Marshall Test

An-Najah National University Civil Engineering Department Pavement Laboratory Ex. Name : Marshall Test Prepared by : Rania Sabbah , Sanabil Masharqah, Toqa Ja’far Submitted to: Eng. Ahmad Al-Ahmad Section: Wednesday (10-12) Contents: Report Element Description Page No. Grade Contents 2 Introduction Overview of Marshall test ,its importance and objective 3 Objectives The main objective of experiment 3 Standards 3 Theory 4 Apparatus and Procedure Apparatus with a photos and clear steps for procedure 4-8 Results Results obtained from laboratory 9 Analysis and Calculations All calculations listed in tables and Figures , the optimal Asphalt content , some comments 10-14 Discussion and Conclusion Comments on results ,importance ,recommendations, errors and conclusion 15 Sources of Errors 15 References 15 Total Grade Introduction: Bituminous mixes (sometimes called asphalt mixes) are used in the surface layer of road and airfield pavements. The mix is composed usually of aggregate and asphalt cements. Some types of bituminous mixes are also used in base coarse. The design of asphalt paving mix, as with the design of other engineering materials is largely a matter of selecting and proportioning constituent materials to obtain the desired properties in the finished pavement structure. The desirable properties of Asphalt mixes are: 1. Resistance to permanent deformation: The mix should not distort or be displaced when subjected to traffic loads. The resistance to permanent deformation is more important at high temperatures. 2. Fatigue resistance: the mix should not crack when subjected to repeated loads over a period of time. 3. Resistance to low temperature cracking. This mix property is important in coldregions. 4. Durability: the mix should contain sufficient asphalt cement to ensure an adequate film thickness around the aggregate particles. The compacted mix should not havevery high air voids, which accelerates the aging process. 5. Resistance to moisture-induced damage. 6. Skid resistance. 7. Workability: the mix must be capable of being placed and compacted with reasonable effort. 8. Low noise and good drainage properties: If the mix is to be used for the surface(wearing) layer of the pavement structure. Marshall stability and Hveem stabilometer tests are largely used for the routine testing. Criteria for the suitable mix design have been specified by the Asphalt Institute. Objective: To measure the strength and flexibility of asphalt mixtures and to determine voids properties using briquettes prepared by the marshall method. Standard: ASTM D 1559-76 Theory: strength and flexibility are two important properties required of asphalt concrete for use in pavements. The most widely used method of bituminous mix design for pavements which can achieve these properties is the marshall method developed by crops of engineers during world war II. In this test, samples of 4 inch diameter and 2.5 inch high (Briquette Size) are prepared by compacting in a mold with a compaction hammer that ways 10 1b and has a free fall of 18 inch. Depending upon the design traffic, either 35, 50, or 75 bellows of the hammer are applied to each side of the specimen after overnight during the density and voids are determined, and the specimen is heated to 60 C (140 F) for the marshall stability and flow tests. This temperature represents the weakest condition for an asphalt pavement in use. The maximum load registered during the test is taken as the marshall stability of the specimen. The amount of movement, or strain, occurring between no load and the maximum load in units of 0.01 inch is called the flow value of the specimen. This flow or change in diameter indicates the brittleness or flexibility of the mixture. Stability values are corrected to allow for variation from the standard 2.5 inch thickness. Apparatus : Specimen Mold Assembly : briquettes 4 in. (101.6 mm ) in diameter by 3 in. (76.2 mm) in height, base plates and extension collars. Specimen Mold Holder. Compaction Hammer that weighs 10 1b and has fall of 18 in. (457.2 mm). Compaction