用溶胶-凝胶膨胀法对碱-硅酸反应机理的研究

利用溶胶-凝胶膨胀法,将碱与蛋白石直接反应再一次证实,渗透压是碱-硅酸反应的主要膨胀力的来源,而凝胶膨胀所引起的膨胀量确实是有限的;并利用蛋白石对碱-硅酸反应的“最劣点”现象进行了研究,发现最劣点的产生实际上与溶液中碱的有限度含量密切相关。当活性矿物中的SiO_2与碱的摩尔比在某一值附近时,溶解出来的SiO_2浓度最大,粒子数最多,有可能产生最大的渗透压,因而此时产生的膨胀力与膨胀量最大。通过调整骨料的掺量和混凝土中可溶碱的含量有可能达到抑制碱骨料反应的目的。

MECHANISM OF ALKALI- SILICA REACTION IN A SOL- GEL EXPANSION METHOD

Expansion properties of the reaction products of alkali and opal after imbibing water were investigated by a sol - gel expansion method. It is showed that there is a remarkable osmotic pressure in the products, which is the major destroy force of alkali - silica reaction( ASR) , while the expansion value of the products caused by swell is tiny. The pessimum effect of alkali -silica reaction(ASR) is correlated with the limited alkali in solution. At a certain mole ratio of SiO2/ Na2O, for the dissolved silica from opal to alkali in solution, quantity and grains numbers of the dissolved SiO2 will reach to maximum values, resulting in the maximum osmotic pressure, and causing the maximum expansion stress. It is also indicated that ASR can be controlled feasibly by adjusting both the aggregate proportion and the soluble alkali in concrete.