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Manual for Emulsion-Based Chip Seals for Pavement Preservation (2011)

Chapter: Appendix - Recommended Test Methods

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Page 29
Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
×
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
×
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
×
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
×
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
×
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
×
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
×
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
×
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Suggested Citation:"Appendix - Recommended Test Methods." National Academies of Sciences, Engineering, and Medicine. 2011. Manual for Emulsion-Based Chip Seals for Pavement Preservation. Washington, DC: The National Academies Press. doi: 10.17226/14421.
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29 The proposed test methods, prepared as part of NCHRP Project 14-17, Manual for Emulsion-Based Chip Seals for Pavement Preservation, are the recommendations of the NCHRP Project 14-17 staff at Colorado State University. These test methods have not been approved by NCHRP or any AASHTO committee nor have they been accepted as AASHTO specifications. A P P E N D I X Recommended Test Methods CONTENTS Recommended Standard Method of Test for Embedment Depth of Chip-Seal Aggregates in the Lab and the Field, 30 Recommended Standard Method of Test for Laboratory Chip Loss from Emulsified Asphalt Chip Seal Samples, 39 Recommended Standard Method of Test for Measuring Moisture Loss from Chip Seals, 53 Recommended Standard Method of Test for Recovery of Asphalt from Emulsion by Stirred-Can Method, 59 Recommended Standard Method of Test for Determining the Strain Sensitivity of Asphalt Emulsion Residue Using Strain Sweeps Performed on a Dynamic Shear Rheometer (DSR), 63

Recommended Standard Method of Test for Embedment Depth of Chip-Seal Aggregates in the Lab and the Field AASHTO Designation: Txxx-xx 1. SCOPE 1.1 This test method provides the average aggregate embedment depth, in asphalt, of field chip seals and laboratory specimens. 1.2 The values stated in SI units are to be regarded as the standard unless otherwise indicated. 1.3 A precision and bias statement for this standard has not been developed at this time. Therefore, this standard should not be used for acceptance or rejection of a material for purchasing purposes. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1 ASTM Standard: • D 8, Terminology Relating to Materials for Roads and Pavements 3. SUMMARY OF TEST METHOD 3.1 Where the void ratio of an area of chip seal may be estimated with acceptable accuracy, and where voids (Note 1) between all chip-seal particles are filled with a given mass of glass beads of known packing density, the average height of beads within the chip seal layer may be determined. This average height of beads between the surface level of the asphalt and the average height level of the chip- seal particles would reflect the chip seal’s texture height. Given the average particle height of the chip-seal aggregate, one may perform a calculation, using the evaluated texture height, to yield the chip-seal embedment depth. 30

Figure 1. Undulating profile over particle peaks and voids. Figure 2. Profile remains unchanged at all embedments. Chip Seal Bedding Plane Height of average particle Asphalt Aggregate Imaginary undulating surface: upper bound of chip seal voids H E Volume of chip seal voids T Voids filled by asphalt Profile of voids remains unchanged at all embedments Chip Seal Bedding Plane Height of average particle Asphalt Aggregate Imaginary undulating surface: upper bound of chip seal voids H E T Volume of chip seal voids Note 1—For the purposes of this test method, it is assumed that the actual chip- seal voids are those that exist above the asphalt surface and below the profile of an imaginary, three-dimensionally undulating, flexible membrane that is draped over aggregate particles and forced to come into contact with the peak of each particle (see Figure 1 and Figure 2). 31

32 Two procedures are provided, each of which ma y be used to evaluate a field chip seal or a specimen chip seal for embedment depth. In the first, the “spreading procedure,” a known, fixed volume of glass beads is spread into a circular area over the surface of a chip seal to fill th e voids between the particles, which are illustrated in Figure 1. The glass beads bridge between the peaks of the chip-seal particles in all directions and form an undulating profile. Effectively the average height of glass beads covering the specimen is the same as the height of the chip seal’s average particle (Note 2). The circular area, achieved with the fixed volume of glass beads, is used to evaluate embedment depth. Note 2— For simplification, it is assumed that an “equivalent” chip seal, constructed with one-sized, identical particles, each with height equal to the average particle height, may be substituted for the actual chip seal that contains voids as defined in Note 1. It is further assumed that the constituents of such an equivalent chip seal, of the same area as the actual chip seal, would precisely reflect the height of asphalt and the volumes of asphalt, aggregate particles, and voids that exist in the actual chip seal. In this regard, the texture height is the height between the level of the asphalt surface and the level of the top of particles in the equivalent chip seal (Figure 3). Figure 3. Equivalent chip seal. Chip Seal Bedding Plane Height of average particle Volume of chip seal voids H E T Asphalt Aggregate In the second procedure, the “submerging procedure,” a known, variable volume of glass beads is used to completely cover all chip-seal particles within a fixed area to a fixed level above the height level of the chip seal’s average particle (Figure 4). In order to determine the volume of beads within the chip-seal voids, a calculation is first performed using the concept of the flat-topped equivalent chip seal (Note 2) to determine the excess volume of beads that occupies the space above the chip seal (Figure 5). The void volume is obtained by subtracting the excess volume of beads from the total volume of glass beads on the chip-seal area. This allows for evalua- tion of the embedment depth.

33 Figure 4. Submerging procedure. Figure 5. Equivalent model for the submerged chip seal. Chip Seal Bedding Plane Height of average particle S H E T “C” is the volume of all beads deposited directly on the chip seal of fixed area “A” M Base (optional), of area “R,” under laboratory chip seal Top of mold Mold of area “W” Excess beads, “C – B,” above chip seal Glass beads, “B,” in voids Asphalt Aggregate Chip Seal Bedding Plane Height of average particle Asphalt Aggregate Glass beads, “C – B,” above voids S M Base (optional), of area “R,” under laboratory chip seal Top of mold Imaginary undulating surface: upper bound of chip seal voids H E T “C” is the volume of all beads deposited directly on the chip seal of fixed area “A” Mold of area “W” Glass beads, “B,” in voids Note 3—The submerging procedure, which may be used for any degree of embedment, has been devised primarily to account for the situation, at very high embedment depths, where the asphalt surface intersects the imaginary membrane defined in Note 1. In this situation, where some particle peaks are covered, it may become difficult to spread the beads to follow the required profile illustrated in Figure 2.

34 4. SIGNIFICANCE AND USE 4.1 This test method is intended to be used in the evaluation of embedment depth in field and specimen chip seals. 4.2 In predicting future performance of a chip seal, embedment depth evaluation is critical. This is because performance, in certain aspects such as reduced aggregate loss, is likely to increase as embedment depth increases. Performance in terms of high skid resistance and reduced construction cost, on the other hand, is likely to decrease with increased embedment beyond a certain level. 4.3 Additionally, embedment depth evaluation is important simply because it is often the only practical means by which an apparently sound field chip seal may be evaluated. 4.4 Ultimately, the results of embedment depth evaluations enable better quantification of the relative risk associated with apparently sound roads. 5. APPARATUS 5.1 Balance – The balance must be capable of weighing approximately 10,000 g of glass beads per square meter of chip seal to within +0.1 g. 5.2 Glass Cylinder/Container – A smooth-bottomed glass cylinder is to be used for the spreading procedure. A drinking glass (a shot glass) used for this purpose also doubles as a container for weighing glass beads and pouring them onto the chip- seal surface. 5.3 Measuring Tape – This is used to measure the diameter of glass bead circles achieved using the spreading procedure. The tape is to be graduated in millimeters. 5.4 Laboratory Mold – Used in the submerging procedure in the laboratory, the mold is to have a constant height (M) and a constant cross sectional area (W) large enough to accommodate the specimen chip seal. Additionally, when filled to its rim, the mold must provide for complete submergence of the specimen chip seal. the tallest chip seal particle in order to allow smooth screeding of the surface. 5.5 Working Platform – For precision, the specimen chip seal and laboratory mold should always be prepared and configured on a flat and level platform. Note 4—The top elevation of the mold needs only to be some 3 mm higher than

