High Performance Concrete Pavements Project Summary
Chapter 32. VIRGINIA 1 (I-64, Newport News)
Concrete pavements constructed in Virginia over 20 years ago commonly incorporated a 50-mm (2-in.) maximum coarse aggregate size in the PCC mix design (Ozyildirim 2000). These pavements generally performed well, but over time concerns with the availability, stockpiling, and segregation of the aggregate led to a reduction in the specified maximum coarse aggregate size (Ozyildirim 2000). However, while smaller coarse aggregate size is inherently more durable, concrete using smaller coarse aggregate commonly exhibits greater shrinkage (and increased potential for slab cracking) because of increased paste requirements. Larger maximum coarse aggregate sizes, on the other hand, require less paste, less cementitious material, and less water, thereby resulting in reduced shrinkage; they also provide increased mechanical interlock at joints and cracks (Ozyildirim 2000).
To investigate the effect of maximum coarse aggregate on concrete material properties and pavement performance, the Virginia Department of Transportation (VDOT) constructed an experimental concrete pavement project as part of the TE-30 program. The project is located on I-64 near Newport News (see Figure 89) and was constructed in 1998 and 1999 (Ozyildirim 2000).
Figure 89. Location of VA 1 project.
The objectives of this project are (Ozyildirim 2000):
- To develop concrete mixtures that have low shrinkage and high flexural strength.
- To determine the properties of such concretes.
- To instrument and test jointed pavement slabs for volumetric changes.
- To determine the air void distribution (indicative of consolidation) from cores.
Project Design and Layout
This project was constructed on I-64 in Newport News, beginning about 2.4 km (1.5 mi) west of Route 143 and ending about 1.6 km (1 mi) east of Route 143 (Ozyildirim 2000). The project involved removing and replacing the two existing traffic lanes in both the eastbound and westbound directions, and constructing an additional lane in each direction (Ozyildirim 2000). The nominal pavement design used for these sections is as follows (Ozyildirim 2001):
- 280-mm (11-in.) JPCP.
- 75-mm (3-in.) asphalt-stabilized open-graded drainage layer (OGDL).
- 150-mm (6-in.) cement-treated subbase.
- 4.6-m (15-ft) transverse joint spacing.
- Silicone sealant in all transverse joints.
- 32-mm (1.25-in.) diameter epoxy-coated steel dowel bars (511 mm [18 in.] long and spaced 300 mm [12 in.] apart).
- Widened slabs (4.3 m [14 ft]) in the outer traffic lane.
Three experimental sections were constructed in the westbound lanes in November 1998, and then replicated in the construction of the eastbound lanes in July 1999 (Ozyildirim 2000). Each of the three sections incorporated a different concrete mix design (Ozyildirim 2001):
- Section 1 EB/WB - concrete mixture using a 50-mm (2-in.) maximum coarse aggregate and including ground granulated blast furnace slag (GGBFS).
- Section 2 EB/WB - concrete mixture using a 25-mm (1-in.) maximum coarse aggregate and including GGBFS.
- Section 3 EB/WB - concrete mixture using a 25-mm (1-in.) maximum coarse aggregate and including Class F fly ash. This section represents VDOT's current conventional concrete mix design.
Figure 90 illustrates the layout of these test sections, while Table 50 summarizes the concrete mix design information. The mix designs for sections 1 and 2 contain 30 percent slag, whereas the mix design for section 3 contains 25 percent fly ash. The coarse aggregate was a crushed biotite gneiss and granite, whereas the fine aggregate was a natural sand (Ozyildirim 2001). The coarse aggregate used in section 1 was a blend of No. 3 and No. 57 aggregates (Ozyildirim 2001).
Figure 90. Layout of VA 1 test sections (Ozyildirim 2000).
