Technical Note Assessment of technological properties of calcareous and non-calcareous clays used for the brick-making industry of Zaragoza (Spain) Blanca Bauluz a , Maria Jose ´ Mayayo a , Constanza Ferna ´ndez-Nieto a , Giuseppe Cultrone b , Jose ´ Manuel Gonza ´lez Lo ´pez a, * a Cristalografı ´a y Mineralogı ´a, Departamento Ciencias de la Tierra, Universidad de Zaragoza, Pedro Cerbuna 12. 50.009 Zaragoza, Spain b Departamento de Mineralogı ´a y Petrologı ´a, Facultad de Ciencias, Universidad de Granada, Granada, Spain Received 22 March 2002; received in revised form 29 April 2003; accepted 3 June 2003 Abstract The granulometric, mineralogical, and geochemical features of two different types of clayey raw materials (carbonated clays, CC; and non-carbonated clays, NCC) used for the brickmaking industry near Zaragoza (Spain) have been studied. Their particle-size distribution suggests that they may be classified as silty clays and are suitable for use as thin-walled hollow bricks. For technological testing, prismatic bars obtained by extrusion under vacuum conditions from raw materials were fired from 800 to 1050 jC. Technological determinations, such as linear shrinkage, bulk density, hydric tests, and an accelerated decay test, indicate that both CC and NCC are suitable to be used as bricks for building, although bricks made of NCC would be of better quality. In addition, pore-size distribution suggests that the durability of the highest temperature fired products will be higher because of an increase both in the dominant pore access radius and in the percentage of larger pore sizes. D 2003 Elsevier B.V. All rights reserved. Keywords: Ceramic materials; Clays; Shaping; Firing; Ceramic properties; Decay tests 1. Introduction Different types of natural clayey raw materials are used in the manufacture of heavy clay products. They may differ in mineralogical and chemical composi- tion, as well as in the granulometric distribution and, consequently, they show different drying and firing properties that are of decisive importance for the quality of the end products (Fabbri and Fiori, 1985; de Andre ´s Go ´mez de Barreda et al., 1990; Parras et al., 1996; Gonza ´lez et al., 1998; Dondi, 1999). This note discusses the granulometric, mineralog- ical, and chemical compositions of several clayey raw materials used in the brickmaking industry in Zara- goza (Spain). The specific behavior of these materials during drying and firing at several temperatures (T) has been studied to assess their technological prop- erties. This research is part of a more extensive program aimed at characterizing clays and structural 0169-1317/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0169-1317(03)00152-2 * Corresponding author. Tel.: +34-976761097; fax: +34- 976761106. E-mail address: jmglez@posta.unizar.es (J.M. Gonza ´lez Lo ´pez). www.elsevier.com/locate/clay Applied Clay Science 24 (2003) 121 – 126