Soda residue is the waste residue released during the production of soda by an ammonia soda method. The improper treatment and disposal of soda residue have an adverse environmental impact and there is an urgent need to utilize this material to safeguard nature. After the process of dechlorinating, drying and crushing, the soda residual powder is utilized as an internal curing agent for the high-strength and high-performance concrete (HS-HPC) with the water binder ratio of 0.35 and 0.25. This work has evaluated the effect of the processed soda residue internal curing agent (SR) on the autogenous shrinkage and early crack resistance of HS-HPC. The results show that the SR is a fine powder mainly consisting of porous calcium carbonate particles with dihydrate gypsum as a part. The SR has exhibited a relatively high capacity of water absorption and release. Besides the positive effect of SR itself on the internal relative humidity, the additional water introduced by the SR can further improve the internal relative humidity of HS-HPC. Without reducing the 28 d compressive strength of HS-HPC, the results have shown that replacing 5.25% cement (by mass) with SR can reduce the 3 d autogenous deformation by about 30% and reduce the 3 d tensile stress by over 20% tested by the ring constraint method, particularly for the HS-HPC with lower water binder ratio. The SR has been examined to be a reliable internal curing agent for HS-HPC and there are three mechanisms collectively contributing to mitigating autogenous shrinkage. Firstly, the dihydrate gypsum in SR reacts with C3A to form an expansive ettringite to compensate for the autogenous shrinkage partially. Moreover, the SR partially replaces the cement and thus fundamentally reduces the autogenous shrinkage. Finally, the porous structure of SR allows the absorbed water to be released gradually, which improves the internal relative humidity of HS-HPC and thus reduces the capillary stress for the autogenous shrinkage. © 2022, Materials Review Magazine. All right reserved.
