| 摘要 |
1505626 Pressing prehydrated hydraulic binding agents CEMENTA AB 12 April 1976 [16 April 1975] 14885/76 Heading B5A An article is produced from hydraulic binding agent (e.g. cement) by prehydrating (i.e. adding water to) the agent at a time period not exceeding 48 hours before moulding, and then pressing the agent mixed with other ingredients. A pressure of (0À5-10) kbar. is built up over a time period of (30-240) seconds, kept constant for (0-900) seconds, and unloaded over (0-240) seconds. As described, cement is mixed with water in a weight ratio less than 0À15, and left to prehydrate at room temperature for 48 hours or less if accelerated by additives or by heating to less than 100‹ C. After screening of the prehydrated cement, a mix is formed (including steel fibres or mesh) and moulded in a normal press or isostatically to produce slabs, panels or cylindrical items. Storage is effected in (90-100)% humidity or under water. Metal, steel foil, cellulose or plastics sheets are attached during pressing. Prior art.-Cement at less than 0‹ C. is mixed with pulverized ice and hot pressed. |
