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Red mud and iron tailings are representative solid wastes in China, which have caused serious environmental pollution and potential harmful risk to people. Based on the alkali characteristic of Bayer red mud and natural fine-grained feature of iron tailings, these two solid wastes were used as raw materials to prepare alkali-activated cementitious...
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... a small amount of 52.5 Portland cement was added to provide calcium-based precursor. Table 1 shows the chemical composition and origin information of the relevant raw materials used in this work. As the most important raw materials, Figure 1 shows XRD patterns of Bayer red mud and iron tailings. ...Similar publications
The use of winery solid waste compost (WSW) on croplands represents an important strategy for WSW management. However, the full benefits of the use of this compost as an organic fertilizer can be derived with accurate recommendations. Hence, a 4×7×2 factorial experiment was conducted under tunnel-house conditions to determine the optimum rates of t...
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... The simplified manufacturing process of SS-SGMs is illustrated in Fig. 6. The utilization of ternary precursor materials and the activator solution in this work resulted in the formation of calcium aluminum silicate hydrate (C-A-S-H) gels and sodium aluminum silicate hydrate (N-A-S-H) gels in SS-SGMs products [49]. It should be noted that the curing method significantly influences the strength development of geopolymers. ...
This study aimed to explore the feasibility of utilizing geopolymer as alternatives to Ordinary Portland Cement (OPC) in marine engineering. Eco-friendly seawater sea-sand slag-based geopolymer mortars (SS-SGMs) were prepared by blending seawater, sea-sand, Basalt Fibres (BF), Polypropylene Fibres (PPF), and ternary solid waste. The effects of activator modulus, alkaline content, water-to-binder ratio, and the volume fractions of BF and PPF on the mechanical performance, environmental impact, and cost of SS-SGMs were researched using the L 16 (4) 5 Taguchi orthogonal method. Three evaluation methods were used to assess the impact of the different factors. First, the influence of a single factor was analyzed using methods of range and variance analysis. Subsequently, three new evaluation metrics were proposed to consider the synergistic effects of mechanical performance, environment , and cost. Finally, a Gray-Technique of Ordering Preferences by Similarity to Ideal Solution (Gray-TOPSIS) model was established, and the influence weights of each factor were proposed, thereby determining the optimal solution in a multi-index evaluation system. The recommended optimal mix proportion for SS-SGMs was determined as follows: activator modulus of 1.0, alkaline content of 4%, water-to-binder ratio of 0.42, PPF volume fraction of 0.4%, and BF volume fraction of 0.3%. Compared to OPC with the same strength grade, SS-SGMs demonstrated similar costs, a reduction in carbon emissions by approximately 75-83%, a decrease in energy consumption by around 50-67%, and lower drying shrinkage than traditional geopolymer. Under the influence of seawater, the products of SS-SGMs were capable of forming chloride-ion adsorbing products like hydrotalcite and Brucite. Additionally, the formation of C 4 AH 13 and ion clusters can enhance the matrix density, thereby improving the mechanical performance of SS-SGMs.
... Iron ore tailing (IOT), as an industrial solid waste generated during iron ore beneficiation, discharges more than 10 billion tons of tailings and waste rocks every year in the world [1]. Over the past thirty years of reform and opening up, with the rapid development of China's iron and steel industry, IOT has become one of the major industrial solid wastes in China [2]. ...
The massive accumulation of iron ore tailing (IOT) results in land resource wastage and increases the possibility of environmental pollution. In this study, the feasibility of using low-carbon alkali-activated ground granulated blast-furnace slag (lime/Carbide slag (CS)-GGBS) and coal fly ash (CFA) instead of portland cement (PC) for solidifying IOT was investigated. The effects of different binders on strength development and durability of cured IOT were analyzed through unconfined compressive strength (UCS), water stability, and dry-wet cycles tests. Furthermore, the microstructure characteristics of cured IOT were conducted by using scanning electron microscope (SEM) method, X-ray diffraction (XRD) analysis, and thermogravimetric analysis (TGA). The results showed that, using the low-carbon material lime/CS-GGBS to replace about 70% of PC (i.e., PC:lime/CS: GGBS=1:1:1) with 9% binder content, the strength and durability of cured IOT were significantly improved compared with using pure PC. The 28d-UCS of cured IOT was 4.86 MPa, which was twice higher than that with pure PC. The 7d-UCS of cured IOT was 8.22 MPa after 12 dry-wet cycles, which was 2.8 times higher than that with pure PC. Moreover, the water stability coefficient of 27 + 1d-cured IOT was 90%. The micro-analysis showed that, the amount of hydration products (i.e., CSH, CAH and ettringite) in IOT cured with low-carbon materials increased significantly, and the structure became denser, resulting in the increase of strength. This study develops a low-carbon binder instead of pure PC to solidify IOT, and the results can provide a theoretical basis and scientific guidance for the comprehensive utilization of IOT as a filler solid waste.