pedestal. Breaking Head. Loading Jack. Specimen Extractor. Ring Dynamometer Assembly. Flowmeter. Oven or hot plate. Mixing apparatus. Water bath. Air bath Container, thermometer, balance, spoons, scoop and mixing tools. Procedure: Measure out 1200 gm of aggregates, blended in the desired proportions as will be shown in the lab. Heat the aggregates in the oven to the mixing temperature which is about 350 to 375 F (177 to 190 C). In order to obtain the optimum moisture content for a particular blend of gradation of aggregates, a series of test specimen is prepared for a range of different asphalt content so that test data curve show a well-defined optimum value. Tests should be scheduled on the basis of 0.5% increments of asphalt content, with at least two asphalt contents above optimum and two below optimum. In order to do so, weight the required quantity of asphalt as part per hundred parts of aggregates and heat it to a temperature from 250 to 280 F (121 to 138 C) and add it to the heated aggregates. Mix the materials in a heated pan with heated mixing tools. Return the mixture to the oven and reheat it to the compacting temperature which is at least 225 F (107 C). Place the mixture in a heated Marshall mold with a collar and base. Spade the mixture around the sides of the mold. Place filter papers under the sample and on top of the sample. Place the mold in the Marshall compaction pedestal. Compact the material with 50 blows of hammer (or as specified) invert the sample, and compact the other face with the same number of blows. After compaction, invert the mold. With the collar on the bottom, remove the base and extract the sample by pushing it out with the extractor. Allow the sample to stand for a few hours to cool. Obtain the sample mass in air and submerge. Place the briquettes in a water bath 60C +_ 1C (140+-1.8F) for 30-40 minutes. Place one briquette in the loading yoke , add the top part of the yoke , place the flow meter over one of the posts , and adjust it to read zero. Apply a load at a rate of 50 mm (2 inch) per minute until the max. load reading is obtained. Record the max. load reading . at the same instant , obtain the flow as recorded on the flow meter ( note: a stopwatch can be used to measure the time from start of leading to max. load. Using a rate of loading of 50 mm (2 in)/ minute , the flow in millimeters are units of 0.01 inch can be calculated. Notes: The proportion of each agg. Size to be used will be given later in the lab. The densities of agg. & bitumen will be determined in the lab , which are necessary to do the calculations. The data & calculations must be tabulated in the table which you will receive in the lab. The recorded stability values must be corrected by multiplying by a factor dependent on the volume of the briquetted as in the following table: Volume (cm3) factor 457-470 1.19 471-482 1.14 483-495 1.09 496-508 1.04 509-522 1.00 523-535 0.96 536-546 0.93 547-559 0.89 560-573 0.86 Results from Lab. : Bitumen Content % Thickness "before" (mm) Weight in Air (g) Sample 1 Sample 2 Sample 3 Sample 1 Sample 2 Sample 3 3.50% 63.13 62.48 61.61 1228.3 1219.5 1205.5 4.00% 65.23 63.96 63.16 1276.9 1252.6 1243.5 4.50% 63.58 63.00 63.32 1254.4 1238.3 1239 5.00% 62.93 66.05 64.87 1237.9 1300 1273.6 5.50% 63.21 64.46 65.77 1237.3 1264 1286.4 Weight in Water (g) Stability (Kg) Flow (0.25 mm) Sample 1 Sample 2 Sample 3 Sample 1 Sample 2 Sample 3 Sample 1 Sample 2 Sample 3 716.3 712.2 705.3 918.5 844.6 826.0 11 10 8 747.3 733.3 730.7 957.1 918.5 904.9 10 9 9 738.2 726.8 724.9 929.9 950.3 957.1 12 9 10 727 763.6 746.9 850.5 966.2 861.8 14 10 12 724.1 740.6 752.4 657.7 694.0 732.6 12 14 13 Component Specific Gravity Weight (g) Coarse aggregate 2.75 2900 Fine Aggregate 2.66 1450 Filler 2.77 150 Bitumen 1.04 Depends on % Calculations and analysis: first to draw bulk density versus the Asphalt content ,we need some calculations they are summarized in a table: Bitumen Content % Bulk specific gravity Gmb=Wa/(Wa-Ww) Bulk density γ =Gmb9.81 kN/m3 Sample 1 Sample 2 Sample 3 average 3.50% 2.399023 