A cold in-place recycling (CIR) layer is typically overlaid by hot-mix asphalt (HMA) to protect it from water ingress and traffic load. Most public agencies have different curing requirements that specify the number of curing days or the maximum moisture content for the CIR layer before placing the HMA overlay. However, these criteria are not well-founded on sound engineering principles and are often challenged by contractors, especially in inclement weather conditions. This study was performed to explore technically sound ways to identify the minimum in-place CIR properties necessary to permit the placement of an HMA overlay. The primary objective of this research was to determine how curing time and moisture content affect the development of indirect tensile strength, dynamic modulus, and flow number of CIR mixtures composed of foamed asphalt (CIR-foam) or emulsified asphalt (CIR-emulsion). On the basis of the limited test results, the indirect tensile strength of CIR specimens did not increase during a...

The need for a Cold In-place Recycling using emulsified asphalt (CIR-emulsion) mixture with specific engineering properties calls for the use of a mix design and, recently, a new mix design procedure was developed for CIR-emulsion. As a part of CIR-emulsion mix design process, dynamic modulus, flow number, flow time and raveling tests were conducted to evaluate short- and long-term performance of CIR-emulsion mixtures at various testing temperatures and loading conditions. Based on the test results, the optimum emulsified asphalt content for CIR was determined. Dynamic modulus, flow number and flow time of CIR-emulsion mixtures using CSS-1h (cationic slow setting emulsion) were higher than those of HFMS-2P (high-float medium-setting emulsion modified with a polymer). Flow number and flow time of CIR-emulsion mixtures using RAP materials with softer residual asphalt was higher than those of CIR-emulsion mixtures using RAP materials with harder residual asphalt. The dynamic modulus, flow number and flow time were affected by both emulsion type and residual asphalt stiffness of RAP materials. Raveling loss of CIR-emulsion mixtures with 1.5% emulsified asphalt was significantly less than those with 0.5% and 1.0%.

In the summer of 2005, exclusive bus lanes were constructed in the median of busy streets in Seoul, South Korea, as color polymer concrete pavements with a transparent synthetic resin binder and a red pigment. However, early distresses, such as shoving, potholes, stripping, and rutting have occurred from these color polymer concrete pavements. Potential causes for early distresses from color polymer concrete pavements were investigated: inadequate quality of color polymer concrete, inadequate quality control during construction, and insufficient subgrade support. Historically, polymer concrete mixtures have been designed and evaluated by using predominantly hydraulic cement concrete technology because polymer concretes are used in concrete structures. This paper adopted asphalt mix technology to evaluate polymer concrete for use in a roadway overlay. Laboratory evaluation was performed on color polymer concretes by conducting the following tests: Marshall stability test, indirect tensile strength test, and modified Lottman moisture sensitivity test. These test results of color polymer concrete mixes were significantly more positive than those of typical asphalt mixes, and the mixes met the minimum requirements. On the basis of test results, it can be concluded that the color polymer concrete with a synthetic resin is stronger and less susceptible to moisture than are typical asphalt mixtures.

Cold in-place recycling (CIR) is one of the most effective methods to rehabilitate asphalt pavements. In fact, most CIR roads have performed well at low cost in Iowa since the first CIR road was constructed in 1986. However, some CIR roads have reached failures earlier than their expected design lives because there is no design standard for designing CIR roads with a limited amount of past performance information. Some of the most prominent problems seemed to have come from selecting CIR in areas where there are poor subgrades. Therefore, it is critical to collect CIR performance data along with falling weight deflectometer (FWD) data in order to develop performance models. The main purpose of this paper is to document that effort. The performance models were developed on the basis of historical data collected from CIR roads in Iowa. First, an inventory of CIR roads was created which includes construction information, subgrade and base characteristics, and traffic levels. In consideration of pavement age,...

The temperature of the existing asphalt pavement, which is to be recycled, would change from a low morning temperature of the spring/fall season to a high afternoon temperature of summer. However, most agencies do not consider the temperature of the reclaimed asphalt pavement (RAP) materials when they design cold in-place recycling using foamed asphalt (CIR-foam) mixtures. The main objective of this research is to determine whether the temperature of RAP materials would affect the optimum foamed asphalt content (FAC), which would produce the highest wet indirect tensile strength. On the basis of the limited laboratory test results, the temperature of RAP materials would have a significant impact on the wet indirect tensile strength of CIR-foam mixtures. This research supports the field reduction of FAC up to 0.5% when the RAP temperature reaches up to 55°C. The change in the wet indirect tensile strength caused by RAP temperatures was not sufficient to warrant a design method change. Also, improved compac...

The application of Ultra-High-Performance Concrete (UHPC) materials in rehabilitating bridges and constructing primary bridge components is increasing rapidly across the world because of their superior strength and durability characteristics when compared to regular concretes. However, there have been few new bridges constructed using UHPC materials with regular formworks, ready-mix trucks, and construction equipment. This paper presents a comprehensive report encompassing the design, construction, and performance monitoring of a new bridge constructed in Iowa using a unique UHPC technology that includes steel fibers of two different lengths embedded in the concrete. By using optimized lengths of steel fibers, both the tensile strength and the toughness were increased. The UHPC material was produced with local cement and aggregates in the US using typical ready-mix concrete equipment. This paper discusses the experience gained from the design and construction process including mix design, batching, delivery of steel fibers to the ready-mix concrete batch unit, and post-tensioning of precast slabs at the jobsite. For four years after construction, the joints of the bridge decks were monitored using strain sensors mounted on both sides of the deck joints. The strain values were quite similar between the two sides of each joint, indicating a good load transfer between precast bridge girders. A bridge was successfully constructed using a unique UHPC technology incorporating two different lengths of steel fibers and utilizing local cement and aggregates and a ready-mix truck, and has been performing satisfactorily with a good load transfer across post-tensioned precast girder joints.