Chapter 6, Achieving a High Level of Smoothness in Concrete Pavements, FHWA-HRT-05-068 - PCCP - Pavements

Achieving a High Level of Smoothness in Concrete Pavements Without Sacrificing Long-Term Performance

CHAPTER 6. SHORT-TERM CHANGES IN INITIAL SMOOTHNESS OF CONCRETE PAVEMENTS

INTRODUCTION

All SHAs that construct PCC pavements have a smoothness specification. Some smoothness specifications will give a timeframe after construction within which smoothness measurements must be performed while others do not. An issue with PCC pavements is the effect of curling and warping of PCC slabs on smoothness. Some contractors perform smoothness measurements as soon as possible after construction because they perceive that curling and warping effects on the pavement will be negligible immediately after construction. However, if curling and warping occurs in the pavement during its early life, causing a significant reduction in smoothness, the validity of bonuses paid based on smoothness measurements obtained immediately after construction becomes questionable.

A study was performed to investigate how the smoothness of a PCC pavement changes during the first 3 months of its life. Test sections were established at the following paving projects for this study:

State Route (S.R.) 6220, Centre County, PA.
U.S. Route 20 (U.S. 20), Hardin County, IA.
Interstate 80 (I-80), Pottawattamie County, IA.
U.S. Route 23 (U.S. 23), Monroe County, MI.
Interstate 69 (I-69), Calhoun County, MI.

All of these pavements were doweled JPC pavements. The smoothness measurements were generally performed at the following time periods using an inertial profiler:

1 day after paving.
3 days after paving.
1 week after paving.
3 months after paving.

Smoothness measurements were performed in each wheel path, and three repeat measurements were performed for each data set. At several test sections, measurements were obtained in the morning and the afternoon during the 1-week and 3-month testing. At one test section, measurements were also obtained approximately 1 year after construction.

The following analyses were performed on the collected profile data:

Obtain average IRI and RN: Compute IRI and RN for all profile runs. Then compute an average IRI and RN for each data set using the values obtained for the three repeat runs.
Investigate the repeatability of the profiler: The IRI values obtained for the entire test section from the repeat runs for each data set were evaluated to determine the repeatability of the profiler.
Investigate the short-interval IRI repeatability: This investigation was performed by comparing IRI values at 15-m (49-ft) intervals for the repeat runs in each data set. This investigation indicates whether the distribution of the roughness within the section for the three repeat runs was repeatable. In some cases, IRI from the repeat runs for a pavement section can be very close to each other; however, the distribution of roughness within the section for the repeat runs can be variable. When the overall roughness for the section is computed, the roughness variability within the section can cancel out, and give close IRI values for repeat runs even though they may have very different roughness distributions within a section.
Evaluate changes in IRI and RN: Compare IRI and RN obtained the first time the section was profiled with values obtained from subsequent profiling. This analysis provides information on how the smoothness of PCC pavements changes during the first few months of their life relative to the smoothness obtained immediately after paving.
Evaluate the effect of joints on profile data and smoothness indices: In the two projects in Iowa, a sawcut that is 6 mm (0.25 inches) wide and 25 mm (1 inch) deep is made on the pavement. Thereafter, the joint is sealed. Profile data collected for these two conditions of the joint were available for the two Iowa projects. In the Michigan and the Pennsylvania projects, a 3-mm (0.12-inch)-wide initial sawcut is made on the pavement. Thereafter, the joint is widened to form a reservoir and then sealed. Profile data collected for all three conditions of the joint were available. These profile data were analyzed to see how the joint appeared in the profile data and to investigate the impact of these different joint conditions on IRI and RN.
Use roughness profiles to investigate the distribution of roughness: For this analysis, IRI roughness profiles based on an 8-m (26-ft) base length were used. Roughness profiles for the left wheel path, right wheel path, and an overlaid plot that showed profiles for both wheel paths were used in this analysis.
Evaluate profile characteristics: Profile data collected at different time periods were analyzed using profile plots and PSD plots to investigate changes in profile, and to see whether a dominant wavelength or a dominant waveband that is affecting IRI is present in the profile. The CI values of the profiles also were computed to investigate slab curvature.
CTE values and microscopical examination: Cores obtained from the pavement or cylinders cast from concrete used in the project were used to determine the CTE of the concrete and to perform a microscopical examination to identify the coarse and the fine aggregate in the concrete. The CTE test was carried out using the test procedure CRD-C 39-81 that is described in the U.S. Army Corps of Engineers Materials Testing Handbook⁽³⁶⁾. The microscopical examination of the concrete cylinder or core was performed in accordance with portions of ASTM C 856-02, Standard Practice for Petrographic Examination of Hardened Concrete⁽³⁷⁾.

