Research paper The effect of the substitution of hydrated lime with phyllite on mortar quality Thays F. de Oliveira a , Márcia H. Beck a , Pedro V. Escosteguy b , Edson C. Bortoluzzi b , Marcio L. Modolo a, ⁎ a Instituto Federal de Educação, Ciência e Tecnologia do Paraná, Av. Araucária, 780, Vila A, 85860-000 Foz do Iguaçu, Paraná, Brazil b Universidade de Passo Fundo, BR 282-Km 292, Bairro São José, 99001-970 Passo Fundo, Rio Grande do Sul, Brazil abstract article info Article history: Received 30 June 2014 Received in revised form 24 December 2014 Accepted 27 December 2014 Available online xxxx Keywords: Mortar Lime Phyllite Coating Porosity In Brazil, phyllite began to be used as a substitute for hydrated lime for binary cement/lime mortar. Phyllite is cheaper and contributes more to the health of the workers than hydrated lime. However, this substitution has generated problems in coatings. Here we evaluate the effect of this substitution on a binary cement/phyllite mor- tar quality. The cement:phyllite:sand ratio tested was 1:0.4:6.5, which is the more common ratio used in Brazil, providing greater savings. The chemical and mineralogical compositions of hydrated lime and phyllite as well as some mortar properties were characterized. Overall, our results show that phyllite mortars have greater porosity, lower linear retraction, and lower pullout strength. These characteristics are due to the properties of expansion and retraction of the material and the absence of lamellar structure in hydrated lime. Although phyllite has been used as a substitute for hydrated lime due to economic and health reasons, our study indicates that the con- tribution of phyllite for mortar quality is lower than that of lime, therefore decreasing mortar quality rather than improving it. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Mortar is a mixture of binder (cement or lime), mineral aggregates with fine granulometry (sand), and water, with a capacity for hardening and adherence (Guimarães, 2002; Gleize et al., 2003). Two types of limes are used to make mortars: hydraulic lime (natural hydraulic, formulated or hydraulic lime) or air lime (EN 459-1:2011, 2011). According to EN 459-1:2011 (2011), hydrated lime is composed pri- marily of calcium oxides (CaO) or calcium hydroxides [Ca(OH) 2 ] and smaller fractions of magnesium oxides. Then, this kind of lime confers water retention and workability properties to the mortars when in the plastic state (Hendry, 2001; Silva et al., 2006). Although water retention is related to the reaction times of mortar hardening and the degree of hydration of the cement, maintaining the plastic state of the mass (Hendry, 2001), workability is related to the consistency and plasticity of the mortar. Mortar plasticity affects the degree to which it spreads on the surface of the substrate (Haach et al., 2011). The quality of lime is regulated by the Brazilian Standard (Norma Brasileira (NBR) 7175) (ABNT, 2003), which follows the same criteria as the American Society for Testing and Materials (ASTM) C206-03 and C207-06 (ASTM — American Society for Testing and Materials, 2007a,b,c). Binary cement/hydrated lime mortars have greater deformability (low modulus of elasticity), which leads to better absorp- tion of initial accommodations of the structure (Paiva et al., 2007). These mortars have the capacity to cover small cracks in coatings, which occur over time, due to mortar retraction (Izaguirre et al., 2011; Binici et al., 2012). This retraction results from water evaporation and carbonation reaction (Binici et al., 2012) of the lime, in which carbonic gas (CO 2 ) from the air penetrates the pores of the mortar with relative ease. If there is moisture in the coating, CO 2 reacts with the calcium hydroxide [Ca(OH) 2 ] of the mortar, forming calcium carbonate [CaCO 3 ] and water [H 2 O] (Arandigoyen et al., 2006), according to Reaction 1: CaðOHÞ 2ðsÞ þ CO 2ðgÞ ↔CaCO 3ðsÞ þ H 2 O ðaqÞ ð1Þ Recently, in some Brazilian regions, such as the Southeast, South and Midwest, phyllite began to be used as a substitute for hydrated lime, which is generally used in mortars. The phyllite used for this purpose is used due to the lower acquisition cost relative to hydrated lime. This difference is because phyllite is a granulated metamorphic rock (Arnold et al., 1998). Additionally, the effect of using phyllite in the mortar must be simi- lar to that provided by lime when the mortars are in the plastic state (Souza et al., 2009). Therefore, the water retention and workability of mortars produced with phyllite are similar to the mortars formulated with lime (Romano et al., 2011). In contrast to hydrated lime, phyllite does not cause accentuated drying of the hands of the workers, and its particles do not disperse in the air, decreasing the inhalation of the product and thus contributing to the health of the workers. Another advantage of phyllite is that it has been used in lower pro- portions than hydrated lime. Although this must vary between traces, Applied Clay Science 105–106 (2015) 113–117 ⁎ Corresponding author. Tel.: +55 45 3422 5300. E-mail address: marcio.modolo@ifpr.edu.br (M.L. Modolo). http://dx.doi.org/10.1016/j.clay.2014.12.028 0169-1317/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay