Critical aspects in the handling of reactive silica in cementitious materials: Effectiveness of rice husk ash vs nano-silica in mortar dosage

Abstract

Nano-silica addition improves mechanical and durability behavior in mortars. However, nanomaterial handling requires use of occupational risk prevention measures as Individual Protection Equipment for the workers. Moreover, the high agglomeration of nanomaterials produces uncertainty in the expected mortar performance. Rice husk ash as a source of reactive silica in cement compositions is compared with nano-silica. The use of rice husk ash provides similar physical-chemical cementitious materials than other commercial nano-silica providing relevant differences during the composition. Near 50% wt of volatility is found for the silica nanoparticles during the handling dosage. Thus, the rice husk ash presents a reduced volatility, ∼12% wt and it allows ensuring high content with adequate workability. Mortars with addition of rice husk ash reach higher compressive strength and resistivity in correlation with lower porosity. For that, the use of rice husk ash is viable as safer alternative material than nano-silica in the cementitious compositions. In addition, as the rice husk ash comes from agricultural waste resources their use as secondary raw material will contributes to circularity in the economy by reducing engineered nanomaterials consumption.