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Saw-Cutting Guidelines for Concrete Pavements

Kambiz RaoufiTony TheirW. Jason WeissJan OlekTommy E. Nantung

出版	Purdue University Press, 2009-01-15
主題	Transportation / General
ISBN	16226011499781622601141
URL	http://books.google.com.hk/books?id=OTtVLwEACAAJ&hl=&source=gbs_api

註釋Joints are placed in portland cement concrete pavements (PCCP) to control random cracking. These joints provide a weakened plane that enables a crack to form in a controlled manner, relieving residual stresses that develop when thermal, hygral, or hydration movements are resisted by subgrade and adjoining pavement. While the concept of creating a weakened plane through saw-cutting is straightforward, determining the time and depth of the saw-cut has proven to be complicated. The goal of this project was to reduce the risk for joint raveling and random cracking. Specifically, this project has focused on: developing a procedure for determining the appropriate saw-cutting time window for typical pavements constructed in the state of Indiana, determining the depth of the saw-cut that minimizes the risk of micro-cracking and random crack development, and developing tools and training materials for paving contractors and state inspectors that aid in implementing the findings of this study in concrete pavements. Toward this end the project was divided into three phases. The first phase of the project consisted of shadowing five pavement projects in Indiana. From these field investigations practical information was gained which was useful in developing the laboratory testing program. The second phase of this work involved in the development of the laboratory testing program. This phase in large part was involved in the development and commissioning of a new tensile wedge testing approach to determine the early age properties of concrete. Finally, finite element simulations were performed to simulate the early-age behavior of pavements constructed under a variety of saw-cutting sequences, environmental conditions. A strength reduction factor was computed based on the depth of the saw-cut. It was shown that the time of the saw-cut introduction needs to occur before the residual stress divided by the product of the strength reduction factor and tensile strength was equal to unity. It was also shown that shallower saw-cut depths were more prone to construction and material property variability. Recommendations are made to assist contractors in determining when saw-cuts are placed that can greatly improve field operations.