Damage assessment in cellulose–cement composites using dynamic mechanical characteristics

Abstract

This paper reports on an experimental investigation of test methods that can detect damage in cement composites, incorporating cellulose macro-nodule fibers, subjected to freezing/thawing and immersion in hot water. Conventional methods of ascertaining damage, such as porosity and flexural strength testing, were carried out, along with dynamic mechanical testing for determination of elastic modulus and damping capacity. Increase in porosity and reduction in flexural strength (as compared to normally cured specimens) were observed for low fiber volume composites subjected to freezing and thawing, whereas no significant changes were observed for specimens with higher fiber volumes. Determination of dynamic elastic modulus and specific damping capacity at regular intervals of exposure showed that the high volume of porous macro-nodules in the mixture prevented damage due to freezing and thawing by acting as stress release sites. No appreciable change in porosity and flexural strength was observed for specimens continuously exposed to hot water; however, reduction in relative modulus and increase in damping capacity was observed. The changes in these system properties suggest that a certain degree of damage might be occurring under sustained hot water exposure, which the determination of porosity and flexural strength could not capture. Using a stiffness-loss map, it is shown in this paper that the damping characteristic is more sensitive than the stiffness in detecting damage as a result of continuous exposure to hot and wet conditions.