... It can be seen that the broad fronts at 3330 cm the presence of carbonate.The sample was attacked by CO 2 during conservation and reacted to form CaCO 3 [49][50] . The presence of a distinct peak near 872 cm − 1 in the meso-[SiO 4 ] tetrahedron of the C-S-H gel, which is a result of the Si-O-Si bond's vibration, suggests that a copolymerization reaction has occurred, con rming that the CLSM reaction product is mainly a C-S-H gel [51] .The bending vibration of T-O (Si-O or Al-O) [52] , which is mainly found in the silica-aluminate component of the product, has produced many small absorption peaks between 400 cm − 1 and 600 cm − 1 . ...
Aiming at the environmental problems caused by waste incineration ash, a reuse solution was proposed to use waste incineration ash and red mud for the preparation of Controlled Low Strength Material (CLSM), to determine the effect of each parameter on the performance of the material by using a one-way test and to determine the reasonable interval of each parameter, and to design the test by using the Box-Behnken Response Surface Method. Three factors, namely, red mud percentage, water-gum ratio, and glue-sand ratio, were used as test variables, and 14d unconfined compressive strength, mobility, and cost were used as response values to optimize the objectives. The heavy metal toxicity and micro-morphology of CLSM were investigated by using microscopic means such as heavy metal leaching concentration, XRD, and FTIR. The results of the study showed that the optimal mixing ratio of CLSM was 0.5 for red mud percentage, 0.667 for water-gum ratio, and 0.45 for gum-sand ratio, which can effectively utilize the waste incineration ash and reduce environmental pollution. It was found that under alkali activation, the red mud-refuse incineration ash cementation system would change and produce new substances, with crystals as the framework and gel as the filling, forming a dense structure.
... The unit cost, EC, and EE of the ingredients required for CTB preparation are summarized in Table 4 (M. Chen et al., 2021b;Du et al., 2022;Li et al., 2021;Norgate and Haque, 2010;Zhong and Zhang, 2021). According to the J o u r n a l P r e -p r o o f inventory data in the table, the estimated results of all samples are presented in Fig. 13(a). ...
... Inventory of cost, EC, and EE of all ingredients in CTB (M.Chen et al., 2021b;Du et al., 2022;Li et al., 2021;Norgate and Haque, 2010;Zhong and Zhang, 2021). ...
... In addition, characteristic peaks of ettringite, a mineral phase commonly presented in cement hydration systems, appear around 28° and 39°. Figure 9 shows the XRD patterns of graphite-ore-incorporated mortar and GTTM after curing for 28 days. The wide peaks around 25-35 • corresponded to amorphous C-A-S-H gels, which were the main hydration products of cementitious materials that incorporated iron tailings [25,26]. The peaks near 29 • and 50 • corresponded to the presence of the hydration product Ca(OH) 2 . ...
... Figure 9 shows the XRD patterns of graphite-ore-incorporated mortar and GTTM after curing for 28 days. The wide peaks around 25-35° corresponded to amorphous C-A-S-H gels, which were the main hydration products of cementitious materials that incorporated iron tailings [25,26]. The peaks near 29° and 50° corresponded to the presence of the hydration product Ca(OH)2. ...
... The grap ite tailings could fill holes in the mortar structure and enhanced the mortar's mechanic properties. The comparison between Figures 10 and 11 clearly indicates that there was bett densification between the graphite tailings and the C-A-S-H gels, which is consistent wi the results from other studies [25][26][27]. When a graphite tailings content of 40 wt% w incorporated, hydration products, such as columnar ettringite and amorphous C-A-Sgels, were present in large quantities, combining with the aggregate to densify the mort structure, further increasing the mechanical strength of the cementitious mortar. ...