CTB = cement-treated subbase; GGBFS = ground granulated blast furnace slag;
JPCP = jointed plain concrete pavement; OGDL = open-graded drainage layer
(SLAG MIX #2)
(SLAG MIX #1)
|Portland cement quantity, lb/yd3 (kg/m3)||374 (222)||394 (234)||423 (251)|
|GGBFS quantity, lb/yd3 (kg/m3)||160 (95)||169 (100)||-|
|Class F fly ash quantity, lb/yd3 (kg/m3)||-||-||142 (84)|
|Pozzolan quantity, lb/yd3 (kg/m3)||30 percent||30 percent||25 percent|
|Course aggregate No.||357||57||57|
|Maximum top size, in (mm)||2 in (50 mm)||1 in (25 mm)||1 in (25 mm)|
|Course aggregate quantity, lb/yd3 (kg/m3)||1935 (1148)||1841 (1092)||1841 (1092)|
|Fine aggregate quantity, lb/yd3 (kg/m3)||1171 (695)||1217 (722)||1229 (729)|
|Water, lb/yd3 (kg/m3)||243 (144)||249 (148)||249 (148)|
|Water-to-cementitious materials ratio (w/cm)||0.45||0.44||0.44|
agent + retarder
agent + retarder
agent + retarder
Comparing the mix design of section 1 (the larger aggregate) with the mix designs for the other two sections, it is observed that the use of the larger aggregate did slightly reduce the required quantities of water and cementitious materials (Ozyildirim 2000).
Dowel bars were placed in baskets at the predetermined joint locations prior to the paving operations (Ozyildirim 2001). Transverse joints were cut initially 4.75 mm (0.19 in.) wide to a depth of one-third of the slab thickness (Ozyildirim 2001). A secondary cut was made 2 weeks later to establish the joint reservoir for the silicone sealant.
A water-based curing compound was used to cure the pavement, except that the appropriate materials could not be obtained during the placement of the westbound lanes (Ozyildirim 2001). Consequently, a white plastic sheeting was used to cure the pavement for 10 days (Ozyildirim 2001).
During construction, one outside slab in each of the three sections in the westbound lanes was instrumented to record strains, displacements, and temperatures in the slab (Ozyildirim 2000). Two vibrating wire strain gauges were placed in the middle of each slab, one 38 mm (1.5 in.) from the top of the slab and one 38 mm (1.5 in.) from the bottom of the slab (Ozyildirim 2000). Two additional vibrating wire strain gauges were tied to two stainless steel stakes and driven into the base (Ozyildirim 2001). The gauges were placed 2 m (6.5 ft) from the outside edge to avoid the vibrator of the paver (Ozyildirim 2001).
Two linear variable differential transformers (LVDTs) were installed in each of the slag concrete pavement sections to measure vertical displacements due to curling (Ozyildirim 2001). One LVDT was placed at the center of the slab and the other 280 mm (11 in.) from the joint (Ozyildirim 2001).
Type T thermocouples were placed at each location in the slab where the vibrating gauges were placed. The thermocouples were placed at 6 mm (0.25 in.), 76 mm (3 in.), 140 mm (5.5 in.), 203 mm (8 in.), and 273 mm (10.75 in.) above the base (Ozyildirim 2001). In addition, the vibrating wire gauges included thermistors that provide temperatures at the each location (Ozyildirim 2001).
Finally, 10 consecutive joints in each section were instrumented to monitor transverse joint movements (Ozyildirim 2001). Gauges were placed on either side of the joints 1 week after paving (Ozyildirim 2001).
State Monitoring Activities
During and immediately after construction, VDOT conducted an evaluation of the fresh and hardened concrete properties of each pavement section. Table 51 summarizes some of the selected concrete properties obtained from the monitoring. Both the fresh concrete properties and the hardened concrete properties generally met design requirements, but there was a noticeable difference in the properties of the mixtures between the westbound and eastbound lanes. Generally speaking, the westbound lanes had lower strengths and higher air contents than the eastbound lanes.
Comparisons of the different mixes show that the slag mixes (sections 1 and 2) have higher strengths than the fly ash mixes. Interestingly, the section 2 mixes had higher strengths than the section 1 mixes, even though the section 1 mixes had a larger coarse aggregate size.
