The use of magnetic resonance imaging techniques in assessing the uptake of surface treatments and water movement through stone faces

Abstract

This paper addresses some practical questions regarding the influence of hydrophobic treatments on the movement of water in sandstone. The broad line gradient echo magnetic resonance imaging technique has been used for monitoring the depth of penetration of alkyl alkoxysilane treatment into untreated sandstone and subsequently to visualise the movement and spatial distribution profile of water in the untreated and silane treated sandstone matrix. The experimental results show that the effect of hyrdrophobic treatment depends on whether the stone is in short-term or prolonged contact with water. For short term exposure, the presence of a silane treatment prevents the movement of water into and out of the sandstone matrix. However, after continuous long-term contact with water the hydrophobic treatment is unable to prevent the ingress and internal redistribution of water. The ability of water to infiltrate treated regions of sandstone has significant practical implication for stone structures where deterioration may be due to outward movement of water from the interior to the surface of the stone matrix

Pore-structure and water transport properties of surfacetreated building stones

“…Thus whilst the hydrophobic treatment is initially effective in resisting the ingress of water, it becomes ineffective when the water is in contact with the treated material for long periods of time. The efficiency of silane treatments in preventing water movement through porous sanstone materials has been considered in more detail elsewhere [6,7].…”

“…One such technique is the repetitive pulse gradient echo method [5]. This novel method has prevously been successfully applied to imaging the uptake of surface treatments and subsequent movement of water in both building stone [6,7] and cementitiuous materials [8].…”