Guidelines for repairing of concrete pavement construction. Figure 1 typical examples of lane separation and ruptured tie bar. Kansas dot, concrete pavement details, crossstitching of joints and cracks. The second, slotstitching, uses deformed tie bars grouted into slots cut across a joint or crack. This study evaluated the longitudinal joint tie bar system currently used by cdot, examining the criteria for proper use of tie bars and determining the maximum number of lanes that can be tied together without negatively impacting the concrete pavement structure.
Control joint a left with lowseverity crack above a tie bar and test joint b right. As it can be observed from figure2, jointed unreinforced concrete pavement is composed of batch work of concrete slab layers, which are small square units, connected by employing tie bars and dowels or joints that is provided to prevent cracks. New transverse cracks occur rough ly at the midpoint between two previously formed cracks, where the maximum concrete stress occurs. Each tech nique is beneficial for certain circumstances. The tie bars used in crossstitching prevent the crack from vertical and horizontal movement or widening. Crossstitching uses deformed tie bars epoxied or grouted into holes drilled at an angle through a crack. Grade 60 or above deformed steel bars that meet the requirements of item 440 are used.
Further verification is necessary for crack control in plain concrete on stabilized subbases that induce more restraint. In ubar stitching, slots are cut using a slot cutting machine and concrete is broken and removed by pneumatic hammer. Jagnnath mallela, alex gotlif, paul littleton, suri sadasivam, michael darter, keywords. Crossstitching uses deformed tiebars epoxied or grouted into holes drilled at an angle through a crack. They are not designed to work as a load transfer device. If this type of reinforcing steel is used in concrete pavement, care must be taken that these bars are not diverted to other uses on the project. Many miles of continuously reinforced concrete pavement crcp in texas. In crcp, the continuous reinforcement results in internal restraint and produces transverse cracks that are closely spaced with small crack widths that help to maximize the aggregate. Dec 08, 2015 cross stitch is a process of drilling alternately inclined holes into concrete techniques outlined in the concrete pavement restoration guidelines in aci concrete repair.
For continuously reinforced concrete pavements, spot check. Stitching concrete pavement cracks and joints there are two stitching methods used to repair and strengthen cracks or joints in concrete pavement. These distress in pavements and their details are discussed. Types of distresses in concrete pavements and their causes. The unit weight of concrete is 2400, the coefficient of friction is 1. They are also used in plain jointed concrete pavement to connect two lanes. An approved chemical anchoring system, generally epoxy, is used to secure the tie bar in the hole. Concrete pavement construction basics placing dowel baskets dowel bars transfer heavy loads across joints in the pavement, preventing faulting at the joint that can lead to pavement damage. Crossstitching is a repair technique for longitudinal cracks which are in reasonably good condition. Holes are drilled into the existing pavement for the epoxy coated tie bars. Dec 06, 2012 this project addresses a pavement performance issue at this intersection, as well as highlighting the innovative use of fast track concrete repair construction methods. Construct hydraulic cement concrete pavement with or without curbs on the concrete pavement. Bars and tie bars for fulldepth concrete pavement repairs vi see remark must be a qualified product 603.
Note that the goal is to place the tie bars at middepth of the slab. There are two stitching methods used to repair and strengthen cracks or joints in concrete pavement. These distresses may appear in the form of uncontrolled cracking, plastic shrinkage cracking, settlement cracking mainly over pipe culverts and near slab culverts, popouts, crack over dowel bars etc. Types of concrete pavements construction details and. The purpose of crossstitching is to maintain aggregate interlock and provide added reinforcement and strength. Deformed tie bars are grouted into holes drilled at an angle to the pavement surface, used on lowseverity longitudinal cracks and unreinforced joints, reduces slab. Difference between dowel bars and tie bars we civil. Longitudinal cracking in widened portland cement concrete. Other specialized repairs in clude continually reinforced concrete pavement crcp, retrofitting load transfer with dowel bars and texture planing concrete surfaces to restore ride diamond grinding.
Early cracking of concrete pavement causes and repairs. Figure 105 shows the drilling operation using a single drill. This technique knits the cracked portions of the slab together and reduces the chances of crack to grow further. Although tied curb and gutter sections usually contain tie bars, the tie bars are too small in either size or number to transfer load stresses effectively by themselves. Concrete pavements safer, smoother, and sustainable 3 most transverse cracks form at very early ages before a pavement is open to trafic, and. Ensure the contractor is properly identifying and constructing contraction joints relative to pavement references and bar centroids in conformance with the contract requirements and the contractors quality control plan. An approach to detect misaligned dowel bars in concrete pavements using gpr is. Zollinger verified the effectiveness of earlyage sawing methods with field experience on 330 mm in. Crossstitching cracks american concrete pavement association. Division 5 surface treatments and pavements 501 cement concrete pavement rehabilitation 501.
