Angularity number of coarse aggregate test

Name of the experiment: Angularity number of coarse aggregate test

Aim of the experiment: To determine the Angularity number of a given coarse aggregate sample.

Referred Standards:

 IS : 2386 (Part I) – 1963 : Indian standard methods of test for aggregates for concrete particle size and shape.

Summary of test method:

• The aggregate was compacted in three layers, each layer were given 100 blows using the standard tamping rod at a rate of 2 blows/second by lifting the rod 5 cm above the surface of the aggregate and then allowing it to fall freely.
• After compacting the third layer, the cylinder was filled to overflowing and excess material was removed off with temping rod as a straight.
• The aggregate with cylinder was then weighed. Three separate determinations were made and mean weight of the aggregate in the cylinder was calculated.

 Significance and use:

Degree of packing of particles of one size depends on their shape. The angularity of aggregates can be estimated from the proportion of voids among particles compacted in a standard manner. Rounded aggregates results to minimum void content and angular aggregates results into more voids. Void in a aggregate system depends on the shape of the aggregate. All other shapes except rounded aggregates result into more voids. This concept is utilized in determining the shape of the aggregate by indirect method i.e. Angularity Number .Angularity number is 67- % of solid volume in a vessel filled with aggregates in a standard manner. The number 67 represents solid volume of most rounded gravel.

Observations and Calculations:

Where, W = mean weight of the aggregate filling cylinder. C = Weight of water required to completely fill the cylinder (i.e. Volume of cylinder) Gs = Specific Gravity of the aggregate Weight of empty cylinder Weight    of cylinder + water Weight of water Weight of  cylinder +aggregate Angularity no 2693 5632 2939 7281 9.17 2693 5632 2939 7299 8.955 2693 5632 2939 7287 9.106

Results:

The Angularity number of given sample is given by 9.077

Discussion:

As obtained value is in the range of 8-11  so there is no problem in using these aggregates in pavement design with binders.

Marshall stability and flow test of bitumen

NAME OF THE EXPERIMENT: Marshall stability and flow test

AIM OF THE EXPERIMENT: To determine the resistance to plastic flow of cylindrical specimens of asphalt paving mixture loaded in a direction perpendicular to the cylindrical axis by means of the Marshall apparatus.

REFERRED STANDARDS:

Ø  ASTM D6927-15

            Standard Test Method for Marshall Stability and Flow of Asphalt Mixtures.

Ø  IRC: 111 – 2009 Specifications for Dense Graded Bituminous Mixes.

SUMMARY OF TEST METHOD:

(i) A series of specimens were prepared with varying quantities of bitumen content, with an increment of 0.5%, three specimens for one bitumen content.

(ii) Before testing of the mould it was kept in the water bath having a temperature of 60˚C for half an hour.

(iii) Loaded the specimen in the Marshall testing head and brought the loading ram into contact with testing head.  

 (iv) Load-deformation were recorded simultaneously by using a load cell and linear variable differential transducer (LVDT).

Significance and use:

Ø  Marshall flow is a measure of deformation (elastic plus plastic) of the bituminous mix determined during the stability test.  

Ø  Marshall Stability and flow values along with density, air voids in the total mix, voids in the mineral aggregate and voids filled with asphalt are used for laboratory mix design and evaluation of asphalt mixtures.

Ø  Marshall Stability and flow may also be used to relatively evaluate different mixes and the effects of conditioning such as with water. 

OBSERVATIONS AND CALCULATIONS:

Bitumen content (%) Corrected Stability(kN) Flow(mm) 4.0 10.71 2.28 4.5 11.76 2.31 5.0 13.33 2.97 5.5 13.78 2.30 6.0 13.52 2.95 6.5 12.13 3.62

RESULTS:

The Marshall Stability at the expected bitumen content of 5.0 % is found to be 13.33 kN and the Marshall flow at that bitumen content is found to be 2.97mm.

Discussion:

Ø  The Marshall Stability and flow we got here in the test are satisfying the specification given in IRC: 111 – 2009.

Ø  Depending on the composition and behaviour of the mixture, a less defined type of failure can also be observed.

Methylene Blue Index for Clay

Experiment Name: Methylene Blue Index

Aim of the Experiment: Measurement of the adsorption of methylene blue dye by clay

Referred Standards: ASTM C837 - 09 (Reapproved 2014) - Standard Test Method for Methylene Blue Index of Clay.

Summary of Test Method:

·         2 gram of oven dried clay sample to be mixed in 300 ml of distilled water taken in 600 ml beaker.

·         If required pH of the slurry to be maintained between 2.5 to 3.8 by addition of Sulphuric acid and slurry to be stirred for 10 to 15 minutes.

·         Methylene blue solution to be prepared by dissolving 1 g of methylene blue in distilled water to produce 200 ml of solution.

·         5 ml of methylene blue solution from burette to be added to slurry and stirred for 2 minutes.

·         A drop of the slurry to be taken and placedon the edge of the filter paper and appearance of the drop to be observed.The end point is indicated by the formation of a light blue haloaround the drop.

·         Addition of the methylene blue solutionto the slurry to be continued in 1.0-mL increments with 1 to 2 min of stirringafter each addition, then testing, until the end point is reached.

