Saw-Cutting Guidelines for Concrete Pavements: Examining the Requirements for Time and Depth of Saw-Cutting

Abstract

Prepared in cooperation with the Indiana Department of Transportation and Federal Highway Administration. AbstractJoints 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. Joints can be induced in early age concrete using several methods which include the use of hand-tools, preformed strips, and saw-cutting. While these three approaches are all valid, practical considerations for slip-form paving operations result in the nearly exclusive use of saw-cutting as the method of choice for inducing joints. Generally it is thought that three main methods of saw-cutting joints exist including conventional wetcut (water-injection) saws, conventional dry-cut saws, and the more recently developed early-entry dry-cut saws.While the concept of creating a weakened plane by saw-cutting may appear straightforward, determining the time and depth of the saw-cut has p...

Synthesis: Accelerating Implementation of Research Findings to Reduce Potential Concrete Pavement Joint Deterioration

“…Pavements: Examining the Requirements for Time and Depth of Saw-Cutting (Raoufi, Their, Weiss, Olek, & Nantung, 2009)…”

“…It has historically been reported that saw-cutting needs to be performed before the stress reaches the tensile strength of the pavement to reduce the potential for random cracking; however this is un-conservative and a stress reduction factor is needed to prevent premature damage. Raoufi et al (2009) related the stress reduction factor to the depth of the saw-cut being used as shown in Figure 4.2 to have stable cracking after saw-cutting. This indicates that deeper saw cuts require a greater reduction in the stress to strength ratio used for saw-cutting.…”

Durability of Saw-Cut Joints in Plain Cement Concrete Pavements

“…This initial saw-cut is used to control random cracking. A previous INDOT study examined the time that this saw-cut should be placed (1). In that study computer simulations were performed to indicate how the time of saw-cutting varied depending on the mixture proportions, the saw-cut geometry, and the environmental conditions.…”

Using accelerated pavement testing to examine traffic opening criteria for concrete pavements

“…mixtures with less cement or mixtures when a large volume of cement is replaced with supplementary materials [14,15]. Further, pavements that have higher early strengths might be less prone to crack as designed at saw-cuts and longitudinal joints [16]. This may lead to random cracking [17][18][19] or joints that do not crack [20] and hold moisture resulting in potential durability issues affecting the life span of the material [21].…”