The strength of fused quartz in water vapour

Abstract
The effect of water vapour on the strength of fused quartz has been investigated by measuring the bending strengthS, at 20 and 40 °C, of microscope cover slides in varying humidities (p/p0) relative to the bending strengthin vacuoS0, and correlating this with the adsorption of water vapour on crushed slides at the samep/p0and temperatures.S/S0was found to vary withp/p0in the anomalous way previously observed for soda-lime glass. While an overall reduction in strength of about one-third occurred, a restoration in strength at intermediate pressures was observed at 20 °C. This restoration was not observed at 40 °C. These phenomena, combined with the reversible and irreversible nature of the adsorption of water vapour on the surface of the powder at the samep/p0, provided a means of interpreting the surface reactions between water and fused quartz. A model of these reactions is proposed which led to a prediction that a delay in failure with a further reduction in strength should be observed if the time of load application is increased from a few minutes to a number of hours. Subsequent experiments confirmed this prediction.