Thermal cracking includes both low temperature cracking and thermal fatigue

Thermal cracking includes both low temperature

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rutting to a tolerable amount (12 mm normally). Thermal cracking includes both low-temperature cracking and thermal fatigue cracking. JNTU World JNTU World Downloaded From JNTU World ()
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78 Portland Cement Concrete Base or Subbase Course 150 − 300 MM 100 − 300 MM Figure 19:3: Typical Cross section of Rigid pavement Elastic plate Viscous foundation Contact Pressure Figure 19:4: Elastic plate resting on Viscous foundation Rigid pavements Rigid pavements have sufficient flexural strength to transmit the wheel load stresses to a wider area below. A typical cross section of the rigid pavement is shown in Figure 19:3. Compared to exible pavement, rigid pavements are placed either directly on the prepared sub-grade or on a single layer of granular or stabilized material. Since there is only one layer of material between the concrete and the sub-grade, this layer can be called as base or sub-base course. In rigid pavement, load is distributed by the slab action, and the pavement behaves like an elastic plate resting on a viscous medium (Figure 19:4). Rigid pavements are constructed by Portland cement concrete (PCC) and should be analyzed by plate theory instead of layer theory, assuming an elastic plate resting on viscous foundation. Plate theory is a simplified version of layer theory that assumes the concrete slab as a medium thick plate which is plane before loading and to remain plane after loading. Bending of the slab due to wheel load and temperature variation and the resulting tensile and flexural stress. Types of Rigid Pavements Rigid pavements can be classified into four types: 1. Jointed plain concrete pavement (JPCP), 2. Jointed reinforced concrete pavement (JRCP), 3. Continuous reinforced concrete pavement (CRCP), and Pre-stressed concrete pavement (PCP). Jointed Plain Concrete Pavement: are plain cement concrete pavements constructed with closely spaced contraction joints. Dowel bars or aggregate interlocks are normally used for load transfer across joints. They normally has a joint spacing of 5 to 10m. Jointed Reinforced Concrete Pavement: Although reinforcements do not improve the structural capacity significantly, they can drastically increase the joint spacing to 10 to 30m. Dowel bars are required for load transfer. Reinforcement’s help to keep the slab together even after cracks. JNTU World JNTU World Downloaded From JNTU World ()
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