In this study, the effect of sludge filler content on the properties of epoxy mortar for repair of concrete structures was investigated. The sludge filler content was varied between 0 and 40% and that of epoxy between 10 and 25% by weight fraction of mortar. Samples were prepared and tested for flow, compressive strength, flexural strength and modulus of elasticity, bond strength, linear shrinkage and coefficient of thermal expansion of properties.
For a given epoxy content, the addition of sludge filler created a favorable mix of epoxy mortar up to 20 wt% beyond which either a dry or an overly thick mix was created; the compressive, flexural strength and modulus of elasticity of epoxy mortar increased up to optimum level of sludge content at which they demonstrated maximum strength and stiffness and then subsequently decreased or remained almost constant with the further increase in sludge content. The mortars containing sludge filler from 10 to 20 wt% with epoxy at 10 wt% were found to have adequate compressive and flexural strength for concrete repair; however, showed poor bond strength with concrete which was lower than 0.7 MPa. Conversely, control mortar prepared with 15 wt % of epoxy was found to show sufficient strength and adhesion with concrete. Moreover, the addition of sludge filler up to 20 wt% improved its bond strength with concrete by more than 50% when compared to the mortars with no sludge filler.
The shrinkage and linear coefficient of expansion of epoxy mortar increased with the rise in epoxy content. However, all the shrinkage-expansion values of the mix proportion prepared in this study were found to be within the allowable limit (-1500 μm < X < 1500 μm) suggested by KS F 4043. On the other hand, the coefficient of thermal expansion of the epoxy mortars prepared were found to be 2 - 4 folds higher than that of ordinary Portland cement concrete. Therefore, to obtain a coefficient of thermal expansion of epoxy mortar close to concrete, the epoxy content should be reduced below 15 wt%.