What is cracking and spalling?
What is cracking and spalling?
Shrinkage cracking is caused by rapid drying of the concrete surface by wind or high heat. Proper placement and curing practices are required to prevent this. Spalling is caused by one or more of the following: a poor concrete mix, poor finishing, or overwatering.
What is meant by spalling of joint?
Joint spalling is the breakdown of the slab edges within 2 ft (0.6 m) of the side of the joint. A joint spall usually does not extend vertically through the slab, but instead intersects the joint at an angle.
What are the failures of rigid pavement?
Structural inadequacy: If the pavement system is structurally unstable such as inadequate pavement thickness, inadequate subgrade support, poor subgrade soil, incorrect spacing of joints, etc., the rigid pavements develop various failures in the form of widening of joints, cracking of slab corners, etc.
What is pumping in rigid pavement?
Pumping is among the leading distresses in both flexible and rigid pavement. Pumping is defined as the ejection of water and fine materials of the pavement system under pore water pressure generated by repetitious traffic loading through larger voids or cracks.
What is spalling in construction?
A spall is defined as flakes of material that are broken off of a larger solid body. Concrete spalling typically begins when the steel reinforcing embedded within the concrete member rusts. Contrary to popular belief, concrete is porous.
Why does spalling happen?
There are a number of reasons why spalling occurs including freeze thaw cycling, the expansive effects of Alkali Silica Reaction or exposure to fire. However, the most common cause of spalling is the corrosion of embedded steel reinforcement bars or steel sections.
What causes spalling in concrete?
There are many causes of concrete spalling; they include the improper placement of concrete and its reinforcing, electrochemical (galvanic) reactions between embedded metals within the concrete matrix, and corrosion of embedded reinforcing steel due to exposure to water and/or chemicals.
What is spalling construction?
Spalling is the flaking or peeling away of small particles of cement paste from the near-surface portion of the finished slab. In most instances, the defect does not affect the slab’s service life if untreated. Freezing and thawing cycles can cause concrete to spall.
What is scaling in rigid pavement?
Scaling is local flaking or peeling of a finished surface of hardened concrete as a result of exposure to freezing and thawing. Generally, it starts as localized small patches which later may merge and extend to expose large areas.
Why dowel bar is used?
The primary advantage of dowel bars is to transfer load without restricting horizontal joint movements due to temperature and moisture expansion and contraction in the concrete slabs. Also, dowel bars play a role to maintain the vertical and horizontal alignment of slabs.
What is raveling in pavement?
Raveling is the disintegration of an asphalt road surface. It is due to the dislodgment of the aggregate materials (gravel, sand, and crushed stone). It reduces skid resistance, roughens the road surface, and exposes the layers underneath to further deterioration.
How does spalling occur in concrete?
Spalling is a term used to describe areas of concrete which have cracked and delaminated from the substrate. There are a number of reasons why spalling occurs including freeze thaw cycling, the expansive effects of Alkali Silica Reaction or exposure to fire.
