This section deals with the process of evaluating noise barrier products designed and manufactured privately before they are installed. The evaluation of new products for possible use in highway construction is not a new concept for highway and transportation agencies. In fact, the evaluation of new materials and processes was often a principal activity in the highway agencies that were formed at the beginning of highway expansion following the introduction of the automobile. As practice became more standardized, principal attention shifted to other matters, and new product evaluation became a routine function to be initiated and undertaken along with other activities by staff members of various transportation agencies.
New product evaluation offers the best opportunities for control and standardization of the evaluation process. It also offers the opportunity to apply budgeting and funding practices that permit the measurement of productivity and benefits accruing from new product evaluation.
Most agencies have adopted a one-window concept for this type of external contact. That is, all evaluations are carried through with the overall responsibility assigned to a single division head regardless of where the evaluation takes place. This concept also ensures the focalization of all vendor activities to a single area, which reduces the number of unnecessary calls by vendors to several divisions and offers the opportunity for improving control over new-product evaluations.
The total process of evaluating new noise barrier products can be broken down into the following six steps:
The presentation of the noise barrier design submission for acceptance to a transportation agency is probably the most critical stage in getting a noise barrier product approved. It can also be the most frustrating for both the manufacturers and the approving agencies. The key is knowing what the requirements and specifications are for acceptance by the responsible organization. And, just as important, in what format are the agencies accustomed to seeing these submissions?
Since transportation agencies are dealing with public funds, they are obligated to ensure that every product used on a roadway meets durability, safety, and functionality requirements. In addition, they should address life cycle costing and be cost effective. The methodologies used to meet these requirements vary substantially between agencies. Many agencies have adopted, to some degree, the approval strategy and principles outlined in the National Cooperative Highway Research Program, Synthesis of Highway Practice, Report 90: New-Product Evaluation Procedures.ref. 44
Although this section details the procedures for the evaluation of new or unusual noise barrier products, designs, and concepts, it is equally as relevant for recycled material and common noise barrier products from new or existing manufacturers.
If specific requirements are not available or have not been developed by a particular organization, which is particularly typical for recycled materials, then the basic acceptance principles of durability, safety, functionality, life-cycle costs, and cost effectiveness should be thoroughly addressed and proven.
The current trend in writing specifications is leaning toward performance oriented requirements rather than detailing such things as specific ingredients in a compound or how to manufacture a specific component. This has allowed the manufacturer to be more creative in both the materials used and in the overall design of the product. Generally, this has resulted in a more durable and better designed product with much more competitive prices. This type of specification is also particularly suited for dealing with new design concepts as well as composite, virgin and recycled materials.
The following is a detailed look at what is required in preparing a complete submission:
Material Description - Every submission should have a detailed description of all materials used in the noise barrier structure including details of the standards to which each component was manufactured. This would encompass everything from the panels, posts, and footings, down to the type of material used for mandrels in rivets. If the specifications stipulate restrictions on the materials that can be used, then a statement to this fact should be included in the submission. Otherwise, the manufacturer should be responsible for proving that it would be of benefit to the responsible organization that these restricted materials be used.
If common construction materials are being used, such as concrete, steel, or wood, the specific requirements are probably included in the noise barrier specifications. However, the proliferation of materials such as new plastics and recycled materials has most likely not been addressed in many specifications. Most specifications will have only general references to these, which generates another instance when the acceptance fundamentals, as described before, along with performance criteria, should be used.
Test Results - Test reports are crucial to any acceptance process. How tests are conducted and by whom could mean the difference between acceptance and rejection of the submission. All testing should be done by an accredited, independent laboratory acceptable to the approving responsible organization. However, on some occasions, it may be necessary to have specific testing conducted by the manufacturer. This should only be allowed in the presence of the responsible organization's representative knowledgeable in the specific test procedure.
Whenever possible, testing of samples should be performed using full, production run products. In some cases, it might be advantageous to have the approving organization select the samples for testing. Caution should be taken when the tests are conducted on samples made specifically for testing purposes.
The submission should include complete copies of all required test results. Names of the laboratories, technicians, and telephone numbers should also be available.
