Mary Vancura

Reappraisal of Recycled Concrete Aggregate as Coarse Aggregate in Concretes for Rigid Pavements

State departments of transportation began using recycled concrete aggregate (RCA) as aggregate in portland cement concrete pavement in the United States in the late 1970s. Although RCA is rarely used in current U.S. rigid pavement slabs, the impetus for its continued use remains the same: a lack of landfill space, a shortage of nearby quality natural aggregates, or both. However, as American pavement engineers and researchers place a greater emphasis on sustainable, reusable roadways, the status quo for RCA in American roadways should be reconsidered along with these new priorities. This study proposes to revisit the use of recycled concrete as aggregate in rigid pavement slabs by using overlooked research to address the concerns that prevented the wide-scale adoption of recycled concrete as an aggregate in pavement slabs by state departments of transportation. Experiences encountered in countries (mostly restricted to Europe) where the use of RCA in rigid pavement is more common are also described. New opportunities for the use of RCA as a structural component in pavement concretes are detailed.

Structural Analysis of Pervious Concrete Pavement

Pervious concrete pavement must perform as both a stormwater management tool and a pavement. While much research has focused on porosity and permeability of pervious concrete, few guidelines exist for structural analysis and design of such pavement. In this paper, an existing pervious concrete pavement was analyzed for stiffness and fatigue by means of Westergaards theory of a medium-thick plate on a Winkler foundation. The stiffness evaluation compared the responses of pervious and conventional concrete pavements to falling weight deflectometer stresses and to models created in ISLAB2005. Although pervious concrete had a lower modulus of elasticity than conventional concrete pavement, Wester-gaards model adequately described the behavior of pervious pavements. Additionally, a fatigue analysis of pervious concrete was completed through use of the StreetPave fatigue model.

Composite Pavement Systems Volume 1: HMA/PCC Composite Pavements

Composite pavements have proved in Europe and the United States to have long service life with excellent surface characteristics, structural capacity, and rapid renewal when needed. This project developed the guidance needed to design and construct new composite pavement systems. Volume 1 presents the state of the practice and guidelines for designing and constructing new hot-mix asphalt (HMA) concrete over a portland cement concrete (PCC) composite pavement that takes full advantage of using differing materials. Volume 2 provides guidance on the design and construction of two-layer, wet-on-wet PCC pavements where the upper layer is a thin high-quality layer (hard nonpolishing aggregate, higher cement content, higher quality binder) and excellent surface characteristics with the lower layer containing a higher percentage of local aggregates and recycled materials. Both volumes detail performance data on existing composite pavement systems and provide step-by-step guidance on the design of composite pavements using mechanistic-empirical design methods for both types of new composite pavements.

Concrete Pavement Thickness Variation Assessment with Cores and Nondestructive Testing Measurements

Concrete pavement thickness data were collected from sections of two concrete pavements with a nondestructive testing (NDT) device and by measuring concrete core thickness. The NDT device allowed thickness measurements every 15 ft compared with 1,000 ft for each core. Comparison of the core and NDT data showed that core thickness data do not capture the extreme peaks and valleys of pavement thickness variation. Further analysis of the core and NDT thickness data with the Minnesota Department of Transportations concrete pavement thickness specifications highlighted that contractor pay deductions based on thickness deficiencies were not realized. Autocorrelation analysis of the data showed that concrete pavement thickness variation is not random but is correlated to thicknesses of lag between 30 and 270 ft. This correlation lag is a starting point for answering the question, how often must a thickness measurement be taken to accurately characterize the thickness variation of a concrete pavement?

Freeze–Thaw Durability and Salt Scaling Resistance Assessment of Portland Cement Concrete Composite Pavement

The SHRP 2 R21 project on composite pavement investigated the durability of various mixtures of portland cement concrete (PCC) used in the construction of a two-layer composite PCC pavement. Project consultants in Europe, where composite PCC over PCC pavement was more common than in the United States, advised the R21 research team to consider using the CIF (capillary suction, internal damage, and freeze–thaw) standard of the International Union of Laboratories and Experts in Construction Materials, Systems, and Structures (RILEM), Paris, rather than the familiar ASTM standards. As a result, the R21 project adopted the RILEM CIF standard to evaluate the freeze–thaw durability and salt scaling resistance of concretes. The research also explored a modified RILEM CIF test (using pure water instead of a sodium chloride solution in scaling tests) alongside the standard RILEM CIF tests. The paper describes this experience to expose other institutions and agencies in the United States to the RILEM standards for the freeze–thaw durability and salt scaling resistance testing of concretes.