35 5.6 Offset Spacers – To perform the submergence procedure in the field, offset spacers of known height are used to establish an offset distance from the bedding plane of the chip seal. The tops of the spacers are equidistant from the bedding plane and higher than the average particle height in order to achieve submergence of chip-seal particles. Note 5—The submerging procedure is not a suitable candidate on steeply sloping roadways or where the level of the bedding plane is unknown. The procedure is suitable on areas where the bedding plane level has been recorded and where the plane is flat and approximately level in the area to be tested. 5.7 Field Mold – When carrying out the submerging procedure in the field, a field mold is to be used to form the glass beads over a fixed area of chip seal. The field mold is to be built up using a perimeter gasket wall and a flat metal surface with a cutout. The vertical-faced gasket wall, which may consist of moldable putty or silicone, must be shaped such that it dams the spaces between chip-seal particles and finishes flush with the cut-out area of the metal surface. Placement of the metal surface is to be accommodated by the use of offset spacers such that it is flat, at a known height above the average chip-seal particle, and allows full submergence of the chip seal. 6. PREPARATION OF MATERIALS 6.1 Specimen Chip Seal – For the purposes of this test method, a specimen chip seal is constructed on a flat and level base, or sheet, of known thickness (S) and area (R). Additionally, for the submerging procedure, it must be possible to place the specimen into a mold or to form a mold around the chip seal. 6.2 Area of Chip Seal – Precisely measure the chip seal area (A), which is being evaluated for embedment. 6.3 Glass Beads – These are fine particles of glass that are able to fit between chip- seal particles and, en masse, follow the contours of the particles’ surface. 6.4 Packing Density of Glass Beads – Fill the tared mold, of known volume (K), with glass beads and weigh the filled container. Establish the packed glass beads’ mass per unit volume (P) for use in the following procedures. 7. SPREADING PROCEDURE IN THE LAB AND IN THE FIELD 7.1 Using the tared glass cylinder/container, weigh out a pre-calculated mass of glass beads that will provide a chosen volume (B) at a packed density (P) (defined in section 6). Record the mass to the nearest 0.1 g.

36 7.2 Pour the glass beads onto the center of the specimen to form a pile. Position the glass cylinder on the pile of glass beads and move it in a circle to spread the beads into a circular area. 7.3 Use the fingers to continue spreading the beads outward in a circle while allowing the beads to accumulate between particle peaks, completely and exactly filling the void volume (Note 1). This is achieved when only the highest point of each aggregate particle (not otherwise submerged by asphalt) is exposed. 7.4 Place a marker at the approximate center of the circular area of beads. Rotating about the marker, take four diameter measurements, with the measuring tape, in line with the marker and rotationally offset 45 degrees from each other. Calculate the average circle diameter (D). 8. SUBMERGING PROCEDURE IN THE LAB AND IN THE FIELD 8.1 Weigh and record, to the nearest 0.1 g, the mass of a volume (Y) of glass beads, which will be more than enough to cover the chip seal and fill the mold. 8.2 For the lab procedure, place the specimen chip seal into the mold or form the mold around the specimen, ensuring that the mold and the specimen are flat and level and that complete submergence of the chip seal will be achieved. 8.3 For the field procedure, install the offset spacers such that they are elevated a known height above the bedding plane of the chip seal as a guide for the installation height of the field mold. 8.4 Sweep the field chip seal clean and install the mold over the area to be evaluated such that the mold’s top surface is flat and at a known offset distance above the bedding plane of the chip seal. 8.5 Pour glass beads into the mold and screed the surface of the beads flush with the top of the mold. The chip-seal aggregate particles should be completely covered by glass beads. 8.6 Carefully recover the glass beads that were screeded off the mold. Weigh the unused portion of beads and calculate the total mass of beads deposited into the mold. In turn, use this result along with the packing density (P) to calculate the total volume (G) of beads deposited into the mold. 8.7 For laboratory molds that are larger in area than the specimen chip seal, also calculate the volume of beads (C) (section 9), which is deposited directly on the chip seal surface area under evaluation.

37 9. CALCULATIONS 9.1 The chip seal’s texture height ( T ) is the average height dimension of the un-embedded portion of particles. The average height level of this un-embedded portion is the same as the average height level of the chip-seal particles. Therefore, the texture height is equivalent to the dimension difference between the depth of asphalt ( E ) and the average particle height ( H ). Where a volume of beads ( B ) is shaped such that it fills the chip seal voids, the texture height can be calculated from the following: aggregate and beads of area plan surface asphalt the above aggregate and beads of volume T = That is: T = { B + [ T (1 – V ) A ]}/ A ; T = B /( A * V ) (1) And the embedment is obtained using the following: E = H – T (2) Where Where T = texture height (mm), B = volume of glass beads (mm 3 ) on the chip seal surface, filling only voids between particles, A = plan area of chip seal covered by beads (mm 2 ), V = the void ratio, E = the particle embedment depth in asphalt (mm), and H = the average particle height (mm). the submerging procedure has been used, whether in the lab or in the field, obtain B by subtracting the volume of beads that would lay above the top level of an equivalent chip seal (Note 2) from the total volume ( C ) of beads filling the voids and submerging the chip seal (Figures 4 and 5). B = C – [ ( M – S – H ) * A ] (3) Where B = volume of glass beads (mm 3 ) on the chip-seal surface, filling only voids between particles ; C = total volume of beads (mm 3 ) deposited directly on the chip-seal surface area; S = thickness of base, or sheet, on which specimen chip seal has been constructed (mm) (Note: S = 0 for field chip seals); M = height of top of mold (mm) above bottom level of chip-seal base; H = the average particle height (mm); and A = plan area of chip seal covered by beads (mm 2 ).

38 For laboratory specimens where the plan area of the mold is larger than that of the chip seal under evaluation, obtain C using the following: C = G – [(WM) – (RS) – (A{M – S})] (4) Where C = total volume of beads (mm3) deposited directly on the chip-seal surface area; G = total volume of beads (mm3) deposited into the mold; W = area of mold (mm2); M = height of top of mold (mm) above bottom level of chip seal base; S = thickness (mm) of base, or sheet, on which specimen chip seal has been constructed; R = area of base (mm2); and A = plan area of chip seal covered by beads (mm2).