Drawings and Associated Notes
The drawings should include the following items:
The accompanying notes should include:
All drawings and accompanying notes should be dated, stamped, and signed by a registered engineer.
Calculations - Typically, noise barrier manufacturers are responsible for the structural integrity of their noise barrier system. Therefore, copies of comprehensive design calculations should be provided demonstrating that the panels, posts, and footings are capable of withstanding various wind loads, ice credations, and soil conditions in accordance with the codes stipulated by the approving organization.
Quality Control Plan - The quality control plan should outline the manufacturer's procedures to ensure production of a consistently acceptable product. This plan will vary considerably depending on the type of materials used as well as the differences in the manufacturing processes.
Maintenance - Details should be provided to indicate what protection has been used to address the graffiti issue, and, specifically, how to restore the components to their original appearance. Also, in cases of minor damage, a description of the repair technique should be included.
After a review of the information presented in the submission, the first of several decisions should be made with respect to adoption, rejection, or further evaluation of the product.
New product evaluation forms should be used to obtain information from the manufacturer to aid in properly evaluating the new product. These forms assist in providing orderly and concise information, reducing misunderstandings, and avoiding delays resulting from the absence of needed information that may be available but is not included in the submittal.
A generic new product evaluation form is typically designed to obtain the following information:
This form can also be used to notify the manufacturer of any conditions that must be met before evaluation will be considered.
The second step of the new product evaluation process typically includes an in-depth study of all material submitted by the manufacturer. At this time a needs assessment should be made. Acceptance of products for routine use at the completion of this stage is rare. However, most products offering no more than moderate promise may be rejected at this time.
The third step in the new product evaluation process may consist of laboratory testing and/or field trials to test performance under local field conditions. This is likely to be the most time consuming part of the evaluation process and is applied only to those new products that appear to have a particularly good chance of filling a need. Some caution should be exercised in the acceptance of samples for testing to be certain that the samples truly represent the product to be furnished. Randomly chosen samples are preferable to stock samples. In many cases, the field trials will provide the final evidence that a new proposed noise barrier product will meet established requirements.
Well-designed experiments, careful attention to performance observations, accurate record keeping, and thorough reporting of the results are the essential components of any successful product evaluation system. Improperly designed and conducted experiments that result in early failure can be both expensive and a source of public embarrassment and can also lead to inconclusive results that may unnecessarily prolong testing or, when serving as the basis for rejection of a product, produce controversy between the manufacturer and the responsible organization.
Each material should also be assessed for their ability to be recycled or disposed of in an acceptable and cost effective manner at the end of their useful life. This is particularly critical when considering the use of components already made of recycled materials.
Completion of this stage of the new product evaluation process usually leads to either acceptance or rejection of a product, except in those few instances where the need for further evaluation becomes evident.
Once a product has been found to be acceptable, evaluation results should be converted into the "media of practice," which include standards, specifications, manuals, policy statements, and the like.
Manufacturers usually can be expected to apply their promotional expertise in encouraging the use of approved new products. However, internal measures considered to be within the scope of the total new product evaluation process may also be necessary for a new product to reach its full potential of usefulness. Some of these measures may include demonstrations, policy statements, training materials, documentation feedback, workshops, and promotional announcements.
Follow-up observations and evaluations of the in-service performance of approved new products can provide documentation of benefits, point out early failures, and call attention to adjustments that may be needed to achieve intended objectives. To ensure that the evaluation process works, it is essential that a comprehensive regiment of conducting routine observations of service performance be established. It is also important to involve field staff in this stage of evaluation by encouraging them to routinely check for early signs of problems by instructing them on what to look for and how to report it.
Well organized channels of communications within agencies regarding new product evaluation and use are necessary to receive full value from evaluation systems. Well planned evaluations that produce conclusive results and orderly and understandable reports with appropriate documentation have an important bearing on the correctness of decisions regarding the disposal of products that have undergone evaluation.
The regular exchange of information on new products among states and on a national and international level is also valuable for locating useful new products and avoiding unnecessary duplication of evaluation efforts.
