CE328 Highway Materials Testing Experiments. By Dr. Tom. V. Mathew IIT Bombay

Transcription

1 CE328 Highway Materials Testing Experiments By Dr. Tom. V. Mathew IIT Bombay

2 List of Tests 1. Aggregate crushing test 2. Aggregate impact test 3. Abrasion Test (L.A. abrasion test) 4. Shape test (FI, EI, Angularity No.) 5. Penetration Test 6. Ductility Test 7. Softening Point 8. Marshall Stability Test 9. Bitumen Extraction Test 10.Traffic studies: Volume study

3 Requirements of Pavements Types Flexible Pavement Rigid Pavement Structural Requirements to withstand the design factors to serve during the design life / minimum service life Functional Requirements considering pavement deterioration considering road user requirement

4 Flexible Pavements

5 Loading in FP

6 Overview Pavement materials Soil (sub-grade, embankment) Aggregates (coarse, fine) Binders (Bitumen, cement)

7 Aggregate Aggregate is the major component of all materials used in road construction It is used in granular bases and sub base, bituminous courses and in cement concrete pavements

8 Desirable properties of Aggregate Strength:The aggregate should be sufficiently strong to withstand the stresses due to traffic wheel load Hardness: Aggregate should have hard enough to resist the wear due to abrasive action of traffic Toughness: Aggregate should have resistance to impact or toughness

9 Desirable properties of Aggregate Durability: The aggregate used in pavement should resistance to disintegration due to the action of weather Shape of aggregate: Should not be Flaky and elongated Adhesion with Bitumen: Should have good affinity to bitumen

10 Soil Soil is all unindurated mineral material lying above rock strata including air, water, and organic matter It is non-homogeneous and porous Properties greatly influenced by moisture, density and compaction A number of pavement failure is attributed to soil failures

11 Properties of soil Shape of soil particles (bulky, flaky) Particle size classification (clay, silt, sand, gravel) Grain size distribution (sedimentation analysis for <75m) Porosity and void ratio Soil density (dry and wet density)

12 Properties of soil Moisture-density relationship (Proctor density, OMC) Chemical properties (Organic matter, minerals, ph) Soil-water (Capillary water, water table) Physical properties (Permeability, compressibility, shear resistance)

13 Petroleum distillation Flow Chart

14 Desirable Properties of Bitumen

15 Desirable Properties of Bitumen It should be fluid enough at the time of mixing to coat the aggregate evenly by a thin film It should have low temperature susceptibility It should show uniform viscosity characteristics Bitumen should have good amount of volatiles in it, and it should not lose them excessively when subjected to higher temperature

16 Desirable Properties of Bitumen The bitumen should be ductile and not brittle The bitumen should be capable of being heated to the temperature at which it can be easily mixed without any fire hazards The bitumen should have good affinity to the aggregate and should not be stripped off in the continued presence off water

17 Quality Control Tests: Soil 1. Gradation 2. Atterberg Limits and indices (LL, PL,PI, SL) 3. Laboratory Compaction (MDD and OMC) 4. Field density test 5. CBR Test 6. Plate bearing test

18 Quality control tests: Aggregate 1. Sieve analysis 2. Aggregate crushing test 3. Aggregate impact test 4. Abrasion Test (L.A. abrasion test) 5. Shape test (FI, EI, Angul. No.) 6. Soundness Test 7. Specific gravity and Water absorption test 8. Stripping value test

19 Quality control tests: Bitumen 1. Penetration 2. Ductility 3. Softening point 4. Specific gravity 5. Loss on heating 6. Flash & Fire point 7. Viscosity 8. Solubility

20 California bearing ratio (CBR) A simple test that compares the bearing capacity of a material with that of a well-graded crushed stone A high quality crushed stone material should have a CBR of about 100% CBR is basically a measure of strength

21 CBR CBR value is the measure of resistance of material to the penetration of standard plunger under controlled density and moisture condition. The CBR test can be made in the laboratory on undisturbed or remoulded soil samples. The CBR value of sub grade is normally evaluated on a soaked sample compacted at optimum moisture content to maximum dry density.

22 Basic Test This consists of causing a plunger of 50 mm diameter to penetrate a soil sample at the rate of 1.25 mm/min. The force (load) required to cause the penetration is plotted against measured penetration. The loads at 2.5 mm and 5 mm penetration are recorded. This load corresponding to 2.5 mm or 5 mm penetration is expressed as a percentage of standard load sustained by the crushed aggregates at the same penetration to obtain CBR value.

