粉煤灰粒径对地质聚合物孔结构及性能的影响

对原状粉煤灰进行分级处理,获得3种不同粒径特征(D50=5.02μm、D50=15.74μm、D50=35.32μm)的粉煤灰颗粒,并利用其制备地质聚合物,研究粉煤灰颗粒粒径对地质聚合物孔隙率、孔径分布、显微结构、抗压强度的影响,探讨了影响抗压强度的关键因素,建立了该体系抗压强度与孔隙率的关系式。结果表明:细化粉煤灰粒径可制备具有高强度、低孔隙率地质聚合物。利用粉煤灰细灰取代粗灰,促进了致密凝胶相的产生,凝胶孔孔隙率明显减小,试样总孔隙率由18.72%降至11.04%;细灰颗粒与铝硅酸盐凝胶结合良好,试样早期强度基本无变化,28 d强度提升明显,达到62.6 MPa。地质聚合物的抗压强度与孔隙率符合y=80.53e~(-2.32x)的指数关系。

Effect of Particle Size of Fly Ash on Pore Structure and Properties of Geopolymers

In this paper, raw fly ash was classified and three different size fractions of fly ash (with characteristic particle diameter D50 of 5.02, 15.74 and 35.32 μm respectively) which was used to prepare geopolymer were obtained. The effect of fly ash particle size characteristics on the porosity, pore size distribution, microstructure and compressive strength of geopolymer were studied, key factors promoting compressive strength were discussed and the relationship between the compressive strength and porosity was established. The results showed that geopolymer with higher compressive strength and lower porosity could be prepared by refining particle size of fly ash. When the coarse fly ash was replaced by fine fly ash, porosity of gel pore in sample was decreased as a result of the formation of denser gel, the total porosity of sample decreased from 18.72% to 11.04%. Microstructure indicated that fine size of geopolymer combined with the gel of aluminum-silicate tightly. The early compressive strength had no evident change, however, the compressive strength at the age of 28 d improved obviously, reached 62.6 MPa. The relationship between compressive strength and porosity of the geopolymer conformed to the exponential equation: y=80.53e-2.32x.