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

Chapter: Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report

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Suggested Citation:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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:"Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report." 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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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

66 A T T A C H M E N T Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report

67 C O N T E N T S 68 Chapter 1 Introduction 68 1.1 Background 68 1.2 Project Objectives and Scope 68 1.3 Organization of the Report 69 Chapter 2 Research Methodology 69 2.1 Introduction 69 2.2 Chip Adhesion to Emulsion and Residue 72 2.3 Time Required Before Brooming or Traffic 73 2.4 Emulsion Consistency in the Field 74 2.5 Pavement Texture Testing 76 2.6 Residue Recovery Methods and Properties 79 2.7 Estimating Chip Embedment Depth During Construction 81 Chapter 3 Results and Analysis 81 3.1 Sweep Test 81 3.2 Field Moisture Tests 81 3.3 Laboratory Sweep Test for Field Materials 85 3.4 Emulsion Consistency in the Field 87 3.5 Pavement Texture Measurement 87 3.6 Residue Recovery Methods and Properties 93 3.7 Estimating Embedment in the Field 95 Chapter 4 Practical Application of the Research 95 4.1 Modified Sweep Test and Critical Moisture Contents 95 4.2 Field Consistency Test 95 4.3 Pavement Texture 95 4.4 Residue Recovery and Desirable Properties 95 4.5 Measuring Aggregate Embedment in the Field 96 Chapter 5 Conclusions and Recommendations 96 5.1 Conclusions 96 5.2 Recommendations 98 References 100 Appendices A through J

68 1.1 Background Emulsion-based chip seals are the most commonly used type of chip seal in the United States for preserving asphalt pavements. The purpose of these preservation treatments is to seal fine cracks in the underlying pavement surface and pre- vent water intrusion into the base and subgrade. Chip seals are not expected to provide additional structural capacity to the pavement. Benefits are obtained by reducing pavement dete- rioration before significant distress is exhibited. A large body of research is available on chip-seal design practices (NCHRP Synthesis 342: Chip Seal Best Practices), and they were further investigated in this project. However, chip-seal design in the United States has not been developed significantly beyond early work (McLeod 1960, 1969; Epps 1981). In spite of their apparent benefits, the use of chip seals for pavement preservation in the United States has been hampered by the lack of nationally accepted guidance on their design and construction and appropriate specifications and testing proce- dures for constituent materials. Therefore, research was needed to develop a manual that identifies factors that influence chip- seal design, construction, and performance and provides guide- lines that enable practitioners to improve the opportunity for success when building these systems. 1.2 Project Objectives and Scope This research was conducted to develop a manual describ- ing the best methods to use for designing and constructing chip seals placed on hot mix asphalt pavements. A signifi- cant body of knowledge existed about chip-seal design and construction before this research, much of which is con- tained in this manual. However, other practices in chip-seal technology have been subjective for many years and are considered an art by some. Therefore, the research con- ducted in this study focused on elements of chip-seal tech- nology that were subjective or not practiced in the United States. The research presented in this report includes a rec- ommended manual that could replace the subjective or qualitative judgments previously used during chip-seal design and construction with field and laboratory testing, and thus can be used to improve the opportunity for success when building chip seals. 1.3 Organization of the Report This research report has five chapters. Chapter 1 is the introduction and describes the purpose of the research and the scope of the work. Chapter 2 describes the state of the practice of chip-seal design and construction. Chapter 3 describes the results and analysis of a series of laboratory and field tests. Chapter 4 discusses the application of research find- ings. The final chapter presents the study conclusions and recommendations. Further elaborations on the research are provided in Appendices A through J, which are not published herein but are available on the TRB website at http://www. trb.org/Main/Blurbs/164090.aspx. C H A P T E R 1 Introduction

69 2.1 Introduction Research conducted in this project focused on aspects of chip-seal technology that have been qualitative in the past or were based on material properties that did not necessarily relate to chip-seal performance. Quantitative methods were developed to help replace past subjective practices and allow improved prediction of chip-seal behavior in the field. The following issues were addressed in the research through lab- oratory and field experiments: • Chip adhesion to emulsion and residue, • Time required before sweeping and uncontrolled traffic, • Emulsion consistency in the field, • Surface texture measurement, and • Residue recovery and properties. 2.1.1 Chip Seal Definition Chip seals considered in this research are based on emulsi- fied asphalt binders and natural mineral aggregate chips. The chip seal is constructed by spraying the asphalt emulsion onto the existing asphalt pavement, dropping the aggregate chips into the asphalt emulsion, and embedding the chips in the emulsion using pneumatic-tired rollers. The purposes of the chip seal are to preserve existing asphalt pavement by sealing the surface before cracking occurs or after minor cracks have emerged and to provide additional surface friction. 2.2 Chip Adhesion to Emulsion and Residue The required adhesive and cohesive strength of the emul- sion residue used as the binder in a chip seal directly influ- ences when the chip seal can be opened to traffic after construction. This strength is usually judged subjectively during construction by experienced personnel who decide based on how easily chips can be dislodged from the emul- sion. This experience is often gained by trial and error, some- times leading to vehicle damage when residues that have not gained sufficient strength release chips under traffic loads (Gransberg and James 2005; Shuler 1998). Several tests such as Vialit (Vialit plate shock test), frosted marble (Howard et al. 2009), and the sweep test (Cornet 1999; Barnat 2001; ASTM D7000) attempt to quantify this adhesive behavior and identify when chip seals are ready to accept uncontrolled traffic. However, these tests have shown high variability and have therefore not been widely adopted. One method uses a hand broom to sweep the chips, and the chip seal is judged ready for traffic when the amount of chips dislodged during this procedure is less than 10%. This test is attractive since it uses actual construction materials and with practice could be a means to evaluate adhesion. The sweep test described by ASTM D7000, Standard Test Method for Sweep Test of Bituminous Surface Treatment Samples, appeared to be a reasonable approach to simulating the forces that dislodge aggregate chips from chip seals. This procedure is relatively effective at evaluating differences in adhesive abilities of dif- ferent emulsions with a single aggregate. This test utilizes a template for specific aggregate gradations to establish the emulsion application rate. While a single emulsion applica- tion rate is suitable for relative comparison between emul- sions, when aggregate sizes differ, the embedment percentage changes, which affects chip retention. In addition, the test describes a procedure of “hand casting” the aggregates onto the emulsion prior to testing. Attempts to repeatedly place precise amounts of aggregate on test samples during this research proved difficult to replicate. Therefore, the test apparatus was modified so that the exact amount of chips was placed on the test pad each time. To determine if the modified test proce- dure would be useful to evaluate the adhesive ability of dif- ferent emulsions and different aggregate chips under varying moisture conditions, a controlled laboratory experiment was conducted. C H A P T E R 2 Research Methodology

70 2.2.1 Experiment Design Because of variability associated with the manner with which aggregate chips are prepared for testing according to ASTM D7000, a modification to the procedure was made to precisely control how chips are placed on the test pad prior to sweeping. To determine if the modified procedure was an improvement over the ASTM procedure, an experiment was conducted to measure the ability of the modified sweep test to discriminate between four independent variables believed to affect early chip-seal performance. These variables were aggre- gate source, emulsion type, emulsion cure level, and aggregate chip moisture content. 2.2.1.1 Independent Variables Independent variables in this experiment are the following: Aggregate source: basalt, granite, limestone, alluvial Emulsion type: RS-2, RS-2P, CRS-2, CRS-2P, HFRS-2P Emulsion cure level: 40%, 80% Aggregate chip moisture content: dry, saturated surface dry (SSD) A full-factorial, randomized experiment was designed for each emulsion according to the model shown below (Anderson 1993): Where Yikl = chip loss, %; μ = mean loss, %; Ai = effect of aggregate i on mean loss; Wk = effect of water removed k on mean loss; Ml = effect of aggregate moisture l on mean loss; AWik, etc. = effect of interactions on mean loss; and ikl = random error for the ith aggregate, kth water removed, and lth replicate. This experiment design was chosen because results can be easily evaluated using conventional analysis of variance tech- Y A W M AW AM WM AWMikl i k l ik il kl ikl ikl= + + + + + + + +μ  niques (ANOVA). The experiment was repeated for each emul- sion to eliminate potential variability that could be associated with differences in emulsion behavior due to aging. 2.2.2 Materials A variety of emulsions were selected to represent the range available for construction. These included conventional and polymer modified anionic (RS-2 and RS-2P), high float (HFRS-2P), and cationic types (CRS-2 and CRS-2P). Pro- duction of these emulsions using a laboratory emulsion mill in close proximity to the research laboratory was desirable since emulsions have limited shelf life. These factors helped to reduce variability of the emulsion materials. Properties of the emulsions are shown in Table 1. A variety of aggregates were used to determine if the mod- ified sweep test could discriminate between different miner- alogy, shape, and texture. These were a limestone (LSTN) aggregate from Colorado Springs, CO, granite (GRNT) from Pueblo, CO, basalt (BSLT) from Golden, CO, and an alluvial source (ALLV) from Silverthorne, CO. The properties of these materials are presented in Table 2. 2.2.3 Sweep Test Procedure The test procedure is described in detail in Appendix B. Differences between the procedure conducted in the research and that described by ASTM D7000 include the following: • 40% initial embedment of the aggregate chips, • 40% and 80% emulsion moisture loss, and • Consistent, uniform application of the aggregates to the test pad. In this procedure, asphalt emulsion is applied to a 15-pound per square yard roofing felt substrate in a circle by means of a steel template with an 11-in. diameter cutout. Emulsified asphalt is screeded level with the template by means of a strike- off rod as shown in Figure 1. Aggregate is then placed mechan- ically using a dropping apparatus as shown in Figure 2. The Emulsion Tests RS-2P RS-2 CRS-2 CRS-2P HFRS-2P Viscosity, SFS 122F 108 96 78 119 132 Storage Stability, 1 day, % 0.1 0.1 0.2 Sieve Test, % 0.0 0.0 0.0 0.1 0.2 0.0 0.0 Demulsibility, 35 ml 65 72 76 76 42 Residue, by evaporation, % 65.1 68.0 67.9 67.7 65.3 Residue Tests Penetration, 77F, 100g, 5s 115 112 125 121 115 Ductility, 77F, 5cm/min 100+ 100+ 55 65 60 Float, 140F, s na na na na 1290 Table 1. Emulsion properties.