23 Definition of CBR California bearing ratio is defined as the ratio (expressed as percentage) between the load sustained by the soil sample at a specified penetration of a standard plunger (50 mm diameter) and the load sustained by the standard crushed stones at the same penetration.

24 Standard Load values on Crushed Stones for Different Penetration Values Penetration, mm Standard Load, kg Unit Standard Load, kg/cm

25 Apparatus Loading frame Cylindrical mould, Collar, Base Plate and spacer Disc Compaction hammer Expansion Measuring Apparatus - Perforated plate with adjustable stem, tripod and dial gauge reading to 0.01 mm Annular Surcharge Weights

26 With a capacity of at least 5000 kg and equipped with a movable head or base that travels at an uniform rate of 1.25 mm/min. Loading Machine

27 Cylindrical mould with inside diameter 150 mm and height 175 mm, provided with a detachable extension collar 50 mm height and a detachable perforated base plate 10 mm thick. Cylindrical Mould

28 Compaction Rammer Weight 2.6 kg with a drop of 310 mm (or) Weight 4.89 kg a drop 450 mm.

29 Adjustable stem, perforated plate, tripod and dial gauge

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31 Preparation of Test Specimen Prepare the remoulded specimen at Proctor s maximum dry density or any other density at which C.B.R is required. Maintain the specimen at optimum moisture content or the field moisture as required. The material used should pass 20 mm I.S. sieve. Prepare the specimen either by dynamic compaction or by static compaction.

32 Dynamic Compaction Take about 4.5 to 5.5 kg of soil and mix thoroughly with the required water. Just before making the compacted mould of soil, take representative sample for determining water content. Fix the extension collar and the base plate to the mould. Insert the spacer disc over the base. Place the filter paper on the top of the spacer disc.

33 Dynamic Compaction Compact the soil in the mould using either light compaction or heavy compaction. For light compaction, compact the soil in 3 equal layers, each layer being given 55 blows by the 2.6 kg rammer. For heavy compaction compact the soil in 5 layers, by giving 56 blows to each layer by the 4.89 kg rammer.

34 Dynamic Compaction Remove the collar and trim the specimen smooth and flush with the mould. Remove the base plate and the displacer disc, weigh the mould with compacted soil, and determine the wet unit weight. Place a filter paper on the base plate, invert the specimen (5 cm gap is on the top) and attach the base plate so that the soil is in contact with the filter paper on the base.

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36 Penetration Test Place the mould assembly with the surcharge weights on the penetration test machine. Seat the penetration piston at the center of the specimen with the smallest possible load, but in no case in excess of 4 kg so that full contact of the piston on the sample is established. Set the stress and strain dial gauge to read zero. Apply the load on the piston so that the penetration rate is about 1.25 mm/min. Record the load readings at penetrations of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 7.5, 10 and 12.5 mm. Note the maximum load and corresponding penetration if it occurs for a penetration less than 12.5 mm. Detach the mould from the loading equipment. Take about 20 to 50 g of soil from the top 3 cm layer and determine the moisture content.

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39 Data from a Typical CBR Test for Sample No.1 Penetration (mm) Proving Ring Reading (div) Load on Plunger Penetration (mm) Proving Ring Reading (div) Load on Plunger

40 Load Vs Penetration Curve for Sample No Load Penetration

41 Initial Concavity The load penetration curve may show initial concavity due to the following reasons: The top layer of the sample might have become too soft due to soaking in water The surface of the plunger or the surface of the sample might not be horizontal

42 Correction Draw a tangent to the load-penetration curve where it changes concavity to convexity The point of intersection of this tangent line with the x-axis is taken as the new origin Shift the origin to this point (new origin) and correct all the penetration values

43 Corrected Penetration Values for Sample No

44 Computation of CBR for Sample No.1 Compute CBR at 2.5 mm penetration CBR of Specimen at 2.5 mm penetration = (80/1370)*100 = 5.84 % Compute CBR at 5 mm penetration CBR of Specimen at 5 mm penetration = (117/2055)*100 = 5.69 %

45 Variation in CBR Values At least three samples should be tested on each type of soil at the same density and moisture content to take care of the variation in the values This will enable a reliable average value to be obtained in most cases Where variation with in CBR values is more than the permissible maximum variation the design CBR value should be the average of six samples and not three

46 Permissible Variation in CBR Value CBR (per cent) and above Maximum variation in CBR value ± 1 ± 2 ± 3 ± 5

47 Design CBR The average CBR values corresponding to 2.5 mm and 5 mm penetration values should be worked out If the average CBR at 2.5 mm penetration is more than that at 5 mm penetration, then the design CBR is the average CBR at 2.5 mm penetration If the CBR at 5mm penetration is more than that at 2.5 mm penetration, then the test should be repeated. Even after the repetition, if CBR at 5mm is more than CBR at 2.5 mm, CBR at 5 mm could be adopted as the design CBR.