It is useful to recognize that the concepts and techniques of new product evaluation are similar in many ways to the concepts and methodologies of value engineering. NCHRP Synthesis 78: Value Engineering in Preconstruction and Construction, contains a considerable amount of information on methodology that applies to new product evaluation as well as to value engineering.ref.45
Although value engineering concerns a broader area, the basic aims of new product evaluation and value engineering are the same. Both seek to do more with available resources and without loss of service and both apply user-oriented approaches. Further understanding of the similarities can be gained from the following definition of value engineering as provided by the Society of American Value Engineers: "Value engineering is the systematic application of recognized techniques, which identifies the function of a product or service, establishes a value for that function, and provides the necessary function reliably at the least overall cost."
Due to the many similarities between the aims and processes of new product evaluation and the carefully structured and tested methodologies that characterize value engineering, it is recommended that these methodologies be considered in any review of an existing new product evaluation system for the purpose of improvement.
Handling and storage requirements should be detailed for all of the various components while at the manufacturing facility, en route to the project, and on the project site.
Every product that is installed along highways should be required to meet certain expectations for safety, performance, and durability. Noise barriers are no exception to these requirements. With respect to safety and performance, the requirements and evaluation of noise barriers are specific, and are usually described in great detail by local structural design codes and environmental regulations. However, when it comes to durability, the individual specifying agencies are usually left to develop their own evaluation procedures. Defining an appropriate test method that predicts long-term performance under actual field conditions is the challenging task.
To obtain valid results, the specimens used should be taken from a finished production run product as opposed to small handmade pieces that were specifically made for the test. By insisting on this, the test results can also be used to evaluate in-plant quality control and production operations.
In general, the tests discussed below apply to all types of barrier systems. Additional tests applicable to specific barrier systems (concrete, metal, and wood) follow in Sections 10.3.1 through 10.3.3.
Slump Test (Suitable for Wet-Cast Concrete Only) - This test determines the stiffness and consistency of freshly mixed concrete and, in general, is a good indicator of the amount of water in the mix. Although water is essential in the production of concrete products, too much water tends to increase the distance between the particles in the mix to a point where they are too far apart to create a good strong link with each other. Not enough water will prevent the mix from hydrating properly and, hence, prevent the chemical reaction needed to develop a strong bond between the particles in the mix.
Samples should be taken just before pouring into the molds or form work. Slump should be measured in accordance with CAN/CSA A23.2-5C (Methods of Test for Concrete). This test is not applicable for dry cast concrete mix, since it is only slightly dampened and does not tend to deform under it's own weight.ref.48
Air Content (Suitable for Wet-Cast Concrete Only) - This test determines the amount of air in cured concrete. The test is a good indicator of durability of concrete which may be frequently exposed to freezing and thawing conditions. The measure of the volume of air entrained and entrapped in the concrete is expressed as a percentage of the total volume of the sample. Samples should be taken just prior to pouring into the molds or form work. Testing should be performed in accordance with CAN/CSA A23.2-4C (Air Content of Plastic Concrete by the Pressure Method).ref.49
This test is not applicable for dry cast concrete mix due to the difference in void structure and consistency of dry cast concrete.
Compressive Strength - This test determines the maximum compressive strength of cured concrete samples. A load is applied uniformly over the entire surface area of the sample ends. The strength is measured at the point of failure and is expressed in MPa (PSI) which represent the average cross-sectional area of the sample.
There are 2 methods of obtaining samples: One is molding a cylinder from the fresh concrete mixture during the pouring stage of the casting process. The other is by cutting a sample from a cured finished product. The cylinder method is more suitable for wet cast products. The cut sample method is more suitable for dry cast products. Samples should be prepared according to ASTM C684.ref.50
No reinforcing bars or mesh should be present in the cut samples since the cutting or coring operation may damage the concrete surrounding the reinforcing when the cutting or coring bit comes in contact with the metal. Testing should be in accordance with ASTM C496.ref.51
Air Void Analysis (More Suitable for dry-cast concrete products) - This test determines the shape and size of air voids in cured concrete samples. Testing should be in accordance with ASTM C457.ref.52
Freeze-Thaw/Salt Scaling - There are 2 standard test methods currently available for this test: (1) ASTM C666; and (2) ASTM C672.ref.53 and ref.54
ASTM C666 determines the resistance of concrete specimens to rapidly repeated cycles of freezing and thawing in the laboratory by two different procedures: A-Rapid Freezing and Thawing in Water, and B-Rapid Freezing in Air and Thawing in Water. This method is not an appropriate test for noise barriers on the basis that, by its own admission, the standard states that "Neither procedure (A or B) is intended to provide a quantitative measure of the length of service that may be expected from (any) type of concrete." In addition, only distilled water is used during the procedure. This does not represent common field conditions in northern or coastal regions where these products are constantly subjected to salt laden moisture.