71 aggregate is then set in place, one stone thick, by means of a compactor as shown in Figure 3. The specimen is then placed in a 160°F oven to allow the emulsified asphalt to cure to 40% moisture loss or 80% moisture loss after which the specimen is removed from the oven. It is then cooled, and any loose parti- cles are removed. The specimen is then swept under the action of a weighted brush which is spun by a planetary motion mixer for 1 min as shown in Figure 4. The specimen is then removed from the machine and brushed by hand to remove all particles that were mechanically dislodged from the specimen surface. The mass loss is then determined, which is expressed as percent loss of the original aggregate mass. Sieve No. (in.) Sieve Size (mm) LSTN GRNT BSLT ALLV 3/4 19.0 100 100 100 100 1/2 12.5 100 100 100 100 3/8 9.5 100 99 100 99 5/16 8.0 100 50 79 73 1/4 6.3 48 9 30 33 4 4.75 1 1 1 2 1 1 1 2 1 1 1 2 1 1 1 2 1 1 1 2 1 1 1 2 1 1 1 2 8 2.36 16 1.18 30 0.60 50 0.30 100 0.15 200 0.075 2.615 2.612 2.773 2.566 78.3 84.0 92.2 86.1 26.3 27.8 20.1 22.0 Flakiness Index 33.8 5.8 13.1 10.5 Passing, % Los Angeles Abrasion Loss, % Bulk specific gravity Loose unit weight, lbs/cf Table 2. Aggregate properties. Figure 1. Emulsion strike-off apparatus.

72 Figure 2. Dropping apparatus placing aggregate on test pad. Figure 3. Compactor setting aggregates on test pad. 2.3 Time Required Before Brooming or Traffic Determining when the first brooming can be accomplished to remove excess chips or when to open a fresh chip seal to traffic is one of the most subjective decisions that must be made. Releasing traffic too soon can lead to vehicle damage due to flying aggregate particles. Releasing traffic too late can lead to delays and congestion. Also, if light brooming results in damage to the chip seal, the chip seal is often left unbroomed until binder strength increases. However, allowing traffic on the fresh, unswept chip seal can lead to flying chips and potential damage. The modified sweep test, which measures the relative adhesive strength of emulsions and emulsion residues in the laboratory, was used to evaluate materials from full-scale

73 chip seals. The objective of this experiment was to deter- mine if the moisture content of the chip seal in the field affects the ability of the chip seal to withstand brooming and traffic stresses. 2.3.1 Full-Scale Field Tests Three full-scale chip-seal projects were included in this research. Test pavements were located on County Road 11 near Frederick, Colorado, approximately 30 miles north of Denver, Colorado; the Main Entrance Road in Arches National Park, Utah, approximately 15 miles north of Moab, Utah; and US- 101 near Forks, Washington, on the western edge of Olympic National Park. 2.3.2 Moisture Tests Moisture in a chip seal comes from two sources: the chips and the asphalt emulsion. In addition, on some projects addi- tional moisture may be present in the roadway. If the amount of moisture in the chips and the emulsion is known at the time the chip seal is constructed, the amount of moisture that evap- orates after emulsion and chip application can be measured. The objective of this part of the research was to measure the moisture loss in the three chip-seal projects and develop a relationship to chip adhesion. The amount of moisture remaining in each chip seal was measured and compared with the relative strength of the residue on a scale of 1 (no strength) to 10 (ready for traffic), judged by pulling three chips out of the fresh seal and qualita- tively judging dislodgement potential. This qualitative evalua- tion was conducted after rolling. Moisture remaining in the emulsion was determined by placing plywood pads covered with aluminum foil measuring 24 in. by 24 in. in front of the asphalt distributor prior to spraying with emulsion. The pads were weighed before and after spraying and chipping, and the loss in weight was determined periodically during the day until approximately 95% of the water had evaporated. Figure 5 shows the setup used to measure the tare weight of the apparatus prior to spraying and chipping. The tared pad was placed in front of the asphalt distribu- tor and chip spreader before chip-seal operations began. After the emulsion and chips were applied to the pavement and tared pad, the pad was removed from the pavement and re-weighed. As moisture evaporated from the pad the weight was recorded and the strength of the emulsion residue was evaluated using the 1 to 10 scale. The resulting relationship between emulsion strength and moisture loss was developed. 2.4 Emulsion Consistency in the Field The consistency of the emulsion is an important factor that influences performance of the chip seal. An emulsion with viscosity too low may not have the ability to hold chips in place or could flow off the pavement. An emulsion with viscosity Figure 4. Modified sweep test mixer.

74 too high could be difficult to spray evenly or may not have the wetting ability needed to coat chips. Emulsions are often tested at the point of manufacture and a certificate of compli- ance is issued by the manufacturer indicating compliance to state, local, ASTM, or AASHTO specifications. However, because changes to physical properties of emulsions used for chip seals can occur during transportation, a means of mea- suring the consistency of the emulsion at the construction site is desirable. Some highway agencies have portable laborato- ries capable of conducting viscosity tests in the field (Santi 2009). However, most agencies do not have laboratories or trained personnel to conduct such tests. Therefore, a simple method of verifying the ability of the emulsion to be used as a chip-seal binder was identified in this research. 2.4.1 Full-Scale Field Tests Two simple methods for measuring the consistency of asphalt emulsions in the field were evaluated. One method based on a procedure developed by Wyoming DOT (Morgenstern 2008) requires a Wagner Part #0153165 funnel, wind protec- tion, 16-ounce plastic cups, thermometer, and a stop watch. The other method was a falling cylinder viscometer which was found to be cumbersome to operate and time consuming to clean and not appropriate for use in the field. The first tests were conducted at the Arches site using the Wagner funnel with a 4 mm orifice. However, the emulsion required over 90 s to empty the funnel. This resulted in large differences between test results because the emulsion viscosity increased as the temperature decreased, increasing the time to empty the Wagner cup. Therefore, the orifice was drilled out to increase the diameter until the cup emptied in approxi- mately 60 s or less. This process was repeated for the Frederick, CO, and Forks field tests. The test proved simple to conduct, low cost, and required a simple apparatus. Although this test would require more development to be used for determining specification com- pliance in the field, the test will help a field inspector rapidly determine the suitability of an emulsion upon delivery to the construction site. 2.5 Pavement Texture Testing Adjusting the emulsion spray rate to compensate for dif- ferences in pavement surface texture is one of the most sub- jective adjustments made during chip-seal construction. Figure 5. Moisture test pads prior to spraying/chipping.

75 Except for the sand patch test used in South Africa and Australia/New Zealand (Austroads 2006, South African Roads Agency 2007), adjustments in the United States are made using judgment based on past experience. The objec- tive of this experiment was to provide a more quantitative method for evaluating pavement texture and adjustment of emulsion application rate. Macrotexture is the texture type that is relevant to chip seals. Macrotexture is surface roughness that is caused by the mixture properties of an asphalt concrete surface or by the finishing/ texturing method of a portland cement concrete surface (Hall et al. 2006). Previous work has indicated that either the sand patch test (ASTM E 965) or the circular texture meter (CT meter) profile (ASTM E 2157) can be used to effectively evaluate pavement macrotexture (Abe et al. 2001, Hall et al. 2006, Hanson and Prowell 2004). Both of these measurements are easily performed in the field, but traffic control is needed during these measurements. The sand patch test has been used for texture measurement because it requires inexpen- sive equipment that is easy to obtain, and it provides accept- able measurements (Austroads 2006, South African Roads Agency 2007). However, conducting the test is slow and exposes personnel to traffic, and results are influenced by wind and moisture. The CT meter evaluation of surface macrotexture can be made more quickly than sand patch testing and therefore exposes the technician to less traffic and accident risk. Also, the CT meter measurements do not depend upon operator skill. Figure 6 shows the interior of the CT meter, which faces the pavement when taking measurements. 2.5.1 Laboratory Texture Testing One part of this research involved testing three slabs of varying surface texture. These test slabs provided a range of textures for evaluating three texture measurement techniques. The slabs were fabricated to simulate three surfaces ranging from very rough, simulating a highly raveled and pocked sur- face, to very smooth, simulating a very flushed surface. The slabs were cast over asphalt pavements using a very low viscosity self-consolidating concrete. The self-consolidating concrete was used to make the texture specimens because of the concrete’s ability to flow into the smallest voids in the surface of the asphalt pavements. This created texture test specimens that mimicked the texture of the three pavement surfaces. Texture of the three slabs was measured using sand patch, CT Meter, and the Aggregate Imaging System (AIMS). 2.5.1.1 Sand Patch Test The sand patch test (ASTM E 965) is a volumetric technique for determining the average depth of pavement surface macro- texture. A known volume of small particles (either sieved sand or small glass beads) is poured onto the pavement surface and spread evenly into a circle using a spreading tool. Four diame- ters of the circle are measured and an average profile depth is calculated from the known material volume and the averaged circle area. This depth is reported as the mean texture depth (MTD). The method provides an average depth value and is insensitive to pavement microtexture characteristics. The CT meter test method (ASTM E 2157) is used to measure and analyze pavement macrotexture profiles with Figure 6. CT meter.

