Polypropylene fiber and cement were used to modify iron tailings and applying it to roadbed engineering is an important way to promote the sustainable development of the mining industry. However, the existing studies are mostly concerned with the static mechanical properties, and lack the deformation characteristics of cyclic loading under different loading modes. The effects of fiber content, dynamic-static ratio (Rcr) and curing age on the deformation characteristics of fiber cement modified iron tailing (FCIT) under different cyclic loading modes were explored through dynamic triaxial tests. The research results show that: (1) Polypropylene fibers significantly reduced the cumulative strain of FCIT. Under intermittent loading, the cumulative strain decreased by 36 similar to 43 %, and under continuous loading, the cumulative strain decreased by 48 similar to 55 %. (2) The deformation behavior of FCIT under both intermittent and progressive loading was in a plastic steady state with cumulative strain <= 1 %. (3) The cumulative strain variation of FCIT with intermittent loading of 0.316 % was significantly lower than that with continuous loading of 0.417 %, and the resilience modulus was higher with intermittent loading. (4) The stress history effect of step-by-step loading can be eliminated by the translational superposition method, and the strain evolution law under continuous loading is predicted based on the progressive loading data, and the minimum error between the expected and actual results is 6.5 % when Rcr is 0.1.

The ionic soil stabilizer (ISS) can synergistically enhance the mechanical properties and improve the engineering characteristics of iron tailings soil in conjunction with cementitious materials such as cement. In this paper, the influence of ISS on the cement hydration process and the charge repulsion between iron tailings soil particles was studied. By means of Isothermal calorimetry, X-ray diffraction (XRD), Scanning electron microscope (SEM), and Low-field nuclear magnetic resonance microscopic analysis methods such as (LF-NMR), X-ray photoelectron spectroscopy (XPS), Non-evaporable water content and Zeta potential were used to clarify the mechanism of ISS-enhanced cement stabilization of the mechanical properties of iron tailings soil. The results show that in the cement system, ISS weakens the mechanical properties of cement mortar. When ISS content is 1.67%, the 7 d compressive strength of cement mortar decreases by 59.8% compared with the reference group. This retardation arises due to carboxyl in ISS forming complexes with Ca2+, creating a barrier on cement particle surfaces, hindering the hydration reaction of the cement. In the cement-stabilized iron tailings soil system, ISS has a positive modification effect. At 0.33% ISS, compared with the reference group, the maximum dry density of the samples increased by 6.5%, the 7 d unconfined compressive strength increased by 35.3%, and the porosity decreased from 13.58% to 11.85%. This is because ISS reduces the double electric layer structure on the surface of iron tailings soil particles, reduces the electrostatic repulsion between particles, and increases the compactness of cement-stabilized iron tailings soil. In addition, the contact area between cement particles increases, the reaction energy barrier height decreases, the formation of Ca(COOH)2 reduces, and the retarding effect on hydration weakens. Consequently, ISS exerts a beneficial effect on augmenting the mechanical performance of cement-stabilized iron tailings soil.

Seeking ways to effectively utilise iron tailings within the green building sector is a pressing issue at present. In this study, using iron tailings as the main raw material and cement as the auxiliary cementitious material, the effects of sodium silicate (SS) content and carbonation curing on the compressive strength, stiffness, microstructure and mineral composition of cemented iron tailings (SSCIT) were investigated. The results showed that a certain amount of SS could increase the strength and stiffness of SSCIT. By adding 6% SS, the strength and stiffness of SSCIT reached the maximum value. The addition of SS promoted the dissolution of silicate minerals, and the generated geopolymerised gel binder filled the pores of specimens, enhanced the bonding force between the interfaces of soil particles, and improved the specimen compactness. However, carbonation curing adversely affected the strength of SSCIT. Carbonation caused the hydration products of SSCIT to change, and the decalcification and decomposition of the C-S-H gel increased the porosity of SSCIT, leading to a decrease in strength. In addition, using iron tailings for road base materials is an efficient and feasible method of utilisation.

The secondary utilization of iron tailings solid waste meets the green development requirements of road construction in the new era. Currently, there is a lack of research on the equivalent confining pressure effect of fiber, the influence of complex stress paths on the mechanical properties of modified soil, and the internal damage in soil based on energy dissipation theory. The effects of different polypropylene fiber content, confining pressure, curing age, and complex stress path on the mechanical properties of fiber cement-modified iron tailings (FCIT) were investigated by triaxial tests and energy angle. Combined with the actual subgrade engineering, the stress path test is set up, and the strength index of the FCIT under different working conditions is obtained. From the thermodynamic point of view, the failure process for the FCIT is further revealed. The results show that: (1) the optimal fiber content of FCITs is 0.75%. At this time, the mechanical properties of FCIT are optimal, the strength is high, and shear failure is not easy. The fiber has the equivalent confining pressure effect, which could provide better shear performance for FCITs so that the FCIT is resistant to collapse in embankment construction; (2) the influence of multislope stress path on the secant modulus of the FCIT is worse than that of a single-slope stress path. The influence of curing age on the secant modulus of these two kinds of stress path is consistent, and the secant modulus of the FCIT at 28-day curing is 1.2 times that at 7-day curing; (3) after 7 and 28-day curing, the dissipation energy of the FCIT was consistent when the fiber content was 1%. Due to the equivalent confining pressure of the fiber, the fiber dissipation energy of the FCIT is not affected by the curing age. The total dissipated energy of the FCIT with a stress path slope of 1.5 is 5-6 times that with a stress path slope of 2.5. The total dissipated energy of the single-slope and multislope stress paths decreases with the increase in curing age. (c) 2024 American Society of Civil Engineers.

