硅胶对水玻璃砂抗吸湿性的影响

Effect of Silica Gel on Moisture Resistance of Sodium Silicate Sand

综括以往水玻璃砂抗吸湿性研究,大多都是通过增加水玻璃的加入量并加入多种添加剂,以牺牲水玻璃砂24 h强度为代价的,不仅抗吸湿性效果不够明显,而且导致水玻璃砂的溃散性变差。作者在水玻璃砂中添加和不添加硅胶,测量了水玻璃砂试样在正常湿度条件(RH 68%)和高湿度条件(RH 95%~98%)下硬化后试样的抗压强度变化。结果表明:在高湿度条件下存放24 h后,加入0.1%~0.3%硅胶添加剂比不加硅胶的水玻璃砂强度要提高近2倍。分析认为,硅胶提高水玻璃砂抗吸湿性能的主要原因是:硅胶比表面积大,易吸收水分子,减缓水分子对水玻璃硅酸凝胶硅氧键的破坏过程,阻碍了水分子对粘结桥强度的破坏作用;硅胶使水玻璃脱水,产生的游离SiO2提高了水玻璃模数,加快了水玻璃硅酸凝胶的生成速度,提高了模数的水玻璃在高湿度条件下更抗吸湿。

To sum up the previous research on the moisture resistance of sodium silicate sand,most of them are at the expense of the 24 h strength of the sodium silicate sand by increasing the amount of sodium silicate added and adding various additives.The collapsibility of the sand becomes worse.The author measured the change of compressive strength of the sodium silicate sand sample after hardening under normal humidity conditions(RH 68%)and high humidity conditions(RH95%-98%)with and without adding silica gel to the sodium silicate sand.The results show that after 24 h storage under high humidity conditions,adding 0.1%-0.3%silica gel additive can increase the strength of the sodium silicate sand by nearly 2 times compared with that without the silica gel.The analysis believes that the main reason why the silica gel improves the moisture absorption resistance of the sodium silicate sand is:the silica gel has a large specific surface area and is easy to absorb water molecules,which slows down the destruction of water molecules on the silicon-oxygen bond of the sodium silicate silicate gel and hinders the bonding of the water molecules.The free SiO2 produced by silica gel dehydrates sodium silicate increases the modulus of the sodium silicate,accelerates the formation speed of the silicate gel,and increased the modulus of the sodium silicate in the condition of the high humidity.