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10 Properties of Material Passing the aggregate particles. It was found that the higher the rugosity 0.075-mm Sieve of the coarse aggregate, the larger the size of fine particles that result in higher HMA mixture shear strength. Addition of mineral filler, material passing the 0.075-mm The amount of mineral filler used in HMA mixtures does sieve, affects HMA mixture performance. Depending on the not seem to affect rutting performance adversely as measured particle size, mineral filler can act as filler or as an extender of by the Repeated Shear at Constant Height (RSCH) test. The the binder. When the mineral filler functions as a binder RSCH test is performed by applying shear load pulses to a extender, over-rich HMA mixtures can result and lead to cylindrical HMA specimen and keeping the specimen height flushing and/or rutting. Some p0.075 materials cause stiffen- constant (AASHTO TP 7). Although increasing the amount ing of the binder and/or HMA mixtures and thus increase of filler does not affect the test result, increasing the mineral fatigue cracking. The amount and characteristics of the filler content does lead to decreased optimum binder content. p0.075 material can also contribute to HMA mixtures that Ultimately, this can lead to durability and fatigue problems become susceptible to moisture damage. This can lead to a (20). Also, coarse-graded mixtures that have gradations plot- loss of mixture integrity, lower shear strength, cracking, and ting below the MDL have been found to be sensitive to the increased rutting. amount of p0.075 material (3). Kandhal and Parker (1) investigated the effect of mineral Kandhal and Parker (1) indicated that decreasing the size filler by examining filler-binder mortar stiffness of mortars of D60 (particle size at which 60 percent of the material with filler-binder ratios of 0.8 and 1.5 by weight. They found passes) of the p0.075 increases the HMA mixture's stiffness that the MBV of the p0.075 material was related to the filler- and resistance to rutting. Logically, this increase in mixture binder mortar stiffness. The higher the MBV value, the stiffer stiffness would also reduce the mixture's resistance to fatigue was the filler-binder mortar. They also found a strong rela- cracking. The HMA mixtures tested consisted of coarse and tionship between the MBV of the p0.075 material and the fine limestone aggregates of sizes larger than the 0.075-mm stiffness parameters |G*| /sin and |G*| sin, obtained from sieve. Different types of p0.075 material were incorporated the SST tests. The G* parameter is the complex modulus with the coarse and fine limestone to study the effects on rut- and is the phase angle of material tested under dynamic ting, fatigue, and stripping performance. loading. The |G*| /sin parameter is a measure of HMA In addition to D60 (particle size at which 60 percent is stiffness at high temperatures or slow loading rates. High smaller) of the p0.075 material, the MBV and D10 (particle |G*| /sin values indicate high stiffness HMA mixtures and size at which 10 percent is smaller) of the p0.075 material high resistance against rutting at high temperature. The were also related to HMA mixture rutting performance. The product |G*| sin is a measure of HMA stiffness at inter- higher the MBV, the stiffer was the HMA mixture. Increasing mediate temperatures or high loading rates. High |G*| sin the D10 particle size was found to reduce the tensile strength indicates high HMA mixture stiffness and thus low resistance ratio of HMA mixtures (1). These findings were based on the to fatigue cracking. AASHTO T 283 test, the SST Frequency Sweep at Constant Khedaywi and Tons (11) suggested introduction of a spe- Height (FSCH), and Simple Shear at Constant Height cific size of fine particles into the HMA mixtures could (SSCH) tests (AASHTO TP 7). AASHTO T 283 determines increase mixture shear strength. The surface characteristics of the ratio between the tensile strength of unconditioned and the coarse aggregate (rugosity) determines