76 a laser displacement sensor. The laser sensor is mounted on an arm which follows a circular track of 284 mm (11.2 in.) diameter. Depth profiles are measured at a sample spacing of 0.87 mm, and the data are “segmented into eight 111.5 mm (4.39 in.) arcs of 128 samples each” (ASTM E 2157). A mean profile depth (MPD) is calculated for each segment, and an average MPD is then calculated for the entire circular profile. 2.5.1.2 AIMS The AIMS was created to quantitatively describe the charac- teristics of aggregates (Masad 2005). The system consists of a camera mounted above a table with several lighting arrange- ments. Using AIMS, coarse aggregate is characterized by parti- cle shape, angularity, and texture. Samples of coarse aggregate are placed on the AIMS table under the camera and lighted from above, below, or both, and camera images are used to quantify the aggregate characteristics. Analyzing macrotexture of coarse aggregates can be compared to measuring macro- texture of a pavement surface. Using AIMS, microtexture or macrotexture of coarse aggregate surfaces can be quantified using wavelet analysis of a grayscale digital photo. Camera focal length can be adjusted depending on whether macrotexture or microtexture is of interest. Using AIMS, depth measurements were generated every 1 mm for four scanlines of 100 mm length each, 20 mm apart, and in two perpendicular directions, for a total of eight scanlines per test slab. The total of eight scanlines at 100 mm length each was chosen to be similar to the eight segments of the CT meter profile. The two sets of four scanlines each were taken in perpendicular directions to account for direc- tional differences in pavement texture. This arrangement could be used to estimate directional differences in texture, which is texture in the direction of traffic versus texture perpendicular to the direction of traffic. Profiles were gen- erated for the scanlines and analyzed in a procedure simi- lar to the CT meter analysis (ASTM E 1845). A mean profile depth, MPD, was calculated from the AIMS data for each of the three test slabs. 2.6 Residue Recovery Methods and Properties The performance grading (PG) asphalt binder grading sys- tem (Asphalt Institute, SP-1) is widely used as the specification for grading and selecting asphalt binders. The PG specification was developed for use in hot mix asphalt concrete (HMAC) pavement layers. However, the PG system is not applicable to classifying and choosing binders for use in pavement chip seals. Chip seals differ from full-depth HMAC layers in construction methods, structural functions, behavioral responses, distress types, and effects of environmental exposure. Therefore, the binder grading system, surface performance grading (SPG), was first suggested to classify emulsion residues or hot-applied binders for use in chip seals (Epps et al. 2001, Barcena et al. 2002). This grading system utilizes the same test methods as the PG system, but applies limits on test parameters that are con- sistent with the mechanics of chip seals rather than hot mix asphalt. An emulsion residue specification requires a standardized emulsion residue recovery method that produces a material representative of the emulsion residue in situ. Currently, emul- sion residues are recovered by distillation (ASTM D 6997) that exposes the material to high temperatures and may destroy or change any polymer networks present in modified emulsion residues. This section describes the experiment used to compare emulsion residue recovery methods, characterizes the emul- sion residues by both the PG and SPG grading systems and some additional tests, and recommends an emulsion residue recovery method and emulsion residue specification. 2.6.1 The Surface Performance-Graded Specification The tests used in the SPG grading system are conducted with standard PG testing equipment and the analyses are performance-based and consistent with chip-seal design, con- struction, behavior, in-service performance, and associated distresses (Epps et al. 2001, Barcena et al. 2002). Field validation of the initial SPG system was completed in Texas (Walubita et al. 2005, Walubita et al. 2004) and resulted in the proposed three SPG grades shown in Table 3. 2.6.2 Residue Recovery Experiment The standard PG system (Asphalt Institute, SP-1) and the modified SPG system (Epps et al. 2001, Barcena et al. 2002, Walubita et al. 2005, Walubita et al. 2004) were both used to grade all base binders and corresponding recovered emulsion residues in this experiment. 2.6.2.1 Materials Eight emulsions were included in this research, five of which, identified as emulsions 1 through 5, were laboratory prepared. The other three emulsions were obtained from the full-scale test pavements in Utah Arches National Park; Frederick, Colorado, CR-11; and Forks, Washington, US-101. Table 4 lists the types of emulsions and, when known, the PG grades of the base binders as reported by the supplier.

77 Surface Performance Grade* SPG 58 SPG 61 SPG 64 10 16 22 28 10 16 22 28 10 16 22 28 Average 7-day Maximum Surface Pavement Design Temperature, °C <58 <61 <64 Minimum Surface Pavement Design Temperature, °C ≥10 ≥16 ≥22 ≥28 ≥10 ≥16 ≥22 ≥28 ≥10 ≥16 ≥22 ≥28 Original Binder Viscosity ASTM D 4402 Maximum: 0.15 Pa·s; Minimum: 0.10 Pa·s Test Temperature, °C 205 205 205 Dynamic Shear, AASHTO TP5 * Sin G , minimum: 0.65 kPa Test Temperature @10 rad/s, °C 58 61 64 PAV Residue (AASHTO PP1) PAV Aging Temperature, °C 90 100 100 Creep Stiffness, AASHTO TP1 S, Maximum: 500 MPa m-value, minimum: 0.240 Test Temperature @ 8 s, °C −10 −16 −22 −28 −10 −16 −22 −28 −10 −16 −22 −28 *The table presents only three SPG grades as an example, but the grades are unlimited and can be extended in both directions of the temperature spectrum using 3 oC and 6oC increments. For illustration, SPG 58−10 indicates a material suitable for construction in an environment from 58oC to 10oC. Table 3. Criteria for SPG grades for emulsion residues (Walubita et al. 2005, Walubita et al. 2004).

78 2.6.2.2 Emulsion Residue Recovery Methods Hot oven (with nitrogen blanket) and stirred can (with nitrogen purge) emulsion residue recovery (SCERR) methods were used to extract the water from the emulsions and to sup- ply dewatered residue for the material properties testing. A third residue recovery method known as “warm oven” or “low temperature evaporative technique” (Kadrmas 2008, Hanz et al. 2009) was also compared with the hot oven and stirred can techniques (Prapaitrakul et al. 2009). 2.6.2.3 Laboratory Tests Rheology Tests. Binder characterization tests utilized the same equipment and some of the same tests as specified Emul- sion AASHTO Emulsion Type Expected Base Grade Batch # Recovery Method PG Grade from Tests Continuous PG Grade SPG Grade from Tests Continuous SPG Grade 1 RS-2P PG 64 28 1 Base Asphalt PG 64−34 67.8 34.2 SPG 70 24 71.7 24.0 6 Stirred Can with N PG 64−34 69.3 34.1 SPG 73 18 73.0 21.3 11 Hot Oven- N Blnkt PG 64−34 69.5 34.1 SPG 73 18 73.4 21.1 2 CRS-2 n/a 2 Base Asphalt PG 58−28 60.2 30.7 SPG 61 18 63.1 19.4 7 Stirred Can with N PG 58−28 62.9 31.0 SPG 64 18 66.4 19.2 12 Hot Oven- N Blnkt PG 58−28 61.9 32.1 SPG 64 18 64.5 20.7 3 RS-2 PG 64−22 3 Base Asphalt PG 64−22 66.9 27.1 SPG 67 12 69.7 14.7 8 Stirred Can with N PG 64−22 68.2 26.8 SPG 70 12 71.4 15.9 13 Hot Oven- N Blnkt PG 64−22 68.5 26.5 SPG 70 12 71.7 15.1 4 CRS-2P PG 64−28 4 Base Asphalt PG 64−28 67.6 32.9 SPG 70 18 70.8 22.2 9 Stirred Can with N PG 64−28 68.6 33.2 SPG 70 18 72.3 22.9 14 Hot Oven- N Blnkt PG 64−28 69.2 33.7 SPG 70 18 72.9 23.4 5 HFRS-2P PG 70−28 5 Base Asphalt PG 58−28 62.3 30.4 SPG 64 18 65.7 18.7 10 Stirred Can with N PG 58−28 63.4 31.6 SPG 67 18 67.0 20.1 15 Hot Oven- N Blnkt PG 58−28 63.3 31.8 SPG 64 18 66.9 20.0 6 − UT LMCRS-2 n/a 16 Stirred Can with N PG 70−22 74.7 26.4 SPG 76 12 78.7 15.3 17 Hot Oven- N Blnkt PG 76−22 76.7 26.3 SPG 79 12 80.9 15.7 7 − CO HFRS-2P n/a 18 Stirred Can with N PG 70−28 72.0 32.0 SPG 76 18 76.6 21.1 19 Hot Oven- N Blnkt PG 70−28 72.7 31.6 SPG 76 18 77.0 20.3 8 − WA CRS-2P PG 64−22 20 Hot Oven- N Blnkt PG 64−28 64.1 28.0 SPG 67 18 67.6 18 21 Stirred Can with N PG 64− − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − −22 64.0 27.9 SPG 67 12 67.1 17.1 Table 4. Binders and PG and SPG grades.

