Design mix method of bitumenous materials by Marshall stability method

Sr. QA/QC Engineer at Larson and Toubro Ltd. em Larson and Toubro Ltd.
6 de Sep de 2017
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Design mix method of bitumenous materials by Marshall stability method

• 2. 2 Marshall Stability Test • Marshall stability test is mix design method to find out optimum binder content of given mix. In this test we find out the stability of the mix ( strength ) for desired flow ( workability ) on different binder contents in worst conditions. Worst condition may be understood as, • “When in summer season a highly rainfall occurs and most of the bituminous road surface become water logged and water penetrates or tend to penetrate the bituminous surfacing………… After the rain fall stops and again the sun shines the environment becomes hot and moist.” At this condition the bituminous bonding between road aggregates starts to break down thus damage to road starts. • This condition is considered the worst condition for a bituminous pavement and Marshall stability test is performed equaling to this condition as the prepared specimens are kept for 30-40 mins in water bath at 60o C temp. at which stability and flow is measured.
• 3. 3 Marshall Stability Test Hammer Marshall Stability test Apparatus Mould
• 5. 5 Marshall Stability Test Volume of Specimen in cc Approx. Thickness of specimen in mm Correction factors 457-470 57.1 1.19 471-482 58.7 1.14 483-495 60.3 1.09 496-508 61.9 1.04 509-522 63.5 1.00 523-535 65.1 0.96 536-546 66.7 0.93 547-559 68.3 0.89 560-573 69.9 0.86 Correction factors for height and volume basis
• 6. 6 Marshall Stability Test • Example : Adding the % (Ps) age of aggregate and binder to make mix for prepare the one specimen mould. The blending %ages of diff. aggregates are A = 75%,B = 5%,C = 23%and D = 2% respectively and %age of bitumen is 5% Eg. Weight of sample taken 1210 gms to fill the mould at 5% of Bitumen. Binder = 5% of 1210 gms = 60.5 gms The total aggregates becomes 1210 – 60.5 = 1149.5 gms Then A,75% of 1149.5gm = 805 gms B,5% of 1149.5 gms = 58 gms C,23% of 1149.5 gms = 264 gms D,2% of 1149.5 gms = 23 gms
• 7. 7 Marshall Stability Test JOB MIX FORMULAE (JMF) for DBM 50 mm Thick IS SIEVES BY WEIGHT % PASSING OF COARSE & FINE AGGREGATE Percentage required JMF SPECIFIED LIMIT MIDDLE LIMIT 40% 23% 35% 2% P1 P2 P3 P4 (mm) A (20.0 mm) B (10.0 mm) C (fine agg.) D (lime) A) B) C) D) A+B+C+ D 37.50 100.00 100.00 100.00 100.00 40.00 23.00 35.00 2.00 100.0 100.00 100.00 26.50 98.20 100.00 100.00 100.00 39.28 23.00 35.00 2.00 99.3 90-100 95.00 19.00 81.30 100.00 100.00 100.00 32.52 23.00 35.00 2.00 92.5 71-95 82.50 13.20 42.20 100.00 100.00 100.00 16.88 23.00 35.00 2.00 76.9 56-80 68.00 4.75 6.20 15.80 99.50 100.00 2.48 3.63 34.83 2.00 42.9 38-54 46.00 2.36 0.80 2.90 91.80 100.00 0.32 0.67 32.13 2.00 35.1 28-42 35.00 0.30 0.00 0.00 46.30 99.40 0.00 0.00 16.21 1.99 18.2 7-21 14.00 0.075 0.00 0.00 16.90 93.80 0.00 0.00 5.92 1.88 7.8 2-8 5.50 JOB MIX FORMULAE (JMF) for DBM 50 mm Thick Pavement Step 1 Set the percentages of different aggregates for given mix
• 8. 8 Marshall Stability Test S.no Material Specific Gravity Apparent Specific Gravity Water Absorption 1. 20 mm 2.644 2.674 0.428 2. 10 mm 2.636 2.669 0.479 3. Sand 2.604 2.690 1.23 4. Lime 2.625 Step 2 Find specific gravity and apparent specific gravity S.no Material Gsb Gse 1. 20 mm,10mm, sand, lime 2.628 2.647 Step 3 Find Gsb, Gse of mixed aggregates When the aggregates and lime mixed in decided ratios then it has its own specific gravity and apparent specific gravities. Gsb is specific gravity and Gse is apparent specific gravity of mixed aggregates. Specific gravity of bitumen Gb is generally a constant value for different grades of bitumen, i.e. 1.02
