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Impact of Low Shrinkage Mixes on Late-Age Random Cracking in Pavements with Use of Early Entry Sawing

项目名称：	Impact of Low Shrinkage Mixes on Late-Age Random Cracking in Pavements with Use of Early Entry Sawing
摘要：	Random cracking in concrete pavement is primarily controlled by two important factors: (a) concrete shrinkage behavior and (b) restraint condition. Saw cutting is the most effective way to reduce the random cracking of concrete because the saw cuts or joints release the restraint and allow concrete segments to deform more freely, thus lowering the level of stresses built in the concrete. Depending upon the sawing time, space, and depth, sawing operations may or may not reduce or eliminate the random cracking in concrete pavement. The goal of the proposed study is to investigate whether or not there is an increased risk of delayed random cracking in early entry sawed pavements. Since cracking is related to the stress development in concrete, the specific objective of this study is to examine the levels of stresses developed at early entry sawed joints of pavements in comparison to conventional depth joints. The results of the study will therefore help in assessing the risk of late age random cracking in early entry sawed pavements. Concrete research and practice until now has assumed that the early entry sawing joints should crack. No study has addressed whether or not delayed random cracking occurs in the pavements if few or no cracks form at the early entry sawing joints several months after paving. A field pavement project will be selected, and a side-by-side comparison of two different concrete sawing methods, early entry sawing and conventional sawing, will be performed. Strain gauges will be installed across the joints and the movement of concrete across the joints will be monitored along with the timing of the cracking. The results from both the early entry and conventional sawed pavement segments will be compared and used for assessing the risk of random cracking in the pavement. The proposed study will include five major tasks: Strain Gauge Selection, Field Project Preparation, Field Testing (Strain Gauge Installation and Data Collection), Data Analysis, and completion of a final report. The results of the present study can be used by the Iowa DOT and the paving industry to identify potential late-age random cracking problems (if any) in the pavement constructed with the early entry sawing operation. The results can also provide the Iowa DOT and paving contractors with insight into any modifications of the current early entry operation, such as a change of sawing depth and joint spacing, for low shrinkage concrete mix pavements.
状态：	Completed
资金：	40,000
资助组织：	Iowa Department of Transportation
项目负责人：	Dunn, Mark
执行机构：	Iowa State University, Ames
开始时间：	20080201
预计完成日期：	20090228
主题领域：	Highways；Maintenance and Preservation；Pavements；Research