Significance and Use:

·         Tests run on many clays generally indicate that astraight-line relationship exists between the methylene blueindex (MBI) and fundamental clay propertiessuch as cationexchange capacity, dry bond strength, and casting rate.

·         When the colloidal portion of the clay is kaolinite, there is adirect correlation of adsorption with specific surface (as determined bynitrogen adsorption).

·         When the colloidal portion containssignificant amounts of illite or montmorillonite, the same closecorrelation does not exist.

Observations and Calculations:

·         Volume of methylene blue solution required to form blue halo ring (ml) = 10

·         Methylene Blue Index (MBI) = [(E*V)/W]*100= [(0.01*10)/2]*100 = 5

Where, MBI = methylene blue index for the clay in meq/100 g clay,

E = milli-equivalents of methylene blue per ml

V = methylene blue solution required forthe titration (in ml)

W = weight of dry material (in grams).

Results:

·         The methylene blue index for the clay is found to be 5.

Discussion:

·         The MBI value we get here in the experiment is 5, which indicates towards the excellent expected performance of aggregate in pavement.

·          But we have not followed the complete procedure due to unavailability of pH meter, which was necessary to know about the pH of slurry and to maintain the acidic range of the slurry.

·         That is why we cannot be sure about the reliability of the test results.

Marshall stability and flow test of bituminous mix

NAME OF THE EXPERIMENT: Marshall stability and flow test

AIM OF THE EXPERIMENT: To determine the resistance to plastic flow of cylindrical specimens of asphalt paving mixture loaded in a direction perpendicular to the cylindrical axis by means of the Marshall apparatus.

REFERRED STANDARDS:

Ø  ASTM D6927-15

            Standard Test Method for Marshall Stability and Flow of Asphalt Mixtures.

Ø  IRC: 111 – 2009 Specifications for Dense Graded Bituminous Mixes.

SUMMARY OF TEST METHOD:

(i) A series of specimens were prepared with varying quantities of bitumen content, with an increment of 0.5%, three specimens for one bitumen content.

(ii) Before testing of the mould it was kept in the water bath having a temperature of 60˚C for half an hour.

(iii) Loaded the specimen in the Marshall testing head and brought the loading ram into contact with testing head.  

 (iv) Load-deformation were recorded simultaneously by using a load cell and linear variable differential transducer (LVDT).

Significance and use:

Ø  Marshall flow is a measure of deformation (elastic plus plastic) of the bituminous mix determined during the stability test.  

Ø  Marshall Stability and flow values along with density, air voids in the total mix, voids in the mineral aggregate and voids filled with asphalt are used for laboratory mix design and evaluation of asphalt mixtures.

Ø  Marshall Stability and flow may also be used to relatively evaluate different mixes and the effects of conditioning such as with water. 

OBSERVATIONS AND CALCULATIONS:

Bitumen content (%) Corrected Stability(kN) Flow(mm) 4.0 10.71 2.28 4.5 11.76 2.31 5.0 13.33 2.97 5.5 13.78 2.30 6.0 13.52 2.95 6.5 12.13 3.62

RESULTS:

The Marshall Stability at the expected bitumen content of 5.0 % is found to be 13.33 kN and the Marshall flow at that bitumen content is found to be 2.97mm.

Discussion:

Ø  The Marshall Stability and flow we got here in the test are satisfying the specification given in IRC: 111 – 2009.

Ø  Depending on the composition and behaviour of the mixture, a less defined type of failure can also be observed.

Hansen’s bearing capacity theory

Hansen’s bearing capacity theory

For cohesive soils, Values obtained by Terzaghi’s bearing capacity theory are more than the experimental values. But however it is showing same values for cohesion less soils. So Hansen modified the equation by considering shape, depth and inclination factors.

According to Hansen’s

qu = c’Nc Sc dc ic +  Df Nq Sq dq iq + 0.5  B Ny Sy dy iy

Where Nc, Nq, Ny = Hansen’s bearing capacity factors

Sc, Sq, Sy = shape factors

dc, dq, dy = depth factors

ic, iq, iy = inclination factors

Bearing capacity factors are calculated by following equations.

For different values of  Hansen bearing capacity factors are calculated in the below table.

	Nc	Nq	Ny
0	5.14	1	0
5	6.48	1.57	0.09
10	8.34	2.47	0.09
15	10.97	3.94	1.42
20	14.83	6.4	3.54
25	20.72	10.66	8.11
30	30.14	18.40	18.08
35	46.13	33.29	40.69
40	75.32	64.18	95.41
45	133.89	134.85	240.85
50	266.89	318.96	681.84

Shape factors for different shapes of footing are given in below table.

Shape of footing	Sc	Sq	Sy
Continuous	1	1	1
Rectangular	1+0.2B/L	1+0.2B/L	1-0.4B/L
Square	1.3	1.2	0.8
Circular	1.3	1.2	0.6

Depth factors are considered according to the following table.

Depth factors	Values
dc	1+0.35(D/B)
dq	1+0.35(D/B)
dy	1.0

Similarly inclination factors are considered from below table.

Inclination factors	Values
ic	1 – [H/(2 c B L)]
iq	1 – 1.5 (H/V)
iy	(iq)2

Where H = horizontal component of inclined load

B = width of footing

L = length of footing.