the size of fine moisture-conditioned specimens subjected to a freeze-thaw particles that contribute the most to the interlocking mecha- cycle. In the FSCH test, an HMA specimen is subjected to a nism between the coarse aggregate particles in an HMA mix- sinusoidal shear strain applied at different frequencies while ture. It was suggested that, depending on the relative size of a vertical load is also applied to keep the specimen height con- the fine particles and the size of coarse particle surface voids, stant. In this test, the stiffness of the specimen is determined the fine particles can be completely or partially lost in the sur- as a function of frequency. In the SSCH test, a constant shear face voids of the larger particles. When completely lost inside load is applied to an HMA specimen while keeping the spec- the surface rugosities, fine particles do not participate in imen height constant. HMA shear resistance. When partially lost by rugosity, fine particles can either improve or reduce the interlock between the coarse aggregate particles. Increased interlock occurs Aggregate Test Results when parts of the fine particles are embedded in surface voids Coarse Aggregate of adjoining coarse particles. Reduction of interlock occurs when the average size of the fine particles is larger than the Table 6 lists the type, source location, and properties of the average size of the coarse aggregate surface voids. In this case, coarse aggregates used in the study. Two traprock sources were the fine particles act like roller bearings between the coarse evaluated, but only Traprock #88 was used in the performance

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11 Table 6. Coarse aggregate description, location, and properties. Trap- Lime- Uncrushed rock Aggregate Type Dolomite stone Gravel Granite #78 Traprock #88 Designation CA-1 CA-2 CA-3 CA-4 CA-5 CA-5b Source Location Indiana Indiana Indiana North Virginia Virginia Carolina Nominal Maximum Size (mm) 12.5 12.5 12.5 12.5 12.5 12.5 Percent Passing 19.0 100 100.0 12.5 100 100 100 100 89.0 100.0 9.5 87.0 87.9 84.1 90.0 60.0 85.4 Sieve Size (mm) 4.75 25.0 24.7 18.1 23.0 7.0 11.2 2.36 1.4 4.7 1.1 4.0 2.0 1.3 1.18 0.4 2.0 0.2 3.0 0.6 0.6 0.60 0.4 1.7 0.2 2.0 0.6 0.6 0.30 0.3 1.5 0.2 1.0 0.6 0.6 0.15 0.3 1.4 0.2 1.0 0.6 0.6 0.075 0.2 1.3 0.2 0.5 0.6 0.6 Dry Bulk Specific Gravity 2.734 2.550 2.598 2.649 2.897 2.910 (ASTM C127) Apparent Specific Gravity 2.825 2.752 2.742 2.705 2.981 2.989 (ASTM C127) Water Absorption, % 1.2 2.9 2.0 0.8 0.7 0.9 (ASTM C127) Flat or Elongated Particles (ASTM D4791), % 2:1 Ratio 44.9 48.4 28.8 47.5 34.2 35.5 3:1 Ratio 4.6 6.0 2.6 3.3 5.8 2.0 5:1 Ratio 0.7 1.3 0.0 0.0 0.0 0 Flat and Elongated Particles (ASTM D4791), % 3:1 Ratio 21.7 28.0 13.2 20.1 18.6 11.6 5:1 Ratio 6.3 8.1 1.8 2.7 2.3 2.7 Uncompacted Voids, % Method A AASHTO TP56 51.2 48.2 42.2 48.9 46.8 48.0 Method B AASHTO TP56 49.8 49.6 42.9 49.1 48.4 48.8 Micro-Deval (AASHTO TP58), % 7.0 10.9 8.8 5.5 5.1 4.6 LA Abrasion Test (Type C 23.0 24.8 18.8 18.9 13.6 14.3 Gradation - ASTM C96), % Percent Fractured Particles (ASTM D5821), % 1 or more than 1 100 100 15 100 100 100 2 or more than 2 100 100 12 100 100 100 Clay Lumps and Friable Particles 0 0 0 0 0 0 (AASHTO T112), % Magnesium Sulfate Soundness Test, 0.8 6.3 6.6 0.4 0.9 1.0 5 cycles (AASHTO T104), % tests. The research team was unable to produce an acceptable coarse aggregate gradation. Determining the percentage of mixture design with the coarser traprock (#78). flat or elongated and flat and elongated particles at the 3:1 ratio was added during the course of the research. The uncompacted voids of Method A (UVA) were meas- Laboratory Sample Results ured on a standard coarse aggregate specimen consisting of Before completing mixture designs, samples of each coarse 1,970 g of 12.5-mm to 9.5-mm and 3,030 g of 9.5-mm to aggregate were received in the laboratory from the aggregate 4.75-mm aggregate sizes. Uncompacted voids of Method B manufacturers. These samples were tested for the various (UVB) were measured on two size fractions, 12.5 mm to 9.5 properties shown in Table 6. mm and 9.5 mm to 4.75 mm, separately. The void measure- Flat or elongated particle percentages were separately ments on the two fractions were averaged and are reported as determined on two size fractions, 12.5 mm to 9.5 mm and 9.5 Method B values. mm to 4.75 mm. The weighted averages reported were com- The Micro-Deval (AASHTO TP 58) tests were performed puted based on the amount of each size fraction in the actual on a standard specimen consisting of 750 g of 12.5-mm

