Effects of natural zeolite addition to lime based render layers for restoration of historical buildings

Abstract

Renders, as the most exposed elements of historical buildings, have limited durability therefore their periodical inspection and replacements are necessary. Various studies have been made with a purpose to develop renders with improved resistance to environmental conditions, yet compatible with originally used materials (mortars and masonry). Although traditional renders were applied in several layers with different properties, most of the studies are based on only one layer production and testing. Natural zeolites are crystalline hydrated alumnosilicates with a specific three-dimensional framework structure. They have been used as a pozzolanic addition in lime mortars since ancient times. This paper presents the effects of natural zeolite addition on physical and mechanical properties of lime-based historical mortars, representing both base and superficial layer of traditional renders. Only locally available materials were used in the mix design. Capillary water absorption coefficient, water absorption after 48 hours, open porosity, flexural and compressive strength were measured on prismatic samples after 14, 28 and 60 days, and compared with the recommended properties for each render layer. The results demonstrate positive effects of zeolite addition to lime based render layers for restoration of historical buildings.