Sidewalk Replacement Criteria

The sidewalk replacement criteria was developed by the engineering division with help from the city attorney and approved by the city commission. The program targets an area of the City each calendar year between 2012 and 2017.


The city deems that sidewalks which exhibit the following criteria will be removed and replaced:



1. Sidewalks that exhibit differential sidewalk elevations.
  • Differentials typically occur at the joint between two sidewalk slabs. A differential consists of a lip or elevation difference at the joint and is measured along the vertical face of the joint. A differential sidewalk that exceeds 1/2” is a condition that warrants removal and replacement.  The differential may have been caused by tree roots, trench settlements, or heavy weights placed on the sidewalks.
2. Cracked or broken sidewalk with any of the following:
  • Hairline or crazing (alligator cracking)
  • Deteriorating joints (at least 4 inches long by 1 inch wide at any point)
  • Spalled areas (at least 3 inches along any one side)
3. Other Surface condition issues:
  • Pitted sidewalks with any pit larger than 1 1/2” and at least 1/2” deep
  • Surface deterioration consisting of scaling or popping (greater than 50% of at least two quadrants of the sidewalk slab)
4. Grade or miscellaneous conditions:
  • Sidewalks that show signs of ponding water due to settlement
  • Excessive sloping, greater than 1” per 12”
  • Sidewalks not complying with the 5’ wide city standard
It should be noted that sidewalks may exhibit more than one type of deficiency. It should also be noted that the program not only addresses correcting identifiable sidewalk hazards, but includes defective sidewalks that may become hazardous before the next scheduled review and repair project occurs.

You can download a copy of the Marking Key here.



Deterioration Details

Pitting


Pitting in sidewalk occurs over time as individual stones break up through the freeze/thaw cycle leaving a void in the sidewalk surface. This type of deterioration in small amounts may not necessarily constitute a hazardous walking surface. In large quantities, however, these defects diminish the smooth walking surface, compromise the sidewalk’s structural integrity, and contribute to poor drainage which propagates further pitting and surface defects.
Pitting 500x500

Scaling


Scaling is the general loss of surface mortar exposed to freezing and thawing. The aggregate is usually clearly exposed and often stands out from the concrete. Scaling is primarily a physical action caused by hydraulic pressure from water freezing within the concrete and not usually caused by chemical corrosive action. When pressure exceeds the tensile strength of concrete, scaling can result if entrained-air voids are not present to act as internal pressure relief valves.

Scaling 500x500

Spalling


Spalling is a deeper surface defect than scaling, often appearing as circular or oval depressions on surfaces or as elongated cavities along joints. Spalls may be 1 inch or more in depth and 6 inches or more in diameter, although smaller spalls also occur.  

Spalls are caused by pressure or expansion within the concrete, bond failure in two-course construction, impact loads, fire, or weathering. Improperly constructed joints and corroded reinforcing steel are two common causes of spalls. If left unrepaired, spalls can accelerate pavement deterioration.
Spalling 500x500

Popping (pop-outs)


A pop-out is a conical fragment that breaks out of the surface of the concrete leaving a hole that may vary in size generally from 1/4 inch to 2 inches, but up to as much as 1 foot in diameter.  Usually a fractured aggregate particle will be found at the bottom of the hole, with part of the aggregate still adhering to the point of the pop-out cone.

Most pop-outs appear within the first year after placement. Pop-outs caused by alkali-silica reactivity (ASR) may occur as early as a few hours to a few weeks, or even a year, after the concrete is placed. Pop-outs caused by moisture-induced swelling may occur shortly after placement due to the absorption of water from the plastic concrete, or they may not appear until after a season or year of high humidity or rainfall or after the concrete has been exposed to freezing temperatures. Pop-outs are considered a cosmetic detraction and generally do not affect the service life of the concrete.
Pop Out

Differentials


Differentials typically occur at the joint between two sidewalk slabs. A differential consists of a lip or elevation difference at the joint and is measured along the vertical face of the joint. A differential sidewalk that exceeds 1/2” is a condition that warrants removal and replacement.  The differential may have been caused by tree roots, trench settlements, or heavy weights placed on the sidewalks.

differential sidewalk elevation 500x500

Sidewalk lifted from tree roots

Lifted 500x500

Sidewalk shows signs of ponding

signs of ponding 500x500