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

Abstract

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. After the analysis, the paper suggests an improveed 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 % (NH4)2SO4 solution and the concentration of SO42- in the solution and the material was measured. As a parameter that quantifies cement degradation, the quantity of bonded SO42- 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.

Keywords

• sulfate
• corrosion
• Portland cement
• coal fly ash
• mathematical model