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Xjenza Online Vol. 1 Iss. 2 - October 2013
A Study of Nano-Particle Based Silane Consolidants for Globigerina Limestone

Authors: Sophie M Briffa, Daniel Vella, Maria J Mosquera

Corresponding: Sophie M Briffa (sbri0012@um.edu.mt)

Keywords: Globigerina Limestone, Nanoparticles, Hybrid, Alkoxysilane, Sol-gel

Doi: http://dx.medra.org/10.7423/XJENZA.2013.2.07

Issue: Xjenza Online Vol. 1 Iss. 2 - October 2013

Abstract:
This STEPS funded study focuses on the application of hybrid and nanoparticle loaded hybrid silane consolidants for the treatment of 'Franka' Globigerina Limestone. Consolidants act by gluing deteriorated stone material to underlying healthy stone (Dukes, 1972; Gutt, 1973; Garrod, 2001). The consolidants evaluated were a laboratory prepared hybrid silane based on a mixture of tetraethylorthosilicate (TEOS) and 3-(glycidoxypropyl) trimethoxysilane (GPTMS), the same hybrid loaded with silica nanoparticles and loaded with GPTMS-modi ed silica nanoparticles. In addition, a consolidant based on the hydrolysis product of TEOS was also tested. Prepared consolidants were applied to test blocks by complete immersion. Untreated stone block were used as benchmarks. Following application, half of the treated samples were subjected to accelerated weathering. All limestone blocks were then characterised by colorimetry and optical and electron microscopy. The pore size distribution was assessed by Mercury Intrusion Porosimetry. A water absorption by capillarity technique was also carried out to assess any changes in water uptake rate. The mechanical properties were assessed by resistance to sodium sulfate crystallisation. Microscopy observations showed that penetration into the stone occurred to different extents depending on the consolidant. The hybrid consolidant led to yellowing of the limestone but the addition of nanoparticles to the hybrid (modi ed or not) appeared to help restore the original colour of the stone. The porosity of the limestone was only marginally affected by the different treatments but the somewhat hydrophobic nature of the consolidants led to a disruption in the capillary ow of water into the limestone.