| 摘要 |
A cementitious composition and, by extension, an article of manufacture and a curable composition of particulate of comminuted silica, an alkalimetal silicate and, optionally, an alkyl silicate and/or ester catalyst. The silica, (80-75%, 80-95%, 80-92.5%), is preferably sand, either pure silica sand for a white effect, or naturally/artificially coloured for colour effects. The alkali metal silicate, (20-25%, 20-5%, 20-7.5%), may be either sodium and/or potassium. The alkyl silicate is preferably ethyl silicate and the ester catalysts are generally esters of long chain organic, (preferably unsaturated aliphatic), carboxylic acids. Ester catalysts usually employed in foundry sand moulding may also be used. The addition of an alkyl silicate and/or ester catalyst (5-15%) appear(s) to give added strength to the product over that by the alkali-metal silicate alone. The alkali-metal & alkyl silicate combination, moreover, is useful for the prevention of rough surface texture. The preferred compositions shown in parentheses above for silica and alkali-metal silicate indicate the amounts used in the absence of an additive and in the presence of the alkyl silicate and/or ester catalyst(s) respectively. The curable composition/article of manufacture is prepared by mixing an amount of 5-20% of finely ground or comminuted "flour" of silica with the balance of the mix to exclude voids, occlusions or rough surface texture. The alkali-metal silicate may be added or prepared in situ by mixing the sand with caustic alkali. After mixing all the constituents together and reaction, if any, has ceased, the mixture is then allowed to cure for several hours at temperatures up to 200<o>C. to stabilise and increase the strength of the composition. Cementitious compositions of the above type and reaction, if any, has ceased, the mixture is then allowed to cure for several hours at temperatures up to 200<o>C. to stabilise and increase the strength of the composition. Cementitious compositions of the above type have particular advantages, as they are resistant to the acid constituents in the urban atmosphere, finding applications in the manufacture of building units, such as various tiles, paving materials and special plastering compounds. |
