Modeling of Sulfate Resistance of Flyash Blended Cement Concrete Materials

Sulfate attack in concrete structures is among the major durability concerns in civil infrastructure systems. Proper modeling techniques can help us understand the influence of aggressive environments on the concrete performance, and improve the decision making process in every stage of construction and maintenance. Test procedures were developed to analytically and experimentally correlate the service condition of concrete with variable flyash levels subjected to external sulfate attack. Expansion tests were conducted according to ASTM C1012 using 1×1×11 in. specimens and the results were compared to the modified test using 0.4×0.4×1 in. specimens. Microstructure of the specimens were studied with Scanning Electron Microscopy (SEM) for compositional changes and formation of crack patterns due to sulfate exposure. A simplified model is presented which used cement chemistry, concrete physics, and mechanics to develop a diffusion-reaction solution for predicting sulfate penetration, reaction, damage evolution and expansion, leading to degradation. A simplified approach is presented to compute the rate of degradation and expansion potential using a series solution approach. The model can address the interaction effects of various parameters using calibration data from various flyash compositions