What is the difference between expansion and construction joint?

Replies

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  CIVILPRINCESS

  you must be meaning "expansion and contraction joints" 😀 They just help the structure to expand or contract according to the surrounding temperatures without the formation of any stresses.
  
  The expansion joint may have any material capable of taking compression like rubber or any other material. The bridge girders (for example) are built in sections and joined with these joints in between. So if due to high temperature the reinforced concrete tends to expand, the expansion is allowed and the forces due to these expansion and contraction is made less. once the temperature comes back to the normal the material comes back to the original position as it was earlier.
  
  Hope you understand the concept 😀
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  Mohamed Amir

  construction joint is a separation of either vertical or concrete pours designed to offer movement in case of wind loading or other loads so as not to compromise the integrity of the concrete structure itself. The construction joint is usually joined together by non-metallic strap to hold the two slabs in place; at the same time giving flex when there is movement
  
  
  expansion joint or movement joint is an assembly designed to safely absorb the heat-induced expansion and contraction of various construction materials
  
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  rekcah

  Concrete expands and shrinks with changes in moisture and temperature. The overall tendency is to shrink
  and this can cause cracking at an early age. Irregular
  cracks are unsightly and difficult to maintain but generally do not affect the integrity of concrete. Joints
  are simply pre-planned cracks. Joints in concrete slabs
  can be created by forming, tooling, sawing, and placement of joint formers.
  Some forms of joints are:
  a. Contraction joints – are intended to create weakened planes in the concrete and regulate the location where cracks, resulting from dimensional
  changes, will occur.
  b. Isolation or expansion joints – separate or isolate
  slabs from other parts of the structure, such as walls,
  footings, or columns; and driveways and patios
  from sidewalks, garage slabs, stairs, lightpoles and
  other points of restraint. They permit independent
  vertical and horizontal movement between adjoining parts of the structure and help minimize cracking when such movements are restrained.
  c. Construction joints – are surfaces where two successive placements of concrete meet. They are typically placed at the end of a day’s work but may be
  required when concrete placement is stopped for
  longer than the initial setting time of concrete. In
  slabs they may be designed to permit movement
  and/or to transfer load. The location of construction joints should be planned. It may be desirable to achieve bond and continue reinforcement
  through a construction joint.
  
  WHY THIS JOINTS CONSTRUCTED?
  
  Cracks in concrete cannot be prevented entirely, but
  they can be controlled and minimized by properly designed joints. Concrete cracks because:
  a. Concrete is weak in tension and, therefore, if its
  natural tendency to shrink is restrained, tensile
  stresses that exceed its tensile strength can develop,
  resulting in cracking.
  b. At early ages, before the concrete dries out, most
  cracking is caused by temperature changes or by
  the slight contraction that takes place as the concrete sets and hardens. Later, as the concrete dries,
  it will shrink further and either additional cracks
  may form or preexisting cracks may become wider.
  Joints provide relief from the tensile stresses, are easy
  to maintain and are less objectionable than uncontrolled or irregular cracks.