TYPES OF CONNECTIONS ON RIGID PAVEMENT
Transverse Shrink Joint
Defined transverse shrinkage joints (according to the guidelines / SNI) is a type of transverse connection with the aim of controlling shrinkage cracks in concrete, as well as limiting the effect of elastic stresses that arise on the slab due to the influence of changes in temperature and humidity. The distance between each shrinkage joint, generally made the same.
Shrinkage joints on pavements with light traffic loads, may only be interlocking aggregates along the joint. Meanwhile, for heavier traffic loads, use spokes as a load distributor for the connection. The spokes prevent vertical movement or faulting between the slabs, but allow the joints to open and close to release stresses caused by changes in temperature and moisture content of the concrete pavement. The blade is equipped with an anti-rust coating shown in the figure below.
The spoke holder installation is equipped with an anti-rust coating
(Source : Diklat Perkerasan Kaku, 2017)
In jointed pavements, the transverse joints (usually studded) are perpendicular to the direction of traffic. The main function of the transverse shrinkage joint is to control cracking as a result of tensile and flexural stresses in the concrete slab caused by the hydration process of cement, traffic loads and environmental influences. Because there are so many of these joints, their performance will significantly affect the pavement performance. Damage that occurs in the connection in general “faulting” and or spalling (bumps). Poor connection performance will result in further damage such as broken corners, blows up, and plate cracks. The performance of the cross-shrink joint is related to three main factors, namely the distance between the joints, the load distribution across the joint and the shape of the connection and the nature of the covering material. (joint sealent).
Expansion Elongated
A longitudinal joint is a connection between two plates that allows the plate to bend without splitting or cracking the plate. Longitudinal joints are used to relieve flexural stresses and are generally required when the slab is more than 4.6 meters wide. Slab widths that are less than or equal to 4.6 meters show satisfactory performance without longitudinal joints, although some longitudinal cracks may occur. Longitudinal connections whenever possible, preferably one line with the pavement line, to improve traffic service. A “straight strip paint” marking is placed on the pavement strip. Distribution of the load on the longitudinal joint is obtained through the interlock aggregate. To aid load transfer, tie rods are often used which are installed transversely in longitudinal joints. The tie rod is smaller in size than the spokes, and is a fin iron (groove iron). The tie rods on the stand are installed between the rows and are also coated with an epoxy coating to prevent rust as shown in Figure Longitudinal connection installation.
Longitudinal joints can be made by sawing or made as construction joints. If sawed off, the holder is installed first and the joint is sawn as in the method of making transverse shrinkage joints. If made as a construction joint, tie rods are used to bind the concrete slab that has been and has just been laid.
Longitudinal connection installation
Expansion Execution
The implementation joint is the connection between the slabs when the concrete is poured at the same time. This type of connection can be further divided into transverse and longitudinal execution joints. The drawing of the cross-execution joint is shown in Fig Transverse execution joint. After the spread reaches the joint area, the separation board will be removed. In the next laying, the new concrete mix is directly attached to the cross-sectional surface of the old concrete.
Transverse joints generally replace shrinkage joints, but should not be tilted, as perfect laying and compaction will be difficult to obtain. Transverse construction joints should be studded and attached directly to the old concrete. Grooved transverse joints tend to chip, so they are not recommended. It is recommended that cross-cutting joints, sawed and covered (joint sealent).
Transverse execution joint
Expansion Extended Execution
The tie rods must be firmly attached to the concrete, the tie rods should be inserted into the concrete which is still plastic. It is strongly recommended to carry out a “pull out” test to ensure that the tie rods are firmly embedded in the concrete. Bending of the tie rods is not recommended. If bending must be carried out, then straightened during execution, the reinforcement used is grade 40 (the yield stress is less than 276 MPa), because this type of reinforcement is more tolerant of bending. It may be necessary to reapply the rust-resistant coating on the tie rods after they have been re-aligned. When a pull out test is carried out, the test shall be carried out after the tie rods have been re-aligned. It is recommended that longitudinal joints be sawed and covered. The size of the reservoir should be the same as the size of the cross-joint.
Longitudinal joint in the form of a groove tongue, has been used in the past and is now very rare. This connection is a configuration of a short tongue and a groove (notch) that is just the right size to transfer shear forces. The choice to use a longitudinal execution joint with a groove tongue type should be made with care. The upper part of the plate above the groove tongue is often damaged by shear. For this reason, it is recommended that grooved joints are not used when the plate thickness is less than 25 cm. In longitudinal construction joints, the longitudinal joints need to be displaced about 10 to 40 cm from the longitudinal construction joints in the concrete slab, in order to prevent reflection cracking. The longitudinal execution connection is shown in the figure Longitudinal execution joints on unreinforced continuous pavement.
Longitudinal execution joints on unreinforced continuous pavement
Expansion Joint
An expansion joint is a joint located at a specific location to allow the pavement to expand without damaging adjacent structures or damaging the pavement itself. Generally these are used in areas near the head of bridges and utilities embedded in roads. The initial pavement design used transverse expansion joints such as shrinkage joints, but the performance was not good. One of the early designs incorporates expansion joints every 28 meters with a shrink joint every 9 meters. If the joint expands and closes allows the shrinkage joint to open very wide.
Good design and maintenance of shrink joints can actually eliminate the need for expansion joints, except for objects such as structures. When expansion joints are used, the pavement moves closer to expansion joints within a few years. This causes several adjacent shrink joints to be exposed and damage the cover and interlock aggregates. The width of the expansion joint is generally 19 mm or more and is installed 19 mm – 25 mm below the plate surface, to provide space for the installation of a joint sealant. Plain spokes are most commonly used as load transfer devices in this expansion joint. Each spoke in the expansion joint is provided with a cover at one end, which provides space for the plate to accommodate the movement of spokes, when the adjacent plate approaches the expansion joint, as shown in the figure. Expansion Joint