39 Recommended Standard Method of Test for Laborator y Chip Loss from Emulsified Asphalt Chip Seal Samples AASHTO Designation: Txxxx-xx 1. SCOPE 1.1 This test method measures the quantity of aggregate lost, at variable moisture levels of systems of asphalt emulsion and aggregate chips, by simulating the brooming of a chip seal in the laboratory. 1.2 The values stated in SI units are to be regarded as the standard unless otherwise indicated. 1.3 A precision and bias statement for this standard has not been developed at this time. Therefore, this standard should not be used for acceptance or rejection of a material for purchasing purposes. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the ap plicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1 AASHTO Standards: • T 19, Standard Test Method for Bulk Density (“Unit Weight”) and Voids in Aggregate 2.2 ASTM Standards: • Coarse Aggregate • T 27, Sieve Analysis of Fine and Coarse Aggregates • T 2, Practice for Sampling Aggregates • T 40, Practice for Sampling Bituminous Materials • M 140, Specification for Emulsified Asphalt • M 208, Specification for Cationic Emulsified Asphalt • D 226, Specification for Asphalt-Saturated Organic Felt Used in Roofing and Waterproofing T 85, Test Method for Density, Relative Density (Specific Gravity), and Absorption of • D 7000, Standard Test Method for Sweep Test of Bituminous Emulsion Surface Treatment Samples

40 2.3 ISSA Document: ISSA Technical Bulletin No. 100 Test Method for Wet Track Abrasion of 2.4 Texas Transportation Institute: Field Manual on Design and Construction of Seal Coats, Research Report 214-25, July 1981 Slurry Surfaces 2.5 Hanson, F. M. Bituminous Surface Treatments on Rural Highways, Proceedings of the New Zealand Society of Civil Engineers, Vol. 21, 1934–1935, p. 89. 3. SUMMARY OF TEST METHOD 3.1 4. SIGNIFICANCE AND USE 4.1 This test method is useful for classifying the interaction of rapid-setting asphalt emulsions with various aggregate types and is applicable to surface treatments that require a quick return to traffic. The test has the ability to predict the relative speed with which a binder–aggregate combination will develop a traffic-sustaining bond in comparison with other combinations. It also has the capability to predict surface treatment performance in the formative stage using project materials. This performance test is intended to evaluate the potential curing characteristics of a binder–aggregate combination to ensure that the surface treatment is sufficiently cured before allowing traffic onto the chip seal. This test is effective for defining the film formation stage and relative binding ability of asphalt emulsions interacting with aggregates when the result of this test is compared to that produced by other combinations of emulsions and aggregates. A brush (designed to closely replicate the sweeping action of a broom) exerts a force on the aggregate used on surface treatments. Asphalt emulsion and a single layer of aggregate chips are applied to an asphalt felt disk. The sample is then conditioned in an oven to arrive at a prescribed emulsion/chip moisture content before testing. A mixer abrades the surface of the sample using a nylon brush. After 1 min of abrasion, the test is stopped, any loose aggregate is removed, and the percent mass loss is calculated. 5. APPARATUS 5.1 Mixer – Use to abrade the sample. 5.2 Quick-Clamp Mounting Base – This base must be an adequate and level support for clamping the sample in place. The test sample should not move during abrasion. 5.3 Pan – An appropriate pan will contain the test sample on the mixer and hold dislodged aggregate.

41 5.4 Oven – The conditioning oven shall be a constant-temperature, forced-draft oven meeting the requirements given in Table 1 and containing shelves with at least 65% voids. The shelves shall be placed at least 120 mm apart and 100 mm away from the top and floor. Table 1. Oven specifications. Oven Type Forced-draft oven Min. Inside D x W x H 460 x 460 x 460 mm Accuracy + 1.0º C 5.5 Balance – A balance capable of weighing 800 g or more to within +0.1 g. A minimum platform length and width of 240 mm is required. 5.6 Dimensions ID Name mm A Collar diameter 36 B Collar height 76 C Brush head length 128 D Overall brush head height 19 E Groove height 17 F Groove width 18 H Slot height 19 W Slot width 7 Removable Brush Holder – The brush holder (Figure 1) shall be attachable to the mixer and capable of a free-floating vertical movement of 19 ± 1 mm and having the dimensions listed in the table below. The total mass of the brush head and the attached weight shall be 1,500 ± 15 g. The collar and nylon strip brush are not included in this mass. The brush clamping system shall hold the nylon strip brush in place so that it will not move or dislodge during testing. Figure 1. Brush holder.

42 5.7 Nylon Strip Brush – The brush shall conform to the specifications given in Table 2. Table 2. Brush specifications. Overall Trim 25.4 mm Overall Length 127 + 1 mm Backing Size # 7 Fill Material Crimped black nylon Nylon Type 6.0 Fill Diameter 0.254 mm Weight 35 + 2 g 5.8 Strike-Off Template – The template should consist of a flat, stainless steel metal plate with approximate overall dimensions of 600 mm x 450 mm to allow for accumulation of excess (struck-off) emulsion on the template surface. It shall include a 280 + 3-mm diameter circular cutout with a flush edge. A template fabricated from 16-gauge U.S. Standard (plate and sheet metal) material will suffice in most cases. Where several templates are to be used, it is helpful to fabricate all templates with the same overall dimensions and location of the circular cutout. Note 1—Emulsion mass may vary according to emulsion viscosity and applied strike-off pressure. Alternative gauges may be necessary for emulsion mass correction for varying aggregate sizes and shapes. See Appendix A2 for guidelines to calculate the required emulsion volume (and, therefore, the required template gauge) for varying emulsion residual contents and aggregate sizes. 5.9 Strike-Off Rod – The 750 + 100-mm-long rod shall be made of 12.5-mm electrical metal conduit or 12.5-mm wide x 3-mm thick metal for striking off emulsion from the template surface. See Note 2 for other recommendations. Note 2—Emulsion viscosity and the cross-sectional thickness of the strike-off rod directly affect the formed emulsion volume. In this regard, it is prudent to experiment with differently shaped strike-off rods in order to arrive at a tool that is compatible with the emulsion in producing an emulsion volume that is consistently related to the template volume. A more viscous emulsion is recommended for this test since it enables easier handling and specimen manufacture. Additionally, a narrow area of contact, such as that between a 3-mm thick, rounded-edged strike-off rod and the emulsion, is recommended to allow for a more consistent strike-off result with a wide range of emulsion viscosities. The rod must be approximately 12.5-mm wide to avoid emulsion mounting over the top edge. It is crucial that the rod be stiff and resistant to flexure and be handled in a manner in order to avoid flexure. 6.0 Sweep Test Compactor – A suitable compaction device with a minimum curved surface radius of 550 + 30 mm and weighing 7,500 + 500 g. A picture of this apparatus can be seen in Figure 2.

43 Figure 2. Sweep test compactor. Figure 3. Working platform. table. It should be placed at a corner of the work table such that it is comfortably accessible from the two perpendicular sides at the corner of the table. A circular etching is made on the platform surface to allow positioning of the asphalt disks. A metal strip with appropriate markings is permanently fixed to the platform at a location such that the strike-off template may be quickly and easily positioned with its cutout centered over the asphalt disk. The platform also has markings and keyholes for positioning and temporarily fixing the sliding-plate chip-dropper apparatus. See Figure 3. 6.1 Working Platform – Specimens are manufactured on the 600-mm x 600-mm working platform, which shall be made horizontally level and shall be fixed to a stationary work 6.2 Sliding-Plate Chip-Dropper – It consists of rails elevating two sliding plates above the formed emulsion. This apparatus is temporarily attached to the working platform and centered over the emulsion previously formed on the asphalt disk. The plates are used to position and suspend aggregate chips. When pulled away, the sliding plates no longer suspend the aggregate chips and these fall onto the asphalt emulsion. See Figure 4. 6.3 Aggregate Former – A circular metal hoop of the same internal diameter as the circular cutout in the strike-off template. This device is positioned centrally on the sliding plates of the chip dropper and is used to form a pre-calculated mass of aggregate chips into a circular horizontal area one stone deep. See Figure 5. 6.4 Pin Grabber – After aggregate chips have been formed into a single layer, the aggregate former is removed and the pin grabber is positioned over the aggregate chips and attached to the chip dropper. The grabber consists of thousands of pins spaced apart from each other by uniformly perforated plates. The plates prevent any appreciable lateral motion of the pins and, practically, allow only vertical motion of the pins. As the grabber is

44 lowered, by means of guides fixed to the chip dropper, over the aggregate chips, the pins come into contact with the aggregate chips. When the chip-dropper plates are slid horizontally, the pins prevent aggregate chips from moving horizontally. As the plates are Figure 6. Pin grabber. slid from beneath aggregate chips, the chips fall vertically onto the asphalt emulsion and assume the same orientations that were given to them on the plates prior to sliding. See Figure 6. 6.5 Glass Bowl – A glass container with a secure and airtight cover that will allow mixing of the moisture with aggregate, thus enabling absorption. Figure 4. Sliding-plate chip-dropper. Figure 5. Aggregate former.

