Nano-micron soda residue as green nucleation seeding additive for silicate cement

Abstract

Soda residue (SR) is a kind of by-product by the ammonia-alkali process in the soda ash production, which contains calcium components, such as calcium sulfate and calcium chloride. In this work, the feasibility of using SR as an accelerating additive for Portland cement (PC) was investigated. Wet milling method was used to prepare nano-micron SR seed with D50 of 246 nm. A binary system of PC and SR seed was designed, and its compressive strength, hydration kinetics and microstructure were studied. Results showed that the 12-hour compressive strength of PC was greatly increased by 1.69 times when the dosage of SR seed was 6%. This improvement was attributed not only to the nucleation seeding and filling effect of the SR seed, but also to the presence of pre-dissolved chlorine and sulfate ions from SR particles. Furthermore, the pore volume was reduced by more than 16%, the critical pre radius was decreased by 86.3%, and the gel pore content was 2.3 times that of reference group, indicating a high microstructure refinement and gel binding contribution of SR seed.