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From page 148... ... When complete mixing occurs, the total binder content of the mixture includes both the binder contained in the RAP and the amount of new binder added. In this situation, the properties of the binder in the mixture are the blended properties of the new binder and the RAP binder. Read the entire page →
From page 149... ... The design of HMA containing RAP requires substantial testing to characterize the properties of the RAP -- testing that is not needed in mix designs that do not contain RAP. To effectively design and produce any mixture with RAP, the following properties of the RAP must be determined: • RAP binder content • RAP aggregate gradation • Specific gravity of the RAP aggregate • Angularity of the coarse aggregate particles in the RAP • Flat and elongated particles for the coarse aggregate in the RAP • Angularity of the fine aggregate in the RAP To determine these properties, the binder must be removed from the RAP using either an ignition oven or solvent extraction. Read the entire page →
From page 150... ... SAMPLE RAP STOCKPILES 8 - 10 LOCATIONS SPLIT SAMPLE FOR BINDER CONTENT AND GRADATION ANALYSIS DETERMINE AVERAGE AND STANDARD DEVIATION OF BINDER CONTENT AND GRADATION DETERMINE FEASIBLE RAP CONTENTS BASED ON GRADATION AND VARIABILITY DESIRED RAP CONTENT >15 % ? COMBINE INDIVIDUAL SAMPLES TO OBTAIN REPRESENTATIVE SAMPLE SPLIT SAMPLE FOR CHARACTERIZING RAP AGGREGATE AND BINDER PROPERTIES RAP AGGREGATE PROPERTIES RAP BINDER PROPERTIES BLENDING CHART ANALYSIS Yes VOLUMETRIC MIXTURE DESIGN PERFORMANCE TESTING AS REQUIRED No Figure 9-1. Read the entire page →
From page 151... ... Many aspects of the mix design process, such as determining binder grades for mix designs containing RAP, will be essentially the same regardless of how the RAP is handled. One important aspect of the mix design process that will depend on how RAP materials are handled at the plant is the effect of RAP variability on the allowable RAP content. Read the entire page →
From page 152... ... RAP stockpiles should be sampled from at least five locations distributed throughout the pile. A larger number of samples -- up to 20 or more -- is desirable, since this will allow a more accurate characterization of the RAP and permit the highest possible RAP content in the final mix design(s) Read the entire page →
From page 153... ... + 5 kg SELECT 8 -10 RANDOM SAMPLING LOCATIONS BINDER CONTENT AND GRADATION FOR BLENDING AND VARIABILITY ANALYSIS CHARACTERIZE RAP AGGREGATE PROPERTIES VOLUMETRIC MIXTURE DESIGN AND PERFORMANCE ANALYSIS CHARACTERIZE RAP BINDER PROPERTIES IF REQUIRED SPLIT SAMPLE AASHTO T248 SPLIT SAMPLE AASHTO T248 5 kg COMBINE WITH OTHER LOCATIONS TO CREATE REPRESENTATIVE SAMPLE REMAINDER 2.5 kg COMBINE WITH OTHER LOCATIONS TO CREATE REPRESENTATIVE SAMPLE 2.5 kg SPLIT SAMPLE AASHTO T248 2.5 kg REMAINDER Figure 9-2. Flow chart for recommended sampling of RAP stockpiles. Read the entire page →
From page 154... ... Because many state highway agencies already have specifications in place establishing allowable RAP contents in HMA mixtures, HMA Tools allows any RAP content in the design process. If desired, HMA Tools can be used to perform the statistical analysis of RAP stockpiles and to determine the maximum allowable RAP content. Read the entire page →
From page 155... ... The target VMA should be 16.0% and the target air void content 4.0%. The specific gravity value for both the new binder and the RAP binders is 1.030. Read the entire page →
From page 156... ... There is a relatively small chance that the true standard deviation will be much, much higher than the estimated value. Because the standard deviation values calculated for the RAP stockpiles are only estimates, the values used by HMA Tools in determining the maximum allowable RAP content is an upper confidence limit, rather than the calculated value. Read the entire page →
From page 157... ... Also, using HMA Tools determine the maximum allowable RAP content for this RAP stockpile. Solution The values for percent passing and asphalt binder content given in Table 9-3 are entered in cells B19:K31 and B33:K33 in the worksheet "RAP_Variability." The reliability level in cell B6 should be the default value of 80%. Read the entire page →
