¹H pulsed NMR measurement of reactivity of silane coupling agents for conservation of cultural heritage sites

Abstract

The network structure and reactivity of suitable restoration agent consisting of silane coupling agents (SCAs) of the brittle walls of a cultural heritage site located underground in a desert area in Egypt were investigated using 1H pulsed nuclear magnetic resonance (pulse NMR). It should possess both high coagulation strength and ductility to ensure that it can withstand an earthquake; it should also contain ethoxy rather than methoxy groups, which generate toxic methanol. The solidification rate for the SCA or oligomer with ethoxy groups was lower than those with methoxy groups; however, the final polycondensates showed the same relaxation time (hardness). The difference spectrum was developed newly to analyze the network structure combined higher strength and ductility. The distribution of crosslinking degree of such polycondensates was narrow, and the amount of lower crosslinking degree was small. On the other hand, the distribution was wide in the polycondensates with ductility but lower strength. From the compression tests of model sand solidified with the restoration agent for both methoxy and ethoxy types showed the superior properties combined higher strength and ductility. The pulse NMR experiment was useful for estimating the solidification rate and the network structure.