RIGID PAVEMENT
Rigid Pavement
Rigid pavement (cement concrete) is a pavement construction with aggregate as raw material and uses cement as the binding material, so it has a relatively high level of rigidity, especially when compared to asphalt pavement (flexible pavement), so it is known and referred to as rigid pavement or rigid pavement.
Modulus of Elasticity (E) is one of the parameters that shows the level of construction stiffness in addition to its dimensions; and can be used as a reference for the illustration of the stiffness level of the pavement construction. For asphalt pavements (flexible pavements), the elastic modulus (Ea) is around 4,000 MPa, while for rigid pavements (cement concrete) the average elastic modulus (Eb) is around 40,000 MPa or 10 times that of asphalt pavements.
The brief description above provides an understanding that this type of pavement construction is very reasonable and appropriate to be called or referred to as rigid pavement construction. In this rigid pavement, one layer of high strength cement concrete (according to its class) in the pavement construction is the main construction. (Source : Diklat Perkerasan Kaku, 2017)
History of Rigid Pavement
- Rigid Pavement Technology Development in the World
- Rigid Pavement in Indonesia
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General Properties of Rigid Pavement
- Load Spreading Capability to Subgrade
- Rigid Pavement Structure
- Rigid Pavement Construction Capacity
- Effect of Rigid Pavement Construction Shoulders
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Rigid Pavement Type
Rigid pavement in the form of concrete slabs is equipped with several connections, such as transverse shrinkage joints, longitudinal joints, implementation joints and expansion joints. Each connection and its location is shown in the figure below.
Type and location of joints in rigid pavement
(Source : Diklat Perkerasan Kaku, 2017)
There are several known types of rigid pavements, but two are the most important. The first is the strength against traffic loads which is expressed by the flexural tensile strength of the concrete. If reinforcement is used, it is used to control cracks and not to carry traffic loads. The second point is that rigid pavements shrink due to shrinkage of the concrete itself during the hardening process, and expand and contract under the influence of temperature, and these movements must be taken into account. There are 5 types of rigid pavements, namely:
- Jointed unreinforced (plain) concrete pavement' (JPCP)
- Jointed unreinforced (plain) concrete pavement' (JPCP)
- Continuously reinforced concrete pavement (CRCP)
- “Prestressed” cement concrete pavement or “prestressed concrete pavement”
- Precast cement concrete pavement (with and without prestressing)
Continuous rigid pavement without reinforcement, continuous rigid pavement with reinforcement, and continuous rigid pavement with reinforcement are included in the conventional rigid pavement group. The design and details of the joints are very important for this type of pavement. The three types of conventional pavements have also been used as backcoats, although the most common is rigid continuous pavement without reinforcement.
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Types of Connections in Rigid Pavement
Conventional rigid pavements (JPCP, J RCP, CRCP) use multiple transverse and longitudinal joints. Transverse shrinkage joints are used in JPCP and JRCP, generally using spokes. At the end of each day of the daily pavement construction, or the implementation of the overlay that is delayed, a transverse joint is used, generally at the planned shrinkage joint location from JPCP and JRCP. Transverse expansion joints or insulating joints are installed where expansion of the pavement will damage the bridge or adjoining drainage facilities. Longitudinal shrinkage joints are made when two or more pavements or road shoulders are carried out at the same time. While the longitudinal implementation connection is used between two lanes or hardened road shoulders at different times.
- Transverse Shrink Joint
- Expansion Elongated
- Expansion Execution
- Expansion Extended Execution
- Expansion Joint
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Rigid Pavement Equipment Development
Initially, the implementation of rigid pavement construction used a fixed form of iron. This reference price was considered expensive, so a spreader known as slip form was developed. In this sliding form there is no need for a fixed reference, because the reference unites with the laying machine and moves forward during laying. In the construction with this slip model, the slump of the concrete is designed to be smaller than the slump of the concrete for the fixed form, so that the edge of the concrete slab does not collapse when left by the slip form. This slip reference was first developed in Iowa between 1946 and 1949 by two road experts, James W Johnson and Bet Myers. This innovation was first used in 1949 on a pavement with a width of 2.7 m and a plate thickness of 15 cm. By using two spreaders simultaneously, the path can be made in one go. By 1955, the Quad City Construction company had developed and improved upon it so that the paver could be made 7.3 m wide by 25 cm thick, and then even larger pavers were developed.
The sections of modern, slip-referenced hardening are shown in FIGS. 1 to 3. FIG. 1 shows the spokes being positioned and fixed securely on the stand, to complete load transfer at the cross-saw joint. Figure 2 shows the slide reference itself in operation. Figure 3 shows how slip templates can be used in making bends.
At this time the implementation of rigid pavements still uses a fixed reference in addition to the slip reference.
Before Overlay With Slip Form
Slipform spreading machine
Final completion of the Slip Form
Overlay
Rigid coatings can also be used for re-coating, whether on asphalt pavements or over old rigid pavements. There are two classifications of the overlay, based on whether the backcoat is bonded to the old pavement or whether the bond is ignored or unbounded.
Unbounded concrete coating is that which is built on the old concrete pavement, with certain conditions to prevent the bond between the two layers. Generally bond breaker (bond breaker) is a thin layer of hot asphalt mixture. The reason for using this bond breaker is to prevent cracks and other damage in the old pavement from spreading to the new layer (reflection crack). With the bond breaker layer, the old pavement functions as a high quality base to support the new pavement.
The added layer with the bonded system is a coating on the old pavement with a bond between the two layers. Additional coating in this way, the thickness can be up to 5 cm, because of the composite system with the old pavement.
However, because any damage to the old concrete layer, will spread to the layer above it, the added layer of concrete with a bonded system is limited to the old pavement which has a fairly good condition. This may be the main reason why coatings with this system are rarely used. Road managers are reluctant to allocate their funds to roads that are still in relatively good condition and tend to allocate their funds to pavements with poorer conditions. Another reason why it is rarely used, is that if a "bond" is not achieved, the added coating will deteriorate quickly. The additional layer with the bonded system can be seen in the image below.
