High Performance Concrete Pavements
CHAPTER 19. MARYLAND 1 (US 50, Salisbury Bypass)
Maryland's TE-30 project was constructed in 2001. It is located on the Salisbury Bypass on US 50, in the southeastern part of the State (see Figure 49). The project is being undertaken jointly by the Maryland State Highway Administration (MSHA), the University of Maryland, and the FHWA.
Figure 49. Location of MD 1 project.
This project is designed to research the benefits of using fiber-reinforced concrete (FRC) and low-shrinkage concrete in Maryland paving operations (Goulias and Schwartz 1999). The researchers believe that the use of these materials may lead to increases in flexural fatigue resistance and reductions in crack development and slab warping effects (Goulias and Schwartz 1999). The objectives of the study will be completed in three phases:
- Phase I - Laboratory examination of the design and performance of fiber-reinforced concrete and low-shrinkage concrete for Maryland conditions.
- Phase II - Actual construction of the test sections.
- Phase III - Short- and long-term monitoring of the test sections, and quantification of benefits for possible incorporation into PCC pavement design.
Project Design and Layout
Laboratory tests were conducted to evaluate the properties of fiber-reinforced and low-shrinkage concrete mixtures. Maryland's standard concrete mixture for highway pavements, MD Mix 7, was used as the control mixture. The low shrinkage mixtures were developed by using the MD #375 aggregate in place of the MD #57 aggregate, or by modifying the w/c ratio. The fiber-reinforced mixtures used the mix design of the control mixture by adding different fiber contents (0.1, 0.2, 0.3, and 0.4 percent). Seven mixtures were evaluated and their characteristics are summarized in Table 23 (Goulias and Schwartz 2003). The characteristics of the fiber used in this study are shown in Table 24 (Goulias and Schwartz 2003). The mixture properties evaluated in the lab included compressive strength, unrestrained shrinkage of hardened concrete, restrained shrinkage of plastic concrete, flexural strength and toughness, fatigue endurance, elastic modulus, temperature, slump, and air content.
Table 23. Mixture Properties of Concrete Used on MD 1
|COMPONENT||MIX A||MIX B||MIX C||MIX D||MIX E||MIX F||MIX G|
|Aggregate type||#57||#57||#57||#57||#57||#375 LS||#57 LS|
|Air content* (%)||6.6%||4.6%||6.6%||7.0%||5.8%||5.0%||6.0%|
|Air entrainment||1.7 oz/|
|Water reducer||(M)5 oz/|
|Note: (M) = middle range water reducing admixture; (H) = high range water reducing admixture; LS = low shrinkage;|
* Target air content 6.5%
Table 24. Fiber Characteristics for MD 2
|ASPECT RATIO (L/D)||YIELD STRENGTH|
Three different concrete pavement test sections were constructed by MSHA in 2001 (Goulias and Schwartz 2003):
- Control section using MD Mix 7.
- Fiber-reinforced concrete section containing 0.1 percent polypropylene fiber.
- Low-shrinkage concrete section using MD #375 aggregate.
The pavement sections were extensively instrumented to provide feedback on the structural responses of the different designs.
State Monitoring Activities
A variety of information has been collected on the three experimental sections (Goulias and Schwartz 2003). Two MSHA trucks (with 18 kip and 32 kip axles) were used for field load testing. Condition surveys/profile measurements were conducted using a dipstick device. Nondestructive testing was also conducted using an ultrasound device.
Analyses were carried out utilizing both the lab results and field instrumentation data to evaluate the response and behavior of the control, fiber-reinforced and low shrinkage concrete pavement sections and mixtures. The following conclusions have been reached (Goulias and Schwartz 2003):
- The lab results indicated that fibers reduce the workability of concrete. However, the use of admixtures permits acceptable levels of workability.
- The flexural strength of concrete for fiber contents > 0.1 percent was higher than that of the control concrete mixture. The toughness of concrete increased with increasing fiber content.
- Shrinkage testing indicated that there were small differences in unrestrained shrinkage for the control and the two low shrinkage mixtures. However, fiber-reinforced concrete mixtures exhibited higher levels of shrinkage.
- The fatigue analysis indicated that the addition of polypropylene fibers resulted in higher fatigue strengths. The fatigue strength of FRC increased with decreasing fiber content until 0.3 percent. The endurance limit expressed as a percentage of the modulus of rupture of the mixture showed an increase with decreasing fiber content until 0.3 percent. Overall, the best fatigue performance was obtained for mixes containing 0.1 percent fiber.
- The field data indicated that overall the sections with the 0.1 percent fiber-reinforced concrete mixture had lower deflections than the control mix and the low shrinkage mixture. Analytical evaluations indicated that the best estimates of the modulus of subgrade reaction (k) and elastic modulus of concrete (Ec) are k of 350 lbf/in2/in. and 5,000,000 lbf/in2, respectively.
Points of Contact
University of Maryland
Department of Civil and
0147A Engineering Lab Building
College Park, MD 20742
University of Maryland
Department of Civil and
College Park, MD 20742-0001
Goulias, D., and C. Schwartz. 1999. High Performance Portland Cement Concrete Pavement. Project Work Plan. University of Maryland, Department of Civil and Environmental Engineering, College Park.
---. 2003. High Performance Portland Cement Concrete Pavement. Final Research Report. University of Maryland, Department of Civil and Environmental Engineering, College Park.