Prediction Method of Dowel-Looseness in Jointed Plain Concrete Pavement Based on Time Difference of FWD Sensors
Jian Chen, Harbin Institute of TechnologyShow Abstract
Xinkai Li, Harbin Institute of Technology
Decheng Feng, Harbin Institute of Technology
To ensure long term performance of Jointed-Plain Concrete Pavement (JPCP) subjected to heavy traffic, dowel bars are necessary for JPCP’s joint to keep high load transfer efficiency (LTE). Therefore, in this paper gap element in ABAQUS program was used to simulate the clearance of dowel-concrete. Based on numerical results the effects of dowel-concrete looseness on LTE behavior were analyzed and discussed. The results indicate that if there is no dowel looseness, LTE will remain constantly on a high level. As the looseness increase, it must be considered in the deflection ratio of LTE. When the loose-ness is larger than slab deflection induced by FWD, although measured LTE value exist, no load can be transferred through dowel in fact. Based on the numerical analysis the dowel looseness evaluation method based on FWD history data was proposed. The pro-posed method was validated with the measured LTE data of joints with the FWD.
Polymer-Modified Cement Mortar in Crack Repairing of Concrete Pavements
Yinchuan Guo, Louisiana Transportation Research Center (LTRC)Show Abstract
Xiaohui Sun, LTRC
Aiqin Shen, Chang'an University
Zhong Wu, Louisiana Transportation Research Center (LTRC)
Concrete pavement cracking becomes a serious problem on southern China freeways under a high temperature and humid climate environment. Non-modified cementitious mortars and organic crack-repair materials such as epoxy resins are commonly used in routine practice. To explore potentially more durable and cost-effective alternatives for repairing cracked concrete pavements under a high temperature and humid pavement condition, four polymer modified cementitious crack-repair mortar materials were investigated in the study. The selected polymer modifiers were first mixed with an ordinary Portland cement and a superfine Portland cement into cementitious mortars at various polymer-cement ratios. Then a suite of mechanical, durability and microstructure tests were performed. The results showed that the modified cementitious mortars have good workability, high bond strengths to aged concrete surfaces, low shrinkage and cost-effectiveness as compared to the routinely-used crack-repair materials. In summary, one polymer modified superfine cement mortar is suitable for repairing of fine concrete cracks and another modified ordinary cement mortar is appropriate for repairing wider cracks under a high-temperature and humid pavement condition.
New Quality Assurance (Acceptance/QC) Tests for Building a Quality Concrete Pavement
Jagan Gudimettla, ATI Inc.Show Abstract
Michael Praul, Federal Highway Administration (FHWA)
James Grove, ATI Inc.
Concrete materials and paving technologies have evolved considerably over the last century. However, testing technologies for concrete during construction have not kept pace. Some of the tests that are routinely used are not necessarily performance indicators and some are not real time. This paper brings together seven new technologies that are simple, real-time, field implementable, economical and in many cases are performance indicators. While some of these technologies could be used during the mixture design stage, other could be used during construction and some for both purposes. These technologies can be used to supplement or, in some cases, replace the traditional tests for paving concrete.
The paper focuses on three items: 1) Traditional tests for paving concrete, 2) New tests/technologies that could be used to supplement or replace the traditional tests, and 3) Suggested future specifications. Data collected by the FHWA Mobile Concrete Laboratory from its technology implementation efforts are presented to support the narrative on the benefits of these new technologies.
Field and Laboratory Properties of Roller-Compacted Concrete Pavements
Jeff LaHucik, Tigerbrain Engineering, Inc.Show Abstract
Jeffery Roesler, University of Illinois at Urbana-Champaign
Roller-compacted concrete (RCC) pavements present three primary challenges relative to conventional concrete pavement: mixture design, structural design details, and construction process and verification. An investigation was initiated to reconcile the discrepancy between the field and laboratory properties of RCC pavements because of differences in laboratory mixture design procedures and field construction processes. Four RCC pavement projects in Illinois were selected for field coring along with sampling of RCC constituent materials for replication of the laboratory mixture design. Density measurements of field cores indicated that density decreased with depth into the pavement structure and the relative density at paving-lane joints could be as low as 80%. Statistical differences in compressive strength and fracture properties between field and laboratory samples were observed and result from differences in density. th. The reduction in field RCC strength and fracture properties relative to the values obtained in the lab will result in decreased slab flexural capacity and field performance. Application of the gyratory compactor demonstrated that it can be used repeatedly to compact most RCC mixtures to similar target densities as the modified Proctor method and field extracted cores. The gap between field and laboratory properties of RCC can be reduced by application of high-density pavers, improving mixture design procedure with the gyratory compaction method, stiffer and/or thicker foundation layer beneath the RCC, and/or reduced RCC lift thicknesses to achieve specified density.
