摘要
This paper investigates the effectiveness of nano-modification on the strength enhancement of cementstabilized dredged sludge(CDS).Three types of nanoparticles including nano-SiO2(NS),nano-Al2O3(NA)and nano-MgO(NM)were used as cement admixtures for dredged sludge stabilization.Effects of single nanoparticle content,mass ratio of composite nanoparticles and curing time on the strength development of CDS were evaluated via a series of unconfined compressive strength(UCS)tests.The pH evolutions of CDS caused by nanoparticles were also examined by a range of pH tests.Furthermore,micromechanisms reflecting the strength evolutions were analyzed by performing scanning electron microscopy(SEM)and X-ray diffraction(XRD)tests.The results indicated that adding nanoparticles can significantly improve the UCS of CDS.For single nano-modification,the optimum contents of NS,NA and NM were 4%e6%,6%and 8%,which can increase the 7-and 28-d UCSs of CDS by 38%and 50%,17%and 35%,65%and 67%,respectively.Compared with single nano-modification,composite nano-modifications were more effective in improving the strength gain of CDS.The optimum mass ratios of composite nanoparticles,namely NS/NA,NS/NM and NA/NM,were 9/1,3/7 and 3/7,respectively.Based on the strength growth rate,the composite nanoparticles with NS/NM of 3/7 were highly recommended.The addition of nanoparticles obviously affected the pH evolution of CDS,which was mainly determined by the difference of OHproduction and consumption inside nano-modified CDS.The microstructural analysis revealed that C-S-H and C-A-H gels are the main cementitious products,and the addition of nanoparticles can obviously contribute to a denser and more homogenous microstructure of CDS.
基金
This work was financially supported by the National Natural Science Foundation of China(Grant No.51972209).
