NH4)2SO4 corrosion of cement in concrete analyzed by an improved mathematical model

This paper gives a critical analysis of the equation that predicts and estimates the progress of degradation for various building materials, recently proposed by Matsufuji et al. 1 After the analysis, the paper suggests an improve-ed mathematical model, particularly for the modeling of sulfate corrosion. Experiments were performed with two samples of Portland cement and two samples of Portland cement with 30 % coal ash. The samples were immersed into a 10 % (NH 4 ) 2 SO 4 solution and the concentration of SO 2- 4 in the solution and the material was measured. As a parameter that quantifies cement degradation, the quantity of bonded SO 2- 4 was suggested. According to the obtained data, mathematical models for the description of sulfate corrosion were defined for all the examined samples. The models were applied for the analysis of the behavior of ash and non-ash containing samples. They allowed a better explanation of degradation which occurred during the investigated time period and even further they showed that ash systems were significantly more resistant to sulfate corrosion.