Effect of Early Age Loading on Concrete Ultimate Strength
Katelyn Freeseman, Iowa State UniversityShow Abstract
Kyle Hoegh, Minnesota Department of Transportation
Bernard Izevbekhai, Minnesota Department of Transportation
Lev Khazanovich, University of Pittsburgh
Transportation agencies face increased pressures from roadway users to minimize road closures due to rehabilitation and reconstruction efforts. That requires the opening of newly constructed or rehabilitated concrete pavements at earlier ages. This paper presents an investigation of the effect of early age loading on concrete pavements via the experimental loading of concrete flexure beams in the laboratory, supplemented by nondestructive testing efforts. Since the 28-day concrete strength is an important input parameter in the MEPDG for the prediction of long-term pavement performance, a laboratory study was performed to evaluate the effect of early age loading on the 28-day strength. Several rounds of tests were performed, allowing for a variety of variables to be considered, including: loading duration, loading type, curing condition, and the age at which the beams were loaded. The results of this testing and its implication on early opening decisions are presented.
Dowel Alignment, Effective Dowel Diameter, and Joint Score of LTPP Sections
Laxmikanth Premkumar, Applied Research Associates, Inc. (ARA)Show Abstract
Shreenath Rao, Applied Research Associates, Inc. (ARA)
MIT Scan technology is a non-destructive method to measure the alignment of dowel bars placed in transverse joints of jointed plain concrete pavements (JPCP). Misalignment of dowel bars can potentially lead to reduced load transfer efficiency, cracking, spalling, and faulting. Several agencies across the U.S. have adopted specifications for dowel bar misalignment, many using the joint score methodology. However, this methodology has never been validated using field studies. National Cooperative Highway Research Program (NCHRP) Report 637 provides a methodology to determine an effective dowel diameter based on dowel misalignment; however, this was based on limited field studies. The relationship between dowel bar misalignment and long term performance of JPCP is still unclear, but imperative to developing guidelines for construction specifications.
This paper presents results of an ongoing Federal Highway Administration (FHWA) project to collect MIT Scan data on Long Term Pavement Performance (LTPP) sections, and conduct data analysis to evaluate the effects of dowel misalignment on JPCP performance. The results of the dowel bar performance data from LTTP General Pavement Studies (GPS-3), and Specific Pavement Studies (SPS-2) sections is presented in this study. Our preliminary analysis did not indicate any definitive relationship between dowel bar misalignment and field performance. Further analysis of the MIT Scan data and use of statistical methods will provide a better insight on the effect of dowel bar misalignment, and use of joint score and effective dowel diameter method to assess the long term performance of JPCP.
Virginia’s Experience in Developing a Specification for Roller-Compacted Concrete Pavement
M. Shabbir Hossain, Virginia Department of TransportationShow Abstract
H. Celik Ozyildirim, Virginia Department of Transportation
Roller-compacted concrete (RCC) is a stiff hydraulic cement concrete mixture that, unlike conventional concrete, is compacted with a roller rather than by mechanical internal and external vibration. It is a mixture of aggregate, cementitious materials, and water and exhibits zero slump. RCC has the same basic ingredients as conventional concrete and has similar hardened concrete properties. For pavements, RCC is typically placed with asphalt paving equipment in 6 to 8-inch thicknesses. RCC is desirable because of its low-cost, rapid construction, satisfactory early and ultimate strengths, and durable performance. The Virginia Department of Transportation (VDOT) has been investigating RCC for inclusion as an option in its pavement program. This investigation included a literature survey and laboratory study that led to the development of a special provision for the use of RCC in pavements. Subsequently, the special provision was implemented in two field projects.
The initial performance of both field projects was satisfactory. Thus, the special provision for use of RCC developed in this study was workable and it is planned to be incorporated as a standard provision in VDOT’sRoad and Bridge Specifications with minor modifications. This paper summarizes the research that led to the development of VDOT’s RCC specification.