凝灰岩石粉和VF防裂剂对水泥基材料收缩性能的影响

Effect of tuff powder and VF anti-cracking agent on chemical shrinkage and drying shrinkage of cement-based materials

为了探究不同掺量的凝灰岩石粉、VF防裂剂对水泥浆体收缩性能的影响及机理,测定了不同凝灰岩石粉和VF防裂剂掺量的化学收缩和干燥收缩,采用X射线衍射技术(XRD)研究不同龄期的复合水泥浆体水化产物,并采用压汞法(MIP)研究其孔结构。结果表明:凝灰岩石粉早期不参与水化,等量取代水泥后通过减少水泥熟料数量减少水泥浆体的化学收缩,并能填充较大孔隙,增大水泥浆体中较小毛细孔(孔径50 nm以下)所占的比例,使水泥基材料干缩变大;VF防裂剂中的明矾石和石膏与水泥水化过程中析出的Ca(OH)2反应生成膨胀性钙矾石补偿收缩,并填充较小孔隙,减少浆体中较小毛细孔所占的比例,从而减小干缩。凝灰岩石粉中活性成分在VF防裂剂的化学激发下二次反应加剧,复掺石粉和防裂剂的水泥浆体的化学收缩显著减少,生成的水化产物填充孔隙,明显的抑制石粉对浆体干燥收缩的增大效应。

The chemical shrinkage and drying shrinkage of cement-based materials which are mixed tuff powder and VF anti-cracking agent are determined.Using X-ray diffraction （XRD） and Mercury intrusion porosimetry （MIP） analysis, the mechanism of shrinkage was studied.The result are follows, tuff powder is low-active and reduce the chemical shrinkage of cement paste and cause the increase of the proportion of fme pores of cement paste which makes the drying shrinkage increase.VF anti-cracking agent produce ettringite which is of the shrinkage-compensating effect, reducing the proportion of fine pores of cement paste, as a result the drying shrinkage is reduced.VF anti-cracking agent keep the chemical activation towards the active component in tuff which can reduce the chemical shrinkage and effectively suppress the effect of tuff powder on increasing drying shrinkage.