The results obtained at each project are explained separately below.

STATE ROUTE 6220 PROJECT - PENNSYLVANIA

Project Description

This project involved new construction and was located in Centre County, PA. This roadway is a four-lane divided highway with two lanes in each direction. A 168-m (550-ft)-long test section was established for testing on the two southbound lanes. The test section was established between stations 588+00 and 582+50. (Stations are in U.S. customary units).

Pavement Details

Table 21 shows pavement details. The subgrade consisted of blasted rock mixed with fines. Table 22 provides information about the joints in the pavement.

Table 21. Pavement details - S.R. 6220.
Item	Description	Value
Pavement thickness	Concrete thickness	280 mm (10.9 inches)
Pavement thickness	Base thickness	100 mm (3.9 inches) asphalt-treated permeable base over 150 mm (5.9 inches) of aggregate base
Pavement width	Total pavement width	7.30 m (24 ft)
	Width of inside lane	3.65 m (12 ft)
	Width of outside lane	3.65 m (12 ft)
Shoulder	Shoulder type	Concrete, 280 mm (10.9 inches) thick
Shoulder	Width of shoulder	Inside 1.2 m (3.9 ft), outside 3 m (9.8 ft)
Joint spacing	Joint spacing	4.6 m (15.1 ft)
Joint spacing	Joints skewed?	No
Dowels	Dowel type	Epoxy coated
	Dowel diameter	38 mm (1.5 inches)
	Dowel length	457 mm (17.8 inches)
Tining	Tining type	Transverse tining
	Tining spacing	Random spacing
	Tining depth	3.2 to 4.8 mm (0.1 to 0.2 inches)

Table 22. Joint details - S.R. 6220.
Description	Value
Joint formation	Initial sawcut then reservoir widened
Initial sawcut	3 mm (0.12 inch) wide and 93 mm (3.63 inches) deep
Joint reservoir width	9.5 mm (0.37 inch)
Joint reservoir depth	38 mm (1.5 inches)
Sealant type	Hot-pour asphalt
Depth to top of sealant	5 mm (0.2 inches)

Concrete Mix Design

Table 23 presents the mix proportions used for the concrete mix. An entrained air admixture and a water-reducing admixture were added to the concrete mix. Table 24 shows the gradation of the aggregates used in the concrete mix.

Table 23. Mix proportions - S.R. 6220.
Component	Weight Kilograms per cubic meters (kg/m3 (lb/yd3))
Cement Type 1	297 (500)
Fly ash;	52 (88)
Coarse aggregate	1,097 (1,849)
Sand	653 (1,100)

Table 24. Gradation of aggregates - S.R. 6220.
Sieve	Percentage Passing
Sieve	Coarse Aggregate	Sand
37.5 mm (1.5 inches)	100	-
25.0 mm (1 inch)	100	-
12.5 mm (0.5 inch)	45	-
9.5 mm (0.4 inch)	-	100
No. 4	8	99
No. 8	3	80
No. 16	-	68
No. 30	-	48
No. 50	-	21
No. 100	-	6

Paving Details

Table 25 shows the date and time of test section paving and other details related to the paving process. The concrete was placed using a slipform paver.

Table 25. Paving Information - S.R. 6220.
Item	Description	Comment
Date and time	Date of paving	9/17/03
Date and time	Time of paving	9 a.m.
Paving process	Haul route	Adjacent to inside lane
	Stringline	7.6-m (25-ft) spacing, both sides
	Dowels	Fixed to base
	Tie bars	Inserted by paver
	Concrete deposit method	Belt placers
	Spreader used?	Yes, one
	Paver type	GOMACO™ GHP - 2800
Concrete	Temperature	21 ^oC (69.8 ^oF)
Curing method	Curing compound	Water-based curing compound sprayed on pavement

Profiling of Section

Eight sets of profile data were collected over a 3.5-month period. The pavement was first profiled 1 day after paving; the second set of profiles were collected 3 days after paving. The third and fourth sets of data were collected 1 week after paving in the morning and afternoon, respectively. The fifth and sixth sets of data were collected 1 month after paving in the morning and afternoon, respectively. The seventh and eighth sets of data were collected about 3.5 months after paving in the morning and afternoon, respectively. The profile data were collected using an ICC lightweight laser profiler. This profiler recorded data at 31-mm (1.2-inch) intervals.

