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.

Study of Short-Term Flexural Behavior for Glue-Bamboo and Lumber Beams Under Different Pre-Stressed States

“…Thus, if the pre-stressing tendons number and pre-stress value were in the range given from this paper, the above bearing capacity calculation formula could be used for a reference for practical engineering. (1) Under the same pre-stress value, with the increase of pre-stressing tendons number, the beam ultimate load and stiffness increased. Compared to the beams with 2 tendons were arranged, when 4 tendonss were arranged, the ultimate load increased about 12.45%~37.25%; when 6 tendons were arranged, the ultimate load increased about 22.81~86.3%.…”

“…[1][2] To let it fully used, especially in the long-span structures, the pre-stress glue-bamboo and lumber beam was proposed by project team, [3] and the materials selection was studied. As a kind of prestress flexural member composited by steel and lumber, the pre-stressing tendons number and pre-stress value had a big influence on beam flexural behaviour, so it was necessary for further research.…”

Carbonation Curing on Magnetically Separated Steel Slag for the Preparation of Artificial Reefs

“…Howev er, using steel slag as aggregates does not embody the high value of steel slag. Steel slag contains hydraulic materials (i.e., C 2 S and C 3 S), which could replace part of the cementing materials [ 4 , 5 , 6 ].…”

Numerical Simulation Analysis of the Dynamic Mechanical Property of Concrete Based on 3D Meso-mechanical Model

“…There are obvious differences in macro strength and deformation features of concrete under dynamic load and that under static load. The dynamic load-induced response is a rather complex process, involving the evolution of microdefects in the material, the sensitive effect of material strain rate, and the impact of hydrostatic pressure correlation [1][2][3][4][5]. Under dynamic load, the change in concrete deformation and stress is often transmitted in the form of wave, featuring strong instantaneity.…”