Graphite ore and graphite tailings were blended into iron-tailings-based cementitious mortars, and their mechanical properties and microstructure were experimentally investigated. The flexural and compressive strengths of the resulting material were tested to compare the effects of graphite ore and graphite tailings as supplementary cementitious materials and fine aggregates on the mechanical properties of iron-tailings-based cementitious mortars. Additionally, their microstructure and hydration products were mainly analyzed using scanning electronic microscope and X-ray powder diffraction techniques. The experimental results showed that the mechanical properties of the mortar material incorporating graphite ore were reduced due to the lubricating properties of graphite ore. As a result, the unhydrated particles and aggregates were not tightly bound to the gel phase, making the direct application of graphite ore in construction materials unfeasible. In the iron-tailings-based cementitious mortars prepared in this work, the optimal incorporation rate of graphite ore as a supplementary cementitious material was 4 wt%. The compressive strength of the optimal mortar test block after 28 days of hydration was 23.21 MPa, and the flexural strength was 7.76 MPa. The mechanical properties of the mortar block were found to be optimal with a graphite-tailings content of 40 wt% and an iron-tailings content of 10 wt%, resulting in a 28-day compressive strength of 48.8 MPa and a flexural strength of 11.7 MPa. By observing the microstructure and XRD pattern of the 28-day hydrated mortar block, it was determined that the hydration products of the mortar with graphite tailings as an aggregate included ettringite, Ca(OH)2, and C-A-S-H gel.
... The hardening behavior of the ternary cementless materials was assumed to be due to the Ca-Si-Al colloidal system, and the strength development was due to calcium silicate hydrate (C-S-H) or calcium aluminum silicate hydrate (C-A-S-H) produced by the hydration process, which also supported the hypothesis that cementless materials could be made without alkali activators. The results were consistent with the results of previous tests [10,11]. The strength increased with hydration time, and the 28-day compressive strength of the specimens cured in water reached between 15 and 18 MPa. ...
In this study, three industrial by-products (ultrafine fly ash, ground granulated blast-furnace slag (ggbs) and circulating fluidized bed co-fired fly ash) were used to produce ternary cementless composites without using alkali activators. The finenesses of ultrafine fly ash, ggbs and co-fired fly ash were 33,800, 5830 and 5130 cm 2 /g, respectively. The composite material was developed by mixing supplementary cementing materials of different particle sizes and exploiting the high-alkaline properties of the co-fired fly ash to develop a substantial hardening property like cement. The test specimens were made in the form of pastes and the water-to-cementitious-material ratio for the test was fixed at 0.55. The test results show that the flowability of the six different mixtures could be up to 120% and the setting time could be controlled within 24 h. At 60% of the ggbs proportion, the setting time could be held for 8 h. The compressive strength of each proportion reached 7 MPa at 7 days and 14 MPa at 28 days. The water-cured specimens exhibited better strength behavior than the air-cured specimens. Scanning electron microscopy found the main components of strength growth of the specimens to be hydrated reactants of C-AS -H or ettringite. The results of the XRF analysis show that the specimens responded to higher compressive strengths as the Ca/Si and Ca/Al ratios increased.
... Although iron ore tailings are used as an aggregate in GICC, clay minerals such as clinochlore in the iron ore tailings could release active Si and Al to react with Ca(OH)2 to form C-(A)-S-H gels [68,69]. Some previous studies have also shown the formation of C-S-H gel and C-(A)-S-H gel [42,62,70]. The iron ore tailings particles deposit onto the edge of graphene thanks mainly to the binding of C-S-H gels. ...
... Although iron ore tailings are used as an aggregate in GICC, clay minerals such as clinochlore in the iron ore tailings could release active Si and Al to react with Ca(OH) 2 to form C-(A)-S-H gels [68,69]. Some previous studies have also shown the formation of C-S-H gel and C-(A)-S-H gel [42,62,70]. The iron ore tailings particles deposit onto the edge of graphene thanks mainly to the binding of C-S-H gels. ...
... It can also be seen that the C-S-H gels increase with the prolongation of hydration time. In the interface transition zone between the graphene and the ettringite, some deposited crystals and ettringite are covered by C-(A)-S-H gels, further consolidating the composite structure [70]. With the increase of hydration time, the three-dimensional structure of graphene-ettringite-C-(A)-S-H gel is constantly enriched and improved, thereby further enhancing the flexural strength of GICC. ...