The chloride ion permeability test measures the electrical conductance of a sample, and VDOT specifies a maximum of 3500 coulombs (Ozyildirim 2001). All of the mixtures exhibit permeabilities much less than that value, with the fly ash mixtures the lowest of all of the mixtures. All of the sections exhibited similar shrinkage values, with the section 1 mixture (containing the largest maximum coarse aggregate size) exhibiting the least amount of shrinkage.
The acceptance criteria for freeze-thaw data shown in Table 51 are a weight loss of 7 percent or less and a durability factor of 60 or more (Ozyildirim 2001). All mixtures complied with these requirements except the fly ash mixtures exceeded the allowable weight loss. However, this is a severe test and the fly ash mixtures are expected to perform satisfactorily in the field provided that they have adequate strength and an adequate air void system (Ozyildirim 2001).
|CONCRETE PROPERTY||SPECIMEN SIZE, IN.||SECTION 1|
(2-IN. AGG W/SLAG)
(1-IN. AGG W/SLAG)
(1 IN. AGG W/FLY ASH)
|Fresh Concrete||Slump, in.||0.88||1.5||1.88||1.25||1.5||1.25|
|Concrete temperature, °F||86.5||67||85.5||68||82||67|
|Unit weight, lb/yd3||145.6||144.2||147||145.6||147.6||143.8|
|Hardened Concrete||28-day compressive strength, lbf/in2||6 x 12||5446||4530||5540||4625||4612||3920|
|28-day flexural strength, lbf/in2||6 x 6 x 20||704||670||783||685||-||-|
|Permeability, coulombs||4 x 4||1364||1774||1548||1672||680||1265|
|1-year shrinkage, %||6 x 6 x 200||0.041||0.052||0.044||0.059||-||-|
|Freeze-Thaw Data at 300 cycles (ASTM C 666, Procedure A, except air dried 1 week and 2% NaCl in test solution)||Weight loss, %||5.3||4||2.3||6||11.6||14.1|
Monitoring of the instrumented slabs was conducted during the first several weeks after construction, along with transverse joint movements. Generally, larger thermal gradients were observed for section 2, but all of the differences were really quite small (Ozyildirim 2001). Section 1 (larger aggregate) showed less curling than section 2, but again the differences were small (Ozyildirim 2001). Limited FWD testing showed nearly identical load transfer efficiencies of 85, 85, and 88 percent for section 1, 2, and 3, respectively (Ozyildirim 2001).
After 2 years and 6 months of service, respectively, both the westbound sections and the eastbound sections are in excellent condition, with no distress or scaling (Ozyildirim 2001). VDOT will continue monitoring the performance of these pavements and will produce a final report in 2004 (Ozyildirim 2000).
This project has illustrated that air-entrained paving concrete with satisfactory strength, low permeability, and volume stability can be prepared using concrete with Class F fly ash or slag, and with 25- and 50-mm (1- and 2-in.) maximum size aggregates (Ozyildirim 2000; Ozyildirim 2001). The larger maximum size aggregate is expected to provide better performance in the field, and it will be monitored over the next 5 years. Although the reduction in water and cement contents was minimal for the mix with the larger sized aggregate, the use of a more uniform combined grading is expected to reduce water and paste demands (Ozyildirim 2000; Ozyildirim 2001). The instrumentation did not provide any strong results regarding the relative performance of the different pavement sections (Ozyildirim 2000; Ozyildirim 2001).
No interim field testing results have been published, nor were they available for this update. However, an additional field evaluation will be conducted in the spring of 2004 that will include FWD and automated distress measurements. Results of these field reviews will be included in the final project report that is slated to be complete in August 2004.
Point of Contact
Virginia Transportation Research Council
530 Edgemont Road
Charlottesville, VA 22903
Ozyildirim, C. 2000. Evaluation of High-Performance Concrete Pavement in Newport News, VA. Draft Interim Report. Virginia Transportation Research Council, Charlottesville.
---. 2001. "Evaluation of High-Performance Concrete Pavement in Newport News, VA." Preprint Paper 01-3173. 80th Annual Meeting of the Transportation Research Board, Washington, DC.