6.1 SUMMARY
The cost of corrosion of infrastructure elements is significant. As new products are developed to address the challenge of reducing corrosion, these products have to be objectively assessed to determine their effectiveness. SHAs do not have the resources to evaluate all products, nor should it be the responsibility of this agency to do this. However, if products can improve the corrosion resistance of infrastructure components and systems, there could be significant value added by implementing the use of these products. A methodology is needed to validate the corrosion performance of new products while at the same time reducing the time and costs necessary to evaluate the performance of these systems.
This research found that the MM test is relatively simple to perform and provides reasonable results for most products in a reasonable time frame with minimal relative cost. The CCIA and ACT tests can provide reasonable results over short periods with relatively low costs but these tests require polarization resistance testing to provide quantitative data. The polarization resistance testing is not commonly performed in SHAs and is considered difficult and complex. The ASTM G 109 and MG 109 tests are simple but can take significant time and effort to determine effectiveness of a product. In most cases the time required to assess the effectiveness of a product is well beyond the time a manufacturer or producer can wait to implement the new product.
6.2 CONCLUSIONS
Five different corrosion test methods were evaluated in this report to evaluate their effectiveness in assessing corrosion performance. In addition, comparisons between the results were made with the standard conventional test method, ASTM G 109. Results indicated that SHAs can save considerable time and money by using one of the rapid methods instead of the standard ASTM G 109 method. Although no methods can assess all variables that influence corrosion, the research indicates that information can be gleaned from the rapid tests. Although all tests have benefits and could be considered for evaluating the different variables, the expertise and
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time available must be considered before performing the tests. Based on the testing performed in this research, the MM test was identified as providing the most reasonable assessment of different variables for assessing corrosion performance. In addition, this test is relatively economical and can be completed in a relatively short time frame.
6.3 RECOMMENDATIONS
The researchers believe the SHAs should not be required to assess new materials for corrosion performance. Realizing that there could be potential value added to the infrastructure and taxpayers, new products should be evaluated. It is recommended that evaluation of products for improved corrosion resistance be performed by independent organizations qualified to assess the product. TxDOT should provide approval of the organization. In addition to the independent assessment, it is recommended that TxDOT perform or contract an agency to perform a limited number of tests to validate the tests from the independent organization. Simple comparison of means tests can be performed to assess the validity of the results performed by the independent organization and TxDOT (or TxDOT’s representative). Consistent application of procedures by experienced technicians is very important to obtain reasonable results and to analyze and draw correct conclusions from obtained data. Procedures presented in this program should be used.
Although the researchers believe that the task of testing and evaluating new materials and methods should be contracted to experienced independent research agencies and laboratories, the decisions on which method to use and what kind of experimental program to use should still be made by the SHA. Results of this study showed that different test methods may be more sensitive to different variables, and different test methods may be more appropriate to test different materials.
It is recommended that the MM test be specified to evaluate the corrosion performance instead of the standard ASTM G 109 test. The ASTM G 109 samples take excessive time to activate. Evaluation of results obtained from the MM test were compared with the ASTM G 109 results and were found to be similar for regular steel samples embedded in concrete mixtures with a water-cement ratio of 0.55. Both methods showed that the corrosion exhibited by stainless steel was negligible. For conventional steel samples, the MM method was sensitive to different water-cement ratios and corrosion inhibitor levels. An additional advantage of the
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MM test is its fixed duration that would allow the SHAs to know exactly how long it will take to complete the corrosion testing.
Although the MM test is a faster and more feasible alternative to the ASTM G 109 method, results indicate that it cannot be used to test dielectric (epoxy) coated samples. No accelerated test method was identified to quickly evaluate dielectrically coated reinforcement. As such, it is recommended that the MG 109 test be used. However, additional research should be performed to identify alternative reliable and accelerated tests.
If the objective of the SHA is to evaluate the critical chloride threshold of the system being examined, the MM test cannot produce these data. In this case, it is recommended that the CCIA test or ACT test be used. The CCIA test can provide the SHAs with instantaneous corrosion rates as well as total corrosion loss and critical chloride threshold data. Results obtained from the CCIA test were similar to the results of ASTM G 109 testing at a water-cement ratio of 0.55 for conventional steel samples. However, it should be noted that the CCIA method was not found to be an appropriate test to test epoxy coated, galvanized, and stainless steel samples. The ACT test was found to be able to evaluate corrosion resistant reinforcement in earlier studies.
As with any testing, the corrosion test plan will have to determine the number of samples to be tested. Because of the large scatter common with corrosion testing, it is recommended that a minimum of 15 samples of the accelerated test be evaluated by the independent testing agency. Additional samples may be needed. It is also recommended that at least three samples be tested by TxDOT or its representative. Control samples must also be fabricated and tested to compare the performance of the proposed system. It is recommended that 15 control samples be tested by the independent testing agency and 3 control samples be tested by TxDOT or its representative.