Mass Transfer of Gas. Water and Water Vapour Throuhg Concrete for Reactor Buildings

Abstract

Permeability tests of concrete showed that the mass transfer of gas and water vapour was up to 100 times that of liquid water. All categories of mass transfer are affected by water:cement ratio, w0, and, initial mix water per unit volume of concrete W. The dominating influence is that of W. Uncracked, completely compacted concrete is highly effective as a barrier against mass transfer of water, water vapour and gas in containment structures. Failure of this function is attributed to voids arising from imperfect construction


practice and cracks, either due to drying shrinkage, or to unexpected structurally induced stress. Gas flow through cracks was only about 5 per cent of the theoretical value. This was attributed to the combined effects of surface roughness and tortuosity of the crack path. The integrity of reactor buildings may be usefully monitored by means of permanently installed devices for determining ultra-sonic pulse velocity.