• 9. 9 Marshall Stability Test Bulk Specific Gravity of total aggregates, Gsb P1 20 mm = 40 % G1 = 2.644 Ga1 = 2.647 P2 10 mm = 23 % G2 = 2.636 Ga2 = 2.669 P3 fine agg. = 35 % G3 = 2.604 Ga3 = 2.690 P4 lime = 2 % G4 = 2.625 Ga4 = 2.625 = P1+ P2+ P3 + P4 Gsb P1 + P2 + P3 + P4 G1 G2 G3 G4 where P1+P2+P3+P4 = Individual percentages by weight of aggregates G1+G2+G3+G4 = Individual Bulk Specific Gravity of aggregates Gsb = Bulk Specific Gravity of total aggregates 40 + 23 + 35 + 2 = 40 + 23 + 35 + 2 2.644 2.636 2.604 2.6 = 100 15.13 + 8.73 + 13.44 + 0.8 = 100 38.06 Gsb = 2.628 Bulk Apparent Specific Gravity of total aggregates, Gse Gse = 0.5 x (Gsb + Bulk apparent specific gravity of mix) P1+ P2+ P3 + P4 P1 + P2 + P3 + P4 Ga1 Ga2 Ga3 Ga4 wher e P1+P2+P3+P4 = Individual percentages by weight of aggregates Ga1+Ga2+Ga3+Ga4 = Individual Apparent Specific Gravity of aggregates Gse = Effective Bulk Apparent Specific Gravity of total aggregates 40 + 23 + 35 + 2 = 40 + 23 + 35 + 2 2.647 2.66 9 2.690 2.6 = 100 15.11 + 8.62 + 13.01 + 0.8 = 100 = 2.667 37.50 Gse = 2.647
• 10. 10 Marshall Stability Test Step 4 Preparation of specimens • After completion of JMF the blending of diff aggregates used, Put the aggregate in oven and make them as hot as they will used while the execution of work, generally aggregates at 150oc to 170oc and Binder at 150oc (softening point + 90oc), the temp of bitumen and aggregate shall be within limit (diff 14oc specified), after the constitutes become hot mix them & hot them again in oven at 160oc, if required, the assembly should also have to warm up at about 100oc in oven or in water bath. Put the gloves up. During compaction the hammer should be vertical. • Test should be scheduled on the basis of 0.5 % increments of bitumen content and at least 6 no of samples should prepared. Each sample generally requires 1200 gms of mix. The compacted thickness of the specimen should be 63.5mm. The mix is placed and compacted both sides by Hammer with 75 blows. If the process is by modified marshall the weight of rammer will be 10.2 kg dia of mould will be 150 mm.The mix is placed and compacted both sides by Hammer with 113 blows. The stability will be 2.25 times of ordinary method as written in MORT&H.
• 11. 11 Marshall Stability Test Step 5 Find Gmm specific gravity of mix at different % age of binder *Max Theoritical Density ASTM D - 2041 S.no % of bitumen in mix Gmm 1. 4.5 2.470 2. 4.75 2.461 3. 5.0 2.452 4. 5.25 2.443 5. 5.5 2.434 Let bitumen content 5.5% Wt of Flask (A) = 1050 Wt of Flask filled with water (B) = 2003.5 Wt of flask + Full water + Mix (C) = 2610 Wt of Sample in air (D) = 1029.5 D/ Gmm = (D+B)-C = 2.434 gm/cc Example (its same as finding specific gravity in pycnomenter):
• 12. 12 Marshall Stability Test • After 24 hours the specimens are removed from moulds and Density (Gmb) is measured by water bucket immersion method. After measuring its Density specimen are kept immersed in water at temp 60oc for 30-40 mins and the Stability (max load carried in kg) and Flow (the deformation of the specimen in mm until max loading in 0.25 mm units) is recorded in machine, the height of the specimen should be 63.5 mm, if not the correction factors ( as given above ) are applied to meet the results. Graphs are plotted with the values of bitumen content against the values of • Density (Gmb), gm/cc • Marshall Stability, S in kg • Voids in total mix, Va % To find out Optimum Binder Content required for the mix.
