The production of protective earth-based mortars for earth constructions in southeastern Brazil during the 19th century coffee economy

Abstract

The study of materials used in ancient buildings provides a means to shed light on traditional building practices of past societies, but can serve as inspiration to tackle challenges faced by the current generation. Characterising earth-based structures and finishing elements is part of this mission, especially at a time when earthen architecture is the subject of renewed interest due to its many advantages, particularly in terms of sustainability. This paper considers a set of historical earthen houses built during the first phase of the coffee economy (1820-1880) in the middle Paraíba do Sul River valley, in southeastern Brazil. Physical (colour and texture) and chemical (FTIR, TGA, XRF, and XRD) analyses performed on a large set of mortar and local soil samples collected in the region formed the basis for discussing possible soil selection criteria as raw materials, texture solutions, and the stabilisation strategy of the final product. This last aspect implied the addition of small quantities of lime, in the case of external renders and more sporadically in plasters, without the use of fibres or organic additives. Chemical data and historical sources suggest that the raw materials used for this purpose were probably brought to the region from coastal areas.