| http://www.w3.org/ns/prov#value | - and impermeability in solutions, vapours and gases.U.S. Pat. No. 3,498,802 describes a steam treatment process for producing thermoplastic materials and hydraulic cements, which comprises mixing materials, oxides and other ingredients which when melted together produce alkali silicate glasscontaining about 80-94 mol percent SiO.sub.2 and 6-20 mol percent R.sub.2 O, wherein R.sub.2 O consists of N
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