Utilization of Treated Agricultural Residue Ash as Sodium Silicate in Alkali Activated Slag Systems

This study investigated the influence of rice straw ash (RSA), rice husk ash (RHA), and silica fume (SF) on alkali activated slag (AAS) systems. RSA, RHA, and SF were treated with sodium hydroxide to improve their reactivity in AAS systems. Although addition of SF in AAS systems increased compressive strength, samples containing RSA or RHA had higher compressive strength than those having SF. Treated RSA or RHA further increased compressive strength of AAS samples. It was shown that samples containing treated ash samples had similar compressive strength to those made with sodium silica activator. Therefore, it is suggested that treated ash samples could be used as alternative sources of silica for AAS. Drying shrinkage of AAS samples increased considerably when treated RSA or RHA were used as partial replacement of slag. This could be attributed to higher silica modulus (SiO2/Na2O) ratio of samples containing treated ash, which in turn would lead to a finer pore size structure compared to control samples. However, SF significantly reduced drying shrinkage of AAS. This could be because SF reduces the permeability and porosity of AAS samples.

Automated summary

The study found that treated rice straw ash and rice husk ash in alkali activated slag systems can increase compressive strength but also lead to greater drying shrinkage. Treated ash samples have a higher silica modulus, potentially resulting in a finer pore structure. On the other hand, the use of silica fume significantly reduces drying shrinkage in AAS systems.