| With the growing environmental concerns related to the ever increasing waste disposal problem in the US, the utilizing of recycled materials in Civil Engineering construction has become an attractive option, which not only supports the concept of green buildings, but can also bring about economic savings by conserving natural resources and landfill spaces. However, the questionable long-term performance of recycled materials often hinders the widespread use in structural applications. The primary focus of this study was to develop accelerated aging/testing protocols for predicting the durability of recycled aggregate concrete (RAC), Type I Portland Cement, and up to 50% fly ash replacement. Accelerated aging was accomplished by curing the specimens at elevated temperatures regimes for specific durations. Stiffness-time master curves were constructed using Time-Temperature Superposition (TTS) and Stepped Isothermal Method (SIM) based on the Arrhenius Equation. All the methods demonstrated that the stiffness decreased with time regardless of the amount of fly ash. The Arrhenius method allowed stiffness prediction up to an equivalent age of 14,000 hours developed from short-term tests lasting up to 144 hours. It was also found that SIM and TTS provide equitable results, potentially reducing the number of specimens and testing time for durability prediction. |
