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From page 22... ... 22 The main objective of the field study was to evaluate the effects of tack coat material type, application rate, and pavement surface type, on interface bonding and pavement performance during the first 12 months of service. For this purpose, 10 field projects were selected in six states and included 33 in-service test sections. Read the entire page →
From page 23... ... 23 Project Tack Coat Material Type AASHTO Test Method T 59 T 59 T 49 T 53 M 320 Residue by Evaporation, % Viscosity, Saybolt Furol at 25°C, s Penetration at 25°C, 100g, 5s, penetration units Softening Point, Ring and Ball, °C Superpave PG Missouri SS-1H1 61.0 29.2 71.0 51.4 PG 64-22 NTSS-1HM2 63.0 41.5 9.0 82.0 PG 94-10 Louisiana (LA30) SS-11 64.1 32.7 102.0 43.5 PG 46-28 NTSS-1HM2 54.3 34.2 9.0 78.1 PG 82-10 Louisiana (LA1053) Read the entire page →
From page 24... ... 24 followed by PCC, existing HMA, and new HMA. The range of measured MTD values for each surface type is presented in Table 4.2-1. Read the entire page →
From page 25... ... 25 Pavement Surface Type ISS, psi NTSS-1HM1 SS-1H 0.02 gsy2 0.03 gsy 0.02 gsy 0.03 gsy 0M 4M 12M 0M 4M 12M 0M2 4M 12M 0M 4M 12M New HMA AVG 68 93 120 76 105 110 52 80 102 58 90 96 STD 8 12 9 4 7 13 3 6 10 6 4 4 COV, % 12 13 8 5 7 12 6 8 10 10 4 4 Note: 0M, 4M, and 12M indicate ISS at 0, 4, and 12 months, respectively. 1Asphalt Products Unlimited nontracking RS emulsion. Read the entire page →
From page 26... ... 26 4.4 Effect of Tack Coat Material Type on ISS 4.4.1 Missouri Project Figure 4.4-1 presents the effect of two types of tack coat materials: nontracking RS NTSS-1HM and SS SS-1H. Both tack coat materials were sprayed at a 0.05 gsy residual application rate on four types of pavement surfaces: milled HMA, new HMA, existing HMA and PCC. Read the entire page →
From page 27... ... 27 Figure 4.4-3 shows the effect of four types of tack coat materials -- three nontracking RS (two NTSS-1HM and one CBC-1H) and one SS SS-1H -- on ISS on a new HMA pavement surface. Read the entire page →
From page 28... ... 28 residue compared with CBC-1H (PG 70-22) Read the entire page →
From page 29... ... 29 paring CSS-1H at 0.07 gsy with CBC-1H at 0.04 gsy residual application rates. Similar performance of both materials may be attributed to the fact that both CBC-1H (PG 64-22) Read the entire page →
From page 30... ... 30 of ISS. It was observed that the PCC surface in Missouri project exhibited the weakest interface bonding, yielding ISS values below the minimum recommended ISS threshold of 40 psi (1) Read the entire page →
From page 31... ... 0 40 80 120 160 0.02 gsy 0.04 gsy 0.04 gsy 0.04 gsy CRS-1HBC SS-1H In te rf ac e Sh ea r St re ng th , p si Tack Coat Residual Application Rate/ Material Type A B A A Existing HMA Figure 4.6-2. Effect of residual application rate on ISS: Florida project. Read the entire page →
From page 32... ... 32 40 psi (Table 4.3-8) Read the entire page →
From page 33... ... 33 4.7.3 Florida Project This project evaluated the effect of two types of tack coat materials at two residual application rates on ISS at service times of 0, 4, and 12 months on an existing HMA pavement surface. Figure 4.7-4 shows the variation of the mean ISS values at different service times. Read the entire page →
From page 34... ... 34 milled HMA pavement surface. All mean ISS values were significantly higher than the minimum recommended ISS threshold value of 40 psi; see Table 4.3-6. Read the entire page →
From page 35... ... 35 at 0.05 gsy; see Figure 4.7-6. Furthermore, the curing effect seemed more pronounced for the RS nontracking CBC-1H than the SS CSS-1H. Read the entire page →
From page 36... ... 36 the curing effect of tack coat materials seemed to increase with the increase in the residual application rate. 4.8 Analysis of FWD Test Results 4.8.1 Missouri Project A series of FWD tests was performed along the pavement sections before overlay construction and after construction at 7 months and 12 months of service. Read the entire page →
From page 37... ... 37 Further, a slight decrease in FWD deflections occurred in all but two test sections [i.e., NTSS-1HM (Blacklidge) at 0.01 gsy, and SS-1H test sections at 0.02 gsy] Read the entire page →
From page 38... ... 38 FWD testing before and after construction of overlays, problems associated with construction difficulties allowed FWD testing at 3 months of service. The average center deflections for all test sections decreased with time because of densification of HMA overlays and improved interface bonding; see Figure 4.7-5. Read the entire page →
From page 39... ... 39 decrease in the average center deflections occurred after overlay construction because of the combined effect of added structural layer, densification due to trafficking, and improved interface bonding due to tack coat curing. 4.8.7 Summary of FWD Test Results Mean FWD center deflections decreased with service time in all field projects and for all pavement surface types. Read the entire page →
From page 40... ... 40 pavement layers. Further, poor interface bonding (<40 psi) Read the entire page →
From page 41... ... 41 of service according to the procedures described in the Distress Identification Manual for the Long-Term Pavement Perfor mance Program (50) Read the entire page →
From page 42... ... 42 The objective of the experimental program was to measure and to compare the ISS for different surface types, tack coat material types, and residual application rates. Table 4.12-1 presents the experimental factorial conducted in NCHRP Project 09-40. Read the entire page →
From page 43... ... 43 linearity diagnostics (i.e., condition index, variance inflation factor, and tolerance value) Read the entire page →
From page 44... ... 44 the recommended levels in SAS for stepwise regression analysis procedure. Additionally, a linear regression analysis was performed considering all variables to compare the results with the stepwise selection method. Read the entire page →
From page 46... ... 46 variables is correlated with some other combinations of independent variables. The variance inflation factor (VIF) Read the entire page →
From page 47... ... 47 used in model development. This COV is deemed acceptable. Read the entire page →
From page 48... ... 48 of .95 with an RMSE value of 4.8 psi. Recall that the range of measured ISS values used for model development was between 19 and 99 psi, representing both poorly bonded and strongly bonded tack-coated interface. Read the entire page →
From page 49... ... 49 Tack Coat Type HPG RES Predicted ISS NTSS-1HM 84 0.055 87 84 0.045 77 84 0.035 67 CBC-1H/SS-1H/CSS-1H 72 0.055 79 72 0.045 71 72 0.035 62 SS-1 50 0.055 65 50 0.045 59 50 0.035 53 Note: MTD = 1.77 mm; PT = 1. Table 4.16-1. Read the entire page →

From page 22...

... 22 The main objective of the field study was to evaluate the effects of tack coat material type, application rate, and pavement surface type, on interface bonding and pavement performance during the first 12 months of service. For this purpose, 10 field projects were selected in six states and included 33 in-service test sections.