Table 26 shows the dates and times when profile data collection was performed, the approximate age of the pavement at each instance, and the low, high, and mean air temperatures for each profiling day.

The 3-mm (0.12-inch)-wide initial sawcut had been made on the pavement when the profile data were collected 1 day after paving. The joint reservoirs had been formed, but the joints were not sealed when the profile data were collected in the morning of the 1-month data collection. The joints were sealed when the 1-month afternoon runs were performed. During the 3.5-month data collection, it was noted that the first 5.5 m (18 ft) of the inside lane had been diamond ground.

Table 26. Profile data collection - S.R. 6220.
Date of Profiling	Approximate Age of Pavement	Time of Profiling				Air Temperature ^oC (^oF )
		Inside Lane		Outside Lane		Air Temperature ^oC (^oF )
		Left Wheel Path	Right Wheel Path	Left Wheel Path	Right Wheel Path	Low	High	Mean
9/18/03	1 day	2:32 p.m.	2:34 p.m.	2:37 p.m.	N/A	12 (54)	21(70)	17 (63)
9/20/03	3 days	1:02 p.m.	1:14 p.m.	1:35 p.m.	N/A	11(52)	21(70)	16 (61)
9/24/03	7 days	9:44 a.m.	9:53 a.m.	10:04 a.m.	N/A	7 (45)	22 (72)	15 (55)
9/24/03	7 days	5:09 p.m.	5:21 p.m.	5:33 p.m.	N/A	7 (45)	22 (72)	15 (55)
10/15/03	1 month	8:38 a.m.	8:48 a.m.	8:59 a.m.	9:05 a.m.	7 (45)	13 (55)	11 (52)
10/15/03	1 month	2:32 p.m.	2:40 p.m.	2:48 p.m.	2:56 p.m.	7 (45)	13 (55)	11 (52)
12/29/03	3.5 months	9:53 a.m.	10:46 a.m.	11:21 a.m.	11:45 p.m.	1 (34)	16 (61)	8 (46)
12/29/03	3.5 months	3:51 p.m.	4:02 p.m.	4:23 p.m.	4:41 p.m.	1 (34)	16 (61)	8 (46)

N/A: Profile data not collected

Roughness Indices

IRI Values

The average IRI values computed from the three repeat runs are presented in table 27 and shown graphically in figure 71. The IRI for the right wheel path in the outside lane is not shown in this figure, because data were collected along this path only during the 1-month and 3.5-month data collection. Table 28 shows the percentage change in IRI values for different test sequences with respect to the IRI obtained at 1 day. Values for right wheel of outside lane are not presented in this table because profiling was performed along this path only during the 1-month and 3.5-month data collection.

Table 27. IRI values for different test sequences - S.R. 6220.
Date of Profiling	Approximate Age of Pavement	Time of Profiling	IRI (m/km)
			Inside Lane		Outside Lane
			Left Wheel Path	Right Wheel Path	Left Wheel Path	Right Wheel Path
9/18/03	1 day	2:30 to 2:40 p.m.	1.32	1.21.	0.96	N/A
9/20/03	3 days	1 to 1:40 p.m.	1.27	1.24	1.01	N/A
9/24/03	7 days	9:45 to 10 a.m..	1.27	1.18	0.96	N/A
9/24/03	7 days	5:05 to 5:35 p.m.	1.27	1.20	0.98	N/A
10/15/03	1 month	8:40 to 9 a.m.	1.30	1.22	0.97	0.90
10/15/03	1 month	2:30 to 3 p.m.	1.31	1.18	0.94	0.93
12/29/03	3.5 months	10 to 11:30 p.m.	1.21	1.13	0.94	0.91
12/29/03	3.5 months	3:50 to 4:40 p.m.	1.21	1.10	0.94	0.86

N/A: Profile data not collected

1 m/km = 63.4 inches/mi

Figure 71. IRI values for different test sequences - S.R. 6220.

