Effect of Concrete Based Alkali Solutions on Short-Term Durability of E-Glass/Vinylester Composites

Abstract

Although the mechanisms of degradation of bare E-glass fibers by concrete based alkaline solutions are fairly well documented, the effects on ambient temperature cure E-glass/Vinylester composites have heretofore not been well investigated. This paper reports on the results of a study of effects on E-glass/Vinylester composites immersed in a number of concrete-based, and derived, solutions for a period of 18 months. It is shown that degradation is not merely due to pH levels, but to a combination of pH level and solution chemistry. The degradation is at the levels of the fiber-matrix interface and the fiber. A range of damage states are identified and correlated to changes in mechanical properties. In addition to tensile testing, dynamic mechanical thermal analysis, optical microscopy, and SEM/EDX analyses were conducted. It is shown that alkali salts do migrate by diffusion through the composite and by wicking along the fiber-matrix interface into the composite and can cause pitting of the fiber surface.