Devonian micritic limestones used in the historic production of Prague hydraulic lime (‘pasta di Praga’): characterization of the raw material and experimental laboratory burning

P Kozlovcev,R Přikryl

doi:10.3989/mc.2015.06314

Abstract

The Devonian micritic limestones from the Prague Basin (Barrandian area, Bohemian Massif, Czech Republic), which were the primary raw material used for natural hydraulic lime burned in Prague, exhibit a feebly to eminently hydraulic character. Based on a laboratory experimental study, the burned product is composed of dominant free-lime (CaO) and/or portlandite (Ca(OH) 2 ), larnite-belite (bicalcium silicate 2CaO.SiO 2 ), and quartz (SiO 2 ) - i.e. phases formed due to the decomposition of carbonate and quartz, present in the original limestones. Proportions of the newly formed phases depend on: the composition of the raw material, maximum burning temperature (the highest amount of larnite-belite appearing at a burning temperature of 1200 °C), and the granulometry of the experimental batches (a coarsely-ground batch exhibited a higher amount of larnite-belite compared to the finely-ground one). The presence of minor phyllosilicates in the raw material contributed to the formation of gehlenite, brownmillerite, wollastonite, calcium aluminate, and/or spurrite.

Highlights

Despite the dominant use of Ordinary Portland Cement (OPC) as almost the exclusive hydraulic binder in the modern construction industry, the increased interest in the production and application of alternative hydraulic binders can be seen during the past decades [1, 2]
Hydraulic binders belonging to the hydraulic lime series were so well known in the Middle ages that some of their resources and favourable properties were felt worth being mentioned in the general philosophical treatises of that time
The current study aims to explore the mineralogical composition and petrographic character of one of the main types of these Devonian limestones – the so called Dvorce-Prokop Limestones – and the influence of mineralogical/petrographical parameters on the phase composition of the burned product – a Natural hydraulic lime (NHL) and/or natural cement (NC)

Summary

Introduction

Despite the dominant use of Ordinary Portland Cement (OPC) as almost the exclusive hydraulic binder in the modern construction industry, the increased interest in the production and application of alternative hydraulic binders (natural hydraulic lime, natural cement) can be seen during the past decades [1, 2]. The search for corresponding raw materials, the technology of their production, and the modes of u tilisation of NHL and/or NC is motivated by the longevity of ancient structures built of them [16,17,18,19,20,21] The former lands of the Czech crown ( Bohemia, which makes up a major part of the current Czech Republic) are known to have produced diverse types of inorganic constructional binders over many centuries [22]. Non-standardised production of various hydraulic binders was gradually replaced by Portland cement-based binders at the turn of 19/20th c

Methods

Results

Conclusion