2.403903 2.410036 2.404321 23.58639 4.00% 2.411065 2.412093 2.424922 2.416027 23.70122 4.50% 2.430066 2.420919 2.410037 2.420341 23.74354 5.00% 2.422979 2.423565 2.418075 2.421539 23.7553 5.50% 2.410951 2.414979 2.408989 2.41164 23.65818 then the relation can be drawn in a curve of γ vs. AC% as shown below in fig.1 : Fig.1 then we want to draw stability and flow : Diameter =101.7 mm AC% Stability (kg) Flow(0.25 mm) Sample 1 Sample 2 Sample 3 Average factor Corrected Stability Sample 1 Sample 2 Sample 3 Average 3.50% 918.5 844.6 826.0 863.0350827 1.04 897.5565 11 10 8 9.666667 4.00% 957.1 918.5 904.9 926.8404094 1 926.8404 10 9 9 9.333333 4.50% 929.9 950.3 957.1 945.7400915 1 945.7401 12 9 10 10.33333 5.00% 850.5 966.2 861.8 892.8209816 0.96 857.1081 14 10 12 12 5.50% 657.7 694.0 732.6 694.7523134 0.96 666.9622 12 14 13 13 the curve of stability vs. AC% is given below in fig.2: Fig.2 the curve of flow vs. AC% is given below in fig. 3: Fig.3 Now we have to compute percent voids in the mineral aggregates VMA, the calculations are summarized in a table: AC% Gmb Ps Pca Pfa Pmf Gsb = VMA=100-GmbPs/Gsb 14.73067 2.72099 0.033333 0.322222 0.644444 96.50% 2.404321 3.50% 14.75948 2.72099 0.033333 0.322222 0.644444 96.00% 2.416027 4.00% 15.05203 2.72099 0.033333 0.322222 0.644444 95.50% 2.420341 4.50% 15.45496 2.72099 0.033333 0.322222 0.644444 95.00% 2.421539 5.00% 16.24373 2.72099 0.033333 0.322222 0.644444 94.50% 2.41164 5.50% then the curve of VMA vs. AC% can be drawn see fig.4: Fig. 4 Fig.4 then we have to determine the percentage of air voids in each of the pavement mixtures: use the summary table: AC% Wtotal WBitumen Gt Gm Pa 3.50% 157.5 4657.5 2.579972 2.404321 6.808251 4.00% 180 4680 2.561735 2.416027 5.687868 4.50% 202.5 4702.5 2.543925 2.420341 4.858009 5.00% 225 4725 2.526527 2.421539 4.155434 5.50% 247.5 4747.5 2.509527 2.41164 3.900622 then we draw Pa vs. AC% ,we yield with this curve in fig. 5: Fig.5 The asphalt content that meets the design requirements for unit weight, stability, and percent air voids then is selected from the appropriate plot in Figures 1,2,5. The asphalt content having the maximum value of unit weight and stability is selected from each of the respective plots. 1. Maximum unit weight =4.85% [Fig. 1] 2. Maximum stability =4.40 % [Fig.2] 3. Percent air voids in compacted mixture using mean of limits [that is, (3+5)/2=4] =5.20%% [Fig. 5] (Note the limits of 3 and 5% given in Table 18.7 in the text book.) The optimum asphalt content is determined as the average. Therefore, the optimum asphalt cement content is O.A.C. %=(4.85%+4.40%+5.20%)/3=4.81% Checks can be carried on properties using the 4.81% optimum asphalt content ,and using test limits ,see table 18.7. at design AC% =4.68% :stability(900 kg=8829 N), flow(11.2) and Air voids =4.4 they all meet specification for all cases of loading including the heavy traffic case and that is good.. No information are provided to check the voids in mineral aggregates criterion. Discussion and Conclusion: after along procedure and calculations we ended up with the most suitable Asphalt content for the hot mix. after carrying up the checks we noted that this Asphaltic content ( 4.81%) ,meets all the requirements of heavy traffic , and this gives us a good indication about the strength characteristics of our mix and its durability and therefore its uses in future. If any of the check does not meet requirements ,we must do modifications to our mix design , but Thank Allah there is no need. there was some errors due to the loss of soil masses and weighing .but they didn't affect strongly our results, because of good team work these errors were limited. Sources of Errors: Human Errors: we tried to be careful during the test procedure, but we are humans and we can't do our work with zero errors, some were because of the loosing of some mineral filler (dust) mass during transferring it and mixing. mechanical errors. References: our text book. internet sites: http://www.scribd.com/doc/50281691/marshall-test Monday, April 28, 2014 Marshall Test 12 all rights reserved © 2014