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12 to 9.5-mm, 375 g of 9.5-mm to 6.7-mm, and 375 g of Field Results 6.7-mm to 4.75-mm aggregate sizes. The total, combined In addition to testing aggregate samples received from specimen was placed in the Micro-Deval metal container the producers for mixture design purposes, flat and/or and filled with approximately 2 liters of water. The sample was soaked for a minimum of 1 hour. After soaking, 5,000 g elongated tests were conducted on aggregate samples taken of steel balls were introduced into the container. The con- from the HMA plant stockpiles, aggregate recovered from tainer was then placed on the Micro-Deval machine and plant-produced mixtures, and aggregate recovered from rotated for 105 minutes. After this, the sample was washed APT test section cores after binder extractions. Table 7 lists over the 4.75-mm and 1.18-mm sieves, recombined, and the flat and/or elongated values of the coarse aggregates oven dried. The loss is the amount of material passing the from these sources. 1.18-mm sieve expressed as a percentage of the original The data in Table 7 show that the 2:1 flat or elongated sample mass. ratios (FOE21) are somewhat variable throughout the con- Los Angeles abrasion loss (ASTM C 96) was determined on struction process. The FOE21 may show some changes in a Type C specimen consisting of 2,500 g of 9.5-mm to 6.3- particle shape from the stockpiles through the HMA mix- mm and 2,500 g of 6.3-mm to 4.75-mm size particles. ture production and construction process, but it is not con- Magnesium sulfate soundness loss (AASHTO T 104) val- clusive. Some of the variability could result from coring ues were measured on material retained on the 9.5-mm and because it is often difficult to discard all the aggregate pieces 4.75-mm sieves and are reported as the weighted average on on the edge of the core that were cut by the core barrel dur- the basis of the original gradations. ing the coring procedure. As shown in Table 7, the uncom- The bulk specific gravity and water absorption values of pacted voids measured on samples taken from the HMA the coarse aggregates were determined according to the plant stockpiles indicated little change except for dolomite ASTM C 127 method. and granite. Table 7. Coarse aggregate test data. Flat or Elongated Particles, 2:1 Ratio Mixture CA-1 CA-2 CA-3 CA-4 CA-5b Coarse Aggregate Dolomite Limestone Gravel Granite Traprock#88 Mixture Design 49 48 27 46 34 HMA Plant 45 45 35 55 34 Sample Source Stockpile HMA Plant 41 50 29 38 34 Mixture APT Cores 37 49 35 41 33 Flat or Elongated Particles 5:1 Ratio Mixture CA-1 CA-2 CA-3 CA-4 CA-5b Coarse Aggregate Dolomite Limestone Gravel Granite Traprock#88 Mixture Design 1 1 0 0 0 HMA Plant 1 1 0 0 0 Sample Source Stockpile HMA Plant 2 2 0 1 0 Mixture APT Cores 1 0 0 0 0 Flat and Elongated Particles 5:1 Ratio Mixture CA-1 CA-2 CA-3 CA-4 CA-5b Coarse Aggregate Dolomite Limestone Gravel Granite Traprock#88 Mixture Design 6 8 2 3 3 HMA Plant 6 8 1 7 3 Sample Source Stockpile HMA Plant 8 8 1 4 2 Mixture APT Cores 5 4 2 6 2 Uncompacted Voids Content, Method A, % Mixture CA-1 CA-2 CA-3 CA-4 CA-5b Coarse Aggregate Dolomite Limestone Gravel Granite Traprock#88 Mixture Design 51.2 48.2 42.2 48.9 48.0 Sample Source Material HMA Plant Stockpile 48.8 48.3 42.7 50.6 48.5

