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Many cities in Iowa have retained the original brick street surfaces in downtown areas and in older residential areas as the base for modern driving surfaces. The original brick surfaces were not built to handle current and future traffic loadings. In recent years, these surfaces have tended to shift and become uneven, creating problems with safety. Asphaltic concrete overlays have been the typical rehabilitation technique in these situations. This has proven to be successful rehabilitation technique in some cases; in other cases, the combination of movement of the brick and flexibility of the asphalt has proven to accentuate the original problems. Most of the existing literature on rehabilitation of brick streets shows the use of asphaltic concrete. Other rehabilitation methods include reconstruction of the brick surface and strengthening of the surface by placing asphaltic concrete or portland cement concrete, along with sand, underneath the brick layers. To date, little if anything has been done in the area of using portland cement concrete as an overlay of the brick surfaces. This final report documents the planning, construction, and performance of unbonded ultrathin whitetopping rehabilitation of a brick street in Oskaloosa, Iowa, in 2001. It also reports on a similar project in Des Moines that was constructed two years later in 2003.
In Phase I, the research team contacted each of 16 participating states to gather information about concrete and concrete material tests. A preliminary suite of tests to ensure long-term pavement performance was developed. The tests were selected to provide useful and easy-to-interpret results that can be performed reasonably and routinely in terms of time, expertise, training, and cost. The tests examine concrete pavement properties in five focal areas critical to the long life and durability of concrete pavements: (1) workability, (2) strength development, (3) air system, (4) permeability, and (5) shrinkage. The tests were relevant at three stages in the concrete paving process: mix design, preconstruction verification, and construction quality control. In Phase II, the research team conducted field testing in each participating state to evaluate the preliminary suite of tests and demonstrate the testing technologies and procedures using local materials.
Ultra-Thin Whitetopping (UTW) is a pavement rehabilitation technique that involves the placement of a thin Portland Cement Concrete (PCC) overlay, 2 inches (50 mm) to 4 inches (100 mm) thick, over a distressed Hot Mix Asphalt (HMA) pavement. Typically, the HMA pavement is milled and cleaned which helps to create a bond between the existing HMA pavement and the PCC overlay. The bond between the two layers promotes composite action of the pavement section and as a result has a direct impact on the performance of the UTW Pavement. This composite action allows for the reduced thickness in the UTW layer. Additionally, a short joint spacing is typically used, which reduces the UTW flexural and curling stresses. In this study three different test areas were constructed in the INDOT/Purdue University Accelerated Pavement Testing facility. Each test area had different lanes that varied by concrete mix design, bonding preparation, and pavement crosssection. These sections were subjected to 300,000 to 560,000 load applications. An additional test area was constructed outside the facility to evaluate pavement thicknesses and environmental effects. The project resulted in a modified UTW design methodology that takes into account the stiffness of all underlying pavement layers. Additionally, the project provides insight into the effects of pavement section, UTW mix design, mechanical loading, bond conditions, and environmental loading on the performance of UTW.
"The objective of this report is to document various changes in specifications, pavement design and equipment for PCC paving from the early 1900s to present. This includes changes that were made to the specification book and supplemental specifications"--Technical report title page.