Book Description

The primary objective of the present study was to identify the critical properties (based on the laboratory tests) that could be correlated to the field performance of the rapid setting repair materials.The first phase of the project involved laboratory evaluation of six commercial rapid-setting repair materials (RMs). When tested in the laboratory, all but two exhibited acceptable rates of strength gain and three displayed relatively poor freeze-thaw resistance. All the RMs exhibited acceptable values for free-shrinkage, high resistance to cracking and good bond to substrate concrete. The resistance to chloride ion penetration of one of the RMs was very poor.The second phase of the project involved field installation and performance evaluation of the RMs. It was seen that while, in most cases, the controlled laboratory conditions yielded consistent mixes and acceptable performance, the properties of mixes produced on site were more variable. This was the result of somewhat uncontrolled changes in the amount of aggregate extension used, moisture content of the aggregates, amount water added and ambient temperature conditions. Follow-up inspection of the repair patches indicated that all the patches except one underwent premature failures (primarily cracking and edge de-bonding). The ambient temperature during the repairs was around 10°C. This led to an extended set-time for all the materials. The 12-hr compressive strengths values of the specimens from the field-mixes were occasionally lower than the 4-hr compressive strength values of laboratory mixes. Since the repairs were open to traffic after approximately 4 hours after placement, the low early age strengths could be a potential reason for premature failures of some of the patches.In general, several materials were found to be very sensitive to excess water added during mixing, resulting in a significant impact on the durability properties - especially the freeze-thaw resistance. In the field, for most of the materials, the consistency of the mixes varied across batches - this can be attributed to the variations in the aggregate extension adopted, mix-water added and the moisture content of the aggregates used. Construction-related issues (consolidation and finishing) also played an important role in the performance of the repair patches.