Abstract

This study focuses on the mechanical parameters of Miocene limestones from Hungary. Four different lithotypes of porous limestone from two localities were analysed in laboratory conditions. These lithologies have been widely used for centuries as construction material in Central Europe. One type of the Badenian Leithakalk limestone, which is a bioclastic grainstone containing molluscs, foraminifera and Lithothamnium and three types of Sarmatian porous limestone; a fine-grained, medium-grained and a coarse-grained bioclastic lithotype were compared in laboratory conditions. Bulk density, water absorption, apparent porosity, uniaxial compressive and tensile strength tests were performed to obtain data set for correlation analysis. With water saturation under atmospheric pressure, the uniaxial compressive strength and tensile strength of all studied lithotypes were reduced significantly. A good correlation between dry bulk density and apparent porosity was found for two lithotypes; meanwhile, for the two other lithotypes a less significant relationship was found. Bulk density correlates with uniaxial compressive strength and with tensile strength for all lithologies. However, a significant difference was found in the coefficients of determination of the different lithotypes. The coefficients in air-dry conditions were over 70%, but they became smaller after water saturation. According to these results, microstructure, porosity, and water saturation influence porous limestones’ damage mechanism.

Introduction

In this study, two porous limestones from Hungary have been analysed to describe the variations in mechanical properties as a function of textural characteristics. The selected stone types have been widely used as ornamental and building stone in the Central-European region until the 20th century. Numerous emblematic monuments in Budapest and Vienna were constructed from this Miocene porous limestone.

In previous studies, it has been demonstrated that water content reduces the mechanical properties of stones. Rossana and Paola in [1] found that this can be observed even in low porosity rocks since an increase in water content causes a measurable decrease in flexural strength. A few per cent of moisture content significantly reduces the shear strength of sandstones and mudstones [2]. Stones with high porosity absorb a high amount of water, and the reduction of the strength due to water saturation can be very high, such as the uniaxial compressive strength and flexural strength measured in tuffs [3]. Tensile strength is also reduced besides uniaxial compressive strength linked to water saturation at porous limestones (Tuffeau and Sebastpol limestone, [4]).

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