79 in the PG system (Asphalt Institute, SP-1), but with different limiting criteria and test conditions as shown in Table 4. All of the binders in this experiment were aged using the pressure aging vessel (PAV), as described in the PG grading sys- tem (Asphalt Institute, SP-1). Rolling thin film oven (RTFO) aging was not used because emulsion binders are not exposed to this type of heating in chip-seal construction. Unaged binder was tested at the high temperature that is the critical condition for early strength development in the chip seals. PAV aged binder was used in the bending beam rheometer (BBR) to simulate long-term in-service aging that may cause failure at cold temperatures for chip seals. PAV aging simu- lates approximately the first hot and cold seasons of a chip seal, which is when most chip-seal failures occur (Epps et al. 2001, Barcena et al. 2002). Strain Sweep Tests. Strain sweep tests using a dynamic shear rheometer have been correlated to the chip-seal sweep test, ASTM D 7000 (Kucharek 2007). Therefore, strain sweep information collected in this research supplements the SPG system for evaluating strain tolerance and resis- tance to raveling of emulsion residues during curing and at early ages. The strain sweeps were conducted using a dynamic shear rheometer (DSR) at 25°C with 8 mm plates and 2 mm gap on both unaged and PAV aged material to show the change in the complex modulus (G*) with increasing strain. Test results are affected by how the test is performed and by the parame- ters input into the DSR. The DSR is continually oscillating during strain sweep testing. Input to the DSR requested strains of 1% to 50%, and the strain sweeps were initiated at 1%. A 10 min period was allowed after mounting the sample and before testing started for thermal equilibrium to occur. An angular loading frequency of 10 radians/second and a lin- ear loading sequence with time was applied. A delay time of 1 s after the load (strain) was incremented but before the measurements were taken was chosen, and 20 to 30 strain measurements were taken during each test. The test time for each strain sweep was approximately 1 to 2 min (after ther- mal equilibrium). Chemical Tests. Gel permeation chromatography (GPC) was performed on each recovered residue to determine if all of the water had been removed during the residue recovery process. Presence or absence of a peak at a time of 35 to 37.5 min on the GPC chromatogram indicates the presence or absence of water in the residue. Fourier transform infrared (FT-IR) spectroscopy was per- formed on the residues from the five laboratory emulsions to obtain an indication of whether the recovery methods caused oxidation of the materials. The infrared spectra were plotted, and then the area under the wavenumber band from 1,820 to 1,650 cm−1 was integrated to determine the carbonyl area, which is carbonyl used to represent the extent of oxidation in the materials (Epps et al. 2001, Prapraitrakul et al. 2009, Woo et al. 2006). 2.7 Estimating Chip Embedment Depth During Construction Embedment depth is usually determined during construc- tion by pulling several chips out of the binder and visually esti- mating the amount of the chip embedment in the binder. Because it is generally difficult to accurately assess chip embed- ment using this procedure, two methods based on the sand patch test were developed to provide a quantitative measure of embedment depth: the constant volume method and the con- stant diameter method. Both methods were developed using the LSTN and GRNT aggregates from the laboratory sweep test experiment. These aggregates were used because they represent a range of flaki- ness from a high of approximately 34% for the limestone to a low of 6% for the granite. 2.7.1 Constant Volume Method The objective of this experiment was to determine if the diameter of a constant volume of glass beads spread in a cir- cular shape onto the surface of a new chip seal could be used to estimate the embedment of chips in the binder. The aggregate chips (LSTN and GRNT) were oriented on their widest faces so that the average particle heights were their average least dimensions. Embedment percentage was deter- mined for each specimen based on the aggregate average least dimension, weight-to-volume relationships of the materials, and the diameter of the glass bead circle from equation 1. The texture depth (T) is the average distance the aggre- gate chip is exposed above the surface of the asphalt (or ALD − Embedment depth) as shown in Figure 7. Glass Beads Binder Chip Embedment ALDT Agg Chip Figure 7. Embedment depth by constant volume model.

80 Volume of beads between binder surface and the top of the chip, Vbb = Wbb/γb Where Wbb = weight of beads between binder surface and top of chip and γb = unit weight of beads So Since This relationship assumes the volume of glass beads is spread over the chip seal up to the peak of each particle such that the glass beads follow the profile of the particle peaks. Therefore, the average height of the glass beads on the chip seal is equivalent to the void height that would be seen between equal-height particles of a chip seal that is built with exactly one-sized aggregate. Equation 1 can be used to calculate the percent embedment of a chip seal for a known volume of glass beads spread in a cir- cle of a measured diameter. This procedure was used for lime- stone and granite aggregates, and the results were compared with the actual embedment depths to determine if the proce- dure yields appropriate results. 2.7.2 Constant Diameter Method This method uses a constant diameter mold and measures the amount of glass beads necessary to fill the mold above the chip seal. Constant diameter chip-seal specimens were cov- Embedment, % Embedment, % = −( ) = 100 100  ALD T ALD  ALD W A ALDbb b− ( )[ ]{ }γ ( )1 T W Abb b= ( )γ  T = volume of beads between the binder surface and the top of the chip area of glass bead circle (A) ered with glass beads until the peaks of the largest chips were completely submerged in glass beads. A mold was used to confine the glass beads to a constant diameter. By subtracting the volume of beads above the average particle height from the total volume of glass beads used, the volume of beads below the average particle height can be determined. Figure 8 represents the apparatus used in this experiment. To determine embedment percent, the chip-seal specimen is placed in the mold, and the mold is filled with glass beads to the top of the mold. The total mass of beads which fills the space above the specimen is determined and its volume is cal- culated using its density. Knowing the average height of the chip-seal aggregate, the volume of glass beads between the top of the mold and the top of the average particle is calculated from the following: Where: M = mold height, mm, ALD = average particle height, mm, and A = mold cross-sectional area, mm2. The volume of beads between the chips is determined by subtracting Vba from the total volume of beads to fill the mold. This value is used to determine the distance the chips extend above the binder. Where: Vbt = total volume of beads to fill the mold, cm3 = (Wbt/γb) − Vba, Wbt = weight of beads to fill mold, gm, and γb = unit weight of beads, gm/cm3. Percent embedment is calculated as follows: Embedment depth, % (2)= − ( )[ ]ALD V A ALDbb . Volume of beads between the chips, mm3Vbb , = −V Vbt ba Volume of beads above chips to top of mold, mm3V M ALD A ba , = −( ) Glass Beads Binder Chip Embedment ALDT M Agg Chip Figure 8. Embedment depth by constant diameter model.

81 This chapter describes the results of the laboratory and field studies conducted during this project that were used to develop the “Manual for Emulsion-Based Chip Seals for Pavement Preservation” provided with this report. Details of the labora- tory and field testing are provided in the Appendices. 3.1 Sweep Test Chip loss measured after the sweep test is shown in Figures 9 through 12 for each of the dry, SSD, 40% and 80% moisture loss test conditions. Results of ANOVA shown in Table 5 and the Newman-Keuls (Anderson and McLean 1993) multiple comparison test in Table 6 indicate statistically significant dif- ferences between the 40% and 80% moisture loss test speci- mens for all five emulsions. Chip loss with dry aggregates averaged approximately 70% and 15% at 40% and 80% mois- ture loss, respectively. Chip loss for SSD aggregates averaged approximately 65% and 10% moisture loss, also respectively. The sweep test indicates a statistically significant difference in chip loss between aggregates that were dry when embed- ded in the emulsion and those that were in the SSD condition when embedded. The Newman-Keuls multiple range com- parison from Table 6 indicates that dry aggregate has signifi- cantly higher loss than SSD aggregates except when the CRS-2 emulsion is the binder used because damp aggregates allow the emulsion to wick into the aggregate pores and provide improved adhesion and cohesion properties. There are statistically significant differences in chip loss between the emulsions. The RS-2P showed aggregate loss similar to the other emulsions at 40% moisture loss with either dry or SSD chips but higher chip loss at 80% moisture loss with either dry or SSD chips. The CRS-2P performed similarly to the other emulsions under all conditions except at 80% moisture loss with SSD chips, where it showed less aggregate loss than the other binders except the HFRS-2P. The particle charge on the emulsion appears to have little effect on chip loss at 40% moisture loss as shown in Figures 10 and 11. That is, the anionic RS-2 adheres equally well to the limestone as to the granite and basalt, and the cationic CRS- 2 adheres equally well to all of the aggregates. Some difference may be significant with respect to the polymer modified RS- 2P, where adhesion appears much better on the limestone. However, in general, the anionic emulsions do not appear to have a greater affinity to limestone, and the cationic do not appear to have a greater affinity to the granite nor basalt. Table 6 shows an opposite trend for the CRS-2P, which adhered better to the limestone (25% loss) than the granite (38% loss) at α = 0.05. Also, the basalt had the least chip loss and the alluvial had the most loss regardless of the emulsion. This indicates that factors other than surface chemistry affect adhesion. 3.2 Field Moisture Tests The results of this experiment indicate that chip adhesion reaches the point where significant force is required to dis- lodge the chip at approximately 75% to 85% moisture loss. At that time sweeping can commence and traffic can be allowed to travel on the new surface. Figures 13, 14, and 15 show the relationship between chip-seal binder strength and moisture loss for each test pavement. The chip-seal binder strength was judged subjectively by pulling three chips out of the emulsion and rating the relative strength with respect to how difficult the chips were to pull out of the emulsion residue on a scale of 1 (no strength) to 10 (ready for traffic). This qualitative rat- ing was made after rolling. 3.3 Laboratory Sweep Test for Field Materials The sweep test was conducted for aggregates and emul- sions obtained from the three field test pavements. Aggre- gates were tested using two moisture contents and a range of moisture loss percentages. Results are presented in Table 7, C H A P T E R 3 Results and Analysis

