BLOWS

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0.68 1.08 1.32 1.57 1.83 2.0299999999999998 2.2000000000000002 2.6 2.8 3.1

PENETRATION

LOADING

CBR TEST for 30 BLOWS

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 1.1000000000000001 3.2 4.8 6.9 8.3000000000000007 9.4 10.6 11.6 12.3 14.3

PENETRATION

LOADING

CBR TEST for 65 BLOWS

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 1.31 3.66 6.3 9.07 10.9 11.97 12.92 13.76 15.8 19.3

PENETRATION

LOADING

%CBR vs % compaction

20.83 69 85 88.527551942186093 99.954832881662156 100.1806684733514

% Compaction

% CBR

% CBR vs dry density

20.83 69 85 1.96 2.2130000000000001 2.218

Dry Density

% CBR

16