48 Computation of Design CBR CBR (%) Penetration Mean 2.5 mm mm Design CBR 5.71 %

49 1. Sieve Analysis

50 Each type of aggregate test requires a specified aggregate size (E.g mm for crushing test) Each bituminous mix type has a recommended aggregate gradation (% passing 26.5 mm in for GSB1) So aggregate is passed through a set of sieves to get material of various sizes Significance of Test

51 Sieves and Sieve-shaker

52 Procedure Bring the sample to an air dry condition either by drying at room temperature or in oven at a temperature of 100 o C to 110 o C.Take the weight of the sample. Clean all the sieves and sieve the sample successively on the appropriate sieves starting with the largest. Shake each sieve separately over a clean tray. On completion of sieving note down the weight of material retained on each sieve. Report the results as cumulative percentage by weight of sample passing each of the sieves.

53 Observation Sheet I.S. Sieve designation Weight of sample retained (gm) Percent of weight retained (%) Cumulative percent of weight retained (%) Percentage passing (%) 63 mm 40 mm 20 mm 12.5 mm 10 mm 4.75 mm IS:2386 Part I; IS: 383

54 Observation Sheet IS Seive Designation (mm) Weight of sample retained (gm) Weight retained (%) Cumulative weight retained (%) Passing (%)

55 Gradation chart Gradation

56 1. Aggregate Crushing Test

57 Significance Aggregate crushing value provides a relative measure of resistance to crushing under a gradually applied compressive load Aggregates subjected to high stresses during rolling and severe abrasion under traffic Also in India very severe stresses come on pavements due to rigid tyre rims of heavily loaded animal drawn vehicles

58 Test Set-up

59 Procedure Surface dry aggregates passing 12.5 mm and retained on 10 mm selected 3.25 kg aggregate required for one test sample Cylindrical measure filled with aggregates in 3 layers, tamping each layer 25 times After leveling the aggregates at the top surface the test sample is weighed The cylinder is now placed on the base plate

60 Contd. The cylinder with the test sample and plunger in position is placed on compression machine Load is applied at a rate of 4 tonnes per minute upto 40 tonnes The crushed aggregate is taken out, sieved through 2.36 mm IS sieve and weighed to get material passing Aggregate crushing value = W2*100/W1 W2= Weight of crushed material W1=Total weight of sample

61 Sample being loaded in the compression machine at 4 T per minute for 10 minutes (upto 40 T) Load Application

62 Observation Sheet Observations 1 Test No. 2 3 Average Wt. of Aggregate Sample Filling in The Cylinder= W1(gms) Wt. of Aggregate Sample Passing 2.36 mm Sieve After the Test= W2(gms) Aggregate Crushing Value= W1/W2*100 Note: Value recorded up to first decimal place

63 Observation Sheet Observations Wt. of Aggregate Sample Filling in The Cylinder= W1 (gms) Test No Average Wt. of Aggregate Sample Passing 2.36 mm Sieve After the Test= W2 (gms) Aggregate Crushing Value = W1 / W2 x % 28.8 % 24.5 % 28.5 % Note: Value recorded up to first decimal place

64 Specifications Specified By Aggregate Crushing Value for Cement Concrete Pavements As per IRC: And IS: 2386:Part IV 30 % Max for Surface Course 45 % Max for Other Surfaces

65 Discussion Indirect measure of crushing strength Low value indicate strong aggregates Surface course need more strength than base course Should not exceed 30% for cement concrete surface, and 45% for others

66 2. Aggregate Impact Test

67 Significance This test assesses the suitability of aggregate as regards the toughness for use in pavement construction Road aggregates subjected to pounding action due to traffic loads- so possibility of breaking Should be tough enough- so proper aggregates to be used Suitability to be checked by laboratory tests

68 Test Set-up

69 Procedure 1. Aggregate passing through 12.5 mm IS sieve and retained on 10 mm sieve is filled in the cylindrical measure in 3 layers by tamping each layer by 25 blows. Determine the net weight of aggregate in the measure (W1) 2. Sample is transferred from the measure to the cup of aggregate impact testing machine and compacted by tamping 25 times 3. The hammer is raised to height of 38 cm above the upper surface of the aggregates in the cup and is allowed to fall freely on the specimen