82 0% 20% 40% 60% 80% 100% RS-2 RS-2P CRS-2 CRS-2P HFRS-2P LSTN Average GRNT Average B S LT Average ALLVL Average C h ip L o s s , % Figure 9. Sweep test results for dry chips at 40% cure. 0% 20% 40% 60% 80% 100% RS-2 RS-2P CRS-2 CRS-2P HFRS-2P LSTN Average GRNT Average B S LT Average ALLVL Average C h ip L o s s , % Figure 10. Sweep test results for dry chips at 80% cure. 0% 20% 40% 60% 80% 100% RS-2 RS-2P CRS-2 CRS-2P HFRS-2P LSTN Average GRNT Average B S LT Average ALLVL Average C h ip L o s s , % Figure 11. Sweep test results for SSD chips at 40% cure.

83 Alpha Level for Significant Differences Variable Tested RS-2 RS-2P CRS-2 CRS-2P HFRS-2P aggregate <0.0001* <0.0001* 0.3887 0.0049* <0.0001* moisture 0.0169* 0.0220* 0.1597 0.0003* 0.0335* cure <0.0001* <0.0001* <0.0001* <0.0001* <0.0001* agg x ** moist 0.2468 0.3618 0.0994 0.7574 0.5873 agg x cure 0.0001* 0.0020* 0.3927 0.0005* 0.0032* moist x cure 0.5425 0.0136* 1.0000 0.9546 0.6490 agg x moist x cure 0.1064 0.2088 0.8805 0.0114* 0.2366 * Statistical significance at α = 0.05 or less **x indicates the interaction effect of the variables shown on the mean chip loss Table 5. Results of ANOVA for laboratory sweep tests. EmulsionAggregate RS-2 RS-2P CRS-2 CRS-2P HFRS-2P ALL A*(47)** A(57) A(50) A (38) A (44) GRN B(39) A(51) A(49) AB (33) AB (37) LS B(36) A(51) A(47) AB (32) B (28) BST C(29) B(18) A(47) B (25) B (25) *Letters indicate different levels of statistical significance in chip loss average at α = 0.05 for the different aggregates and the same emulsion. For example, there is a significant difference in chip loss between the alluvial (ALL) and the granite (GRN) for the RS-2 (47% vs. 39%), but not for the RS-2P (57% vs. 51%). **Numbers in parentheses are the average percent chip loss after the sweep test Table 6. Results of Student Newman-Keuls multiple comparison test for aggregate. 0% 20% 40% 60% 80% 100% RS-2 RS-2P CRS-2 CRS-2P HFRS-2P LSTN Average GRNT Average B S LT Average ALLVL Average C h ip L o s s , % Figure 12. Sweep test results for SSD chips at 80% cure.

84 and the relationship between moisture loss and chip loss is shown in Figure 16. At approximately 85% moisture loss, residue strength increased to the point where chips could not be dislodged during the test. This suggests that a relationship exists between the laboratory sweep test and actual residue strength in the field as a function of moisture content of the chip-seal system. The results show little difference between the dry and SSD aggregate conditions with respect to chip loss. The regression equations for both moisture conditions were similar, and location had little effect. However, there appears to be a strong relationship between chip-seal moisture loss and chip loss. Therefore, the moisture content of the chip-seal system (i.e., the moisture of the emulsion and the moisture of the 0 1 2 3 4 5 6 7 8 9 10 0 10 20 30 40 50 60 70 80 90 100 Field Moisture Loss, % R e si du e St re n gt h (1 - 10 sc al e) Location 1 Location 2 Location 3 Figure 13. Residue strength versus emulsion moisture at Arches National Park, UT. 0 1 2 3 4 5 6 7 8 9 10 0 10 20 30 40 50 60 70 80 90 100 Field Moisture Loss, % R es id ue S tre ng th (1 -10 sc ale ) Location 1 Location 2 Location 3 Figure 14. Residue strength versus emulsion moisture for CR-11, Frederick, CO.

85 chips) could be used to determine when the chip seal has developed enough adhesive strength to resist the stresses of sweeping and uncontrolled traffic. 3.4 Emulsion Consistency in the Field Results of the tests at Arches National Park, CR-11– Frederick, and US-101–Forks are shown in Figures 17 and 18 for the 6-mm and 7.5-mm orifices, respectively. Arches testing did not include the 7.5-mm orifice. The emulsion consistency at all three test sites was consid- ered acceptable for constructing chip seals, i.e., it remained on the pavement surface and did not flow off but was not so viscous as to prevent wetting of the aggregate chips. Based on this observation, Wagner cup flow times of 20 to 70 s at emul- sion temperatures of 85 to 150°F for a 6-mm orifice or 10 to 60 s at emulsion temperatures of 85 to 140°F for the 7.5-mm orifice may be appropriate for use as a guide for evaluating emulsion flow. A correlation between Wagner cup flow time and Saybolt viscosity was developed by Wyoming DOT (Morgenstern 0 1 2 3 4 5 6 7 8 9 10 0 10 20 30 40 50 60 70 80 Field Moisture Loss, % Re s id u e St re n gt h (1- 10 Sc a le ) Location 1 Location 2 Figure 15. Residue strength versus emulsion moisture at US-101, Forks, WA. Site Aggregate Moisture Chip-Seal Moisture Loss, % Avg. Sweep Test Chip Loss, % Arches Dry 41.0 32.3 Arches Dry 84.0 0.05 Frederick Dry 45.9 39.3 Frederick Dry 81.6 0.00 Forks Dry 40.6 68.2 Forks Dry 75.7 0.05 Arches SSD 38.9 63.3 Arches SSD 80.3 0.21 Frederick SSD 41.6 40.6 Frederick SSD 81.6 0.04 Forks SSD 42.9 47.6 Forks SSD 71.3 0.41 Table 7. Chip loss for test pavement materials.

86 Dry Aggregate Chip Loss, % = -1.2179(Moisture Loss, %) + 98.203 R2 = 0.8254 SSD Aggregate Chip Loss, % = -1.3453(Moisture Loss, %) + 105.33 R2 = 0.9283 0 10 20 30 40 50 60 70 80 30 40 50 60 70 80 90 100 Emulsion Moisture Loss, % Ch ip Lo ss , % Figure 16. Chip loss versus emulsion moisture loss. 0 10 20 30 40 50 60 70 80 80 90 100 110 120 130 140 150 160 Temperature, F Ti m e , s Forks Arches Frederick Figure 17. Field flow time for 6-mm orifice Wagner cup.

87 2008) and is presented in Figure 19 for a CRS-2P. Similar curves could be developed at different temperatures. 3.5 Pavement Texture Measurement Texture of three concrete texture slabs was measured in the laboratory using the sand patch test, the CT meter, and the AIMS apparatus. Texture measurements were also made on the test pavements at Arches–Utah; Frederick, Colorado; and Forks, Washington. Multiple measurements of within-wheel path and between-wheel path textures were made on each project; an average texture depth at each measurement loca- tion was calculated. 3.5.1 Laboratory Texture Measurements The results of texture measurements for the laboratory texture slabs using the sand patch, CT meter, and AIMS test methods are shown in Figure 20. Both the CT meter and AIMS test methods correlate fairly well to the sand patch test. Further testing using the CT meter and sand patch were made at each of the three field test sites. 3.5.2 Field Texture Measurements Texture measurements for the three field test sites and the three laboratory test slabs are shown in Figure 21. Textures ranged from 0.1 mm for one of the test slabs to nearly 3 mm at the Arches site. Linear regression using all data resulted in an R2 of 0.96 with slope of 0.96 and intercept of 0.14 indicat- ing nearly a one-to-one relationship between sand patch and CT meter texture measurements when laboratory and field data are combined. 3.6 Residue Recovery Methods and Properties Rheological Properties At the high temperatures, the base binders in every case exhibited lower G*/sin δ than did the recovered residues, pos- sibly due to stiffening and aging of the residues during either the emulsification process or the residue recovery process. The BBR test results indicated that the base binders and the recovered emulsion residues had similar cold temperature properties, probably due to deterioration of the polymer additive structure over time and with aging (Woo et al. 2006). 0 10 20 30 40 50 60 70 80 80 90 100 110 120 130 140 150 160 Temperature, F Fl ow T im e, s Forks Frederick Figure 18. Field flow time for 7.5-mm orifice Wagner cup.