A number of other concerns related to ASTM C666 test procedures have been documented by the Strategic Highway Research Prograrn, in a 1994 report (SHRP-C-391) identifying problems with the design of the apparatus used for the test as well as the inadvertent drying of the samples during the air freezing cycle.ref.55
ASTM C672 can be used on all concrete products, both precast and cast-in-place, to evaluate the effects of air content, cement factor, slump, water-to-cement ratio, surface treatment, curing and other variables on concrete's resistance to salt scaling and rapid freezing and thawing. It should be noted that some agencies have adopted a slightly modified version of this test method. The modifications include:
-The use of a 3 percent sodium chloride solution for both the preliminary conditioning of the sample and the actual test itself; and
-A quantitative method of measuring deterioration during the test period .
Example:
After 50 freeze/thaw cycles, the loss of mass from the surface of any sample shall not exceed 0.8 kg per m2, and that the samples shall exhibit no deterioration in the form of cracks, spalls, delamination, aggregate disintegration, or other objectionable feature.
Density - Determining the density of the concrete material provides information related to the degree of compaction the concrete mix was subjected to in the mold prior to curing. The denser the product, the better the quality of concrete assuming that a suitable mix design was used and the product was cured properly.
Water Absorption - This test determines the amount of water the sample can absorb over a given time period. Generally, the more water absorbed, the poorer the quality. Samples should be cut from the cured concrete product. By thoroughly drying the samples in an oven and then submerging into a tank of distilled water for a specific length of time, the percentage of absorption can be determined. Since this is a relatively common test with each responsible organization having their own preferences, this section will not suggest any one method to be used.
Minimum Cover Over Reinforcing - Panels and posts should be checked to ensure that the minimum concrete cover over the reinforcing is maintained during the casting operation. Adequate cover is critical in preventing premature penetration of salt laden moisture from reaching the reinforcing bars. This results in the corrosion of the bars and subsequent spalling of the concrete surface along with the drastic deterioration of the structural properties of the components.
There are several methods available to determine the amount of concrete cover over reinforcing bars of mesh. The most accurate method (but also the most destructive) is by cutting through the concrete to expose its core and to physically measure the distance from the concrete surface to the reinforcing bars. A less destructive method is to use specialized x-ray and electronic equipment to detect the location and, depending on the technology used, the amount of cover and the size of the bar or mesh. Although these devices are, to varying degrees, less accurate than the cutting method, it is non-destructive and can usually be performed in-situ.
Dimensions - All precast and cast-in-place concrete products should be checked for proper dimensioning (see Section 11.5.1).
Visual Inspection - All precast and cast-in-place concrete products should be visually examined to identify any unusual and unwanted features which will affect the structure, durability, and performance of the noise barrier wall, such as honey combing, knuckling, cracks, and voids.
This section will discuss the more common procedures for submissions and evaluation leading up to the acceptance of a noise barrier installation. Further guidance can also be obtained from CAN/CSA Z107.9.ref.66 Final acceptance of a noise barrier installation can typically be broken down into 4 major segments:
Common practice includes submission, by owner of the noise barrier system design, for evaluation by the responsible organization. The submission normally would include detailed generic or non-site specific information of a particular noise barrier system. See Section 10.1.1 for details.
Acceptance of a proprietary noise barrier system should be based not only on the test data and documentation submitted with the application but also on subsequent results of laboratory and field testing and trial installations. Further, acceptance should be granted only if the design and materials conform to the required specification and that the system has been demonstrated to be constructable.
