On High-Strength Low-Shrinkage Iots-Based Concrete

Abstract

With iron ore tailings (IOTs) as the main raw material, the author prepares concrete specimens featuring low shrinkage and high bending strength, and reduces the shrinkage with "hot steaming" steel slag as the admixture. Then, the author carries out a series of laboratory tests to characterize the shrinkage, strength, morphology, microstructure and chemical components of the specimens during the curing process. These parameters are measured after 12 hours, 3 days, 7 days and 28 days, respectively. For each mixture, 3 replicates are prepared and analyzed by the strength test, X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The measured shrinkage of the proposed concrete is lower than half of that of the normal concrete for railway sleepers, and its bending strength is almost twice of that of the latter. Further investigation demonstrates that the large decrease in the autogenous shrinkage is attributable to the micro-expansion, which is caused by the hydration of f-CaO, f-MgO and RO phases in the highly dispersed steel slag particles. In the early stage of curing, the shrinkage might be mitigated by the coordinated formation of ettringite and C-S-H gels. Besides, the reduced shrinkage leads to fewer stress loss of prestressed reinforcement in prefabricated structures. The findings indicate that the proposed concrete has a great potential to serve as the material for prefabricated structures or cast-in-situ concretes.