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13 Figure 4 shows the relationship between coarse aggregate 55 UVA and FOE21. Data obtained during the HMA mixture design phase are shown by the larger symbols and those from HMA plant stockpiles are shown by the small symbols. There 50 is a positive correlation between UVA and FOE21. As FOE21 UVA ,% increases, so does the UVA. 45 Fine Aggregate UVA = 0.27FOE21 + 36.31 Description, source location, and properties of the fine R2 = 0.55 aggregates used in the study are listed in Table 8. Initially, six 40 fine aggregate types were used in the HMA mixture designs, 25 35 45 55 65 but acceptable mixture designs could not be obtained using FOE21, % the FA-5 and FA-6 aggregates. As a remedy, different CA-1 CA-2 CA-3 CA-4 CA-5b dolomite (FA-5b) and traprock (FA-6b) sands were used. Note: Large symbols are data from mixture Mixtures using these alternate sands produced desirable vol- design phase. Small symbols are from HMA plant stockpiles. umetric properties. Mixtures with the original dolomite (FA-5) and traprock (FA-6) fine aggregates were not used in Figure 4. Coarse aggregate UVA and the study. FOE21 relationship. Table 8. Fine aggregate description, location, and properties. Natural Crushed Natural Aggregate Type Sand Gravel Sand Granite Dolomite Traprock Dolomite Traprock A Sand B Sand Sand1 #161 Sand2 #132 Designation FA-1 FA-2 FA-3 FA-4 FA-5 FA-6 FA-5b FA-6b Source Location Indiana Indiana Ohio North Indiana Virginia Indiana Virginia Carolina Percent Passing 9.5 100 100 100 100 100 100 100.0 100.0 4.75 100 100 100 99.0 98.4 95.0 100.0 96.0 Sieve Size (mm) 2.36 89.9 81.8 85.3 83.0 71.6 57.0 81.3 70.1 1.18 59.2 50.6 61.9 57.0 31.7 34.0 51.7 49.1 0.60 30.4 30.8 37.5 40.0 15.0 20.0 33.4 35.6 0.30 9.0 17.2 18.0 27.0 6.0 12.0 19.5 25.7 0.15 1.6 7.3 6.1 19.0 1.7 6.0 10.5 16.8 0.075 0.8 3.5 3.2 13.0 0.7 2.7 5.7 9.7 Dry Bulk Specific Gravity 2.585 2.660 2.586 2.639 2.665 2.911 2.634 2.892 (ASTM C128) Apparent Specific Gravity 2.714 2.782 2.735 2.689 2.830 3.003 2.820 3.007 (ASTM C128) Water Absorption, % 1.8 1.6 1.9 0.7 2.2 1.0 2.5 1.3 (ASTM C128) Particle Size of p0.075 Materials D60, microns 20.2 14.3 12.2 13.4 17.9 11.6 18.4 10.9 D30, microns 9.7 7.0 5.6 6.6 8.4 5.4 8.2 5.0 D10, microns 2.8 2.2 2.0 2.8 2.7 2.0 2.5 1.8 Uncompacted Void Content, % Method A - ASTM C1252 40.3 46.1 41.9 49.1 45.0 48.8 46.8 49.2 Method B - ASTM C1252 43.1 50.4 46.4 53.0 49.9 53.6 50.9 53.6 VTM5 44.0 51.6 47.3 54.4 51.4 55.0 51.9 55.1 Methylene Blue Value 3.3 1.3 5.0 8.0 0.5 6.8 2.8 5.1 (AASHTO TP57) Clay Content by Sand 98 90 82 70 100 86 79 70 Equivalent (AASHTO T104), % Magnesium Sulfate Soundness, 9 13 24 13 9 7 30 13 5 cycles (AASHTO T104), % Micro-Deval (Ontario Test 10.0 17.0 20.4 10.6 5.8 12.1 18.1 14.5 Method LS-619), % 1Used during the initial HMA mixture design

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14 Laboratory Sample Results of material on each size fraction was designed such that the combined sample had a fineness modulus of 2.8. In the test, Before completing mixture designs, samples of each of the samples were placed into the Micro-Deval jars and approxi- fine aggregates were received in the laboratory from the mately 750 mL of water was added. The samples were allowed aggregate producers. These samples were tested for the vari- to saturate for 24 hours. Approximately 1,250 g of steel balls ous properties shown in Table 8. were then put into the jars containing the sample and water. The fine aggregate test results in Table 8 show a wide range The jars were placed on the Micro-Deval machine and rotated in test values. The uncompacted voids contents were meas- for 15 minutes. Samples were then washed over the 0.075-mm ured by three methods, Methods A and B of ASTM C 1252, sieve and losses computed as the amount of material passing and the VTM5 method. Equipment for the VTM5 method is the 0.075-mm sieve expressed as the percentage of the origi- basically a larger scale of the ASTM C 1252 apparatus. In nal sample mass. Method A, voids were determined using a standard fine The bulk specific gravity and absorption values of the fine aggregate specimen consisting of 44 g of 2.36- to 1.18-mm, aggregates were determined according to the ASTM C 128 57 g of 1.18- to 0.60-mm, 72 g of 0.60- to 