Degradation of Unsaturated Polyestsr Resin Mortars

An aceelerated aging test of low shrinkage resin mortars in water was carried out. Three kinds of unsaturated polyester resins (UP) were employed as binding materials for the resin mortars. Poly (vinyl acetate) (soluble in UP: single phase) and polystyrene (insoluble in UP: two phase) were used as low shrinkage additives (LSA). A decrease in flexural strength in water was ascribed to both residual stress in the resin mortars and water diffusion into the resin mortars. Two phase and no LSA UP resin mortars showed a similar tendency in strength decrease in water. The main factor in their strength decrease was micro cracks caused by permeated water. Equations by which we can estimate degradation degree of these resin mortars were derived. Water permeates easily through the single phase resin mortar, because fine continuous pores were formed to prevent UP resin shrinkage in its setting process. About 20% of the strength decrease was observed for single phase resin mortar at the early stage of aging test (less than 100 hours). However, the decrease of the strenght was very little over a long period of time.