Properties of Alkali-activated Yellow River Sediment-slag Composite Material

Abstract

In order to consume the Yellow River sediment as much as possible and improve the longterm stability of the Yellow River, Yellow River sediment was utilized as the main raw material to produce a composite material. Ca(OH)2 was used as alkali-activator to activate the active SiO2 and Al2O3 compositions in Yellow River sediment. 10 wt% slag was added into the mixture to further improve the strength of the composites. The effect of activity rate of the Yellow River sediment and dosage of Ca(OH)2 on the compressive strength of the Yellow River sediment-slag composite material at different curing ages was researched. XRD, SEM/ EDS, light microscope and FTIR were used to further explore the products and the microstructure of the composite material. Results showed that the active ratio of sediment had a great influence on the compressive strength of specimen. In addition, the compressive strength of specimen increased with the increase of Ca(OH)2 dosage and curing age. When the dosage of Ca(OH)2 was more than 5 wt% as well as the curing age reached 90 days, the compressive strength of the composite material could meet the engineering requirement. In the alkali-activated process, the main product was hydrated calcium silicate (C-S-H) gel, which filled up the gaps among the sediment particles and decreased the porosity of the specimen. Moreover, the CaCO3 produced by the carbonization of the C-S-H gel and excess Ca(OH)2 also played a role on the strength.