70 Test In progress

71 Contd. After subjecting the test specimen to 15 blows, the crushed aggregate is sieved through IS 2.36 mm sieve Weigh the fraction passing through IS 2.36 mm sieve(w2) Aggregate impact value = W2 / W1 x100 w2 = Weight of fines passing 2.36 mm w1 = Weight of sample Mean of the two values reported

72 Observation Sheet Observations 1 Test No. 2 3 Avg Wt. of Aggregate Sample Filling in The Cylinder= W1(gms) Wt. of Aggregate Sample Passing 2.36 mm Sieve After the Test= W2(gms) Aggregate Impact Value= W2/W1*100 Note: Value Recorded to the Nearest Whole Number

73 Observation Sheet Observations Wt. of Aggregate Sample Filling in The Cylinder= W1 (gms) Test No Avg Wt. of Aggregate Sample Passing 2.36 mm Sieve After the Test= W2 (gms) Aggregate Impact Value= W2 / W1 x Note: Value Recorded to the Nearest Whole Number

74 Specifications Type of Pavement Material/Layer Aggregate Impact Value, Max, % WBM Sub-base course 50 Cement Concrete Base course Bituminous Macadam, Base course WBM Surface course Bituminous Wearing Surfaces IS: 2386: Part IV and IRC: ; MORTH:

75 3. Los Angeles Abrasion Test

76 Significance It is resistance to wear or hardness of aggregates Road aggregates at the top subjected to wearing action Under traffic loads abrasion/attrition action within the layers as well To determine suitability, tests have to be carried out

77 Test Set-up

78 Procedure 1. Aggregates dried in oven at C. to constant weight conforming to any one of the gradings E.g gm of mm, 1250 gm of mm, 1250 gm of mm, 1250 gm of mm, with 12 steel balls 2. Aggregate weighing 5 kg or 10 kg is placed in cylinder of the machine ( W1 gms) 3. Machine is rotated at rpm for 500 revolutions 4. Machine is stopped and complete material is taken out including dust

79 Grading Requirement Grading Wt. in gms of each Sample in the Size Range, mm No. of Spheres Abrasive Charge Wt. of Charge, g A ±25 B ±25 C ±25 D ±25 E ±25 F NA ±25 G ±25

80 After revolutions

81 Contd. 6. Sieved through 1.7 mm sieve 7. Weight passing is determined by washing the portion retained, oven drying and weighing (W2 gms) 8. Aggregate abrasion value is determined LAAV = W2 / W1 x100 W2 = Weight of fines passing 1.7 mm W1 = Weight of the sample

82 Specifications Type of Pavement Layer WBM Sub-base course WBM Base course with bit. Surfacing, BM Base course WBM Surface course, BM binder course Bituminous Carpet, SD, Cement Concrete surface course Bituminous/Cement concrete Wearing course L. A. Abrasion Value, Max, % IS: 2386: Part IV; IRC: ; IS: 383

83 Discussion Select a grading close to the project for testing Simulate both abrasion and impact due to wheel loads It determines the hardness of the stone

84 4. Shape Tests Determination of: a.flakiness Index b.elongation Index c. Angularity Number

85 Significance Shape of crushed aggregates determined by the percentage of flaky and elongated particles Shape of gravel determined by its angularity number Flaky and elongated aggregate particles tend to break under heavy traffic loads Rounded aggregates preferred in cement concrete pavements as more workability at less water cement ratio Angular shape preferred for granular courses/flexible pavement layers due to better interlocking and hence more stability

86 Test Set-up Length Gauge for Elongation Index Thickness Gauge for Flakiness Index

87 Procedure (Flakiness) (a). Flakiness Index: The flakiness index of aggregates is the percentage by weight of particles whose least dimension is less than three-fifths (0.6) of their mean dimension. Applicable to sizes>= 6.3 mm 1.The sample is sieved through IS sieve sizes 63, 50, 40, 31.5, 25, 20, 16, 12.5, 10 and 6.3 mm 2. Minimum 200 pieces of each fraction to be tested are taken and weighed (W1 gm) 3. Separate the flaky material by using the standard thickness gauge

88 Flakiness Index Test in Progress

89 Flakiness The amount of flaky material is weighed to an accuracy of 0.1 percent of the test sample If W 1, W 2,, W i are the total weights of each size of aggregates taken If w 1, w 2,, w i are the weights of material passing the different thickness gauges then: FI wi ( w w2...) 1 i 100 % 100 % ( W W...) W 1 2 i i

