Experimental study on the freezing resistance and microstructure of alkali-activated slag in the presence of rice husk ash

This study illustrates the significant influences of rice husk ash (RHA) addition on the mechanical properties, freezing resistance and microstructure of alkali-activated slag (AAS) material. The results indicate that the incorporation of rice husk ash enhanced the compressive strength, and reduced the mass loss percentage and compressive strength loss percentage during freeze-thaw cycles, improving the freezing resistance of hardened AAS pastes evidently. The primary reasons for this optimization are the synergistic functions from the potential filling effect of RHA particles and gels enrichment in nature and content of AAS samples. The former refined the capillary pores definitely and the later was responsible for the development of compressive strength. However, the excessive contents (more than 20%) of rice husk ash did make a side effect on the development of freezing resistance and microstructure of AAS samples, which was likely related to the structure of rice husk ash itself. The dosage of rice husk ash used in AAS should be within 20% when considering the achievement of better comprehensive properties.

Automated summary

The addition of rice husk ash has significant effects on the mechanical properties and freezing resistance of alkali-activated slag material, enhancing compressive strength and reducing mass loss percentage during freeze-thaw cycles. However, excessive content of rice husk ash may have negative impacts on the performance of the material.