0.30-mm, and 17 g method. of 0.30- to 0.15-mm size fractions. In Method B, the voids of three individual size fractions were determined (i.e., 2.36 mm to 1.18 mm, 1.18 mm to 0.60 mm, and 0.60 mm to 0.30 mm). Field Results These three individual measurements were averaged and reported as the Method B value. The VTM5 procedure is sim- In addition to testing laboratory samples received from ilar to the ASTM C 1252, Method B, procedure. Three size aggregate producers, aggregate samples collected from the fractions, 2.36 to 1.00 mm, 1.00 to 0.60 mm, and 0.60 to 0.30 HMA plant stockpiles and recovered from plant-produced mm, were used. Results indicate that using 1.00 or 1.18 mm mixtures and APT cores were also tested. The fine aggregate as a size break was insignificant because sieving the 2.36- to UVA and MBV test results are listed in Table 9. For the UVA 1.18-mm fraction on the 1.00-mm sieve produced a negligi- results, there is good agreement between the field results and ble number of particles. those obtained from laboratory samples. Some degradation Particle size analyses were conducted on the p0.075 mate- did occur during mixture production and placement. rial using a Horiba LA500 Particle Size Analyzer. The sizes at Similarity of fine aggregate UVA test results obtained for 60 (D60), 30 (D30), and 10 (D10) percent of the fraction the laboratory mixture design aggregate and the aggregate smaller than 0.075 mm were determined. from the HMA plant stockpiles suggests that degradation The MBV test is used to determine the amount and nature during material handling and transportation was not sig- of potentially harmful materials, such as clay and/or organic nificant; however, increased degradation did occur during material, that may be present in the p0.075 fraction. The sand HMA production. The UVA of fine aggregates extracted equivalent test is used to measure the relative amount of clay- from the HMA plant mixtures were consistently lower sized particles in a fine aggregate. Tests were performed on than those from the HMA plant stockpiles. The difference material passing the 4.75-mm sieve. between the UVA values for the HMA plant stockpiles and Magnesium sulfate soundness of each material was the HMA plant mixtures was divided by the initial UVA of determined for material passing the 4.75-mm sieve. Mate- the aggregate sampled from the HMA plant stockpiles. This rial retained on the 2.36-, 1.18-, 0.60-, and 0.30-mm sieves index indicated the amount of relative degradation result- were tested separately. The sample mass of each size frac- ing from HMA mixture production for each aggregate. As tion was approximately 300 g. Each sample was soaked for shown in Figure 5, the degradation is correlated to the ini- 16 to 18 hours and oven dried for 6 to 8 hours. After five tial UVA values. Fine aggregates with initially high UVA val- cycles of soaking and drying, each sample was washed over ues appear to degrade more than do those with initially low the same sieve on which it was retained before the test. UVA values. Material loss of each size fraction was computed as the per- There is reasonable agreement between field MBV values centage of the original mass. Based on the individual frac- and those obtained on laboratory samples, except for FA-1, tion loss, the weighted averages were computed based on FA-4, and FA-6b aggregates. According to the AASHTO TP 57 the percentage of each size fraction in the original fine test method, the mixture design results (laboratory samples) aggregate gradations. for FA-1 and FA-6b indicate that the aggregates should have Micro-Deval tests were performed in accordance with the excellent performance while the stockpile results indicate they Ontario Test Method LS-619. A 500-g mass of each sample are marginally acceptable. However, for the FA-4 aggregates, was prepared by combining six individual size fractions of the stockpile results indicated acceptable performance, but material between the 4.75- and 0.075-mm sieves. The amount the mixture design results were marginally acceptable. For