高炉镍铁渣粉是一种前期火山灰活性较低的绿色可持续新型建筑材料.本文探讨了外掺硅灰对高炉镍铁渣粉水泥土无侧限抗压强度的影响规律,分析高炉镍铁渣粉和硅灰替代率对其无侧限抗压强度和破坏模式的影响.结合扫描电子显微镜(Scanning Electron Microscope,SEM)和X-射线衍射仪(X-ray Diffractometer,XRD)揭示硅灰对高炉镍铁渣粉水泥土性能影响机制.研究结果表明:在一定范围内,高炉镍铁渣粉水泥土的强度随硅灰掺量的增加而提升,归因于硅灰促进水泥水化反应以及硅灰发生二次火山灰反应生成C-S-H凝胶包裹土颗粒表面,未发生水化反应的颗粒减少,凝胶将土壤颗粒、高炉镍铁渣粉颗粒和小硅球等共同构建"网络状"空间骨架填充在大土壤颗粒之间,进一步提升了水泥土的密实性与强度,硅灰的最佳掺量为10%.硅灰掺量高会消耗大量Ca(OH)2,影响硅灰发生二次火山灰反应,特别是掺量增加至30%时,水泥土强度降低3.6%.
Influence Mechanism of Silica Fume on Cement-Soil with Blast Ferronickel Slag
Blast ferronickel slag is a both sustainable and environment-friendly material with low pozzolanic activity.The effect of silica fume on the unconfined compressive strength of cement-soil with blast ferronickel slag is studied,and the effect of the replacement rate of blast ferronickel slag and silica fume on the strength and failure pattern are analyzed.Scanning Electron Microscope and X-ray Diffractometer are used to explore the mechanism of the effect of silica fume on the properties of cement-soil with blast ferronickel slag.The results show that the strength of cement-soil with the increase of silica fume content increases,which is attributed to the fact that silica fume promotes cement hydration reaction and secondary pozzolanic reaction to produce C-S-H gel coating the surface of soil particles,and the particles without hydration reaction are reduced.Moreover,the soil particles,blast ferronickel slag and silica fume are packed by gel between the large soil particles to improve the compactness and strength of cement-soil.The best dosage of silica fume is 10%.However,excessive dosage of silica fume consumes Ca(OH)2 and affects the secondary pozzolanic reaction of silica fume.When the dosage increases to 30%,the strength of cement-soil decreases by 3.6%.
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