SPECIFIC GRAVITY OF COMPACTED SPECIMEN OF BITUMINOUS MIX

The specific gravity values of the different aggregates, filler and bitumen used are determined first. The theoretical specific gravity G_t of the mix is given by-

 Where,

W₁ = percent by weight of coarse aggregate

                        W₂ = percent by weight of fine aggregate

                        W₃ = percent by weight of mineral filler

                        W₄ = percent by weight of bitumen

                        G₁ = apparent specific gravity of coarse aggregate

                        G₂ = apparent specific gravity of fine aggregate

                        G₃ = apparent specific gravity of mineral filler

            G₄ = apparent specific gravity of bitumen

DESIGN PROCEDURE OF BITUMINOUS MIXES

In the design procedure of a bituminous mix, following steps are involved.

i) Selection of aggregate to be employed in the mix.

ii) Selection of aggregate grading.

iii) Determination of the proportion of each aggregate required to develop the design grading.

iv) Determination of the specific-gravity of the aggregate blend.

v) Determination S.G. of the bitumen.

vi) Make up trial specimens with varying bitumen contents.

vii) Determination of the specific-gravity (S.G) of each compacted specimen.

viii) Make stability test on the specimen.

ix) Determine the percentage of voids in each paving specimen and if the design method in use requires it, calculate the VMA and percent voids filled with bitumen.

x) Selection of the optimum bitumen content from the obtained data.

EFFECTS OF POLYETHYLENE AND KEROSENE ON THE PROPERTIES OF BITUMEN

TEST PROCEDURE & GRAPHICAL PRESENTATION

Specific Gravity Test

           (a)        Wt. of bottle at clean and dry condition = A gm

           (b)        Wt. of (bottle+ water full) at 25⁰ C after 30 min = B gm

           (c)        Wt. of (bottle+ bitumen) at 25⁰ C after 60 min = C gm

           (d)        Wt. of (bottle+ bitumen +water full) at 25⁰ C after 30 min = D gm

                                                    Sp. Gr. = (C-A) / ((B-A)-(D-C))

Penetration Test

(a) Bitumen at 100-1100 C was poured into the container and then cooled to room temperature for one hour.
(b) Container with bitumen was submersed in water at 250 C for one hour.

(c) At constant temp. of 250C, the sample was placed in penetrometer and then readings were recorded for a period of 5 seconds.

Ductility Test

(a) Bitumen was strained through 0.6 mm sieves and then poured into the briquette and was cooled to room temperature for 30 min.
(b) Then sample was placed in water at 25 0C for 30 min.
(c) Excess bitumen was cut off and the briquette was placed in water at 250 C for 1.5 hour. 

(d) Briquette was placed in ductility machine and recorded the reading in cm at which the bitumen threads were broken.

Result of Specific gravity, Penetration and Ductility Test.
(Modified Bitumen Sample made with mixing of Pure Bitumen,
Polyethylene and Kerosene)

Type of Sample	% of Polyethylene content	% of Kerosene content	Specific Gravity	Penetration value	Ductility value
Pure bitumen	0	0	1.020	85	100+
Sample-1	1	1	1.016	41	74
Sample-2	2	2	1.013	53	60
Sample-3	3	3	1.009	50	44
Sample-4	4	4	1.006	41	26
Sample-5	5	5	1.003	38	18

 

Result of Penetration Test (only for % of kerosene content)

Type of Sample	% of Kerosene content	Penetration value
Pure bitumen	0	85
Sample-1	1	80
Sample-2	2	60
Sample-3	3	55
Sample-4	4	54
Sample-5	5	82

 

Solubility Test

(a) 0.50 gm asbestos fiber was thoroughly shaked in 150 cc water.

(b) The crucible was filled with some of the suspension of asbestos in water and applied a light suction to draw off the water, leaving a firm mat of asbestos in the crucible.

(c) The crucible was heated for 10 to 15 min. for the constant weight of A.
(d) 2 gm bitumen was stirred in 100 cc CS2 until all lumps were disappeared and no undissolved sample was adhered to the container. (e) The prepared weighed Gooch crucible was placed in the filter flask. Decanted the solution through the asbestos mat of the crucible with light suction. Removing the crucible from the flask and then heating for 10 to 15 min. for constant weight of B gm.

 

Softening Point Test

(a) Completely fluid bitumen was poured in heated rings placed on metal plate.
(b) After cooling the rings in air for 30 min. the excess bitumen was trimmed.
(c) At this time the temperature of water was kept at 50C for 15 min. and then the balls were placed in position. 

(d) The temperature of water was raised at uniform rate of 50C/min. until the bitumen was softened and touched the bottom plate by sinking of balls.

  

Flash and Fire Point Test

(a) Bitumen was poured into the clean and dried cup up to a filling mark.
(b) Sample was then heated at the rate of 5 to 60C/ min.

(c) Test flame was applied at intervals depending upon the expected flash and fire points.

Result of Solubility, Softening, Flash and Fire Point Test.
(Modified Bitumen Sample made with mixing of Pure Bitumen,
Polyethylene and Kerosene)

Type Of Sample	% of Polyethylene content	% of Kerosene content	Solubility (%)	Softening Point (0C)	Flash Point (0C)	Fire Point (0C)
Pure bitumen	0	0	95.70	43	290	300
Sample-1	1	1	90.05	55	280	295
Sample-2	2	2	85.70	56	270	285
Sample-3	3	3	82.13	57	260	275
Sample-4	4	4	84.30	58	255	270
Sample-5	5	5	87.50	59	250	265

SPECIFIC GRAVITY TEST OF BITUMINOUS MATERIAL

The density of a bituminous binder is a fundamental property frequently used as an aid in classifying the binders for use in paving jobs. In most applications, the bitumen is weighted, but finally in use with aggregate system, the bitumen content is converted in volume basis. Thus an accurate density value is required for conversion of weight to volume. The specific gravity is greatly influenced by the chemical composition of the binder. Increased amounts of aromatic type compounds cause an increase in the specific gravity. The test procedure has been standardized by the ISI.

LABORATORY TEST FOR BITUMINOUS MATERIAL

Laboratory Test on Bitumen

Crude petroleum obtained from different sources contains different proportions of different constituents. Hence its properties may differ. Therefore to judge their suitability as binders, following tests are recommended;

i)                    Penetration test

ii)                   Ductility test

iii)                 Softening point test

iv)                 Specific gravity test

v)                  Flash point and fire point test

vi)                 Float test

vii)               Viscosity test

viii)              Loss on heating test

ix)                 Solubility test

 

To determine all of these properties, a variety of tests have been specified by Institutions like ASTM, I.S.I., Asphalt institute and B.S.I. Here ASTM is followed. Prepared samples are tested to determine some of above properties. 

PROCEDURE FOR BITUMINOUS MIX PROPORTIONING

The proportioning of bituminous concrete includes the following steps:

1. Determine the nature and characteristics of the aggregate available.
2. To fix an aggregate grading which meets all the requirements and which is possible to develop practically.
3. Determine the blending percentages of aggregates which will result in the desired gradation aggregate.
4. To determine the gradation limits for the individual aggregates.
5. Preparation of test specimens using the aggregate and a range of bitumen contents.
6. Analyze the test specimen for specific gravity, voids and stability.
7. Selection of the optimum bitumen content from the test data.
8. Consistency and quality of bitumen content.