流化床气相沉积法纳米修饰粉煤灰及其早期水化特征

Nano Coating Fly Ash by Fluidized Bed Reactor Vapor Deposition(FBR VD) and Its Hydration Characteristics at Early Age

摘要:

分别采用NaOH和Na2SO4饱和溶液为改性材料，利用流化床气相沉积(FBRVD)方法对粉煤灰(FA)颗粒进行表面修饰.通过水泥净浆和砂浆试验，测试分析FBRVD方法对FA火山灰活性、水泥净浆需水比和砂浆流动度的影响；通过水化热试验考察不同改性方法对水泥净浆、砂浆早期水化程度的影响；通过扫描电镜及能谱分析(SEMEDS)研究不同改性材料对粉煤灰颗粒的修饰效果及其火山灰反应机理.结果表明：FBRVD方法能够将改性材料的纳米微粒修饰于FA表面，相比直接掺加改性材料，经FBRVD方法修饰的FA掺入水泥后，其净浆、砂浆早期活性指数提高5%～10%；水化热测试结果印证了水泥净浆强度的变化规律，NaOH主要通过促进水泥的水化产物聚集在FA颗粒表面来提高其与水泥石结构的结合力，Na2SO4则通过锚固于FA表面的晶体，增加其与周围水泥石结构的摩擦力，同时促进水泥的水化并吸附较多的水化产物，即通过物理与化学的双重作用来提高其火山灰活性.

Abstract:

Surface of fly ash(FA) was treated by physical vapor deposition(VD) method in a developed fluidized bed reactor(FBR), using NaOH and Na2SO4 saturated solution as modified materials respectively. The paste and mortar samples were prepared to analyse the pozzolanicity and the workability. Hydration heat testing was carried out to explain the hydration degree. The modified effect on FA and the hydration mechanism of paste with FA were investigated by scanning electron microscopy with energy dispersive spectrometer(SEM EDS). Results show that, the nano particles of NaOH or Na2SO4 can coat on the surface of FA by fluidized bed vapor deposition reactor(FBR VD) method, which can improve the activity index by 5% to 10% at early age. The hydration heat testing results indicate the varying trend of compressive strength of paste. NaOH can improve the adhesion between FA particles and the hardened cement, due to it promote the hydration of cement and gathere more hydrated products on the surface of FA particles. Na2SO4 can increase the friction between FA particles and its surroundings in hardened cement, at the same time it can promote the hydration of cement and absorb more hydrated products of cement on the surface of FA particles. Na2SO4 can improve its pozzolanicity through the dual function of physics and chemistry.