Table 28. Percentage change in IRI with respect to 1-day IRI - S.R. 6220.
Date of Profiling	Approximate Age of Pavement	Time of Profiling	Percentage Change in IRI with Respect to 1-Day IRI
			Inside Lane		Outside Lane
			Left Wheel Path	Right Wheel Path	Left Wheel Path
9/20/03	3 days	1 to 1:40 p.m.	-3	2	5
9/24/03	7 days	9:45 to 10 a.m.	-4	-2	0
9/24/03	7 days	5:05 to 5:35 p.m.	-3	-1	2
10/15/03	1 month	8:40 to 9 a.m.	-1	1	1
10/15/03	1 month	2:30 to 3 p.m.	-1	-3	-2
12/29/03	3.5 months	10 to 11:30 p.m.	-8	-7	-2
12/29/03	3.5 months	3:50 to 4:40 p.m.	-8	-9	-3

Note: 1-day profile data not collected along right wheel path of outside lane

The following observations were noted when evaluating the IRI values:

The IRI is showing a decrease transversely across the pavement from the left wheel path of the inside lane to the right wheel path of the outside lane. The 1-month afternoon IRI (obtained after the joints were sealed) indicated the IRI of the left wheel path of inside lane, right wheel path of inside lane, left wheel path of outside lane, and right wheel path of outside lane to be 1.31, 1.18, 0.94, and 0.93 m/km (83, 75, 60, and 59 inches/mi), respectively. The difference in IRI between the two wheel paths of the outside lane was small.
The IRI values obtained during the 3.5-month testing for the inside lane for both the left and the right wheel paths were lower than the IRI obtained during 1-day testing by 8 and 9 percent, respectively. This reduction in IRI is attributed to the diamond grinding that was performed on this lane.
When the data for the case where measurements were obtained after diamond grinding were omitted, the data show the IRI along each test path has remained relatively constant for all data sets. The changes in IRI with respect to 1-day IRI were usually within ±3 percent. The age of pavement and the time of testing do not appear to have affected the IRI.
The joints in the pavement were at three different conditions during testing: (1) initial sawcut performed on the pavement (testing at 1 day, 3 days, and 7 days), (2) joint reservoir sawed but not sealed (1-month morning testing), and (3) joints sealed (1-month afternoon and 3.5-month testing). The condition of the joint during testing had negligible impact on the IRI.

RN Values

The average RN values obtained from the three runs are presented in table 29 and shown in figure 72. Table 30 shows the percentage change in RN values for different test dates with respect to the RN obtained at 1 day. The RN for the right wheel path in the outside lane is not shown in figure 72 and table 30 because data were collected along this path only during the 1-month and 3.5-month data collection.

Table 29. RN values for different test sequences - S.R. 6220.
Date of Profiling	Approximate Age of Pavement	Time of Profiling	Ride Number
			Inside Lane		Outside Lane
			Left Wheel Path	Right Wheel Path	Left Wheel Path	Right Wheel Path
9/18/03	1 day	2:30 to 2:40 p.m.	3.59	3.71	3.84	N/A
9/20/03	3 days	1 to 1:40 p.m.	3.59	3.66	3.80	N/A
9/24/03	7 days	9:45 to 10 a.m..	3.45	3.51	3.62	N/A
9/24/03	7 days	5:05 to 5:35 p.m.	3.44	3.55	3.62	N/A
10/15/03	1 month	8:40 to 9 a.m.	3.37	3.26	3.40	3.40
10/15/03	1 month	2:30 to 3 p.m.	3.68	3.81	3.95	3.88
12/29/03	3.5 months	10 to 11:30 p.m.	3.69	3.78	3.95	3.87
12/29/03	3.5 months	3:50 to 4:40 p.m.	3.67	3.80	3.97	3.93

Figure 72. RN values for different test sequences - S.R. 6220.

Table 30. Percentage change in RN with respect to 1-day RN - S.R. 6220.
Date of Profiling	Approximate Age of Pavement	Time of Profiling	IRI (m/km)
			Inside Lane		Outside Lane
			Left Wheel Path	Right Wheel Path	Left Wheel Path
9/20/03	3 days	1 to 1:40 p.m.	0	-1	-1
9/24/03	7 days	9:45 to 10 a.m..	-4	-5	-6
9/24/03	7 days	5:05 to 5:35 p.m.	-4	-4	-6
10/15/03	1 month	8:40 to 9 a.m.	-6	-12	-11
10/15/03	1 month	2:30 to 3 p.m.	2	3	3
12/29/03	3.5 months	10 to 11:30 p.m.	3	2	3
12/29/03	3.5 months	3:50 to 4:40 p.m.	2	2	3