88 All of the materials met the PG (G*sin δ) criterion at the SP-1 specified intermediate temperatures. PG and SPG Grading Both PG and SPG grades were determined for all of the base binders and recovered residues, and the results are shown in Table 4. Interpolation was used to determine the continu- ous grades. In general, the PG and SPG grades were consis- tent for the base binder and the residues from both recovery methods. However, examination of the continuous grades indicated that the base binder grades were slightly different from the grades of the recovered residues. The SPG system resulted in a higher continuous grade at both the high and the low temperature ends than the continuous grade with the PG system. The average differences in the high and low tempera- R2 = 0.5438 30 40 50 60 70 80 90 100 100 120 140 160 180 200 220 240 260 Saybolt Viscosity, s W ag ne r Cu p Fl ow T im e Figure 19. Saybolt viscosity versus Wagner cup flow time (Morgenstern 2008). AIMS y = 0.8413x + 0.0339 R2 = 0.8625 CT Meter y= 0.7808x + 0.1105 R2 = 0.9203 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 AIMS and CT Meter Texture, mm Sa nd P at c h Te x tu re , m m Figure 20. Laboratory test slab texture by sand patch and AIMS.

89 ture continuous grades (SPG minus PG) were +3.6° C and +11.3° C, respectively. Chemical Properties The GPC chromatograms for all of the residues from both of the recovery processes indicated that water was absent from the recovered emulsion residues and had therefore been completely removed from the emulsions during the recovery procedures. The carbonyl areas calculated from FT-IR spectra for the five laboratory emulsions indicated that the recovered binders were all slightly more oxidized than the base binders. This oxidation could have occurred during emulsification or during the residue recovery process. Statistical Analyses Summary The rheological data collected with the DSR and the BBR were analyzed statistically to determine if there were statis- tical differences between the emulsions and between the recovery methods. ANOVA and Tukey’s honestly signifi- cant differences (HSD) multiple comparison techniques with a level of confidence of α = 0.05 were used in all of the analyses. When comparing the DSR data by recovery method, the analysis results statistically grouped the recovery methods of stirred can and hot oven together, and the base binder (“no recovery”) was grouped separately for the emulsions with base binders available (1 through 5). Both recovered residues were stiffer, with larger values of G*, than the base binders, but not stiff enough to change the high-temperature PG grade for emulsions 1 through 5 as shown in Table 8. With smaller temperature increments, the high-temperature SPG grade did change to a larger value for four of emulsions 1 through 5. Analysis of the BBR measurements showed that the recov- ery procedure (with base binders included as “no recovery”) did not affect the response variables S or m-value of the recov- ered residues. This result seems to indicate that after PAV aging, the polymers and additives no longer have an effect on stiffness properties. The spectroscopic data were also analyzed statistically using ANOVA and Tukey’s HSD multiple comparison techniques for a level of confidence of α = 0.05. Statistical analyses of car- bonyl areas did not differentiate the recovery methods. The base binders and the recovered residues were statistically dif- ferent, but the two recovery methods were similar to each other in terms of oxidative effects. Strain Sweep Results Strain sweeps were conducted on unaged and PAV aged materials. The unaged material represented the binder residue after the chip seal was constructed and the binder had cured with complete water removal. The PAV aged material repre- sented the binder residue after the chip seal would have been in place for approximately one summer (high temperature) and one winter (low temperature). The majority of chip-seal failures occur during either the first summer or the first winter (Epps et al. 2001). Review of the plots of G* versus strain percentage indicate that the magnitudes of the G* and strain values and the shapes and rates of change of the curves can be used to compare 0.00 0.50 1.00 1.50 2.00 2.50 3.00 0.00 1.00 2.00 3.00 CT Meter MPD, mm Sa nd P at ch M TD , m m Colorado Frederick Utah Arches Washington Hwy 101 Test Slabs Figure 21. CT meter versus sand patch texture.

90 materials and characterize strain tolerance. For comparison, the strain sweep data from the stirred can recovery residues for aged and unaged materials are shown in Figure 22. Materials with high strain tolerance exhibit slow deteriora- tion of G* with increasing strain level, indicating that the material maintains stiffness and holds together under repeated and increasing loads. Emulsions 1, 2, 4, and 5 in the unaged state exhibited this behavior and were visibly more adhesive and elastic when handled in the laboratory. After PAV aging, some materials exhibit less strain tolerance and develop a steep decrease in G* with increasing strain. Emulsions 2, 3, and Utah Arches are examples of this type of behavior. These materials were very stiff and broke off of the test plates in a brittle manner after the strain sweep testing was completed. An asphalt binder must develop enough stiffness (G*) to be able to carry vehicle loads before the chip-sealed pavement is broomed or opened to traffic. The amount of moisture remain- ing in the chip seal has been shown to relate to binder strength development. This moisture level could be correlated with G* from strain sweep testing to determine a minimum G* for traffic bearing capacity. Researchers have conducted testing on binders during cur- ing and have recommended the following criteria for deter- mining strain tolerance and failure of the emulsion residue during curing (Hanz et al. 2009): • 10% reduction in G*, or 0.10Gi* characterizes strain toler- ance and indicates that the material is behaving nonlinearly and is accumulating damage; • 50% reduction in G* or 0.50Gi* defines failure of the material. Hanz et al. (2009) found that stiffer emulsion residues after PAV aging are difficult to induce 50% Gi* and even 90% Gi* in strain sweep testing. Most of the unaged and only a few of the PAV aged materials reached 80% Gi*, as shown in Table 8, and none reached 50% Gi*. It is possible that intermediate reductions in Gi* could be used to characterize behavior of the fully cured residues when 50% or 90% Gi* cannot be attained. Besides differing in the rate at which G* decreased with increasing strain, the materials differed in their original stiff- ness, Gi*, and the rate of change of Gi* between the unaged and Emul- sion Recovery UNAGED Gi* (Pa, at 1% ) % at 0.90Gi* % at 0.80Gi* % at 0.50Gi* AGED Gi* (Pa, at 1% ) % at 0.98Gi* % at 0.90Gi* % at 0.80Gi* % at 0.50Gi* 1 base 241,120 21.23 34.74 n/a 987,120 4.95 10.88 12.67* n/a 1 stirred can 326,460 19.20 31.22 n/a 883,620 5.01 11.86 14.15* n/a 1 hot oven 337,500 19.79 32.67 60.06* 844,030 5.53 11.46 14.82* n/a 2 base 248,290 25.72 6.18 84.03* 1,448,300 3.93 7.31 8.62* n/a 2 stirred can 298,170 22.17 38.31 n/a 1,948,300 2.77 5.29 6.40* n/a 2 hot oven 318,660 21.32 36.98 63.37* 1,385,600 4.33 7.68 9.01* n/a 3 base 747,630 14.84 16.71 n/a 3,329,800 2.31 n/a n/a n/a 3 stirred can 825,740 13.26 15.13 n/a 2,811,300 3.62 n/a n/a n/a 3 hot oven 813,970 13.64 15.35 n/a 3,163,400 2.14 n/a n/a n/a 4 base 219,060 25.41 44.14 n/a 954,040 5.24 10.92 13.11* n/a 4 stirred can 289,860 20.77 34.51 n/a 905,480 5.58 11.27 13.82* n/a 4 hot oven 257,750 24.35 34.26 n/a 778,100 4.84 11.11 16.10* n/a 5 base 266,850 22.03 38.45 n/a 1,260,200 4.92 8.81* 9.91* n/a 5 stirred can 297,360 17.79 31.46 67.95* 765,620 5.18 10.76 16.35* n/a 5 hot oven 286,680 17.27 30.57 70.53* 801,740 3.96 10.38 15.54 n/a 6 – UT stirred can 1,182,300 9.18 10.56* n/a 2,486,600 2.45 4.46 n/a n/a 6 – UT hot oven 1,203,200 9.21* 10.37* n/a 2,886,400 3.33 3.84* n/a n/a 7 - CO stirred can 440,260 18.16 28.36 45.86* 1,235,400 3.36 8.41 10.11 n/a 7 - CO hot oven 444,800 17.92 28.20 45.42* 1,198,900 3.06 7.51 10.36 n/a * Max DSR stress was reached; n/a = test didn’t run that far Table 8. Strain sweep test results.

