活化粉煤灰抑制高矿化度水泥土膨胀的研究

Study on inhibiting soil-cement expansion with activated fly-ash in high degree of mineralization zone

水泥土可用做软土地基处理。在高矿化度水环境中,SO4 与水泥水化产生的 AlO3 、Ca2+反应生成大量钙矾石 2- -(3CaO·Al2O3·3CaSO4·31H2O)而引起水泥土膨胀破坏,使水泥土加固体强度降低。加入水泥土中的活化粉煤灰,释放出活性二氧化硅,增加了水泥土中 SiO3 的浓度,使生成反应向有利于生成硅酸钙(CSH)的方向发展,减少了 Ca2+与 SO4 、 2- 2-AlO3 反应,并生成钙矾石的机率,从而对水泥土的膨胀起到了一定的抑制作用。抑制水泥土膨胀的机理,改变离子浓度, -控制化合物的生成方向、微粒充填界面效应。粉煤灰被活化的机理是以粉状硅酸钠为主剂的材料,突破了粉煤灰网络聚合度高的表层,使其内部的活性物质得以释放。

The soil-cement is one of materials that used for ground treatment in soft soil engineering. In the high degree of mineralization zone, the ettringite (3CaO&middotAl2O3&middot3CaSO4 &middot 31H2O), which is the reaction product of hydration of cement (AlO3-, Ca2+) and SO42-, can cause expansion and crack to soil-cement and makes the strength of soil-cement decrease. The activated fly ash is mixed into the soil-cement, which can set free the activated SiO2 to increase the concentration of SiO32- and promoted the reacting speed of hydrated calcium silicate (CSH). Meanwhile, the probability of formation of ettringite is decreased. The expansion inhibiting mechanism of soil-cement is that the activated fly ash absorbs Ca2+ and changes the reaction process; and the reaction product (CSH) fills the hole of soil-cement with its micro-granule. The mechanism of activating fly-ash is the powdery sodium silicate destroys the high network polymerization surface of fly-ash, reaches the inner part of the fly ash and makes the active substance to set free.