N/A: Profile data not collected

The following observations were noted when the RN values were evaluated:

The RN values increased transversely across the pavement from the left wheel path of the inside lane to the left wheel path of the outside lane. The right wheel path of the outside lane had a slightly lower RN than the left wheel path of the outside lane.
The 7-day RN values were less than the 1-day RN values; the values were lower by 4 to 6 percent for the different wheel paths. An evaluation of the profiles indicated that the backer rods put into the joints appear to have settled when 7-day profiling was performed, and this feature was appearing in the profile as a slight depression and causing lower RN values.
The 1-month morning profiles had the lowest RN value; the RN was lower than the 1-day value by 6 to 12 percent for the different wheel paths. The joint reservoirs had been sawed when the data were collected, which caused depressions to be recorded in the profile data at the joint locations. This phenomenon caused a reduction in the RN values.
The RN of profiles collected during the 1-month afternoon profiling when the joints were sealed had higher values than those obtained from profiles collected in the morning when the joint reservoir had been sawed and the joint was unsealed. The afternoon RN values were higher than the morning RN values by 9 to 16 percent for the different wheel paths.
The RN values obtained after the joints were sealed (1-month afternoon runs) were slightly higher than the RN values obtained from the 1-day profiling by values ranging from 0.09 to 0.11 (2 to 3 percent) for the different wheel paths. An evaluation of the profiles did not indicate the cause for this slight increase in RN. There may have been slurry resulting from joint sawing operations adjacent to the joint during the 1-day profiling, which may have caused lower RN values.

Repeatability of IRI Values

An evaluation of the IRI values obtained from repeat runs for each data set indicated good repeatability. Usually when the IRI from three runs were compared, the difference between the maximum and the minimum IRI was between 0.02 to 0.03 m/km (1.27 to 1.90 inches/mi).

The three repeat runs obtained along the left wheel path of the outside lane for the 1-month afternoon runs were used to evaluate the short interval repeatability of IRI within the section. The IRI of each run was computed at 15-m (49-ft) intervals to perform this evaluation. The 165-m (541-ft)-long section has 11 segments that are 15 m (49 ft) long (the last 3 m (10 ft) of the section was ignored). Figure 73 shows the IRI values obtained at 15-m (49-ft) intervals for each run. Overall, reasonable repeatability in IRI values was obtained for the majority of segments. The difference between the maximum and minimum IRI for a segment obtained from the repeat runs ranged from a low of 0.03 m/km (1.9 inches/mi) at segment 2 to a high of 0.21 m/km (13.3 inches/mi) at segment 8. The average of the difference between maximum and minimum IRI for a segment was 0.09 m/km (5.7 inches/mi).

Figure 73. IRI values for repeat runs - S.R. 6220.

Effect of Condition of Joint on Profile Data

During this study, profile data were collected when the joints were in the following conditions:

The initial sawcut that was 3 mm (0.12 inch) in width and 93 mm (3.7 inches) deep had been made on the pavement. A backer rod had been placed inside the joint. Profile data under these conditions were collected during 1-day, 3-day, and 1-week profiling.
The joint reservoir that was 9.5 mm (0.4 inch) wide and 38 mm (1.5 inches) deep had been made on the pavement. Profile data under this condition were collected during the 1-month morning data collection.
The joints had been sealed. Profile data under this condition were collected during the 1-month afternoon and 3.5 month data collection. According to the specification, when the joint is sealed, the depth from the pavement surface to the top of the sealant should be 5 mm (0.2 inch).

Profile data collected when the joint was at each of the three conditions described previously were evaluated to investigate how the joints showed up on the profile. Data collected along the left wheel path of the outside lane at the following profiling times were evaluated: 1 day (initial sawcut), 1-month morning (joint reservoir sawed), and 1-month afternoon (joint sealed). Figures 74 - 76 show how a typical joint appeared on the profile for each of these conditions. The joint appears between 30.4 and 30.6 m (99.7 and 100.3 ft) in the plots. The following observations are noted for each case shown in figures 74 - 76.

Initial Sawcut: The joint appears in the profile as a small depression spread over a distance of about 220 mm (8.7 inches), with a maximum depth about of 1.5 mm (0.06 inch).
Joint Reservoir Sawed: The joint appears in the profile as a small depression spread over a distance of about 220 mm (8.7 inches), with a maximum depth of about 3.5 mm (0.14 inch).
Joint Sealed: The joint appears in the profile as a small depression spread over a distance of about 220 mm (8.7 inches), with a maximum depth of about 1.5 mm (0.06 inch).