91 the PAV aged states as shown in Table 8. The stiffest material in the unaged state was Emulsion residue 6, a latex-modified, rapid-setting emulsion. The stiffest material in the aged state was the Emulsion 3 residue, a rapid-setting unmodified emul- sion. G* increased the most from the unaged to the aged state for the Emulsion 3 residue. It was followed by the Emulsion 2 residue, also a rapid-setting unmodified emulsion, and then by the Emulsion 6 residue. Residues for polymer modified Emulsions 1, 4, 5, and 7 increased in G* and exhibited aged behavior after the PAV aging, but not by as much as the residues for Emulsions 2, 3, and 6. Also, for Emulsions 1, 4, and 5, the base binder increased in G* considerably more than the recov- ered residue did, possibly indicating that either the emulsifi- cation process or the residue recovery process reduced the susceptibility of these materials to the PAV aging process. Based on the results of the strain sweep testing, Emulsions 1, 2, 4, 5, and 7 would be expected to resist raveling due to their high strain tolerances. Emulsions 3 and 6, which had very stiff unaged residues, would be expected to resist flushing and also might be able to be opened to traffic earlier. However, these emulsions became more brittle with aging and could therefore exhibit raveling with age. A comparison between the emulsion residues used at the three field tests and those recommended by the SPG criteria are shown in Table 9. In all three cases the materials used were higher temperature grades than the SPG recommended criteria, and in the case of Washington and Utah, lower temperature grades, as well. The proposed emulsion residue criteria shown in Table 10 are based on those originally proposed in previous research 0 500,000 1,000,000 1,500,000 2,000,000 2,500,000 3,000,000 0 5 10 15 20 25 30 35 40 45 50 Strain (%) Co m pl ex M od ul us G * ( Pa ) Emulsion 3 PAV Aged Utah Arches PAV Aged Emulsion 2 PAV Aged Emulsions 1, 2, 4, and 5 Unaged Figure 22. G* versus shear strain from stirred can recovery method. Field Site SPGRecommendation Actual Material Used Forks, WA 52–12 67–15 Arches NP, Utah 61–12 79–15 Frederick, CO 58–24 76–18 Table 9. Recommended SPG temperature ranges (°C).

Performance Grade* SPG 61 SPG 64 SPG 70 –12 –18 –24 –30 –12 –18 –24 –30 –12 –18 –24 –30 Average 7-day Maximum Surface Pavement Design Temperature, °C <61 <64 <70 Minimum Surface Pavement Design Temperature, °C >–12 >–18 >–24 >–30 >–12 >–18 >–24 >–30 >–12 >–18 >–24 >–30 Original Binder Dynamic Shear, AASHTO TP5 δ * Sin G , Minimum: 0.65 kPa Test temperature @10 rad/s, °C 61 64 70 Shear Strain Sweep % strain @ 0.8Gi*, Minimum: 25 Test Temperature @10 rad/s linear loading from 1– 50% strain, 1 s delay time with measurement of 20– 30 increments, °C 25 25 25 PAV Residue (AASHTO PP1) PAV Aging Temperature, °C 100 100 100 Creep Stiffness, AASHTO TP1 S, Maximum: 500 MPa m-value, Minimum: 0.240 Test Temperature @ 8 s, °C –12 –18 –24 –30 –12 –18 –24 –30 –12 –18 –24 –30 Shear Strain Sweep Gi*, Maximum: 2.5 MPa Test Temperature @10 rad/s linear loading at 1% strain and 1 s delay time, °C 25 25 25 *This table presents only three SPG grades as an example, but the grades are unlimited and can be extended in both directions of the 3oC and 6oC increments for the high temperature and low temperature grades, respectively.temperature spectrum using Table 10. Proposed emulsion residue criteria.

93 shown in Table 3, including equivalent testing and perfor- mance thresholds for parameters measured in the dynamic shear rheometer and bending beam rheometer for unaged, high-temperature and aged, low-temperature properties, respectively. Additional testing and performance thresholds were added based on strain sweep testing conducted as part of this project and other research (Hanz et al. 2010) and the significantly different performance of Emulsion 3 and the Utah Arches emulsion. The thresholds provided for the DSR and BBR parameters are based on validation with Texas field test sections adjusted for climates in Utah and Colorado. 3.7 Estimating Embedment in the Field Embedment depth is usually determined during construc- tion by pulling several chips out of the binder and visually estimating the amount of embedment. This practice is prob- lematic even if chips have a very low flakiness index because it is difficult to assess quantitatively with any precision. There- fore, two methods based on the sand patch test were developed to estimate embedment depth: the constant volume method and the constant diameter method. 3.7.1 Constant Volume Method Glass beads were spread out in a circle on top of chips embed- ded to 20% and 80% of the chip average least dimension. The diameter of the circle was compared with the theoretical diam- eter that should result based on weight-to-volume characteris- tics of the materials presented in Section 2.7.1. Results of this experiment are shown in Figure 23. At 20% embedment, the measured diameters are reasonably close to the theoretical diameters. However, at 82% embed- ment, the measured diameters are significantly less than the calculated values. At 20% embedment, voids are deep, requiring many beads, and the procedure of spreading the beads from particle peak to peak contributes less to error than it does at higher embed- ment percentages when the amount of beads between the aggregate voids is relatively less. At 80% embedment, many particles were fully covered by asphalt, making it impossible to spread the glass beads between these aggregates. Test results indicate this procedure to be useful when chip- seal particle embedments are closer to 50% or not submerged and chips have low flakiness index. 3.7.2 Constant Diameter Method This method of estimating embedment depth used a mold of constant diameter in which glass beads were poured on top of the aggregate chips and the volume measured. Using weight-to-volume relationships for the materials, the volume of glass beads required to fill the mold was calculated as a function of the aggregate embedment depth. A comparison between the calculated volume of glass beads required to fill the mold and the actual volume measured for the limestone and granite aggregates embedded to 20% and 82% is shown in Figure 24. At 20% embedment, measured values deviate 10% from the theoretical values. At 82% embedment, the deviation is less at 5% from theoretical. Deviations were similar for the limestone and the granite at both levels of embedment. Limestone Theoretical Sand Patch Diameter at 82% Embedment Granite Theoretical Sand Patch Diameter at 82% Embedment 0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 100.0% 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 Sand Patch Diameter (Dia), cm A gg re ga te E m be dm en t, % Granite and Limestone Sand Patch Diameter at Actual 82% Embedment Figure 23. Comparison of calculated to measured embedment depth.

94 Limestone- Calculated Granite- Calculated 0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% 80.0% 90.0% 100.0% 0 20 40 60 80 100 120 140 160 180 Volume of Sand below ALD ht, cm3 A gg re ga te E m be dm en t, % Limestone- Actual Granite- Actual Figure 24. Embedment depth from constant diameter method.

95 Five new products were identified in this research to improve the design and construction of chip seals. This chapter describes these products and their application. 4.1 Modified Sweep Test and Critical Moisture Contents This test provides a method to determine the timing for chip-seal brooming and opening to uncontrolled traffic. The test determines the moisture content of the chip seal, which corresponds to adhesion needed to retain chips under traffic loads. The moisture content of the chip seal can be monitored during construction to determine when the desired moisture content is reached. This moisture content ranged from about 15% to 25% of the total chip-seal moisture. A description of the test method is provided in the appendix to the manual. Results of the modified sweep test indicated that an aggre- gate in the saturated surface dry condition provides better adhesion than dry aggregates. This finding suggests that chip- seal aggregates be moistened prior to construction. 4.2 Field Consistency Test A Wagner cup viscometer was used in this research to measure the consistency of emulsions. By conducting the test at a variety of temperatures in the lab- oratory, a temperature versus flow time relationship can be produced. Flow in the field can then be measured and com- pared with laboratory results to determine actual viscosity at the field temperature. The test method is described in the appendix to the manual. 4.3 Pavement Texture A direct correlation between the sand patch test and the CT meter indicates that pavement texture measurements can be made with the CT meter and used as a substitute for the sand patch test results in the design process. This texture measure- ment can then be used to adjust emulsion spray rates during construction. Recommended adjustments are provided in the manual. 4.4 Residue Recovery and Desirable Properties The SCERR method is recommended for obtaining emul- sion residues for use in tests proposed for measuring physical properties. Proposed emulsion residue criteria are listed in Table 10. The test method is provided in the appendix to the manual. 4.5 Measuring Aggregate Embedment in the Field Two methods for measuring aggregate embedment in the field have been developed. The constant volume method is a simple method, using a constant volume of glass beads spread on the pavement surface in a circle. By measuring the diameter of the circle, the embedment of the aggregate can be estimated. However, this procedure becomes less accurate at embedment over 50%. An alternative procedure, the constant diameter method, can be used to estimate embedment up to 80%. These test methods are provided in the appendix to the manual. C H A P T E R 4 Practical Application of the Research

