PSI - Issue 10

K. Kaklis et al. / Procedia Structural Integrity 10 (2018) 129–134

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K. Kaklis et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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(2011)), is also utilized as a filler material in restoration projects by infilling joint fragments of historic structures, where shear stresses are developed along the mortar-stone interface. Mortars can also be used for filling up grooves carved in stone for inserting metallic connectors. An example application is the metallic “I” shaped connectors placed in sculptured grooves during the restoration process of the Parthenon in Athens, Greece, as presented by Kourkoulis and Pasiou (2015). The overarching goal of the present work is to allow ML mortars to be considered as a potential substitute to cement-based mortars, commonly employed in such applications, in order to minimize salt induced decay and incompatibility due to the cement present in such mortars. Mortar behavior should not be expressed only as a function of elastic constants and strength parameters. Inelastic or plastic deformations are, in fact, often of major significance in determining the stability and long term satisfactory behavior of mortar applications. In previous studies, uniaxial and triaxial compression tests under unloading-reloading cycles (cyclic loading) conditions were conducted on rocks (Gatelier et al. (2002); Jia et al. (2018)) and concrete (Neuenschwander et al. (2016); Li et al. (2017)), in order to evaluate the deformation evolution process as well as the damage evolution. Previous triaxial testing results as presented by Kaklis et al. (2018) clearly show that specimens predominantly exhibit a plastic behavior (Fig.1), which may be beneficial for using this material as a filler between metallic connectors and marble blocks in conditions of high shear stresses.

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2 Deviator stress, σ 1 - σ 3 (MPa) 4 6 8 10

Uniaxial 1.15 MPa 2.09 MPa 3.96 MPa 6.06 MPa 7.96 MPa

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Strain

Fig. 1. The complete deviator stress-strain curves for pozzolanic mortar specimens tested in uniaxial and triaxial loading under five different confining pressures as presented by Kaklis et al. (2018).

In this study, two series of uniaxial and triaxial compression tests under cyclic loading conditions were performed in order to examine the stress-strain behavior and the deformation characteristics of the pozzolanic lime mortar in the pre- peak region. It should be noted that the term “cyclic” does not refer to a fatigue test (cycle test – type 1: the load is cycled between two prescribed limits), but to the unloading-reloading cyclic test (cycle test – type 2: the load is increased from one cycle to the next), as mentioned by Gatelier et al. (2002).

2. Material and methods

2.1. Composition of the pozzolanic mortar

The pozzolanic mortar used in the experiments described below consisted of carbonate sand, a binder of hydrated lime (CaO Hellas) with metakaolin (Metastar 501 by Imerys), and deionized water. As fine aggregates can contribute to decreasing shrinkage and cracking during the setting process, it was deemed important to add sand of carbonate nature with fine grains in the mix design. Therefore, in an effort to improve the bond strength between mortar and porous stone, equal proportions of carbonate sand passing through the 125 and 63 μm sieves were used as aggregates, after being thoroughly washed to remove the harmful soluble salts.