Original article Microtextural and microchemical studies of hydraulic ancient mortars: Two analytical approaches to understand pre-industrial technology processes Maria Pia Riccardi a, * , Marco Lezzerini b , Federico Caro ` a , Marco Franzini b , Bruno Messiga a a Department of Earth SciencedSMALab, University of Pavia, via Ferrata 1, 27100 Pavia, Italy b Department of Earth Science, University of Pisa, via Santa Maria 53, 56126 Pisa, Italy Received 18 January 2007; accepted 5 April 2007 Abstract Two different analytical approaches have been taken into account to investigate the role of Si-rich phases in enhance hydraulic reactions of bedding mortar mixtures from San Lorenzo Church in Milan (Northern Italy) and from the Medicean Aqueduct in Pisa (Central Italy). In the first case, mortars show clear hydraulic type reactions in the form of coronal layers between the reacting additive and the binder mass. In the second one, the hydraulic reactions do not develop visible mineral phases and processes have been inferred from chemical, mineralogical analyses and mass balance calculation. The microstructural studies not always are sufficient to understand the complex dynamics of reaction attained during pre-industrial manufacturing processing of mortars and related binders. In fact, if the reacting raw materials are fine-grained and/or have remark- able chemical reactivity, no relicts are preserved by mortar microtextures. Ó 2007 Elsevier Masson SAS. All rights reserved. Keywords: Hydraulic reactions; Analytical approach; Microtextures; Chemical composition; Mortar recipes 1. Research aims Mortars and plasters are cultural products whose character- istics depend on the raw materials used and are strictly related to the technological know-how achieved in a given historical period [1e18]. Each artefact displays a unique solution that was obtained by adapting the technical properties of locally available raw geo-materials. Unravelling this technological history involves complex analytical strategies suited to each specific case study. This paper aims to describe two different analytical ap- proaches to the study of hydraulic reactions taking place in ancient lime-based mortars. The two strategies represent the end-members of an array of possible analytical approaches which can be applied, according to the nature of the hydraulic additive. In one case, coarse slag retains reaction microstruc- tures which can be studied. In the other, fine-grained hydraulic additive completely reacted without any direct textural evi- dence. Ancient mortar recipes can commonly be identified combining microtextural and chemical analyses into a multi- analytical approach. 2. Experimental section 2.1. Introduction The transformation processes in pre-industrial manufactur- ing are now approached by those analytical techniques com- monly used in the investigation of rock-forming processes, considering microtextures and related mineral phase composi- tion. Mortars from both St. Lorenzo Church in Milan [19] and * Corresponding author. E-mail addresses: mariapia.riccardi@unipv.it (M.P. Riccardi), lezzerini@ dst.unipi.it (M. Lezzerini), federico.caro@manhattan.unipv.it (F. Caro `), franzini@dst.unipi.it (M. Franzini), bruno.messiga@unipv.it (B. Messiga). 1296-2074/$ - see front matter Ó 2007 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.culher.2007.04.005 Available online at www.sciencedirect.com Journal of Cultural Heritage 8 (2007) 350e360 http://france.elsevier.com/direct/CULHER/