Improving lime-based restoration mortars: Effect of type and utilization rate of binder and aggregate

Abstract

Lime-based mortars, frequently used in historic structures, are classified as hydraulic and non-hydraulic according to how they gain strength. In the past, various methods were used to improve the strength and durability properties of lime-based hydraulic mortars such as Khorasan mortar. Today, in studies carried out to increase the strength of lime-based mortars, the effects of binders, aggregates, and additives, which are the basic components of the mortar, are examined. In this study, the mechanical properties of Khorasan mortar mixtures, which are frequently used in the restoration of historical structures, were examined under the influence of different parameters. In particular, the effects of variables such as aggregate type and ratio (river sand and crushed brick), binder type and ratio (natural hydraulic lime, metakaolin, and blast furnace slag), and water/total dry material ratio on the strength of mortars were investigated experimentally. In the experimental study, two different aggregate types (river sand and crushed brick) were used in 1/3 and 1/2 ratios, and three different binders (natural hydraulic lime, metakaolin, and blast furnace slag) were used in different ratios. The water-to-total-dry-material ratios were set at 0.2 and 0.25. Standard test samples were then created from the prepared mortar mixtures, and their flexural and compressive strengths were assessed at 28 and 56 days. A statistical analysis of the experimental data was conducted using the Taguchi method, allowing for a detailed examination of how the different parameters influenced the strength of the mortars. Through this analysis, the optimal mixture ratios that maximized mortar strength were successfully identified.