ABSTRACT
The behavior of portland cement mortars with different water/cement-ratio being immersed in 5% and 1% ammonium sulfate solutions under different load levels was studied within a comprehensive research program. The strength development and the weight changes of the specimens were determined. A life-time coefficient is proposed as a parameter describing stress corrosion process. The corresponding behavior of the mortars immersed in Ca(OH)2 saturated water was determined as reference.
The results show that the strength of the mortars increases at the first stage of the immersion depending on water/cement-ratio and loading level. A high w/c-ratio leads to a comparatively larger increase of strength. The increase in bending is higher than that in compression. Specimens under bending load indicate a smaller increase in strength than the unloaded ones. About 14 to 28 days after the immersion the mortar strengths tend to decrease. The decrease of strengths of the loaded specimens is significantly larger than those of the unloaded ones according to the applied load level. The additional bending tensile stresses accelerate the rate of disintegration by chemical attack, i.e. stress corrosion occurs.