45 7. MATERIALS 7.1 Aggregates – The job aggregates should be sampled and split according to practice D 75. They shall be placed in an oven and dried to a constant weight. Unless naturally sourced aggregate samples are being tested, the aggregates shall be dry sieved to obtain a test sample that has 100% passing the 9.5-mm sieve and <1% passing the 4.75-mm sieve. The amount of aggregate used (Note 3) shall be calculated such that a single layer of aggregate is applied to the specimen. Note 3—Aggregate mass will vary according to bulk specific gravity (BSG), flakiness index, and size and shape of the aggregate particles. Aggregate coverage rates are to be calculated for each source. See Appendix A1 for guidelines to calculate the required aggregate mass. 7.2 Asphalt Emulsion – The asphalt emulsion should meet all applicable specifications for the surface treatment application. The asphalt emulsion shall be equilibrated to a temperature of 60ºC for sample production. Note 4—Emulsion volume will vary according to the void volume that exists between aggregate particles and the residual content of the emulsion. Asphalt emulsion coverage rates are to be calculated for each source and for each combination with different aggregates. See Appendix A2 for guidelines to calculate the required emulsion volume. 7.3 Asphalt Felt Disk – Produce sample disks from 30-lb asphalt felt paper, specification D 226, Type II. The asphalt felt disks shall not have breaks, cracks, tears, protuberances, indentations, or splices. The felt shall be cut to make 300 + 10-mm diameter disks. The disks shall be placed in a 50°C oven for 24 to 72 h to flatten. Manipulate the disks until they are flat and store at room temperature at least three days before use. 8. TEST SPECIMENS 8.1 Pre-weigh and record the aggregate as dry aggregate mass. In a glass bowl, add sufficient water, of known mass (corrected for water loss during specimen production), to the pre- weighed aggregate, targeting the prescribed moisture content for the completed specimen. Immediately cover the bowl to prevent moisture loss. Gently shake, overturn, and orient the covered bowl and its contents to coat the particles with moisture and let stand for at least 5 min to enable absorption of the moisture by the aggregate. Weigh the asphalt felt disk to the nearest 0.1 g and record as the asphalt sample disk mass. Place the asphalt felt emulsion, the disk is moved to the scale and back to the working platform for application of aggregate chips. Where the disks are not perfectly circular or uniform, a system must be developed to enable accurate repositioning of the asphalt disk in its initial position when it is moved back to the platform for application of aggregate chips. A strike-off template is placed over the felt disk, centering the hole of the template over the felt disk. disk on a table. Manipulate the felt disk so that it lies flat against the surface. Replace the disk if the edges curl or bubble or the disk contains foreign matter. Position the disk on the working platform. During specimen manufacture and after the application of

46 Using the aggregate former, the pre-weighed (and moistened) aggregate is now formed on the sliding-plate chip-dropper apparatus, which is assembled near the working platform. The fingertips are used for spreading the aggregate one stone deep, compactly filling the circular area of the former. Next, the aggregate former is removed and the pin grabber is attached to the chip dropper to hold the aggregate in place. Asphalt emulsion in the amount of 83 + 5 g (application rate of 1.42 kg/m2) at 60°C is poured along the top arc of the exposed felt disk. With the thickness of the strike-off rod in contact with the surface of the template, and the width of the strike-off rod held approximately vertically (the top edge of the strike-off rod leaning toward the user), excess asphalt emulsion is removed with the strike-off rod in a gentle side-to-side continuous motion. This shall be completed within a 3 + 1 s period. The strike-off motion should not be stopped until the excess materials are off of the felt disk. The template is quickly removed (Note 5). The asphalt disk is moved to a scale to determine the applied emulsion mass and then accurately repositioned on the working platform. A picture of the strike-off procedure can be seen in Figure 7. Note 5—Downward pressure, strike-off speed, and template thickness can be adjusted to ensure correct emulsion mass. Neat removal of the template is often difficult when low viscosity emulsions are used. In such cases, a bubble forms between the emulsion and the circular edge of the template. When this bubble pops, it splatters, irregularly, onto the asphalt disk. This problem is usually not encountered with the use of thicker-bodied emulsions. 8.2 Immediately position the sliding-plate chip-dropper on the working platform, over the asphalt disk, and apply the pre-weighed aggregate sample onto the asphalt emulsion. Once the aggregate has been placed on the sample, compact the aggregates using the sweep test compactor three half cycles in one direction and three half cycles in a perpendicular direction to set the aggregate. Care should be taken not to apply any additional manual downward force to the compactor. Immediately weigh the sample and Figure 7. Emulsion strike-off in template. record as sample weight. Place the specimen in the forced-draft oven. Sample production and weighing should take no more than 4 min.

47 9.3 When the specimen has achieved the desired cure level ±2%, it is removed from the oven and allowed to cool to a convenient prescribed temperature. The weight is recorded in order to verify the cure level that is actually achieved. At the end of conditioning, the specimen is turned vertically and any loose aggregate is removed by gentle hand brushing of the technician’s fingers back and forth across the sample. The specimen is then weighed, and the mass recorded to the nearest 0.1 g as the initial specimen mass. The time from end of conditioning to being placed in the test apparatus should be no greater than 2 min. Note 8—Brushing using the technician’s fingers across the sample has proven to be the preferred method versus a brush for removing any loose aggregate that has not fallen off when the specimen is turned vertically. 9. CONDITIONING 9.1 The specimen is immediately placed in a forced-draft oven for the specified time, temperature (Note 6), and relative humidity based on desired field performance. Note 6— Typically, where the performance of the binder–aggregate combination is being tested at various emulsion cure levels, specimens are cured at any convenient temperature and for any time period that provides the required specimen cure level. 9.2 The oven temperature shall be kept to a tolerance of 10% of the desired values (Note 7). The tolerance of the relative humidity shall be 25% of the desired value unless otherwise specified. Note 7— To maintain constant curing conditions, the oven door should only be opened once within a 20-min period. 10. PROCEDURE 10.1 Attach and then leave the specimen in the clamping device for 180 + 30 s. During the equilibration time, the brush is secured into the brush head, and the brush head with the weight is attached to the mixer. At the end of the equilibrating time, put the brush head into contact with the sample, making sure there is free-floating vertical movement of the brush head. The mixer is then turned on to setting #1 (0.83 gyrations per second) for 60 s. After the brush head has come to a complete stop, the table is lowered and the sample is removed from the clamping device. The specimen is held vertically, and any loose aggregate is removed by gentle brushing of the technician’s fingers back and forth across the sample (Note 8). The abraded sample is weighed to the nearest 0.1 g, and this is recorded as the final specimen weight. A picture of the configured apparatus, with test specimen, can be seen in Figure 8.

