Testing Laboratory Problems April 1, 2016
Testing laboratories are very useful entities and can provide valuable quality control testing of construction materials or construction procedures. However, some misconceptions need to be cleared up about the proper role and capabilities of testing laboratories.
The most common function of testing laboratories is to test construction materials in accordance with standardized specifications. These specifications include descriptions of the desired material properties or construction outcomes. Other specifications describe methods of testing. The American Society for Testing and Materials has published a number of these standards and specifications. Other organizations also are involved such as the Texas Department of Transportation, various city engineering offices, the U.S. Army Corps of Engineers, American Concrete Institute and others.
Good quality control begins with good design and specifying. The designer (architect or engineer) should state clearly in the contract documents what standards the various materials should meet and specify guidance for a testing program to ensure this quality. Lines of communication and the reporting of results should be clearly identified by those in charge of the construction and protecting the owner’s interest.
A testing laboratory should be qualified to perform the tests after having been provided with the specific requirements described above. Qualifications include having the proper equipment (which is calibrated) and having technicians capable of performing the various tests. A proper testing laboratory should also have engineering supervision by a professional engineer.
Construction testing problems arise in the construction industry because architects, engineers, owners and contractors misunderstand what a testing laboratory can do. Typically, a testing laboratory does not provide “structural” or “project level” inspection. This type of inspection is normally performed by the structural engineer to see that the plans are executed. Supplementing the engineer’s inspection program, the testing of construction materials for quality and conformance is done by a testing laboratory.
Testing laboratories can be involved in the structural or project level inspections in addition to material quality assurance. However, it must be clear that this level of inspection is what is required and qualified people must be available to do these inspections. Examples of these inspections could include soil management, which is a higher level of inspection than simply doing “density tests” on an earthwork job. Another example would be inspection of drilled piers including installation of the concrete and steel. Other examples could include inspecting footings or structural framing for proper reinforcement placing, forming details and concrete placement. To do these type of inspections the technician must be familiar with the specified codes such as ACI regarding concrete reinforcement or AWI for welding, for example.
A common situation arises when a contractor or developer gets a testing lab to come out and “do some density testing” on a site. This is useful as far as it goes but may not have included such features as proper design of a structural fill, qualification of imported materials in accordance with a designer’s specification, proper geometry of the fills, etc. When the job is completed a structural engineer may be asked to design a foundation placed on this fill and he is naturally reluctant unless someone will give him a certification that the fills are capable of supporting his structure. At this point the laboratory usually declines, saying they were simply hired to test densities, which is correct. This is analogous to testing concrete in a bridge beam, but not checking if the beam is deep or wide enough, or properly reinforced.
The same problem can arise with inspection of concrete slabs or foundations. The testing laboratory was hired to perform quality control testing of the concrete, which includes cylinders, slump, air tests, etc. Sometimes architects, structural designers or others assume this also includes inspection of the reinforcement placing, waterproofing, drainage, etc. This is usually not the case. Other examples include testing concrete cylinders brought into the laboratory by the contractor as a substitute for full scale concrete placement inspection and testing, testing of a sample of pit run material for acceptance and moisture density curves (Proctor curves) as a substitute for a designed soil management program for a structural fill with proper independent control of the pit sampling procedures.
The above examples illustrate that there is room for problems ranging from ignorance to outright fraud while the testing laboratories simply perform the duties they were asked to do within the scope of their contract. Another problem with testing laboratories becomes evident when the contractor is given the task of hiring the laboratory. Laboratories are placed in a very uncomfortable position by this. The laboratory is being hired by the contractor to ostensibly protect the owner’s interest but the laboratory’s loyalties will be divided and are heavily concerned with the source of their fees. Even a very conscientious and ethical laboratory is placed under intolerable pressures if it becomes necessary to report failing results on the work done by the contractor that is paying the bill. Sometimes the pressures result in a different laboratory being on the job and this threat is always implied, if not actually present.
Another problem with the hiring of laboratories is that frequently they are done on a low bid basis which, in many cases, tends to permit the laboratory to set the scope of services. Naturally the fewer tests, the lower the bid and elimination of higher level inspections in favor of simple material testing will also lower the bid. The best way to employ the laboratory is for the owner to retain the laboratory separate from any other contracts and to negotiate a proper scope of services guided by the architect, structural engineers or civil engineers on the project. This procedure should keep in mind the purpose of the testing laboratory, which is to provide quality construction and to serve the owner’s interests in getting the value paid for the construction.