From page 158... ... Figure 9-5 gives estimated maximum RAP content based on the average standard deviation for aggregate percent passing for a blend of RAP stockpiles, while Figure 9-6 gives estimated maximum RAP content based on the average 158 A Manual for Design of Hot Mix Asphalt with Commentary 15 20 25 30 35 40 45 50 0 1 2 3 4 5 6 7 8 9 10 Standard Deviation for RAP Aggregate % Passing M ax . Read the entire page →
From page 159... ... Maximum RAP content as a function of average standard deviation for aggregate percent passing. For n = 5 Samples from a blend of RAP stockpiles, and no stockpile making up more than 70% of the RAP blend. Read the entire page →
From page 160... ... The asphalt binder contained 160 A Manual for Design of Hot Mix Asphalt with Commentary Example Problem 9-3. Determination of Maximum Allowable RAP Content Based on Variability Analysis Using the Graphical Approach Using the standard deviation values for aggregate percent passing and asphalt binder content calculated for Example 2, estimate the maximum allowable RAP content based on variability using Figures 9-3 and 9-4. Read the entire page →
From page 161... ... The first is to estimate the bulk specific gravity of the RAP aggregate from the RAP binder content, the maximum specific gravity of the RAP, and estimates of the binder absorption in the RAP and the specific gravity of the RAP binder. The second is to measure the bulk specific gravity of the coarse and fine fraction of the Reclaimed Asphalt Pavement 161 Sample Size, kg Property Method Fraction 12.5-mm NMAS 19.0-mm NMAS Specific Gravity of Coarse Aggregate AASHTO T 85 +2.36 mm 2 3 Specific Gravity of Fine Aggregate AASHTO T 84 -2.36 mm 1 1 Coarse Aggregate Fractured Faces ASTM D 5821 +4.75 mm 0.5 1.5 Fine Aggregate Angularity AASHTO T 304 Method A -2.36 mm 0.5 0.5 Flat and Elongated Particles ASTM D 4791 +4.75 mm 2 5 Table 9-6. Read the entire page →
From page 162... ... The measured maximum specific gravity, the average RAP binder content from the variability analysis, and an estimate of the RAP binder specific gravity are then used to calculate the effective specific gravity of the RAP aggregate using Equation 9-1. where Gse = effective specific gravity of the RAP aggregate Gmm = maximum specific gravity of the RAP measured by AASHTO T 209 Pb = RAP binder content, wt % Gb = estimated specific gravity of the RAP binder The bulk specific gravity of the RAP aggregate can then be estimated from Equation 9-2, which is a rearranged version of the equation used in volumetric analysis to compute asphalt absorption. Read the entire page →
From page 163... ... If the specific gravity values are to be estimated from maximum theoretical specific gravity, binder content, and related information, the data are entered in cells C6:F9 in the worksheet "RAP_Aggregates." If actual measured values for RAP aggregate specific gravity are used, these are entered in cells C11:F14. The calculated values for bulk and apparent specific gravity for each of up to four RAP stockpiles then appear in cells C16:F17. Read the entire page →
From page 164... ... When higher percentages of RAP are used, the properties of the RAP binder must be considered through the use of blending charts as described in this section. Some agency specifications adjust the new binder grade to account for the presence of RAP. Read the entire page →
From page 165... ... These are the same tests used for the performance grading of asphalt binders Reclaimed Asphalt Pavement 165 RAP Binder Content, % Recommended Sample Size, g 3.0 1833 3.2 1719 3.4 1618 3.6 1528 3.8 1447 4.0 1375 4.2 1310 4.4 1250 4.6 1196 4.8 1146 5.0 1100 5.2 1058 5.4 1019 5.6 982 5.8 948 6.0 917 Table 9-7. Recommended sample size for RAP binder extraction and recovery. Read the entire page →
From page 166... ... The interested reader can find a detailed procedure for performing these and related calculations in Appendix A of AASHTO M 323. HMA Tools can be used not only as an aid in grading RAP binders, but also in performing all binder grade calculations typically needed when designing HMA mixtures containing RAP. Read the entire page →