48 APPENDICES The laboratory specimen simulates a chip-seal layer. Aggregate, which is dropped onto the binder, is intended to be placed one stone thick and held in place by a combination of particle interaction, brought on by compaction, and binder–aggregate adhesion. The preceding manufacture and testing procedures account for and test the relative strength of the bond developed between asphalt binder and aggregate particles within the chip seal itself. The required aggregate mass and asphalt cement volume depend on the average aggregate particle dimensions, on an assumed eventual de gree of compaction of the aggregate particles, and on the assumption that each particle will eventually lay on its widest face. In the laboratory specimen, the degree of compaction of the aggregate simulates that which exists in a newly and properly built chip seal. The assumptions made with regard to calculation of the required binder volume (the residual asphalt content of the em ulsion) intend to avoid bleeding by accounting for the compaction of the aggregate over time. 11. CALCULATION 11.1 This equation represents the total mass loss based on the initial aggregate sample weight. The mass loss as a percentage of the area exposed to the abrading force is 33 . 1 100 % ×× C A B A Loss Mass − − = (1) Where A = initial specimen mass, B = final specimen mass, and C = asphalt sample disk mass. Figure 8. Specimen under test in configured apparatus.

49 A1.2 Physical properties of the aggregate are experimentally determined, including oven dry bulk specific gravity ( G ), loose unit weight ( W ), void volume ( V ), and particle size characteristics. A1.3 Dry bulk specific gravity ( G ) is determined according to ASTM C 127, and dry loose unit weight ( W ) is determined according to ASTM C 29. These allow calculation of the initial void volume ( V ) between particles of the loose aggregate from V = (1 – W /62.4 G ) (A1) A1.4 F. M. Hanson (1935) observed that the void volume between aggregate particles is approximately 50% (the loose condition) when the aggregate is dropped onto the asphalt binder. He theorized that due to reorientation, this reduces to approximately 30% (60% of 50% voids) immediately after rolling and to 20% (40% of 50% voids) after plenty of traffic. Hanson’s theory, as it relates to surface treatment densification, is reflected in the following outline of the noted chip-seal design methods. A1.5 Although one-sized and cubical aggregate performs best in chip seals and may simplify the design process, graded and non-cubical aggregate sources often find use. In these cases, it is often helpful to make use of the design method proposed by McLeod (1969), which calculates the required volume of aggregate at an assumed ma ximum density. This calculation is possible after approximating the ultimate average mat thickness (average le ast particle dimension) and through the assumption that, at the ultimate average mat thickness, voids have reduced, after considerable traffic, to 40% of the initial loose-aggregate void volume. Although density. The following useful guidelines for the calculation of required aggregate and em ulsion masses used in the manufacture of laboratory specimens are taken from the McLeod and the modified Kearby single-surface-treatment design methods respectively referenced in the FHWA Asphalt Emulsion Manual , FHWA-IP-79-1, and the USDOT Field Manual on Design and Construction of Seal Coats , Research Report 214-25, July 1981. APPENDIX A1. AGGREGATE MASS A1.1 Although the laboratory compaction of specimen aggregate according to this standard is not equal to that possible in the field with rolling equipment, in the manufacture of the laboratory specimen, care should be taken to ensure that the appropriate mass of aggregate particles is positioned on the working platform as compactly as possible and such that the center of gravity of each particle is as low as possible, or such that a particle’s stability against rotation is maximized. In determining the required chip-seal aggregate c overage, it is necessary to evaluate the proposed aggregate for its ability to compact. In this regard, our calculated required aggregate mass and asphalt volume will only be approximations since it is not possible to conclusively determine what will be the aggregate void volume immediately after construction or at ultimate aggregate

50 i. A sample of the aggregate material is first sieved according to ASTM C 136. From the aggregate gradation curve, the median size is determined as the theoretical sieve size through which 50% by mass of the aggregate would pass. The flakiness of the material is then determined by testing representative sample particles, taken from the various gradation fractions, on the appropriate slot of a slotted sieve. The flakiness index is the combined mass proportion of the total mass of tested material that passes through the slots. ii. The median size and flakiness index results are used in conjunction with a chart for determining average least dimension to arrive at the approximate ultimate mat height of the chip seal. A1.8 Refer to FHWA-IP-79-1 for a more detailed review of this procedure and its relevant modification factors. A1.9 A1.10 Where the maximum beneficial effect of aggregate chip/asphalt binder adhesion is being tested, the aggregate should be washed and dried prior to use. In applying the McLeod procedure for use with lab specimens, since it is assumed that specimen aggregate particles are placed on their widest sides, the average mat depth of the specimen is assumed to be equal to the average least dimension (H). However, since compact particle placement and specimen compaction in the lab is not as effective as what is possible in the field, it is usually necessary to modify the assumed ultimate void volume to a more practical value approaching that associated with the compact bulk density of the aggregate according to ASTM C 29. A1.6 The oven dry bulk specific gravity (G), the void volume (V ) of the loose aggregate, and the ultimate average mat depth (H ), in conjunction with an assumed ultimate void volume (0.4V ), are used to calculate the required coverage mass per unit area at ultimate density. It is important to note that the procedure anticipates that the densification is due to particle reorientation and average mat depth reduction to H as a limit. The coverage mass per unit area, therefore, is assumed to remain practically constant as densification progresses. A1.7 Using the assumption that particles will ultimately orient themselves on their widest sides, with the vertical dimension being the smallest, an approximation of the ultimate average mat height is made by determining the average least dimension of a representative sample of particles. The procedure involves determination of the median particle size and the flakiness index. the ultimate density is not achieved immediately after construction, this assumed ultimate state of the aggregate is also used to determine the asphalt requirement. In calculating the actual aggregate mass to be dropped from a spreader truck, the user may also use modifying factors to suit local conditions.

51 A2.3 The thickness of the strike-off template used in the manufacture of laboratory specimens is specified based on the average particle height and degree of compaction of the aggregate, such that it provides the appropriate struck emulsion volume with the required asphalt residual content. Refer to FHWA-IP-79-1 for a more detailed treatment of this procedure and for further references. A2.4 The McLeod method employs factors for surface correction (S) and seasonality (K) in an effort to avoid flushing. Specifically, however, the McLeod method applies a traffic factor to ensure that the ultimate void volume is filled a maximum of 60% to 85%, the higher percentage being applicable to lower volume roads. Additionally, the McLeod procedure assumes that the ultimate void volume is 40% of the initial void volume of the cover aggregate in the loose weight condition. A2.5 In laboratory specimens, calculation of the required asphalt binder quantity should follow determination of the aggregate quantity and should reflect the void volume that exists in the specimen aggregate. It may be helpful to assume that the applied specimen aggregate has a void volume of 80% of that in the loose weight condition. A2.6 The preceding standard is intended to allow performance evaluation of a combination of asphalt emulsion and aggregate chips as well as relative performance of several combinations of asphalt emulsions with aggregate chips at a certain level of cure. In this regard, it is up to the user to determine the required asphalt quantity based APPENDIX A2. ASPHALT EMULSION VOLUME A2.1 Asphalt emulsion is determined by volume, as opposed to by mass, since the required amount depends primarily on the void volume available, between aggregate particles, to be filled with asphalt cement. A2.2 A balance must be struck so that the young chip seal is bound sufficiently by asphalt, such that it will endure its early life while avoiding the use of too much binder since this will cause the early onset of flushing, reducing the useful life of the chip seal to a shorter time period than otherwise possible. In the field, after a few years when the aggregate particles have been oriented by traffic and the ultimate aggregate density has been achieved, it is typically desired, for good road surface performance, that 70% of the voids be filled with asphalt binder. In this regard, depending on the road traffic volume and aggregate chip shape, which imply a certain compacted state of the aggregate in a few years, and also depending on the nominal size of aggregate chips, the requirements for initial embedment immediately following construction of the chip seal may vary between 20% and 40%. In the manufacture of laboratory specimens, observing these field principles will enable the construction of a representative specimen.

