Geoffrey Hichborn Sr., PE
"Concrete Insights and Experience When You Need It"
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The following is an excerpt from a Concrete Expert Witness Construction Defect Investigation Report:
The play courts do not exemplify the District’s stated goal of exceptional quality: this is due to a large number of reasons that the District may not realize. The slab cracking, the stated object of the investigation, while objectionable, is of less concern to the long term performance of the work than several other concerns which are less obvious.
The longevity, or useful service life, of the courts are compromised by their susceptibility to water at the open joints and the apparent lack of connection between slabs across the joints. Water can enter the joint, saturate the subgrade, lead to expansion or settlement of the soils and distortion of the slab surfaces, possibly coupled with cracking or vertical offsets.
The workmanship of the project, while acceptable for many applications, does not rise to the standard of quality the District reportedly mandated. Examples of questionable workmanship include its general appearance, in which the color, texture, and finish are not uniform, either within any slab or by comparing any two slabs. It is likely that curing was not performed consistently from placement to placement. Joints demonstrate raveling and related distress, which may be indicative
of poor workmanship. Cracking of the comers, where present, may be caused by overloading during, or shortly after, construction. One example of such loading would include equipment rolling over the slab comers. The grades, elevations, form lines and freedom from bird baths, however, demonstrate exceptional workmanship.
The quality of the striping is completely unacceptable and was not installed in a workmanlike
manner. The stripping must be completely redone.
The central reason for the random cracking present about which the District is concerned has to do with improper design. The joint layout and construction details for the slabs, coupled with the boxed out sections at the steel basketball poles, should have been avoided. (The boxed out detail in the slab for each steel pole is particularly prone to cracking and poor performance. If the feature is unavoidable, then several improvements could be made to the details to reduce its likeliness to
create problems.) Due to these details, it should be anticipated that similar cracks will develop at similar locations for the other steel poles in the other slabs. Secondly, since nearly all of the objectionable cracks noted to date are in concrete cast the same day, it is likely that the installation of this day’s concrete was inferior compared to the other days of work. Thus, it is likely for that day’s work, the contractor failed in his duty to respond appropriately to the weather. While there are many possibilities for this, weather conditions frequently lead to these types of conditions. Excessive water additions, to the concrete delivery track, for whatever reason, also lead to the higher shrinkage characteristic of this concrete. Other design deficiencies include: (1) the lack of positive connection between adjacent slabs; (2) the lack of filler material in the joints; and, (3) incomplete material specifications. The standard of workmanship reportedly desired by the District was not conveyed to the bidder and successful contractor in the construction documents reviewed to date.
Except for the quality of the crack repairs and the original cracks themselves (which are the subject of this investigation) the workmanship demonstrated by the quality of this slab is common and generally acceptable in most construction projects. The contractor is required to build what the designer shows in the plans, details, specifications, contract and other construction documents. The contractor generally has no duty to install improvements to a greater, better, or improved standard than required by the construction documents. In fact, he is not allowed to deviate from them in any
direction, absent the owner and designer’s acknowledgment.
Holding the contractor responsible to the high standard the District desired is not supported by the construction documents reviewed thus far.
There was no evidence observed which suggested that the materials installed and purchased for the project did not satisfied appropriate standards.
Examination of random cracking in the north-west section of the play courts was the original purpose of this investigation. Additional repairs (of the same style) to this area will likely not improve the cosmetic appeal of the repaired cracks.
Since the District’s stated desire was for an exceptionally high quality play court, serious attention should be given to filling all joints properly, coating the entire play court surface and then re-striping. Though expensive, additional consideration should be given to providing some connection between the slabs across the joints prior to the application of the coating. If not
performed, the chances of random cracks and vertical offsets is increased, with the attendant danger of trip and fall accidents. Maintenance costs will likely be larger if no provision is made for connecting adjacent slabs. A coating would conceal properly made, flush-with-the-surface-repairs to the subject cracks. A flexible (elastomeric type) coating would also conceal properly made crack repairs and may be beneficial at disguising or concealing future cracking which may occur over the passage of time. It is likely that these repairs will be too costly to perform.
A potential compromise may be to replace either one or both of the two most significantly cracked slabs with improved jointing details, and doweling them in to the adjoining slabs. Then, re-striping of all play courts can proceed.