TYPES OF RIGID PAVEMENT
Joint Plain Concrete Pavement
Continuous rigid pavement without reinforcement is the most commonly used type because it is relatively inexpensive to implement compared to other types. A survey conducted by the American Concrete Pavement Association (ACPA) in 1999, in the United States 70% of state highway agencies (State Highway Agencies) use continuous pavement without reinforcement. In areas where corrosion of reinforcement will be a problem, the absence of reinforcement will eliminate the corrosion problem, although the spoke iron will still be affected by corrosion.
Shrink joints are generally made every between 3.6 m and 6 m (in Indonesia it is generally between 4.5 m and 5 m). This connection has a relatively close distance so that cracks will not form in the slab until the end of the service life of the pavement. Therefore, in continuous rigid pavement without reinforcement, the expansion and shrinkage of the pavement is overcome through the joints, as shown in the figure below.
Schematic of continuous rigid pavement without reinforcement
(Source : Diklat Perkerasan Kaku, 2017)
In continuous rigid pavement without reinforcement, there is no reinforcement in the slab, except for the spokes which are placed on the shrinkage joint, and the tie bar which is located in the longitudinal joint, as shown in the figure below.
Stairs and tie rods on continuous rigid pavement without reinforcement
(Source : Diklat Perkerasan Kaku, 2017)
Ruji is straight plain steel that is installed in each type of transverse connection with the intention of being a load transfer system, so that the adjacent plates can work together without significant differences in settlement. While tie bars are threaded steel rods that are installed in longitudinal connections with the intention of binding the plate so that it does not move horizontally.
One important performance of unreinforced continuous pavement is the distribution of the load across the joint. If the connection is experiencing faulting (perbedaan ketinggian dari kedua sisi pelat pada sambungan), maka pengemudi akan mengalami “bumping” on the connection and cause discomfort while driving. Two methods are used to complete load distribution at JPCP pavement joints, namely aggregate interlocking dan ruji.
If spokes are not used, the load distribution on the joint can be obtained through the shear strength of the interlocking aggregate. Joints with interlocking aggregate are formed during construction by sawing one-fourth to one-third the thickness of the pavement slab to create weakening of the slab in that area. Cracks will continue to propagate through the thickness of the slab that is not sawn as the pavement shrinks. The surface of these cracks will be rough, because the crack propagates around the aggregate through the cement paste or mortar, and as long as the crack remains narrow, the joint can transmit the load from one plate to another through the bearing stresses of each aggregate particle through which the crack passes. The load distribution will adjust if the joint opening is too wide or if the aggregate is worn. The quality and erosion resistance of the material supporting the slab at the joint also affects load transfer.
When the pavement is carrying heavy traffic loads, especially at high speeds, the interlocking aggregates will break down as traffic passes frequently. This will cause the deformation of the joint to become larger, which will eventually lead to faulting and damage to the joint. The position of the tie rod in the longitudinal joint is shown in the figure below.
Position of the tie rod in the longitudinal joint
Jointed Reindforced Concrete Pavement
Continuous rigid pavement with reinforcement or JRCP is similar to continuous rigid pavement without reinforcement (JPCP) except that the plate size is longer and there is additional reinforcement in the plate. The connection distance is generally between 7.5 m and 12 m, although there is also a connection distance of 30 m. The results of a survey by the ACPA in 1999, about 20% of the state highway agency (State Highway Agency) in the United States use rigid pavement connected with reinforcement (JRCP). For plates and longer joint spacings, spokes are highly recommended because the joint openings will be wider and the interlocking aggregate will be ineffective as a load carrier in the joint. The percentage of reinforcement used in the longitudinal direction is generally between 0.1% and 0.2% of the concrete cross-sectional area, while the reinforcement in the transverse direction is smaller. Reinforcement on rigid pavements in conjunction with reinforcement is not intended to carry structural loads, but to "hold" the cracks together, in order to maintain shear along the crack plane as a load carrier that continues to function. The following is an example of a schematic drawing of a rigid pavement connected with reinforcement.
Schematic of rigid pavement connected with reinforcement
Connected pavement with reinforcement
(Source : Diklat Perkerasan Kaku, 2017)
Rigid pavement connected to this reinforcement still uses spokes. Furthermore, because the length of the slab is greater than the rigid continuous pavement without reinforcement, cracks still occur at the same interval, therefore the continuous pavement with reinforcement still has one or two cracks in the slab. The advantage of continuous rigid pavement with reinforcement is that the number of joints is less, but the cost is higher due to the use of reinforcement and poor joint performance and the presence of cracks in the plate. Because the distance between joints is larger than unreinforced continuous rigid pavement, the opening and closing of the joint becomes wider, and the spokes as a load carrier are more vulnerable when the joint is opened wider.
Continuous Reinforced Concrete Pavement
Continuous rigid pavement with reinforcement is a plate with a sufficient amount of reinforcement without shrinkage joints. The amount of reinforcement used in the longitudinal direction is generally between 0.6% and 0.8% of the concrete cross-sectional area, and the amount of reinforcement in the transverse direction is smaller than the longitudinal direction. Experience shows that if the amount of reinforcement used in continuous rigid pavement with reinforcement is less than 0.6%, the potential for punch out damage will be greater.
Hair cracking occurs in continuous rigid pavements with reinforcement, but is not a performance problem. Characteristics of cracks consist of several cracks, generally with a distance between 0.6 m - 2.4 m. The cracks are "held" by the existing reinforcement so that the interlocking aggregate and the shear force distribution can still occur. If aggregate shear interlocking is not maintained, “punch out” damage to the pavement edges will occur, which is typical of continuous rigid pavement damage with reinforcement.