52 A2.8 It is important to note that prior to using a template for a recorded test, several trials should be performed in order to determine the rate and repeatability of asphalt emulsion application using the template and the adopted striking-off technique. A2.7 This standard is not intended to determine the potential for chip-seal flushing due to densification and reorientation of the cover aggregate. It provides the relative performance of chip-seal treatment materials, specifically those of a single surface treatment exhibiting compactly placed and oriented aggregate particles one stone in depth. Through the use of this standard, and as a result of the ability to precisely place a predetermined aggregate mass, it becomes possible to calculate the precise volume of required asphalt emulsion. Additionally, it is possible to repeatedly combine chip-seal materials in constant proportions. on the use of a constant percent embedment or, alternatively, a constant asphalt volume with different chip types and sizes.

53 Recommended Standard Method of Test for Measuring Moisture Loss from Chip Seals AASHTO Designation: Txxxx-xx 1. SCOPE 1.1 This test method approximates the asphalt emulsion moisture content of a newly built chip seal as it cures by close mo nitoring of an equivalently constructed and cured specimen chip seal. 1.2 The values stated in SI units are to be regarded as the standard unless otherwise indicated. 1.3 A precision and bias statement for this standard has not been developed at this time. Therefore, this standard should not be used for acceptance or rejection of a material for purchasing purposes. 1.4 It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use . 2. REFERENCED DOCUMENTS 2.1 ASTM Standards : • D 7000, Standard Test Method for Sweep Test of Bituminous Emulsion Surface Treatment Samples 3. SUMMARY OF TEST METHOD 3.1 By quantifying the mass loss of a specimen chip seal, which is significantly equivalent to a field chip seal, and where the emulsion spray rate, the emulsion residual content, and initial aggregate moisture content can be approximated, it becomes possible to estimate the specimen’s cure level at different monitoring points throughout a workday. 3.2 In this test, a chip-seal specimen is manufactured by site equipment on a board placed on the roadway while the field chip seal is being built. The water-mass loss of materials on the board is then monitored th roughout the day to gauge the specimen’s cure level. These results are projected in evaluating the moisture content of the field chip seal’s asphalt emulsion.

54 asphalt emulsion, and films of water evaporate, the bond can be more readily developed and a chip seal is said to be curing. 4.2 This test method aims at estimating the mass of water that has evaporated from a field chip seal by monitoring a specimen chip seal that is significantly equivalent in material composition to the field chip seal. Where periodic monitoring is performed, the test indicates the approximate rates of curing that may be present in a field chip seal cured under particular environmental conditions. This information is usually intended to track curing throughout a workday and up to the point where the chip seal materials are bound. Additionally, when performance results from sweep tests (ASTM D 7000) at known moisture contents are available, moisture content tracking can assist in decision making regarding the capacity of the chip seal to safely accept traffic at certain moisture contents. 5. APPARATUS 5.1 Balance and (Optional) Pedestal – The balance must be capable of weighing 10 kg or more to within +1 g. A tared pedestal, some 10 in. in height and placed on the scale, is usually required to raise the specimen enough above the scale to avoid the specimen area obstructing view of the scale reading. Note 1—The mass of a configured specimen board is on the order of 1,500 g. In addition to the board mass, the masses of the pedestal and the expected chip seal materials must be considered when determining the adequacy of a scale to bear the full specimen mass (with pedestal). 5.2 Weighing Platform and (Optional) Wind Shield – The platform is any convenient flat surface, shimmed as necessary for levelness, on which the balance is placed for weighing specimens. This is usually sited on top of another stationary structure in the field or in the tray of a parked vehicle. Additionally, where windy conditions are expected, the ability to obtain reliable mass readings may depend on the use of a lightweight enclosure to shield the specimen and prevent wind-induced flutter. 5.3 Pocket Level – This is a portable bubble level that is placed on the weighing platform to check for approximate levelness. 5.4 Infrared Thermometer – This is used to check temperatures of the field chip seal and the specimen chip seal. 5.5 Drying Pan – This metal pan is used to dry sampled aggregate where the moisture content appears to be high or in question. 4. SIGNIFICANCE AND USE 4.1 The rate at which the bond is developed between asphalt and aggregate in a chip seal depends on the chip seal’s curing characteristics. When asphalt breaks with water in an

55 light gauge, z-shaped metal strip is fixed to the perimeter of the board. The vertical legs of the z-shaped metal strip are oriented such that the board is suspended ¼ in. above the pavement by one leg (the inner) of the z-shaped metal edging (for easy removal from the roadway) while the other leg forms a vertical lip protruding above the surface of the board (to prevent the loss of any specimen material as the board is moved). Figure 1. Configured specimen board. 6.2 Aggregate and Asphalt Emulsion – The chip-seal specimens are laid down by the distributor and chipper in the course of placing the actual field chip seal. In this regard, the properties of the specimen aggregate and asphalt emulsion are those of the field chip seal. 6.3 Aggregate – Sample the aggregate from the stockpile that is to be used in the manufacture of the chip seal and store in an airtight container. Where moisture content tracking is to be performed without the need for immediate results on site, laboratory determination of aggregate moisture content (W) may be performed. Alternatively, estimate moisture content (W) according to Note 2 where immediate moisture content results are required and where available time, sufficient resources, and the need for higher on-site accuracy warrant extra care. Note 2—An acceptable on-site approximation of the aggregate moisture content may be obtained by drying a representative sample of chip-seal aggregate over a few hours of the workday. Place approximately 3 kg of aggregate (in its sample state) on the tared drying 18 inch square plywood board z- shaped metal edging on board- perimeter pan and record the wet aggregate mass. Place the drying pan and its contents in a warm (and, preferably, windy) location. When the aggregate becomes dry to the touch, record the mass loss of the aggregate. The aggregate moisture content (W) is the mass loss expressed as a percentage of the dried aggregate mass. 6.4 Asphalt Emulsion – Usually, a good approximation of the project asphalt emulsion’s residual content (R) may be obtained from key site personnel. Where dependable figures are not available, the cure level of the chip seal must be based on conservative and conventional figures (approximately 70% residual content) until a simple lab experiment can be performed such as that outlined in Note 3. 6. MATERIAL PREPARATION 6.1 Specimen Board – Each chip-seal specimen is manufactured on an 18-in. square and 3/16-in. thick plywood board (Figure 1) with an unconditioned surface. A continuous,

