可溶盐对建筑石膏性能及微观结构的影响研究

Study of the Effect on Performances and Micro-structure of Building Gypsum by Blending with Solvable Salt

石膏基胶凝材料强度低、耐水性差是限制其制品应用的主要原因,通过内掺不同种类的可溶盐(Na2CO3、Na3PO4、BaCl2、Na2C2O4)对建筑石膏进行改性,分析盐溶液种类及浓度对半水石膏凝结硬化过程、二水石膏硬化体力学性能及耐水性能的影响。结果表明:Na2CO3、BaCl2对半水石膏凝结时间基本无影响,但两者均导致二水石膏硬化体力学性能的下降;Na3PO4大幅延缓了半水石膏水化进程,使硬化体力学性能大幅下降;Na2C2O4对半水石膏具有显著的促凝作用,二水石膏硬化体抗折、抗压强度及耐水性能大幅提高,吸水率略有下降,Na2C2O4溶液优化质量分数为0.18%。SEM测试分析表明,可溶盐Na2C2O4使二水石膏晶体细化、长径比增大、晶体搭接密实度增加。

Low strength and bad water-resistance are the main limited factors for the application of gypsum-based productions. Influences on setting times, mechanical properties and water-resistance property are investigated by mixing gypsum plasters together with different kinds of solvable salts solutions as modifiers including Na2CO3, Na3PO4, BaCl2 and Na2C2O4. Results indicated that Na2CO3 and BaCl2 have little influences on the setting and hardening process of hemihydrate gypsum while the mechanical properties are decreased by modification. The setting and hydration processes are lengthened significantly by Na3PO4 accompanying with the sever decline of mechanical properties. However, the setting times are greatly shortened by the blending with Na2C2O4. Meanwhile, the flexural strength, compressive strength and water-resistance property are all increased while the water absorption is decreased finally. The optimal dosage is 0.18% for Na2C2O4. The SEM analyses show that the gypsum crystal size is refined and the ratio of length to diameter is increased to make a compacter micro-structure.