Introduction and Background Concrete can be damaged when it is 1) sufficiently wet (has a high degree of saturation) and 2) exposed temperature cycles that enable freezing and thawing. The damage that occurs due to freezing and thawing can lead to premature deterioration, costly repairs, and premature replacement of concrete infrastructure elements. Current specifications for frost durability are largely based on work completed in the 1950s, and while this work included many landmark discoveries (Kleiger 1952, 1954) it may not be completely representative of materials used in modern concrete mixtures. Further, the majority of current frost damage studies investigate freezing and thawing in water. While it is known that the presence of salts alters the freezing behavior, little research on frost damage is performed on air entrained concrete in salt water other than scaling studies. While the use of water greatly simplifies the system, it is not the most representative of what occurs on America’s bridges and highways. Results from recent studies suggest that there are several ways in which frost damage can be reduced through new tests and improve specifications that can lead to extended service life of concrete infrastructure. A brief summary of some of these findings and their relation to this proposal is provided below. The conventional approach that is used to improve the frost durability of concrete is with the addition of an air entraining admixture (AEA) while the concrete is mixed. The AEA creates small well-dispersed air filled bubbles in the fresh concrete. Current theories hypothesize that bubbles act as pressure relief reservoirs for water to move during freezing. These air bubbles also decrease the degree of saturation in the concrete (Li et al. 2011). Because a large number of variables during the batching, mixing, and placement impact how AEAs perform in concrete, it can be challenging to provide a consistent air void system in hardened concrete in practice. Task 1 will review the most relevant findings from the literature and use that information to develop a testing matrix. This work will include information on how certain binders and admixtures may be incompatible in some circumstances. For example, research by Sutter at Michigan Tech has investigated the role of fly ash on air entraining dosage and research by Ley at Oklahoma State University has shown that current frost damage specifications may not always be adequate for mixtures with some modern water reducers. After the test matrix is developed the samples will be created and used throughout the testing for the remainder of the study to enable the various tasks to be compared. Specifically, the work will take advantage of novel techniques that have been developed to measure the quality of the air system. A novel method that has been developed to accurately measure void systems in fresh field concrete. Further, advanced experimental tools have been developed to study the three dimensional distribution of air in hardened concrete. For example, X-ray tomography based techniques can be used to image the 3D distribution of voids (Ley et al, in development). While these novel tests show great promise they will be compared with more conventional tests like two dimensional air void analysis and freeze-thaw testing to provide measures that relate these mixtures to measurements that are more commonly used today. Additional research has investigated the role of absorption and saturation in the freezing process and how this behavior may change in the presence of deicing salts. It has been suggested that the freeze-thaw behavior of concrete can be related to the rate at which the concrete absorbs water and reaches a critical degree of saturation (Fagerlund 2004, Yang et al. 2006, Li et al. 2011). It has been proposed that once the critical degree of saturation is reached the sample begins to crack and the stiffness degrades rapidly. While this

The goal of the research is to produce improved specifications, and test methods; while, improving the understanding of the underlying mechanisms of frost damage. Specifically, this work will seek to develop new test procedures that may be faster and/or more reliable than the existing methods. The objectives of this project are: • Determine the necessary properties of the air-void system to provide satisfactory frost durability in laboratory testing of laboratory and field concretes with different combinations of admixtures, cements, and mixing temperatures in salt environments • Determine the accuracy of a simple field test method that measures air void system quality with field and laboratory concrete • Determine the critical combinations of absorption and the critical degree of saturation on the frost durability in accelerated laboratory testing in the presence of deicer salts • Establish new test methods and specifications for fresh and hardened concrete to determine frost durability and field performance Understanding the research on freeze-thaw mechanisms is important for two main groups: 1) practicing professionals and 2) graduating undergraduate and graduate students. A portion of this project will be dedicated to development of a strong educational technology transfer program. Develop a short course that utilizes streaming video (and could be placed on a DVD for widespread dissemination). Practicing professionals frequently require information in a short time frame to respond to practice-based problems. The DVD/streaming video approach provides the information as it is needed and as such it is perfect for this application.

Task 1: Literature Review and Development of the Testing Matrix Task 2: Sample Preparation Task 3: Validation of the Super Air Meter Task 4: Use of X-Ray Tomography of Air Voids and Frost Damage Task 5: ASTM C 666 Task 6: Absorption and Desorption Task 7: Degree of Saturation and Damage Development Task 8: Rate of Damage Analysis Task 9: Technology Transfer Task 10: Final Report

Budget The estimated budget is $525,000 for a 36 month project ($17,500 per state with 10 partners over 3 years). The use of 100% SPR funds has been approved (waiver attached).