56 Note 3—To evaluate the residual content of the asphalt emulsion that was used on site, dry approximately 50 g of the material, weighed to the nearest 0.1 g, in a 100°C oven, in the laboratory, to obtain the residual asphalt. The asphalt emulsion should be placed in a thin layer in an approximately 11-in.-diameter aluminum foil pan. Monitor the mass of the material until it no longer continues to lose mass over two consecutive readings taken 8 h apart. Record the mass loss and the final residual asphalt mass to the nearest 0.1 g. Estimate the moisture content of the asphalt emulsion to be the mass loss expressed as a percentage of the initial asphalt emulsion mass. The asphalt emulsion’s residual content (R) is the final residual asphalt mass expressed as a percentage of the initial asphalt emulsion mass. 7. SPECIMEN MANUFACTURE AND WEIGHING 7.1 Set up the weighing platform (with optional wind shield) in an off-road location within short walking distance of the location where the specimen is intended to be manufactured. Level the platform and position the scale on the platform (with optional pedestal). 7.2 Record the tare mass (B) of an unused specimen board. 7.3 Place the weighed specimen board at a chosen location on the roadway (Note 4) that is to be chip sealed. Ensure that the board is not positioned in the wheel paths of the distributor, chipper, or other trucks. Note 4—Locations at which specimen chip seals are to be made should be chosen based on the availability of similar off-road locations, in terms of temperature and exposure, to where the specimen may be cured. Additionally, at selected manufacture locations, manufacture should be fast and allow for removal and weighing of the specimens within 5 min of the asphalt emulsion being sprayed onto the board. When monitoring the field chip seal, observations should be made at a location immediately adjacent to where the specimen is manufactured. 7.4 Immediately after chips have been dropped onto the specimen board, move the specimen from the roadway and obtain its initial total mass reading (S). 7.5 Obtain the asphalt emulsion spray rate (E) from appropriate site personnel. 7.6 Throughout the workday, maintain a log of the temperatures and other environmental conditions affecting the cure rates of the specimen and the field chip seals. Relocate the specimen as necessary to ensure similar curing conditions relative to those of the field chip seal.

57 7.7 Record the total mass (C) of the specimen as it cures throughout the day to various cure levels. Note 5—Record the specimen mass as often as practical but at least once per hour until a desired cure level has been achieved. 7.8 Where curing conditions throughout the workday are similar for the specimen and the field chip seal, it may be assumed that the chip-seal moisture content at a certain time after construction is approximated by that of the specimen. 8. CALCULATIONS 8.1 The mass of asphalt emulsion in the specimen is obtained from the following: O = 3785 (UEAG) (1) 8.2 The mass of dry specimen aggregate is obtained from the following: D = (S – B – O)/(1 + W) (2) 8.3 The initial mass of all specimen moisture is obtained from the following: I = S – B – D – (OR) (3) 8.4 The mass of all specimen moisture at cure level (L) is obtained from: F = C – B – D – (OR) (4) 8.5 The percent moisture content of asphalt emulsion at cure level (L) is obtained from: M = [100F]/[(OR) + F] (5) 8.6 The cure level of the specimen asphalt emulsion is obtained from: L = 1 – {F/[O (1 – R)]} (6)

58 Where O = mass of asphalt emulsion on the specimen board (g), U = unit weight of water (g/ml), E = reported emulsion spray rate (gal/sy), A = specimen board area (sy), G = specific gravity of the asphalt emulsion, D = mass of dry specimen aggregate (g), S = initial specimen mass (including board) (g), B = mass of the specimen board (g), W = initial percentage moisture content of specimen aggregate (as percentage of dry aggregate mass), I = initial mass of all specimen moisture (emulsion and aggregate moisture) (g), F = moisture mass in specimen at cure level (L) (g), C = specimen mass (including board) at cure level (L) (g), L = the cure level at which specimen moisture content is being evaluated, M = percentage specimen moisture content at cure level (L) (as percentage mass of current asphalt emulsion), and R = percentage residual asphalt content of emulsion (as percentage mass of initial asphalt emulsion).

59 Recommended Standard Method of Test for Recover y of Asphalt from Emulsion by Stirred-Can Method AASHTO Designation: Txxxx-xx 1. SCOPE 1.1 This method covers the recovery of asphalt from a water-based emulsion by the stirred- can evaporation method. The recovered asphalt reproduces the asphalt with the same properties as those used as the asphalt base in the em ulsion and in quantities sufficient for further testing. 2. SUMMARY OF METHOD 2.1 The water in the asphalt emulsion is evaporated under a nitrogen atmosphere at an elevated temperature. Initially, the set point for the emulsion temperature is above the boiling point of water, but the temperature of the emulsion would stay at the boiling point of water while the evaporating process occurs. After most of the water has been evaporated, the temperature of the emulsion will increase to the initial set point and the remaining water will be completely removed. The recovered asphalt (evaporation residue) can then be subjected to further testing as required. 3. APPARATUS 3.1 Laboratory Mixer – The standard laboratory mixer with mixing blade and shaft that is capable of reaching a mixing speed of 1,000 to 2,000 rpm. 3.2 Tin Ca n – The can should have a volume capacity of 1 gal with a 6½-in. diameter to allow adequate access of mixing head, thermocouple, and nitrogen outlet. 3.3 Heating Unit – The heating unit consists of the heati ng tape and the Variac, which is used to control output power. The length of heating tape should be adequate to wrap around the tin can until it fully covers the bottom half of the can. 3.4 Nitrogen Purge and Nitrogen Blanket System – As shown in Figure 1, these should consist of a nitrogen piping system, nitrogen purge blanket, nitrogen sparge ring, and rotameters that are capable of measuring the gas flow up to 8.5 to 10 L/min. 3.5 Temperature Controlling Unit – The temperature control an d thermocouple must be able to operate at the maximum temperature of 325 ° F. 3.6 Heat Insulator – The insulator pad should be large enough to cover the tin can that is wrapped with heating tape to prevent the heat from the tape escaping to the atmosphere. 4. REAGENTS AND MATERIALS 4.1 Liquid Nitrogen – A pressurized tank, with regulator or pressure-reducing valve.

60 5. SAMPLE 5.1 The sample must be a water-based asphalt emulsion. If a solvent-based emulsion is used, the set point temperature may need to be changed to ensure completion of solvent removal. Also, the properties of the recovered binder may not agree with the base asphalt if there is solvent residue left in the recovered binder. 5.2 Generally, asphalt binder will progressively harden when exposed to air, especially if the asphalt is placed in a high-temperature environment. Therefore, during the recovery process, the emulsion must be under a nitrogen atmosphere when the solvent is evaporated at a high temperature. 1 2 3 4 5 6 7 Figure 1. Schematic view of stirred-can setup: (1) Gallon can, (2) Thermocouple, (3) Impellor and shaft, (4) N 2 blanket tube, (5) N 2 sparger, (6) Heat tape, and (7) Thermal insulation. 6. PROCEDURE 6.1 The experimental setup for the stirred-can procedure is shown in Figure 1. 6.2 Weigh 1,250 ± 0.5 g of asphalt emulsion and add to the gallon can, then wrap the heating tape around the can until the tape covers the bottom half. Cover the side of the can with the heat insulation pad and place the container underneath the laboratory mixer. 6.3 Place the sparge ring into the can, but to prevent overflow due to foaming, do not turn the nitrogen sparge on at the beginning.