90 Observation sheet (Flakiness Index) Size of aggregate Passing through I.S. Seive, (mm) Retained on I.S. Seive, (mm) Wt. Of the fraction consisting of at least 200 pieces (gm) Thickness gauge size, (0.6 times the mean sieve) (mm) Weight of aggregate in each fraction passing thickness gauge (gms) W1= 23.9 w1= W2= 27 w2= W3= 19.5 w3= W4= w4= W5= 13.5 w5= W6= 10.8 w6= W7= 8.55 w7= W8= 6.75 w8= W9= 4.89 w9= Total W= w=

91 Elongation Index Elongation Index: The percentage by weight of particles whose greatest dimension is greater than one and four fifth times (1.8 times) their mean dimension. Applicable to sizes >=6.3 mm 1. The sample is sieved through sieve sizes, 50, 40, 25, 20, 16, 12.5, 10 and Minimum 200 pieces of each fraction to be tested are taken and weighed (W1 gm) 3. Separate the elongated material by using the standard length gauge

92 Elongation Index Test in Progress

93 Elongation Index The amount of elongated material is weighed to an accuracy of 0.1 percent of the test sample If W 1, W 2,, W i are the total weights of each size of aggregates taken If w 1, w 2,, w i are the weights of material retained on different thickness gauges then: EI wi ( w w2...) 1 i 100 % 100 % ( W W...) W 1 2 i i

94 Observation sheet (Elongation Index) Size of aggregate Passing through I.S. Seive, (mm) Retained on I.S. Seive, (mm) Wt. Of the fraction consisting of at least 200 pieces (gm) Length gauge size, (1.8 times the mean sieve) (mm) Weight of aggregate in each fraction retained on length gauge (gms) W1= 81 w1= W2= 58 w2= W3= 40.5 w3= W4= 32.4 w4= W5= 25.5 w5= W6= 20.2 w6= W7= 14.7 w7= Total W= w=

95 Specifications Type of pavement construction Limit of Flakiness Index(%) Bituminous carpet Asphaltic concrete Penetration macadam Bit. Surface dressing Bit. Macadam, WBM base & surfacing course Cement Concrete 30(Combined FI and EI) 25(do) 15(do) 35 IS: 2386, Part I; IRC: ; MORTH: 2001

96 Angularity number The angularity number measures the percent voids in excess of 33 percent which is obtained in the case of the most rounded gravel particles. Range: 0-11 (rounded gravel-crushed angular) 1. The cylinder is calibrated by determining the weight of water at 27 o C required to fill it 2. Aggregate is sieved through 20, 16, 12.5, 10, 6.3 and 4.75 mm IS sieves 3. About 10 kg of the predominant size should be available

97 Test in Progress

98 Contd. 4. The sample of single-size aggregate is dried in an oven at 100 o to 110 o C for 24 hours and then cooled 5. The scoop is filled with aggregate which is allowed to slide gently into the cylinder from the lowest possible height 6. The aggregate is filled in three layers, tamping each layer evenly 100 times with a tamping rod 7. After the third layer is tamped, the aggregates are struck off level with the help of tamping rod and surface finished 8. The aggregate with cylinder is now weighed to the nearest 5 g. The mean weight of aggregate is found

99 Calculations and Observation Sheet Angularity number AN = 67 - W x 100 G x C where, W = mean weight of aggregates in the cylinder,g C = Weight of water required to fill the cylinder,g G = Specific gravity of aggregate (2.71) Weight of water filling the cylinder = C g = Specific gravity of the aggregate = G = Trial number Particulars Mean Weight of aggregate filling the cylinder to the nearest five grams, g Mean weight of aggregate filling the cylinder, Wt =2870 Angularity Number = 67 { (4190/2.71x100)/C } = 13

100 Discussion Elongated, flaky and angular materials decreases the workability of the mix, and not preferred in cement concrete Angular aggregates are preferred in flexible pavement at WBM / WMM Angularity number ranges from zero for perfectly rounded aggregate (rounded pebbles) to about 11 percent for freshly crushed aggregates But for DBM & BC mix design may be modified to incorporate high angularity number

101 5. Penetration test

102 Significance The penetration test determine the hardness or softness of bitumen The bitumen grade is specified in terms of the penetration value 30/40 and 80/100 grade bitumen are commonly used In hot climates a lower penetration grade bitumen is preferred and vise versa

103 Significance Consistency of bitumen varies with temperature, constituents, refining process, etc. Viscosity is an absolute property, but could not be determined easily Viscosity of cutback bitumen by indirect method (orifice viscometer) Too soft for penetration, too hard for orifice then perform float test