General grounds for a noise barrier system being accepted or rejected could be based on, but not limited to, any of the following conditions:
If the vendor changes the design of the system or any of its components, then the system should be reevaluated.
The manufacturer/fabricator of any or all noise barrier systems components should be required to provide information related to the production of the noise barrier system. If, after acceptance, the manufacturer initiates any variations to the system design or any changes to component fabrication and/or plant location, reevaluation and possible re-qualification of the manufacturer/fabricator should be considered. All submissions should at least include the following information:
Acceptance of the noise barrier manufacturer/fabricator should be based not only on the test data and documentation submitted with the application but also on subsequent results of laboratory and field tests trial installations. Further, acceptance should be granted only if the design and materials conform to the required specification, and the manufacturer has demonstrated the ability and has the equipment and facilities necessary to consistently produce an acceptable product.
Free access should be allowed to the place(s) of manufacture of the noise barrier components for the purpose of random inspection and examination of plant quality control records, certificates, materials used, process of manufacturing including, but not limited to, welding, galvanizing, prefabrication, and precasting, and to make any test as may be considered necessary to ensure compliance with this specification.
General grounds for a noise barrier manufacturer/fabricator being accepted or rejected could be based on, but not limited to, any of the following conditions:
The vendor of the noise barrier system, should submit project or site specific design details (shop drawings and documents) for each system to be installed. If, after acceptance, there are any changes made to the system design or to component fabrication and/or plant location, reevaluation and possible re-qualification of the noise barrier system and the manufacturer/fabricator should be considered. The submission shall include at least the following information:
Acceptance of the noise barrier project or site specific design should be based on, but not limited to, the reports, drawings, and documentation submitted with the application as well as subsequent results of laboratory and field tests. Further, acceptance should be granted only if the design and materials conform to the required specifications.
A noise barrier system project could be rejected if it demonstrates any of the following conditions:
The installer of the noise barrier system should provide a noise barrier system using acceptable manufactured/fabricated components in accordance with project specifications (shop details). The installer should provide to the responsible organization, prior to installation, all test and production certificates for each production lot supplied by the manufacturer/ fabricator, showing compliance with all requirements of the prescribed specifications. Any variations or changes during installation from the accepted noise barrier system design, the accepted component fabrication and/or plant location, or the accepted project specific details should warrant reevaluation of the installation and possible re-qualification of the noise barrier system, the manufacturer/fabricator, and/or the project specific details.
Acceptance of the noise barrier installation should be based on compliance with all the requirements and specifications associated with the noise barrier system as detailed by the design, the manufacturer/fabricator the project specific details, and any other prescribed specifications, as well as plant inspections and subsequent results of laboratory and field tests prior to, during, or after installation.
If any part of the installation fails to comply with any of the prescribed requirements, the noise barrier installation should be corrected by the installer so that all components meet those specifications. Further, any components damaged during installation or alterations should be disposed of and replaced by the installer.
A noise barrier installation should be rejected if it demonstrates any of the following conditions:
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Product evaluation considerations for all noise barriers.. |
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|---|---|---|---|---|
| Item# | Main Topic | Sub-Topic | Consideration | See Also Section |
| 10-1 | Evaluation Process | Submission | It is critical to know what the requirements and specifications are for acceptance by the responsible organization. And, just as important, in what format are the agencies accustomed to seeing these submissions? | 10.1.1 |
| Detailed Evaluation | Some caution must be exercised in the acceptance of samples for testing to be certain that the samples truly represent the product to be furnished. | 10.1.3 | ||
| Performance Feedback | It is essential that a comprehensive regiment of conducting routine observations of service performance be established. It is also important to involve field staff by encouraging them to routinely check for early signs of problems, by instructing them on what to look for, and how to report it. | 10.1.6 | ||
| 10-2 | Sampling and Testing Requirements | . | The testing specimens used should be cut from a finished production run product as opposed to small handmade pieces that were specifically made for the test. By insisting on this, the test results can also be used to evaluate in-plant quality control and production operations. | 10.3 |
| 10-3 | Criteria for Approval | Acceptance of Design | If the vendor changes the design of the system or any of its components, then the system should be reevaluated. | 10.4.1 |