61 how thick the emulsion is. After that, insert the thermocouple into the can. To ensure accurate temperature controlling, the thermocouple should not touch the side of the can or mixer head. 6.5 Turn on and adjust nitrogen flow to 8.5 to 10 L/min for the nitrogen blanket tube, then place the nitrogen blanket outlet on the emulsion surface to create a nitrogen blanket. 6.6 Connect the heating tape with the Variac and turn the Variac on to begin the heating process, then set the temperature controller to 163 ° C (325 ° F). The Variac providing power for the heating tape is set to 140 V, with corresponding power of approximately 430 W. After the heat is supplied to the system, the foaming process will start to occur. 6.7 Change the voltage on the Variac to about 100 V (corresponding power is 260 W) when the emulsion temperature reaches 10 0 ° C (212 ° F). The time from the beginning of the experiment to the time to change the voltage is approximately 20 to 30 min. Also, if foaming stops, start the nitrogen flow into the sparge ring (8.5 to 10 L/min). The emulsion temperature should stay at the boiling point of water until the majority of the water is evaporated; the emulsion temperature will then start to increase. 6.8 recovery time is approximately 180 min). After 10 min, turn off the Variac, remove the heat insulation, and loosen the heat tape, but maintain the nitrogen flows and stirring while the sample is cooling. 6.9 Let the emulsion temperature reach 325°F and wait for 10 min at this temperature (total Figure 2 shows a typical temperature versus time evolution curve. Four regions are evident. The first one is from the beginning to about 18 min. In this region, the temperature increases rapidly and nearly linearly from room temperature (around 72°F, or 22°C) to 6.4 Lower the mixer head into the emulsion can and turn the mi xer on. Then place the lid on top of the container and increase the mixi ng rate to 1,000 to 2,000 rpm, depending on 6.10 As the sample starts to cool (<200°F), take out the nitrogen sparge ring but keep nitrogen flowing through the tube to prevent clogging. Then stop the mixer and move the mixer head upward. 6.11 Store the sample in a cool room (25°C). The recovered sample can be used for further testing. 212°F (100°C). The water evaporation rate is low in this region, and power input primarily increases the temperature. The second region is between 18 min to 110 min where the temperature increases slowly from 212°F (100°C) to 250°F (121°C) in about 90 min. Here the power input mainly provides water evaporation. The third region is between 110 min to 135 min, where the temperature increases linearly from 250°F (121°C) to 325°F (163°C) in about 25 min, a slower rate than in the first region. In this region, much of the water has evaporated and the power input primarily increases the temperature. In the fourth region, from 135 min to the end of the experiment at 170 min, the temperature is controlled at 325°F (163°C). (In Figure 2, the temperature evolution after 150 min is not shown because it changes little.)

62 50 100 150 200 250 300 350 0 50 100 150 Temperature (F) Time (min) Figure 2. Temperature evolution of the recovery system.

63 Recommended Standard Method of Test for Determining the Strain Sensitivity of Asphalt Emulsion Residue Using Strain Sweeps Performed on a Dynamic Shear Rheometer (DSR) AASHTO Designation: Txxxx-xx 1. SCOPE 1.1 This test method covers the determination of strain sensitivity of asphalt residue from a water-based emulsion from changes in the dynamic shear modulus obtained from strain sweeps performed using the dynamic shear rheometer (DSR). This test method is method, the asphalt binder is the residue obtained by removing the water from a water- based asphalt emulsion. 1.2 This standard is appropriate for unaged material or material aged in accordance with R28. 2. REFERENCED DOCUMENTS 2.1 AASHTO Standards: • T 315, Determining the Rheological Properties of Asphalt Binder Using a Dynamic Shear Rheometer • M 320, Performance-Graded Asphalt Binder • R 28, Accelerated Aging of Asphalt Binder Using a Pressure Aging Vessel (PAV) • R 29, Grading or Verifying the Performance Grade (PG) of an Asphalt Binder • T40, Sampling of Bituminous Materials 2.2 ASTM Standard: • E1, Specification for ASTM Thermometers 3. SUMMARY OF TEST METHOD 3.1 This standard contains the procedure used to me asure the complex shear modulus (G*) of asphalt residues from water-based em ulsions using a DSR and parallel plate test geometry. 3.2 The standard is suitable for unaged material or material aged in accordance with R28. 3.3 The standard is suitable for use when the emulsion residue is not too stiff to be torqued by the DSR . supplementary to AASHTO T 315 and incorporates all of that standard. For this test

64 4. SIGNIFICANCE AND USE 4.1 The temperature for this test is related to the test temperature experienced by the pavement maintenance treatment in the geographical area for which the asphalt emulsion is to be applied. Typically the maintenance treatment is applied at moderate ambient temperature, and a default temperature of 25ºC can be used for the strain sweep evaluation. 4.2 A plot of dynamic shear modulus G* versus time will be generated and compared as an indication of strain sensitivity of the residue. 4.3 The complex shear mo dulus is an indication of the stiffness and the resistance of the asphalt residue to deformation under load and also is an indication of the ability of the residue to hold aggregate. 5. APPARATUS 5.1 Dynamic Shear Rheometer Test System – Consisting of parallel metal plates, an environmental control system, a loading device, and a control and data acquisition system. 5.2 Test Plates – The 8-mm plates are used for this test with a 2-mm gap. The preliminary gap before trimming must be set to achieve an acceptable bulge in the material after trimming. 6. REAGENTS AND MATERIALS 6.1 Varsol or another suitable agent for cleaning the plates. 6.2 Acetone for removal of all remaining residue from the plates. 7. SAMPLE 7.1 The sample is the residue after the water is removed from the water-based asphalt emulsion. The properties of recovered binder may not agree with the base asphalt since other substances have been added to the base binder in the emulsification process. 8. PROCEDURE 8.1 Procedure is as described in AASHTO T 315 using the 8-mm plates with a 2-mm gap. 8.2 Prepare the emulsion residue specimen according to AASHTO T 315. 8.3 Place the sample in the DSR and trim it according to AASHTO T 315.

65 8.5 Perform the strain sweep. 8.6 Use the following parameters for the strain sweeps: • Intermediate test temperature, with 25ºC being the default temperature. • For strain sweeps, the DSR is set in oscillation mode for amplitude sweeps. • DSR is set for auto-stress so that stress will be automatically adjusted to achieve desired strain. • Frequency is set to 10 radians per second. • Initial stress is set to the lowest stress that the DSR is capable of applying. • Strain is set to increment between 1% and 50%, or between 1% and the highest strain that the DSR can achieve with the material being tested. A preliminary test may be needed, especially with stiff residues, to estimate the highest strain percent that can be set for the test. • Steady shear rate is set to zero and is not used in this test. • Number of periods is set to 1. • Number of points is set to 256. • Number of samples can be between 20 and 30. Determine the number of samples to test at enough points to define the strain sweep curve when plotting G* versus time. • Strain control sensitivity is set to medium or better. • Shear strain sequence is set for “up” so that strains are incremented from low to high. • Time increments are set to linear so that the time increments between measurements are approximately linearly chosen (not logarithmically). • Delay time is set to 1 s. • Check that integration time is between 1 and 2 s, and total test time for the strain sweeps is less than 2 min. 8.7 Visually inspect the sample after the test when removing the sample from the plates. Note whether the sample is wholly or partially adhered to the plates, and note whether the sample has a ductile or a brittle break when the plates are pulled apart. 8.8 Generate a plot of dynamic shear modulus versus time. A flat curve indicates a strain- resilient material. A steep curve indicates a strain-sensitive material. 8.4 Bring the sample and the environmental system to thermal equilibrium according to the manufacturer’s directions and AASHTO T 315.

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TRB’s National Cooperative Highway Research Program (NCHRP) Report 680: Manual for Emulsion-Based Chip Seals for Pavement Preservation examines factors affecting chip performance, highlights design and construction considerations, and explores procedures for selecting the appropriate chip seal materials. The report also contains suggested test methods for use in the design and quality control of chip seals.

Appendices A to J of NCHRP Report 680 provide further elaboration on the work performed in this project.

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