104 Significance Basic principle of penetration test: measurement of penetration in units of 1/10 th of a mm of a standard needle of 100 gm in a bitumen sample kept at 25 C for 5 seconds Higher penetration implies softer grade Purpose is classification

105 Figure Penetrometere Water Bath Dial Temperature Controller Needle Mould Weight

106 Procedure Heat the bitumen to softening point C Pour the bitumen into the container at least 10 mm above the expected penetration Place all the sample containers to cool in atmospheric temperature for 1 hour Place the sample containers in temperature controlled water bath at a temperature of 25 0 C ± 1 o C for a period of 1 hour Fill the transfer dish with water from the water bath to cover the container completely

107

108 Continue.... Take off the sample container from the water bath, place in transfer dish and place under the middle of penetrometer Adjust the needle to make a contact with surface of the sample See the dial reading and release the needle exactly for 5 seconds Note the final reading Difference between the initial and final readings is taken as the penetration value in 1/10th of mm

109 (i) Pouring temperature Observation Sheet = 100 oc (ii) Period of cooling in atmosphere, minutes = 60 mts (iii) Room temperature = 27 oc (iv) Period of cooling in water bath, minutes = 60 mts (v) Actual test temperature = 25 oc Penetrometer dial readings Test 1 Sample No 1 Sample No 2 Test 2 Test 3 Mean value Test 1 Test 2 Test 3 Mean value Initial Final Average Value = 82 (Grade is 80/100)

110 IS Specifications Penetration Grade Above 225 Repeatability 4% 5% 7% Bitumen Grade A25 A35 & S35 A45 & S45 A65 & S65 A90 & S90 A200 & S200 Penetration Value

111 Discussion Test is highly influenced by the pouring temperature, size of needle, weight of needle, test temperature, duration of release of needle IRC suggests 30/40, 60/70, 80/100 for BM High penetration grade is desirable in colder regions Penetration below 20 will result in cracking For lower penetration, bonding is difficult, but once achieved will remain for a long time

112 6. Ductility Test

113 Ductility Machine

114 Significance The ductility of bitumen improves the physical interlocking of the aggregate bitumen mixes Under traffic loads the pavement layer is subjected to repeated deformation. The binder material of low ductility would crack and thus provide pervious pavement surface The test is believed to measure the adhesive property of bitumen and its ability to stretch

115 Significance Ductility and penetration go together, in general, but exception can happen Ductility is the distance in cm to which a standard briquette of bitumen can be stretched before the thread breaks Ductile materials is one which elongates when held in tension

116 Procedure The bitumen sample is melted to temperature of 75 o C to 100 o C above the approx. softening point until it is fluid It is strained through IS sieve 30, poured in mould assembly and placed on a brass plate, after a solution of glycerine or dextrine is applied over all surfaces of the mould exposed to bitumen Thirty to forty minutes after the sample is poured into the moulds, the plate assembly along with the sample is placed in water bath maintained at 27 o C for 30 minutes

117 Briquette Moulds

118 Continue.... The sample and mould assembly are removed from water bath and excess bitumen material is cut off by leveling the surface using hot knife After trimming the specimen, the mould assembly containing sample is replaced in water bath maintained at 27 o C for 85 to 95 minutes The slides of the mould are then removed and the clips are carefully hooked on the machine without causing any initial strain The pointer is set to read zero

119 Ductilometer In Operation

120 Continue.... The machine is started and pulled apart horizontally the two clips are thus While the test is in operation, it is checked whether the sample is immersed in water up to a depth of at least 10mm The distance at which the bitumen thread breaks is recorded (in cm) and reported as ductility value

121 Breaking of Thread

122 Observation sheet (i) Grade of bitumen = 60/70 (ii) Pouring temperature C = 100 oc (iii) Test temperature = 27 oc (iv) Period of cooling (minutes) in Air = 40 min In water bath before trimming = 30 min In water bath after trimming = 90 min Test Property Briquette Number a b c Mean Value Ductility (cm) Repeatability % Reproducibility %

123 IS Specification Repeatability Reproducibility Source of Paving Bitumen & Penetration Grade S 35 S 45,S 65 & S 90 5% 10% Minimum Ductility (cm) Note: S denotes sources other than Assam petroleum

124 Discussion Ductility of bitumen is affected by the pouring temperature, briquette size, placement of briquette, test temperature, rate of pulling Ductility value ranges from Low value implies cracking. Some minimum ductility is needed for flexural strength The lack of ductility does not necessarily indicate poor quality.

