Concrete Aggregate Durability Study: Fid-Bau Portal

Concrete Aggregate Durability Study

T. Van Dam / D. Peshkin

There are many factors that affect the durability of Portland cement concrete (PCC), including the mix design and the materials used, the quality of construction, and the environment. Durability is not an intrinsic property of the concrete, but instead is related to how the material interacts with the environment. Durability-related deterioration is referred to as materials-related distress (MRD). Common MRDs include those caused by physical processes, such as freezing and thawing, or chemical processes, such as alkali-silica reactivity (ASR) and sulfate attack. This research project was undertaken to determine whether concrete used in the ADOT system is experiencing, or is potentially susceptible to, ASR or sulfate attack, and if so, to what degree. Based on this study, ADOTs current practices are consistent with those of its neighboring states, but by no means are they the most rigorous, particularly related to controlling ASR. The following recommendations are made to improve ADOTs approach to ASR and sulfate attack mitigation to ensure success in the future: (1) ADOT should review its supplementary cementitious material (SCM) specifications to ensure that those materials being used in its concrete have the desired effect of mitigating ASR and sulfate attack. (2) A number of neighboring states permit the use of ASTM C1157 performance-specified cements and ADOT should investigate allowing the use of these cements as well. (3) ADOT is following the current state-of-the-practice regarding aggregate screening for ASR susceptibility. New FHWA guidelines (Thomas et al. 2008A) recommend that long-term concrete prism testing be conducted in accordance with ASTM C1293, Standard Test Method for Determination of Length Change of Concrete Due to Alkali-Silica Reaction, to establish an empirical relationship with the ASTM C1260 test results to ensure mitigation. This would require ADOT to embark on a long-term study to test their most common ASR-susceptible aggregates, but it is the only currently acceptable approach to developing confidence that the ASTM C1260/C1567 results accurately predict field performance.