Goins, Elizabeth Stevenson; (1995) Alkoxysilane stone consolidants: The effect of the stone substrate on the polymerization process. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Alkoxysilane sol - gel chemistry and the use of alkoxysilane stone consolidants are reviewed. The consolidated sandstone and limestone samples are subjected to a three - point bend test to determine the modulus of rupture (MOR). Mechanical testing procedures and crack formation theories are reviewed. Scanning Electron Microscopy (SEM) is used to study the fracture surfaces and cross sections of gels deposited within the stone pores. Tetraethoxysilane (TEOS), methyltrimethoxysilane (MTMOS), coupling agents (amino and glycidoxy functional alkoxysilanes), epoxy and acrylic resins are tested. The MOR and SEM results indicate differences between the gels formed in contact with each of the rock types. Fourier Transform Infrared Spectroscopy (FTIR) is used to monitor the hydrolysis and condensation reactions of 2:1:2 and 4:1:3 .5 molar ratios of water, MTMOS and ethanol solutions in contact with powdered marble, limestone, sandstone and weathered sandstone (containing soluble salts). Principal Component Analysis (PCA) is used to identify any major chemical trends in the FTIR spectra. The limestone and sandstone are found to slow the hydrolysis reaction considerably. The time to gelation (Tgel) is determined in order to compare condensation and gelation rates among the different systems. The resulting xerogels are empirically described for each solution. The limestone and marble samples decrease the time to gelation and form weak particulate - type gels.

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