Regulation on strength and pore structure of non-sintered ceramsite filter material derived from coal gasification slag
SUN Hao
JIANG Linliang
CHANG Xinzhuo
TIAN Quanzhi
Abstract：Gasified coal slag serves as a high-quality raw material for preparing non-sintered ceramsite filter media,where mechanical strength and pore structure are critical determinants of filtration performance.Therefore,it is imperative to elucidate the relationship between strength and pore structure in non-sintered ceramsite.By optimizing the formulation of gasified coal slag,metakaolin,and solid alkali activators to develop a non-sintered ceramsite filter material exhibiting a cylinder compressive strength of 25.72 MPa and a bulk density of 1160 kg/m3.Through comprehensive characterization techniques including X-ray diffraction(XRD),scanning electron micro-scopy(SEM),and solid-state nuclear magnetic resonance silicon spectroscopy(29Si NMR),the strength formation mechanism was invest-igated.Results revealed that sodium/calcium aluminosilicate hydrate(N/C-A-S-H)gel constitutes the primary strength-contributing phase.The incorporation of metakaolin elevated the Q4(2Al)polymer content in N/C-A-S-H gel from 40.34%to 56.05%,thereby enhancing the crosslinking degree of the aluminosilicate network and densifying the gel structure,which ultimately improved the mechanical properties.Pore-forming agents(hydrogen peroxide and cetyltrimethylammonium bromide)were employed to modulate porosity,combined with mer-cury intrusion porosimetry,the effect of pore forming agent ratio on the porosity,strength,and density of ceramsite was investigated.It was demonstrated that the porosity could increase from 21.33%to a maximum of 50.60%,accompanied by reductions in cylinder com-pressive strength(8.86 MPa)and bulk density(816 kg/m3).Further analysis of the pore structure characteristics of non-sintered ceramsite was conducted using Menger sponge and thermodynamic fractal models.It was found that the fractal dimension calculated based on the thermodynamic fractal model had a higher linear correlation with the strength of ceramsite,with fractal dimension values ranging from 2.770 to 2.891.This indicates that pore structure evolution in gasified coal slag-based ceramsite is governed by both geometric configura-tion and thermodynamic mechanisms,with compressive strength inversely proportional to fractal dimension.
Keywords：coal gasification slagnon-sintered ceramsitepore structurecylinder compressive strengthfractal dimension
Publication Date：2025-06-30
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：11( 191-201 )