Manual for Emulsion-Based Chip Seals for Pavement Preservation (2011) / Chapter Skim
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Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report
Attachment - Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report
Pages 66-100
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66 A T T A C H M E N T Manual for Emulsion-Based Chip Seals for Pavement Preservation: Research Report
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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
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Therefore, research was needed to develop a manual that identifies factors that influence chipseal design, construction, and performance and provides guidelines 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 describing the best methods to use for designing and constructing chip seals placed on hot mix asphalt pavements.
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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 different emulsions with a single aggregate.
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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.
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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.
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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
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An emulsion with viscosity Figure 4. Modified sweep test mixer.
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2.5 Pavement Texture Testing Adjusting the emulsion spray rate to compensate for differences in pavement surface texture is one of the most subjective adjustments made during chip-seal construction. Figure 5.
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The objective 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.
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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 emulsion residues by both the PG and SPG grading systems and some additional tests, and recommends an emulsion residue recovery method and emulsion residue specification.
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Table 3. Criteria for SPG grades for emulsion residues (Walubita et al.
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emulsion residue recovery (SCERR) methods were used to extract the water from the emulsions and to supply dewatered residue for the material properties testing.
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Because it is generally difficult to accurately assess chip embedment 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 constant diameter method. Both methods were developed using the LSTN and GRNT aggregates from the laboratory sweep test experiment.
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Glass Beads Binder Chip Embedment ALDT M Agg Chip Figure 8. Embedment depth by constant diameter model.
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3.3 Laboratory Sweep Test for Field Materials The sweep test was conducted for aggregates and emulsions obtained from the three field test pavements. Aggregates were tested using two moisture contents and a range of moisture loss percentages.
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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.
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* Numbers in parentheses are the average percent chip loss after the sweep test Table 6.
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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.
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The emulsion consistency at all three test sites was considered 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 emulsion 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.
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+ 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.
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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.
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Laboratory test slab texture by sand patch and AIMS.
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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.
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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*
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considerably more than the recovered residue did, possibly indicating that either the emulsification 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.
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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.
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This practice is problematic even if chips have a very low flakiness index because it is difficult to assess quantitatively with any precision. Therefore, two methods based on the sand patch test were developed to estimate embedment depth: the constant volume method and the constant diameter method.
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94 LimestoneCalculated GraniteCalculated 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, % LimestoneActual GraniteActual Figure 24. Embedment depth from constant diameter method.
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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.
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The test indicated 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 saturated surface dry aggregates.
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2009) to possibly provide a viable and relatively inexpensive alternative to the sand patch test and the CT meter measurements.
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Rheological Behavior of Emulsion 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.
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Initial Validation of a New Surface Performance-Graded Binder Specification. Transportation Research Record: Journal of the Transportation Research Board, No.
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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.
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