125 7. Softening Point

126 Significance Bitumen does not melt, but change gradually from solid to liquid Softening point is the temperature at which the bitumen attains particular degree of softening under specified test conditions Ring and ball apparatus is used for the test

127 Ring & Ball Test Set-up Mechanical Stirrer Temp Controlled Heating Plate Thermometer Glass Beaker Metallic Support Steel Balls ø = 9.5 mm (2.5g) Brass Rings (In Ø=15.9 Mm & Out Ø=17.5mm

128 Procedure Heat the bitumen to a temperature between 125 o C to 150 o C Heat the rings at the same temperature on a hot plate & place on glass plate coated with glycerin Fill up the rings with bitumen Cool for 30 minutes in air and level the surface with a hot knife Set the rings in the assembly and place in the bath containing distilled water at 5 o C and maintain that temperature for 15 minutes

129 Continue. Place the balls on the rings Raise the temperature uniformly at 5 o C per minute till the ball passes trough the rings Note the temperature at which each of the ball and sample touches the bottom plate of the support Temperature shall be recorded as the softening point of the bitumen

130 Observation table (i) Grade of bitumen = 60/70 (ii) Approximate softening point = 40 oc (iii) Liquid used in water bath(water/glycerin) = water (iv) Period of air cooling (minutes) = 30 min (v) Period of cooling in water bath(minutes) = 15 min Test Property Temperature at each sample touches bottom plate Sample a b mean Repeatability % Reproducibility %

131 IS Specifications Softening Point Repeatability ( o C) Reproducibility ( o C) <30 o C o C- 80 o C 1 2 >80 o C 2 4 Bitumen Grades Softening Point ( o c) S A 45, S 45 & A S A 90 & S A 200 & S Note: S denotes sources other than Assam petroleum

132 Discussion Test is affected by quality of liquid, weight of ball, rate of heating etc It gives an idea of the temperature at which the bituminous material attains a certain viscosity Bitumen with higher softening point is used in warmer places Softening point is very critical for thick films like joint and crack fillers, to ensure they will not flow

133 Marshall Mix Design CE 328 Transportation Engineering I

134 Overview Specimen preparation Properties of the mix Marshall stability and flow Optimum bitumen content Numerical examples 1/4/2012 Marshall Mix Design 134

135 Gradation for BC surface course of 40 mm 1/4/2012 Dry Mix Design 135

136 Specimen preparation Approximately 1200gm of aggregates and filler is heated to temperature of C Bitumen is heated to a temperature of C with first trial percentage of bitumen (say 3.5 or 4% by weight of the mineral aggregates) Heated aggregates and bitumen are thoroughly mixed at a temperature of C 1/4/2012 Marshall Mix Design 136

137 Specimen preparation Mix is placed in a preheated mould and compacted by a rammer with 50 blows on either side at temperature of C to C Weight of mixed aggregates taken for the preparation of the specimen may be suitably altered to obtain a compacted thickness of 63.5+/-3 mm 1/4/2012 Marshall Mix Design 137

138 Specimen preparation Diameter 100 mm Thickness 63.5+/-3 mm 1/4/2012 Marshall Mix Design 138

139 Properties of the mix Theoretical specific gravity G t Bulk specific gravity of the mix G m Percent air voids V v Percent volume of bitumen V b Percent void in mixed aggregate VMA Percent voids filled with bitumen VFB 1/4/2012 Marshall Mix Design 139

140 Phase diagram of a bituminous mix 1/4/2012 Marshall Mix Design 140

141 Theoretical specic gravity of mix G t Specific gravity without considering air voids Where W 1 : Weight of coarse aggregate in total mix W 2 : Weight of fine aggregate in total mix W3: Weight of filler in total mix 1/4/2012 Marshall Mix Design 141

142 W b : Weight of bitumen in total mix G 1 : Apparent specific gravity of coarse aggregate G 2 : Apparent specific gravity of fine aggregate G 3 : Apparent specific gravity of filler G b : Apparent specific gravity of bitumen 1/4/2012 Marshall Mix Design 142

143 Bulk specific gravity of mix G m Specific gravity considering air voids Where W m : Weight of mix in air W w : Weight of mix in water W m - W w gives the volume of the mix 1/4/2012 Marshall Mix Design 143

144 Air voids percent V v Percent of air voids by volume in the specimen G t : Theoretical specific gravity of mix G m : Bulk or actual specific gravity of mix 1/4/2012 Marshall Mix Design 144

