Types Of Joints In Cement Concrete Road
The joints provided in cement concrete road are classified into the following two categories:
1. Longitudinal Joints.
2. Transverse Joints.
1. Longitudinal Joints
These joints are provided longitudinally in cement concrete roads which have a width more than 4.5 m. Such joints are provided to prevent longitudinal cracking in the pavement.
The longitudinal cracking in the pavement is formed as a result of differential shrinkage and swelling due to rapid changes in subgrade moisture under the edge than the center of the road. In longitudinal joints tie bars are provided to hold the adjacent slabs.
2. Transverse Joints
Transverse joints in cement concrete roads are further classified into the following categories:
i) Expansion Joints
ii) Contraction Joints
iii) Warping Joints
iv) Construction Joints
i) Expansion Joints
Expansion joints are provided in cement concrete roads to allow for expansion of the slab due to rising in the slab temperature.
These joints are provided at an interval of 50 m to 60 m if the slab is laid in winter and 90 m to 120 m if the slab is laid in summer.
The approximate gap width for this type of joint is 20 mm to 25 mm. These joints also permit the contraction of the slab.
ii) Contraction Joints
Contraction joints are provided in cement concrete roads to allow for contraction of the slab due to falling in the slab temperature.
These joints are spaced closer than expansion joints. As per I.R.C, the maximum spacing of these joints is 4.5m in plain cement concrete slabs and 14 in reinforced cement concrete slab of thickness 20cm.
iii) Warping Joints
Warping joints in cement concrete roads are provided to relieve the stresses included due to warping.
During the mid-day, the top of the pavement slab has a higher temperature than the bottom. This causes the top fibers of the slab to expand more than the bottom fibers and the slab curls at the edge. This phenomenon is known as the warping down of the slab.
Similarly, the slab warps up during midnight due to the higher temperature of the bottom slab as compared to the top. Warping joints are provided to minimize the stresses induced due to warping. These joints are also known as hinged joints. Longitudinal joints with tie bars fall in this class of joints.
iv) Construction Joints
Construction joints are provided in cement concrete road to close the day’s job and for the commencement of the same in the next day.
Read more:
Necessity of Providing Joints in Cement Concrete Road