Crossstitching is a repair technique mostly used for longitudinal cracks which are in reasonably good condition. Using slot stitching for repair of longitundal joint separation on. Pavement with long transverse joint spacing may crack due to tensile stresses from temperature curling. Crossstitching uses deformed tie bars drilled across the crack at an angle of 3040 degrees. When new pavement is to be tied to an existing pavement, tie bars are used to tie the pavements together. How to reinforce concrete slab on ground to control cracking. Tie bars are typically used at longitudinal joints. Design the length and spacing of tie bars given that the pavement thickness is 20cm and width of the road is 7m with one longitudinal joint. These cyclic changes allow free water and noncompressible debris into the joint, increasing the stress on the tie bar with every significant cycle. Pavement joints, dowels, and tie bars benefits of dowel and tie bars dowel and tie bar design construction summary presentation outline 2nd international conference on best november 2, 2011 practices for concrete pavements. Chairs should have sand or base plates and bars should have at least a 4inch square base to ensure they dont sink into the.
This study investigated the occurrence of longitudinal cracking in doweled jointed plain concrete pavements jpcp to determine the maximum allowable pavement width as a. Ncludes stitching concrete pavement cracks and joints. This project addresses a pavement performance issue at this intersection, as well as highlighting the innovative use of fast track concrete repair construction methods. Crossstitching and slotstitching stitching concrete pavement cracks and joints. Jan 16, 2020 multiple piece tie bars are couplers used only in longitudinal construction joints and repair areas of concrete paving. An improved mechanisticempirical tie bar design method was developed. Due to the nature of concrete, slabs longer than about 6. Construction joints usually exist between tied curb and gutter and the concrete pavement. Pavement distresses including slab cracking, spalling and joint faulting. Tie bars used for holding faces of rigid slabs in contact to keep aggregate interlock. Approach to identify misaligned dowel and tie bars in concrete. August 2016 continuously reinforced concrete pavement manual. Crossstitching uses deformed tie bars drilled across a crack at angles of 3045 degrees. Evaluation of premature pccp longitudinal cracking in colorado.
Methodologies for repair of cracks in pqc in concrete. Furnish dowel bars and tie bars as the plans show and conforming to 505. Any negligence during the construction process may lead to premature distresses in concrete pavement slabs. Use for grouting to existing concrete in the same direction of traffic in the same lane as the repair. Stitching concrete pavement cracks and joints there are two stitching methods used to repair and strengthen cracks or joints in concrete pave ment. Portland cement concrete pavement repairs will be measured in place and paid for at the contract unit price per square yard for the pertinent type plain portland cement concrete pavement repair, conventionally reinforced portland cement concrete pavement repair, and continuously reinforced portland cement concrete pavement repair item. Based on the concrete pavement climate region, verify the types of reinforcement, tie bars, dowel bars, tie bar baskets, and dowel bar baskets to be used within the concrete pavement, refer to section 401. Steel reinforcing bars and welded wire reinforcement provide crack width control in nonstructural slabsonground. Provide tie bars at the longitudinal joint by drilling and epoxying. Support reinforcement with chairs or precast concrete bar supports.
Jointed plain concrete pavement pavement interactive. Jointed plain concrete pavement jpcp properties crack control contraction joints, both transverse and longitudinal joint spacing typically between 3. Practices vary from state to state, but dowel bars are typically required in eightinch or thicker pavements. Continuously reinforced concrete pavement performance and. Grouting dowel bars and tie bars for fulldeph concrete pavement repairs. The second, slotstitching, uses deformed tiebars grouted into slots cut across a joint or crack. For jointed plain concrete pavements, ensure that dowel bar baskets, tie bar baskets, and the bars themselves are not being displaced during the concrete placement and paving operations.
All other nonpaving use of couplers shall be performed with couplers on the material producers list for mechanical couplers. The spacing and depth of the holes are specified in the concrete pavement repair standard. Each technique is beneficial for certain circumstances. In slotstitching, the concrete slabs are held together by the shear stress of deformed bars. When the saw was halfway across the pavement, the concrete cracked ahead. The major areas of concrete pavement rehabilitation are partial depth patching, fulldepth patching, slab replacement, joint crack sealing.
Crossstitching uses deformed tie bars inserted into holes drilled across a crack at angles of 35 to 45 degrees depending upon the slab thickness. Provide hydraulic cement concrete in accordance with item 421, hydraulic cement concrete, except that strength overdesign is not required. Continuously reinforced concrete pavement crcp is enjoying a re. Dowel bars dowel bars are placed at the transverse joints of concrete pavement and they take part in partial wheel load transfer from one slab to its adjacent slab. Stitching concrete pavement cracks and joints national center for. Concrete pavement colorado department of transportation. Stitching concrete pavement concrete paving association of.
The dowel bars also allow axial thermal expansion and contraction of the concrete slab along the axis of the dowel. Theoretical and practical studies of concrete pavement have determined that the optimal spacing between joints depends on the slab thickness, subbase stiffness, and concrete strength. Tie bars avoid separation and differential deflection in lanes. Igga 2012 national pavement presentation conference. Tie bars are typically used at longitudinal joints see figure 1 or between an edge joint and a curb or shoulder. For crcp, in addition to the transverse steel, single piece tie bars are spaced at. Jpcp contains enough joints to control the location of all the expected natural cracks. It is important to provide high strength backfill material and good consolidation around the bars and concrete slot surfaces. There are various types of distresses in concrete pavements which may cause its failure. Retrofitted tie bars when new pavement is to be tied to an existing pavement, tie bars are used to tie the pavements together. Research was needed to determine whether the use of wider slabs made the pavement more susceptible to other forms of distress. Hihigh strength concrete new construction and rehbhab.
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