For all three cases, the joint appears in the profile as a small depression spread over a distance of about 220 mm (8.7 inches), when the actual width of the joint is 9.5 mm (0.4 inch). Also, the depth of the joint that appears in the profile for each case is much less than the actual depth. This phenomenon is caused by the averaging performed on the height sensor data and the low-pass filtering that is applied on the profile data to prevent aliasing.

Figure 74. Measurements at a joint, initial sawcut, 1-day - S.R. 6220.

1 m = 3.28 ft
1 mm = 0.039 inch

Figure 75. Measurements at a joint, reservoir widened, 1-month morning - S.R. 6220.

1 m = 3.28 ft
1 mm = 0.039 inch

Figure 76. Measurements at a joint, joint sealed, 1-month afternoon - S.R. 6220.

1 m = 3.28 ft
1 mm = 0.039 inch

The lightweight profiler used for data collection recorded profile data at 31-mm (1.2-inch) intervals. However, the height sensor in the profiler obtains data at much closer intervals, and an averaged height sensor value is used to compute profile data points at 31-mm (1.2-inch) intervals. In addition, a low-pass filter appears to have been applied on the data further attenuating the depth of the joint, and causing the joint to appear as a much wider feature. Although the profiles obtained when the joint reservoirs had been sawed do show a downward feature at the joint that has a higher depth compared to the other two cases, the depth of the features is not large enough to have an effect on the IRI. Hence, the IRI values computed from profiles collected under the three different scenarios were very close to each other. However, the downward spikes of the magnitude seen for 1-month morning profiling where the joint reservoirs had been sawn do have a significant impact on RN. The 1-month afternoon RN values obtained after the joints were sealed were higher than the morning values by 9 to 16 percent for the different wheel paths.

Roughness Profiles

Figures 77 - 79 and figures 80 - 82 show the roughness profiles for a 6-m (20-ft) base length for the outside lane and inside lane, respectively. The roughness profile for the outside lane was computed from data obtained for the 3-month afternoon testing, whereas the roughness profile for the inside lane was computed using data obtained from 3-day testing. The joint spacing of the pavement is 4.6 m (15 ft) and each vertical line in the plots corresponds to a joint. The peaks in the plots indicate areas of high roughness. Many peaks are coinciding with the joint locations or are very close to joint locations. This situation indicates that the dowel baskets may be affecting roughness.

Figure 83 shows a high roughness area along the left wheel path of the inside lane at the start of the section. This area was subsequently diamond ground. Several localized areas of high roughness are noted along the left wheel path of the inside lane, and the roughness of these areas contributed to making this wheel path have the highest roughness of all tested wheel paths.

Evaluation of Profile Data

Apart from the differences in joint conditions, no significant differences between the profiles obtained during the different test sequences could be observed. The profiles obtained along the inside lane during 3.5 months of testing showed the effect of diamond grinding at the start of the section. Also, no distinct profile feature or a dominant waveband could be identified in the profile data.

As described previously, the IRI varied transversely across the section. The difference in IRI between the left wheel path of the inside lane and the right wheel path of the outside lane based on 1-month afternoon testing was 0.38 m/km (24 inches/mi). Evaluation of the profile data did not show a distinct profile feature that was responsible for this difference in IRI.

The CI value was computed for one profile run from each data set, and the computed values are shown in table 31. This table does not show values for the right wheel path of the outside lane because profile data were only collected along this path during the 1-month and 3.5-month data collection. The CI values for all data sets were extremely small, which indicates the slabs are more or less flat with virtually no curvature. No noticeable changes in curvature were observed between the data sets.

Figure 77. Roughness profiles for outside lane, left wheel path - S.R. 6220.

1 m = 3.28 ft
1 m/km =63.4 inches/mi

Figure 78. Roughness profiles for outside lane, right wheel path - S.R. 6220

1 m = 3.28 ft
1 m/km =63.4 inches/mi

Figure 79. Roughness profiles for outside lane, left and right wheel path - S.R. 6220.

1 m = 3.28 ft
1 m/km =63.4 inches/mi

Figure 80. Roughness profiles for inside lane, left wheel path - S.R. 6220.

1 m = 3.28 ft
1 m/km =63.4 inches/mi

Figure 81. Roughness profiles for inside lane, right wheel path - S.R. 6220.

