Highway Concrete Technology Development and Testing Volume IIi: Field Evaluation of SHRP C-205 Test Sites (High Performance Concrete)

Chapter 4. Conclusions and Recommendations

CONCLUSIONS

This study was intended to investigate the durability and integrity of HES concrete patches built in Arkansas, Illinois, Nebraska, New York, and North Carolina. Strength, modulus, resistance to chloride ion penetration, and visual condition of the patches were used as durability indicators. The results and recommendations presented in this report are based on a comprehensive study of the test data using statistical metHods and engineering principles. Chapter 3 discussed in detail the effects of climate and material properties on the HES concrete durability. The following key observations were made from the data analysis:

• In most cases, the concrete continued to gain strength and modulus with time over the entire performance monitoring period.

• The resistance to chloride ion penetration increased only slightly with time in some instances and was relatively constant in other cases.

• Water reducer type had no significant effect on long-term durability.

• Curing metHod (insulated versus uninsulated) also had no significant effect on long-term compressive strength or the other durability indicators.

• Aggregate type used in the concrete mix had a significant effect on the magnitude of compressive strength but no effect on strength gain, chloride permeability, or AC impedance.

• Concrete mixtures made with crushed granite had the highest compressive strengths, typically 16 to 22 percent greater than that for limestone and marine marl.

• The RCPT test results had a good correlation (90 percent) with the 100-Hz AC impedance test results.

• There were insufficient data to determine the reliability of all three durability indicator variables.

RECOMMENDATIONS

The study was successful to a large extent in that it demonstrated that HES concrete patches, when built using a variety of metHods and materials and exposed to different climatic conditions, can perform adequately in the field with no extraordinary signs of durability-related distresses. However, since the study only spanned approximately 7 years into the life of the patches, additional data will be necessary to study in greater detail the effects of climate, construction, and site conditions that influence HES concrete durability.

It is therefore recommended that more data be collected as the patches age, and that these data be analyzed to make further observations of the long-term durability of these materials.