Soil tuff, an industrial solid waste, can serve as a sustainable alternative to cement for modifying iron tailings sand (ITS). To substantiate this claim, the physical properties, durability and microstructure of soil tuff and cement-modified ITSs were analyzed at different modifier dosages, compaction degrees and maintenance ages, with a comprehensive comparison in the perspective of sustainable built environments. The results indicate that the physical properties of soil tuff-modified ITS (STM-ITS) were significantly enhanced in subgrade engineering applications compared with cement-modified ITS (CM-ITS). In addition, compared with CM-ITS, the hydration products of STM-ITS possessed a smaller amount of Ca(OH)2 and were cemented with surrounding binding products, which resulted in fewer cracks. STM-ITS featured a more stable C-S-H gel than CM-ITS due to a lower Ca/Si ratio, contributing to its higher corrosion resistance. Notably, a sustainability analysis demonstrated that incorporating STM-ITS has physical properties comparable to those of CM-ITS and can be obtained at a significantly lower cost, CO2 emission, and energy consumption. Therefore, this study highlights the potential of soil tuff as a promising eco-friendly option for subgrade engineering, promoting waste usage, improving built environments, and contributing to carbon-neutrality goals. These findings have significant implications for the construction industry and the pursuit of sustainable development.

In order to study the deformation and non-coaxial characteristics of fiber cement modified iron tailing sand (FCIT) under different stress paths. The evolution law of the dynamic stress ratio (eta) on the cumulative deformation and non-coaxial angle of FCIT under different tension-compression amplitude ratios (alpha) was explored through hollow torsional shear tests. The deformation behavior of FCIT is analyzed by using the stability theory. The research results show that: 1) The increase of dynamic stress level will deepen the cumulative deformation of FCIT, while the increase of alpha will make the deformation mode of FCIT develop into bulging failure-shear failuretensile failure. 2) According to the development trend of cumulative strain and cumulative strain rate of FCIT, it can be divided into three stages: plastic stability, plastic creep and incremental collapse, and the cumulative strain rate development prediction model is established, and the prediction error distribution is within +/- 20%. 3) The stress path determines the non-coaxiality of FCIT to a certain extent, and the non-coaxial angle fluctuates and decreases with the increase of the principal stress direction angle. When alpha=0.125, the maximum and minimum values of the non-coaxial angle of FCIT are 1.5 rad and 0.4 rad respectively. 4) Cement hydration reaction generates calcium alumina and hydrated calcium silicate (C-S-H) to make FCIT structure more compact, fibermatrix interfacial connections more dense, and play a role in filling the pores.

This article explores the utilization potential of three distinct mine tailings (MT) viz.; red mud (RM), iron tailings (FeT), and zinc tailings (ZT) as geopolymer binders to stabilize the soil for road subgrade application. The strength and durability of soil treated with various MT -based geopolymers are examined through a succession of unconfined compressive strength (UCS), California bearing ratio (CBR) and alternate wetting -drying tests respectively. Furthermore, permeability tests are also conducted to examine the hydraulic response of soil amended with MT -based geopolymers. Finally, leaching study is performed to examine the geo-environmental implications of various geopolymer specimens. The experimental results reveal that the UCS of untreated soil is increased from 0.39 MPa to 5.24 MPa, 5.13 MPa and 3.78 MPa with the use of RM, FeT, and ZT-based geopolymers respectively. The study further shows a 26 -fold, 19 -fold, and 15.8 -fold increase in the soaked CBR values of soil when it is stabilized with RM, FeT, and ZT-based geopolymers respectively. In contrast to untreated soil, soil stabilized with MT -based geopolymers exhibit excellent weathering resistance to alternate wettingdrying cycles showcasing its exceptional durability under challenging environmental conditions. Irrespective of the MT content, curing environment, and the alkali activator concentrations, soil treated with MT -based geopolymers is found to satisfy both the strength (i.e. UCS = 0.75-1.5 MPa and CBR > 5%) as well as durability criteria (i.e. % loss in mass < 10%) specified by Indian Road Congress for subgrade soil. Moreover, the leaching study shows the concentrations of toxic elements (Zn, Cd, Fe, Pb, Ni etc.) to be within the permissible limits specified by USEPA thereby dispelling any environmental concerns associated with the use of MT -based geopolymers.