are set according to the proportions obtained in thecomputation of the final trial blend.Aggregate Blending LimitsFigure 17-7 is an aggregate grading chart (DD Form1207), showing the specification limits for the mix andthe gradation of the blend when mixed in the proportionsshown in figure 17-6A, trial No. 1.Specify Gravity of Bituminous MixComponentsA specific gravity data sheet is shown in figure 17-8(DD Form 1216). This form is used for computing thespecific gravity of all the bituminous mix components.If more aggregate fractions are used than are providedfor on the form, additional forms may be used.Procedures for performing these tests are discussed inchapter 13 of this TRAMAN.Marshall Stability ComputationsDD Form 1218 (figs. 17-9A and 17-9B) is a dataand computation sheet used in the Marshall stability test.The specific gravity values of the aggregates and theaggregate fraction percentages from the trial blendingfurnish the information to compute the fractionalweights and to prepare the test specimens. Record themeasurements made on the test specimens in the upperright-hand corner of the form. Determine, as describedin chapter 13 of this TRAMAN, the stability, flow, unitweight of total mix, and percentage of voids filled withbinder to complete the form.Marshall Method ComputationsTransfer the values from DD Form 1218 (figs.17-9A and 17-9B) for each binder content computationto DD Form 1219 (fig. 17-10). Each graph on the formrepresents a different test property. Plot the values foreach property on their respective graph using the bindercontents as ordinates. Draw a smooth curve through theplotted points.Marshall Test CriteriaTable 17-7 lists the criteria for determiningoptimum asphalt content (OAC). For each test property,you should consider the type of mix to be used and theexpected load. The optimum bitumen content for eachproperty is designated as a definite point on the curvefor that property. The bitumen content percentages (onefor each property) are averaged, and the average is usedto read the corresponding value of each test property.The value, as determined, should be referred to thecriteria portion of table 17-7 to see if it is within thepermissible limits so that the mix will performsatisfactorily.Test Variation for Aggregates with10 Percent or More Larger Than1-Inch Maximum SizeThe procedure described in the Marshall methodand the examples as given in the preceding paragraphsare applicable to hot-mix design where the amount ofaggregate larger than the 1-inch sieve is less than 10percent of the total. When the larger than (plus) 1-inchmaterial exceeds 10 percent of the total, the followingvariations are made in the procedure:1. Mix bitumen at the selected content with theentire aggregate, including the plus 1-inch portion.2. Pass the mixed hot batch through a 1-inch sieve.Discard the plus 1-inch portion.3. Make compacted specimens from the portionthat passes the 1-inch sieve and perform the Marshalltest, except do not calculate the voids of the compactedspecimens at this time.4. Determine the bulk specific gravity of the plus1-inch aggregate, and, with the specific gravity of thecompacted specimens, compute the adjusted specificgravity (GA) as follows:where:A= weight of dry, plus 1-inch materialexpressed as a percentage of the total batchweight (bitumen plus aggregate)B= portion of total batch remaining after thedry, plus 1-inch portion is removed(100%-A%)C =bulk specific gravity of plus 1-inchaggregateD =actual specific gravity of compactedspecimenf= empirical factor = 0.99517-20

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