Continuously rigid pavement with reinforcement requires anchors at the beginning and end of the pavement, to hold the edges from contraction due to shrinkage, and to help crack development as desired. The figure below shows a continuous rigid pavement with reinforcement.
Schematic of continuous rigid pavement with reinforcement
Transverse execution joints and reinforcement in continuous pavement with reinforcement
(Source : Diklat Perkerasan Kaku, 2017)
This continuous rigid pavement with reinforcement will provide better driving comfort, because the surface is flatter, and has a longer life than other types of pavement. A survey conducted by the ACPA in 1999, found that only eight states in the United States built continuous rigid pavements with this reinforcement. Studies conducted in 2000 on the performance of rigid pavements in the southeastern United States against CRCP roads in the states of Alabama, Florida, Mississippi, North Carolina and South Carolina, proved the performance of CRCP to be very good. At the time of the survey, the age of the pavement was between 21 and 30 years and had served heavy traffic, and had very good to extraordinary condition with a serviceability value of 4 or more.
The cost for continuous rigid pavement with reinforcement is more expensive than continuous pavement without reinforcement or continuous pavement with reinforcement, due to the large amount of reinforcement used. However, continuous rigid pavement with reinforcement has been shown to be cost effective on high traffic roads, due to its better long term performance compared to other types of rigid pavement.
Prestres Concrete Pavement
Prestressed rigid pavements were introduced in the late 1940s and were first used in airfields. Around 1959 two prestressed plates were used at Priggs military airfield in Texas. The 60 cm thick unreinforced rigid pavement was replaced with 23 cm thick prestressed rigid pavement. At Chicago O'Hax International Airport, prestressed rigid pavement with a thickness of between 20.3 cm and 22.8 cm is placed on a continuous rigid pavement of 30.5 cm thick.
Some of these projects have strands for prestressing in only one direction, so that cracks tend to occur in the same direction as the strands, due to the absence of compressive stresses in the transverse direction. 15 cm thick prestressed rigid pavement subjected to internal compression stresses in both directions, with a project length of 1600 m in Texas; still in good condition after 17 years old. The Research and Development Center for Roads and Bridges, has made an experimental track with prestressed rigidity in 2011 in Buntu, Central Java, 80 m long, 7 meters wide and 20 cm thick.
The potential of prestressed rigid pavement is related to two things, namely:
- More efficient use of materials
- There are fewer joints required and less chance of cracking, resulting in less maintenance costs and a longer pavement life.
Prestressed rigid pavement scheme
Precast Rigid Pavement
Precast rigid pavement can be divided into 2 types, namely:
- Precast rigid pavement without prestressing
- Precast rigid pavement with prestress
Pre-stressed rigid pavement, was manufactured in the states of Missouri and Indiana, USA in 2005. This pavement consists of individual panels that are pre-cast and pre-stressed with a plate thickness of 20 cm and are printed as wide as the road pavement. This prestressed precast rigid pavement has approximately the capacity to accept traffic loads, equivalent to a 35.5 cm thick conventional rigid pavement.
In this prestressed precast rigid pavement, there are three types of plates used, namely:
- Joint panel, are located at the ends of each member of the prestressed plate series and have spokes at the joints to accommodate the horizontal movement of the plate.
- Central panel, located in the middle of a series of plates and there is a pocket for the placement of the ends of the posttensional strand base panels, the dominant plates forming a pavement system, which is placed between the joint panel and the central panel.
In its implementation, at a stage of activity, at least one segment must be carried out which includes the arrangement of plates from the joint panel to the next joint panel. The plates are placed on a ready and level foundation layer, while the plates are equipped on both sides with a shear key that controls vertical alignment during operation and ensures rider comfort to prevent “faulting”.
The advantages of precast rigid pavement are that the quality of the concrete remains high as planned, the effects of weather are very small, and during implementation it does not disturb traffic too much. Pictures of prestressed precast rigid pavement are shown in Figure 14 and Figure 15 below.
Pre-stressed rigid pavement scheme
Sample Panel ready to be transported to the field
Example Lifting and installing panels
Example of panel arrangement
Example of providing post tension from the central panel
Panel arrangement and panel type and panel installation into pavement layers
(Source : Diklat Perkerasan Kaku, 2017)
In 2010 the type of prestressed precast rigid pavement has been applied in Indonesia on the Kanci – Pejagan (West Java – Central Java) toll road section. This toll road connects Kanci in Cirebon Regency Km 231+000 (Km 0) to Pejagan in Brebes Regency (Central Java province) at Km 266+000 (Km 0 Jkt). The total length of this toll road is 35 km, and the panels are made with a size of 8 m x 2.5 m x 0.20 m (length x width x thickness), and are installed transversely to the road axis.
In 2011, another prestressed precast road made in Indonesia was on the Pantura Road section in the Ciasem – Subang area of West Java. The precast and prestressing implemented here are similar to the prestressed precast road that has been implemented on the Kanci – Pejagan toll road, where the plates are also installed across the road. The length of the prestressed precast road in Ciasem is only 1.8 Km.
One of the differences between the Kanci-Pejagan toll road and the Ciasem - Pantura area (Subang Regency) is that the Kanci-Pejagan toll road is a new road so there is no traffic disturbance while at the location in Ciasem - Subang it is an existing road so that the influence of road width and traffic become things to be considered in the design and implementation.