96 5.1 Conclusions This report documents laboratory testing and field evalu- ation of several new procedures suitable for use by highway agencies, consultants, contractors, and others involved in the design and construction of chip seals. These new procedures were developed to add objective measurement capability to some of the largely subjective judgments made during chip- seal design and construction. A laboratory test that simulates the sweeping action of rotary brooms during chip-seal construction was developed. This test simulates the shear forces applied by brooms and uncontrolled traffic to fresh chip seals, and can be used to predict the time required before brooms or uncontrolled traf- fic can be allowed on the surface of the chip seal. The test indi- cated the following: • The moisture content at which 90% of the aggregate chips are retained during the sweep test is the “critical moisture content” corresponding to very high residue adhesive strength at which traffic could be allowed onto the chip-seal sections. • Significantly higher chip loss was measured for sweep test specimens fabricated with dry aggregates than with satu- rated surface dry aggregates. • No significant difference in chip loss was measured either at 40% or 80% moisture loss between cationic and anionic emulsions used with either calcareous or siliceous aggregates. The Wagner cup viscometer for measuring the consistency of paints was successfully adapted to measuring viscosity of emulsions. The test is inexpensive, field portable, repeatable, simple to operate, and can be correlated to laboratory tests. An adjustment to the emulsion spray quantity should be made to account for pavement surface texture. This process is often done subjectively or measured using the sand patch test in other countries. Although the sand patch test can mea- sure texture effectively, the CT meter and AIMS apparatus were found to be faster and provide very similar results. Extensive testing was done to evaluate new methods of emulsion residue recovery. The methods included hot oven (with nitrogen blanket), stirred can (with nitrogen purge), and warm oven. Residues recovered using these methods were tested using the Superpave PG test methods and chemical analysis to determine which recovery technique mimicked the base asphalts closest and resulted in the least amount of water remaining in the samples. These tests indicated that the SCERR method is rapid and provides a good simulation of the base asphalt material properties. Also, recovered emul- sion residues were shown to be different from their base binders at high temperatures before PAV aging, but similar to the base binders at cold temperatures after PAV aging. The residues obtained from the emulsions used in the three field test sites were characterized using the Superpave PG binder tests. The result of this work is a performance-based criterion for chip-seal residues. Initially, this SPG criterion was calibrated using field test sections in Texas. However, results of this research indicated that adjustments to the orig- inal criteria should be made to accommodate other climates. Therefore, characterization of residues should be done by evaluating the complex shear modulus, G*, over a range of shear strains to evaluate strain resistance. These results could be used to predict when emulsion-based chip seals will develop resistance to raveling and enough stiffness to be opened to traffic, both in newly constructed chip seals and after weather- ing and aging. 5.2 Recommendations The findings of this project were based on a significant amount of field and laboratory measurement. However, additional studies would help improve upon these findings and the recommendations. Such studies may include the following: C H A P T E R 5 Conclusions and Recommendations

97 • Further sweep testing with other sources of aggregate and emulsion to verify the validity of the test as a means of measuring chip adhesion. • Evaluation of grayscale photography and image analysis for quantifying macrotexture of pavement surfaces (Pid- werbesky et al. 2009) to possibly provide a viable and rela- tively inexpensive alternative to the sand patch test and the CT meter measurements. • Monitoring the performance of the three test sites con- structed as part of this research to provide additional validation for setting thresholds in the proposed SPG spec- ification.

98 Abe, H., T. Akinori, J. J. Henry, and J. Wambold. Measurement of Pave- ment Macrotexture with Circular Texture Meter. Transportation Research Record: Journal of the Transportation Research Board, No. 1764, TRB, National Research Council, Washington, D.C., 2001. Anderson, V. I. and R. A. McLean. Design of Experiments: A Realistic Approach, Marcel Dekker, ISBN: 0824761316, 1993. Asphalt Institute. Superpave Performance Graded Asphalt Binder Specs and Testing, SP-1, ISBN: 978193415416. Austroads. Austroads Technical Report AP-T68/06, Update of the Aus- troads Sprayed Seal Design Method. Alan Alderson, ARRB Group, ISBN 1 921139 65 X, 2006. Barcena, R., A. E. Martin, and D. Hazlett. Performance Graded Binder Specification for Surface Treatments. Transportation Research Record: Journal of the Transportation Research Board, No. 1810, Transporta- tion Research Board of the National Academies, Washington, D.C., 2002. Barnat, J., W. McCune, and V. Vopat. The Sweep Test: A Performance Test for Chip Seals. Asphalt Emulsion Manufacturers Association, San Diego, CA, February, 2001. Cornet, E. ESSO Abrasion Cohesion Test: A Description of the Cohe- sive Breaking Emulsions for Chip Seal. International Symposium on Asphalt Emulsion Technology: Manufacturing, Application and Performance, 346–355, 1999. Epps, A. L., C. J. Glover, and R. Barcena. A Performance-Graded Binder Specification for Surface Treatments, Report No. FHWA/TX- 02/1710-1, Texas Department of Transportation and U.S. Depart- ment of Transportation, Federal Highway Administration (FHWA), Washington, D.C., 2001. Epps, J. A., B. M. Gallaway, and C. H. Hughes. Field Manual on Design and Construction of Seal Coats. Texas Transportation Institute, Research Report 214-25, July 1981. Gransberg, D. and D. M. B. James. NCHRP Synthesis 342: Chip Seal Best Practices, Transportation Research Board of the National Academies, Washington, D.C., 2005. Hall, J. W., K. L. Smith, L. Titus-Glover, J. C. Wambold, T. J. Yager, and Z. Rado. NCHRP Web-Only Document 108: Guide for Pavement Friction, Final Report, Project 1-43, Transportation Research Board of the National Academies, Washington, D.C., 2006. http://www.trb. org/Main/Blurbs/161756.aspx. Hanson, D. I. and B. D. Prowell, Evaluation of Circular Texture Meter for Measuring Surface Texture of Pavements. National Center for Asphalt Technology (NCAT), Auburn, AL, 2004. Hanz, A., Z. A. Arega, and H. U. Bahia. Rheological Evaluation of Emulsion Residues Recovered Using Newly Proposed Evaporative Techniques, Paper #09-2877, Presented at the 88th Annual Meet- ing of the Transportation Research Board, Washington, D.C., 2009. Hanz, A., Z. A. Arega, and H. U. Bahia. Rheological Behavior of Emul- sion Residues Recovered Produced by an Evaporative Recovery Method, Paper #10-3845 [CD-ROM], Presented at the 89th Annual Meeting of the Transportation Research Board, 2010. Howard, I. L., M. Hemsley, Jr., G. L. Baumgardner, W. S. Jordan, III. Chip and Scrub Seal Binder Evaluation by Frosted Marble Aggre- gate Retention Test, Paper #09-1662, Presented at the 88th Annual Meeting of the Transportation Research Board, 2009. Kadrmas, A. Report on Comparison of Residue Recovery Methods and Rheological Testing of Latex and Polymer Modified Asphalt Emul- sions. Annual Meeting of the American Emulsion Manufacturers Association, Report #4-AEMA ISAET 08, 2008. Kucharek, A. Measuring the Curing Characteristics of Chip Sealing Emul- sions. Paper Presented at the Joint ARRA-ISSA-AEMA Meeting, Asphalt Emulsion Manufacturers Association and McAsphalt, 2007. Masad, E. Aggregate Imaging System (AIMS): Basics and Applications, Implementation Report FHWA/TX-05/5-1707-01-1, Texas Trans- portation Institute (TTI), College Station, TX, 2005. McLeod, N. Basic Principles for the Design and Construction of Seal Coats and Surface Treatments. Proceedings of the Association of Asphalt Paving Technologist, Vol. 29, 1960, 1–150. McLeod, N. W. Seal Coat Design. Proceedings of the Association of Asphalt Paving Technologists, Vol. 38, February 1969. Morgenstern, B. Wyoming 538.0 (under review), Field Emulsion Viscos- ity Test, 2008. Pidwerbesky, B., J. Waters, D. Gransberg, and R. Stemprok. Road Sur- face Texture Measurement Using Digital Image Processing and Information Theory, Land Transport New Zealand Research Report 290, New Zealand, 2009. Prapaitrakul, N., R. Han, X. Jin, C. J. Glover, D. Hoyt, and A. E. Martin. The Effect of Three Asphalt Emulsion Recovery Methods on Recov- ered Binder Properties. Petersen Asphalt Research Conference, 2009. Santi, M. Case Study of a State Emulsion QA Program. Presentation to the Rocky Mountain Pavement Preservation Partnership, Airport Hilton, Salt Lake City, UT, October 30, 2009. Shuler, S. Design and Construction of Chip Seals for High Traffic Vol- ume. Flexible Pavement Rehabilitation and Maintenance. ASTM Spe- cial Technical Publication (STP) Number 1348. American Society for Testing and Materials. West Conshohocken, PA, 1998. South African National Roads Agency. Technical Recommendations for Highways, TRH3 2007, Design and Construction of Surfacing Seals, May 2007. References

99 Walubita, L. F., A. E. Martin, D. Hazlett, and R. Barcena. Initial Validation of a New Surface Performance-Graded Binder Specification. Trans- portation Research Record: Journal of the Transportation Research Board, No. 1875, Transportation Research Board of the National Academies, Washington, D.C., 2004. Walubita, L. F., A. E. Martin, and C. J. Glover. A Surface Performance- Graded (SPG) Specification for Surface Treatment Binders: Devel- opment and Initial Validation, Report No. FHWA/TX-05/0-1710-2. Texas Department of Transportation and U.S. Department of Trans- portation, FHWA, 2005. Washington State Department of Transportation. Asphalt Seal. Technol- ogy Transfer, March 2003, 1–30. Woo, J. W., E. Ofori-Abebresse, A. Chowdhury, J. Hilbrich, Z. Kraus, A. E. Martin, and C. Glover. Polymer Modified Asphalt Durability in Pavements, Report #FHWA/TX-07/0-4688-1, Texas Transporta- tion Institute, 2006.

100 Appendices A through J of the contractor’s final report for NCHRP Project 14-17 are available on the TRB website at http://www.trb.org/Main/Blurbs/164090.aspx. A P P E N D I X A T H R O U G H A P P E N D I X J

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Manual for Emulsion-Based Chip Seals for Pavement Preservation Get This Book
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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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