1 m = 3.28 ft
1 m/km =63.4 inches/mi

Figure 82. Roughness profiles for inside lane, left and right wheel path - S.R. 6220.

1 m = 3.28 ft
1 m/km =63.4 inches/mi

Table 31. CI values - S.R. 6220.
Date of Profiling	Approximate Age of Pavement	Time of Profiling	Curvature Index x 1,000 (1/m)
			Inside Lane		Outside Lane
			Left Wheel Path	Right Wheel Path	Left Wheel Path
9/18/03	1 day	2:30 to 2:40 p.m.	0.10	-0.10	0.08
9/20/03	3 days	1 to 1:40 p.m.	-0.13	-0.09	-0.05
9/24/03	7 days	9:45 to 10 a.m..	0.07	0.05	0.08
9/24/03	7 days	5:05 to 5:35 p.m.	0.03	0.08	-0.02
10/15/03	1 month	8:40 to 9 a.m.	0.18	0.05	0.13
10/15/03	1 month	2:30 to 3 p.m.	0.16	-0.02	0.02
12/29/03	3.5 months	10 to 11:30 p.m.	0.05	-0.09	-0.03
12/29/03	3.5 months	3:50 to 4:40 p.m.	0.07	-0.10	-0.02

1/m = 1/3.28 ft

Coefficient of Thermal Expansion and Microscopical Examination

A CTE test and a microscopical examination were performed on a 150-by-300 mm (5.9-by-11.8 inch) cylinder that was cast from the concrete used in the project. The CTE value for the specimen was 9.60 x 10^-6 per ^oC (5.33 x 10^-6 per ^oF). The microscopical examination identified the coarse aggregate to be primarily dolomite/dolomitic limestone (carbonate) with traces of granite (silicious). The fine aggregate was classified as silicious.

Summary

The IRI of the pavement was decreasing transversely from the left wheel path of the inside lane to the left wheel path of the outside lane. Along the outside lane, the left and right wheel path IRI values were close to each other. The 1-month afternoon testing indicated that the IRI of the left wheel path of inside lane, right wheel path of inside lane, left wheel path of outside lane, and right wheel path of outside lane were 1.31, 1.18, 0.94, and 0.93 m/km (83, 75, 60, and 59 inches/mi), respectively. No distinct profile feature that had this effect on the IRI could be identified.
Researchers noted that the data collected by the lightweight profiler did not accurately record the shape of the joints in the pavement. A joint appeared in the profile as a small depression spread over a distance of 220 mm (8.7 inches), when the actual width of the joint was 9.5 mm (0.37 inch). The depth of this depression varied depending on the condition of the joint. When the initial sawcut that was 3 mm (0.12 inch) wide was present, a depth of 1.5 mm (0.06 inch) was recorded. When the joint reservoir that was 9.5 mm (0.37 inch) wide and 38 mm (1.50 inches) deep was present with the joint being unsealed, a depth of 3.5 mm (0.14 inch) was recorded. When the joint was sealed, a depth of 1.5 mm (0.06 inch) was recorded.
The profiler showed good repeatability in obtaining IRI values. When the IRI obtained from the three repeat runs for the entire section were evaluated for all data sets, the difference between the maximum and minimum IRI was between 0.02 m/km (2.5 inches/mi) and 0.03 m/km (1.9 inches/mi).
An evaluation of short interval IRI repeatability using 15-m (49-ft) segment lengths indicated that the profiler was providing reasonable repeatability. The average difference between the maximum and minimum IRI obtained for a 15-m (49-ft)-long segment was 0.09 m/km (5.7 inches/mi).
Little change in IRI was noted for the different data sets. The IRI can be considered to have remained at the same value over the 3.5-month period. The IRI was not affected by the condition of the joint or the time of day when profiling was performed. The IRI was not affected by the condition of the joint because the data collected by the profiler was attenuating the depth of the joint, and the recorded depths were of such a magnitude that they did not affect the IRI.
As for the IRI, little change in RN was noted for the different data sets, except for the values obtained when the joint reservoirs had been sawed and the joint was in an unsealed condition. The RN obtained after the joint was sealed was higher than the RN obtained when the joint reservoir was formed but unsealed by 9 to 16 percent for the different wheel paths.
There was negligible curvature in the PCC slabs for the different data sets. The slabs in the pavement can be considered to be flat. No appreciable changes in curvature were noted between the different data sets.

U.S. 20 PROJECT IN IOWA