From page 167... ... = critical temperature for the new binder Tc(RAP) = critical temperature for the RAP binder %RAPB = percentage of total binder content obtained from the RAP, wt % T Blend T New RAPB T RAP T Newc c c C( ) Read the entire page →
From page 168... ... If RAP from more than one stockpile is used in the mix design, HMA Tools assumes that the relative proportions of material in the RAP blend will remain constant as the overall RAP content varies. Two example problems below show how HMA Tools can be used in performing both types of binder grade calculations when designing HMA mixtures containing RAP. Read the entire page →
From page 169... ... Note that the required critical temperatures for the new binder are given in cells C76:C78 as follows: high critical temperature -- 57.7°C, intermediate critical temperature -- 22.9°C, and low critical temperature -- 15.3°C. As in many other locations, HMA Tools reports the required grade by including the intermediate temperature grading of 19°C in parentheses, so cell C80 actually reads "58-(19) Read the entire page →
From page 170... ... However, when RAP stockpiles are used, the weight of the binder contained in the RAP must be accounted for and stockpile percentages based 170 A Manual for Design of Hot Mix Asphalt with Commentary Example Problem 9-6. Calculating the Maximum Allowable RAP Content Given an HMA Design with a Specific New Asphalt Binder The RAP binder from Example 4 will be used in an HMA mixture. Read the entire page →
From page 171... ... The amount of each size fraction of new aggregate needed for a laboratory batch is computed directly from the proportions based on the total weight of aggregate. The amount of each RAP stockpile needed for a laboratory batch must be increased to account for the weight of binder in the RAP using Equation 9-4: where MRAP = mass of RAP required for the laboratory batch, g MRAPAGG = mass of RAP aggregate required for the laboratory batch, g PbRAP = RAP binder content, wt % The mass of binder provided by the RAP is then where MRAPBINDER = mass of RAP binder in the laboratory batch, g MRAP = mass of RAP in the laboratory batch, g PbRAP = RAP binder content, wt % HMA Tools can be used to perform these and all other required calculations for determining batch weights of mix designs containing RAP. Read the entire page →
From page 172... ... 172 A Manual for Design of Hot Mix Asphalt with Commentary Example Problem 9-7. Laboratory Batching for an HMA Mix Design Containing RAP Laboratory specimens of the mixture from Example 1 will be prepared. Read the entire page →
From page 173... ... Bibliography AASHTO Standards M 320, Standard Specification for Performance-Graded Asphalt Binder R 29, Grading or Verifying the Performance Grade of an Asphalt Binder T 2, Standard Method of Test for Sampling Aggregates T 248, Standard Method of Test for Reducing Samples of Aggregate to Testing Size T 308, Standard Method of Test for Determining the Asphalt Binder Content of Hot-Mix Asphalt (HMA) by the Ignition Method T 30, Standard Method of Test for Mechanical Analysis of Extracted Aggregates T 164, Standard Method of Test for Quantitative Extraction of Bitumen for Bituminous Paving Mixtures T 209, Standard Method of Test for Theoretical Maximum Specific Gravity and Density of Bituminous Paving Mixtures T 84, Standard Method of Test for Specific Gravity and Absorption of Fine Aggregate T 85, Standard Method of Test for Specific Gravity and Absorption of Coarse Aggregate T 176, Standard Method of Test for Plastic Fines in Graded Aggregates and Soils by Use of the Sand Equivalent Test T 319, Standard Method of Test for Quantitative Extraction and Recovery of Asphalt Binder from Asphalt Mixtures T 240, Standard Method of Test for Effect of Air on a Moving Film of Asphalt (Rolling Thin-Film Oven Test) Read the entire page →

From page 148...

... When complete mixing occurs, the total binder content of the mixture includes both the binder contained in the RAP and the amount of new binder added. In this situation, the properties of the binder in the mixture are the blended properties of the new binder and the RAP binder.