• 13. 13 Marshall Stability Test Marshall Test Results of individual sample a Bitumen CRMB b % age 4.5% c Specific Gravity of Bitumen 1.02 d % age aggregates 95.5% e Aggregates 20 10 Fine agg. Lime f % age 40 23 35 2 g Sp. Gravity 2.644 2.636 2.604 2.625 h App. Sp. Gravity 2.647 2.669 2.690 2.625 1 Density Wt. in air = 1183.5gm Wt. in water = 668gm SSD wt. = 1206.5gm Density = 2.198gm/cc 2 Average Specific Gravity of mix (without Binder) Gsb = 2.628 3 Effective specific Gravity of mix (without Binder) Gse = 2.647 4 Absorbed bitumen % Pba = 0.29 5 Max Theoritical Density Gmm = 2.470 6 Bulk Density on Basis of Max Theoretical Density = 88.99% 7 Air Voids Va = 11.01% 8 Effective bitumen Pbe = 4.23% 9 Vol of Bitumen Vbe = 9.11% 10 Voids in Mineral Aggregates VMA = 20.12% 11 Voids Filled with Bitumen/Asphalt VFA = 45.26% 12 Reading of Proving ring = 305 correction for ring factor = 3.55 Correction for height = 0.9 Stability = 974.475 kg 13 Flow(mm) = 3.3 mm
• 14. 14 Marshall Stability Test 1 2 3 4 5 6 7 8 9 S. no. % Bitumen by wt of total mix Weight in air (gms) Weight in water ( gms) S.S.D. in air (gms) Bulk volume Unit weight of compacted mix (Gmb) Bulk Specific gravity of comb. Aggregates (Gsb) Effective specific gravity of aggregate (Gse) a b c d e f g h 1 4.50 1240.2 712.6 1248.3 535.7 2.315 2.628 2.647 2 4.75 1244.3 722.7 1251.5 528.8 2.353 2.628 2.647 3 5.00 1238.8 723.1 1244.9 521.8 2.374 2.628 2.647 4 5.25 1250.2 730.5 1255.8 525.3 2.380 2.628 2.647 5 5.50 1248.5 728.8 1253.2 524.4 2.381 2.628 2.647 10 11 12 13 14 15 16 17 S. no. Aggregate content % by mix (Ps) Sp. Gravity of bitumen ( Gb) Absorbrd Bitumen % Pba Max Sp.Gravity of Bitumenous mix (Gmm) ASTM D - 2041 Effective bitumen content % Pbe Voids in mix % Va % VMA % VFA i j k l m n o p 1 95.50 1.02 0.28 2.470 4.23 6.3 15.9 60.5 2 95.25 1.02 0.28 2.461 4.48 4.4 14.7 70.3 3 95.00 1.02 0.28 2.452 4.73 3.2 14.2 77.7 4 94.75 1.02 0.28 2.443 4.98 2.6 14.2 81.9 5 94.50 1.02 0.28 2.434 5.23 2.2 14.4 84.9 Stability and Flow value has to recorded from dial gauges of apparatus
• 15. 15 Marshall Stability Test 2.25 2.26 2.27 2.28 2.29 2.3 2.31 2.32 4 4.25 4.5 4.75 5 5.25 5.5 BulkDensity(gm/cc) Bitumen %
• 16. 16 Marshall Stability Test 3.00 4.00 5.00 6.00 7.00 4.30 4.40 4.50 4.60 4.70 4.80 4.90 5.00 5.10 5.20 5.30 Airvoids(%) Bitumen (%)
• 17. 17 Marshall Stability Test 900 950 1000 1050 1100 1150 1200 1250 4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5 5.1 5.2 5.3 5.4 Stability(Kg.) Bitumen ( % )
• 18. 18 Marshall Stability Test Calculations : Density, Gmb : wt of specimen in air/wt of SSD specimen in air- wt of specimen in water Gsb : as in step 3, 2.628 Gse : as in step 3, 2.647 Aggregate Content %,Ps : 1-percentage of bitumen in mix Specific gravity of bitumen, Gb : 1.02 ( standard value/given in MTC/can be find out) Absorbed bitumen %, Pba : (Gse-Gsb)/(Gse x Gsb) x Gb x 100 Max sp gravity of bitumen mix, Gmm : as in step 5, for different %age of bitumen or theoretically 100/(%age of bitumen in mix/Gb) + (Ps/Gse)
• 19. 19 Marshall Stability Test Effective Bitumen content %,Pbe : % of bitumen in mix – ((Ps x Pba)/100) Voids in mix %, Va : (1-Gmb/Gmm) x 100 Voids in mineral aggregates VMA,% : (Pbe x Gmb/Gb)+Va Voids filled with Asphalt VFA,% : ((Gmb x Pbe/Gb)/VMA) x 100 Some of text books gives different formulas for same calculations. However the results are same in every cases. Asphalt Institute MS-2 may be refer for details.
• 20. 20 Marshall Stability Test FINAL DESIGN PARAMETERS AS PER JMF Sr no GRAPH TYPE Optimum Binder content from graphical representation 1 Bitumen Content v/s Bulk density of mix 5.00% 2 Bitumen Content v/s 4 % Air voids in Mix 5.00% 5 Bitumen Content v/s stability 5.00% Avrage 5.00% DESIGN PARAMETERS AS PER JMF SPECIFIED LIMITS 1 Bitumen 5.00% MIN 5 % 2 Bulk density 2.374 gm/cc ---- 3 Air Void in Mix 3.20% 3% - 5% 4 Voids in Mineral aggregate 14.2% MIN 15 % 5 Voids filled with bitumen 77.7% 65% - 78% 6 Stability 1227 kg MIN 1200 KG 7 Flow 3.3mm 2.5 - 4 MM
• 21. 21 Marshall Stability Test Ways to Increase VMA 1. Reduce the dust content 2. Open the aggregate gradation 3. Gap-grade the aggregate blend 4. Increase manufactured sand 5. Reduce flaky-and-elongated particles
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