145 Air voids percent V v 1/4/2012 Marshall Mix Design 145

146 Percent volume of bitumen V b Percent of volume of bitumen W 1 : Wt of coarse agg. W 2 : Wt of fine agg. W 3 : Wt of filler W b : Wt of bitumen G b : Sp. Gr. of bitumen G m : Bulk sp. gravity 1/4/2012 Marshall Mix Design 146

147 Voids in mineral aggregate VMA Volume of voids in aggregates Sum of air voids & volume of bitumen VMA = V v + V b where V v : Percent air voids in the mix V b : Percent bitumen content in mix 1/4/2012 Marshall Mix Design 147

148 Voids filled with bitumen VFB Voids in mineral aggregate frame work filled with the bitumen VFB = V b / VMA X 100 V b : Percent bitumen content in mix VMA: Percent voids in mineral aggregate 1/4/2012 Marshall Mix Design 148

149 Marshall stability and Flow value Marshall stability and flow test provides the performance prediction measure Stability portion of test measures maximum load supported by test specimen at a loading rate of 50.8 mm/min Load is applied to the specimen till failure, and maximum load is designated as stability 1/4/

150 Marshall stability and Flow value During the loading, an attached dial gauge measures the specimen's plastic flow (deformation) due to the loading Flow value is recorded in 0.25 mm (0.01 inch) increments at the same time when the maximum load is recorded 1/4/2012 Marshall Mix Design 150

151 Marshall stability and Flow value Marshall Stability Maximum load required to produce failure when specimen is preheated to a prescribed temperature placed in a special test head and the load is applied at a constant strain (5 cm per minute) Flow Value The deformation at failure point expressed in units of 0.25 mm 1/4/2012 Marshall Mix Design 151

152 Marshall stability and Flow value 1/4/2012 Marshall Mix Design 152

153 Apply stability correction It is possible while making the specimen thickness slightly vary from standard specification of 63.5mm Measured stability values need to be corrected to those which would have been obtained if specimens had been exactly 63.5mm Multiplying each measured stability value by an appropriated correlation factors 1/4/2012 Marshall Mix Design 153

154 Correction factors for Marshall stability values 1/4/2012 Marshall Mix Design 154

155 Prepare graphical plots Vary the bitumen content in the next trial by % and repeat the above procedure. Number of trials are predetermined. Marshall Test Setup 1/4/2012 Marshall Mix Design 155

156 Prepare graphical plots 1. Binder content versus corrected Marshall stability 2. Binder content versus Marshall ow 3. Binder content versus percentage of void (V v ) in the total mix 4. Binder content versus voids filled with bitumen (VFB) 5. Binder content versus unit weight or bulk specic gravity (G m ) 1/4/2012 Marshall Mix Design 156

157 Marshal graphical plots 1/4/2012 Marshall Mix Design 157

158 Determine optimum bitumen content Average bitumen contents from: 1. Binder content Vs Stability 2. Binder content Vs Gm 3. Binder content at design Vv Air voids V v = 4% 1/4/2012 Marshall Mix Design 158

159 Marshal graphical plots 1/4/2012 Marshall Mix Design 159

160 Determine optimum bitumen content The stability value, flow value, and VFB are checked with Marshall mix design specification chart Mixes with very high stability value and low flow value are not desirable as the pavements constructed with such mixes are likely to develop cracks due to heavy moving loads 1/4/2012 Marshall Mix Design 160

161 Marshall mix design specification 1/4/2012 Marshall Mix Design 161

162 Numerical example - 1 The specific gravities and weight proportions for aggregate and bitumen are as under for the preparation of Marshall mix design Volume and weight of one Marshall specimen was found to be 475 cc and 1100 gm Assuming absorption of bitumen in aggregate is zero Find V v, V b, VMA and VFB 1/4/2012 Marshall Mix Design 162

163 Solution 1/4/2012 Marshall Mix Design 163

164 1/4/2012 Marshall Mix Design 164

165 Numerical example - 2 The results of Marshall test for five specimens is given below. Find the optimum bitumen content of the mix 1/4/2012 Marshall Mix Design 165

166 Solution Plot the graphs bitumen content corresponding to 1. Max stability = 5 % 2. Max Gm = 5 % 3. 4% air void = 3 % Optimum bitumen content = 4.33 % average of above Design bitumen content 1/4/2012 Marshall Mix Design 166

167 Thank You

168 Other tests 8. Marshall Stability Test 9. Bitumen Extraction Test 10. Traffic studies: Volume study