Graphene is a two-dimensional nanomaterial with excellent mechanical, electrical and thermal properties. The application of graphene in cement-based materials has good prospects. However, the mechanical properties of cement-based materials are difficult to be significantly enhanced by ordinary graphene nanoplates. In this paper, nitrogen-doped graphene is first reported as an additive with dosages of 0.01, 0.02, 0.03, 0.04 and 0.05 wt.%, respectively, to prepare iron ore tailings–based cementitious composites. The iron ore tailings–based cementitious composite with 0.02 wt.% graphene shows an extremely high flexural strength of 15.05 MPa at 3 days, which is 134.4% higher than that of the iron ore tailings–based cementitious composite without graphene. The effects of graphene content and curing age on the flexural strength and microstructure of iron ore tailings–based cementitious composites were studied. In particular, the scanning electron microscope was adopted to observe the micromorphology of the composites. It is helpful to understand the graphene reinforcement mechanism for the high early flexural strength of iron ore tailings–based cementitious composites. By altering the morphology of iron ore tailings–based cementitious composites, graphene plays two roles in the composites. One role is to connect C-(A)-S-H gels, ettringite and other hydrated crystals to construct a three-dimensional structure. The other is to attract iron ore tailings distributed on its platform to enhance its flexural strength properties. These findings provide favorable guidance for the performance enhancement and mechanism replenishment of graphene-reinforced cementitious composites.
... The cementitious activity of solid waste is usually evaluated by the content of active Si and Al dissolved in an alkaline environment. Considering that phosphorous slag mainly has a vitreous structure, and its main chemical composition is similar to that of blast furnace slag [39], the cementitious activity of phosphorous slag is compared with blast furnace slag. The dissolved contents of active Si and Al in 1 mol/L NaOH solution for phosphorous slag and blast furnace slag are presented in Figure 9. ...
Phosphorous slag is a solid waste generated in the process of yellow phosphorus production. In order to deeply understand the structural and cementitious characteristics of phosphorous slag, comprehensive characterizations, including X-ray fluorescence spectrometry, X-ray diffraction, thermogravimetry, Fourier transform infrared spectrometry, Raman, scanning electron microscope, and inductively coupled plasma mass spectrometry were adopted to investigate the composition, thermal stability, microstructure, and cementitious activity of phosphorous slag. In addition, scanning electron microscope with energy dispersive X-ray spectroscopy, electron microprobe analysis, and solid-state nuclear magnetic resonance techniques were used to analyze the occurrence state of P in phosphorous slag. The results show that phosphorous slag is mostly vitreous with good thermal stability. Its chemical composition mainly comprises 43.85 wt % CaO, 35.87 wt % SiO2, and 5.57 wt % Al2O3, which is similar to that of blast furnace slag, but it presents lower cementitious activity than blast furnace slag. P is uniformly distributed in the phosphorous slag with P2O5 content of 3.75 wt %. The distribution pattern of P is extremely similar to that of Si. P is mainly existing in orthophosphate of 3CaOP2O5, which forms solid solution with dicalcium silicate (2CaOSiO2). This work specifically clarifies the occurrence state of P in dicalcium silicate within the phosphorous slag. It is theoretically helpful to solve the retarding problem of phosphorous slag in cement and concrete.
... In recent years, the research on alkali-activated cementitious materials mainly focuses on two directions. First, continue to study alkali-activated slag cementitious materials to improve their properties and expand their applications [21][22][23]; Second, other solid wastes with alkali-activated cementitious properties are used to prepare new alkali-activated cementitious materials, such as silicomanganese slag, copper and nickel slag, red mud-iron tailings, copper slag, nickel slag, and ferronickel slag [24][25][26][27][28][29][30]. ...
Modifying the admixture of alkali-activated cementitious materials using components such as fly ash and fine sand may reduce CO2 emissions and conserve natural resources and energy. This study adopted strength testing, scanning electron microscopy, and mercury intrusion porosimetry to investigate the influence of different admixtures on the compressive strength and flexural strength of alkali slag cementing materials and the microstructure characteristics of hardened slurry under the action of load. The flexural strength of alkali slag cement slurry and mortar was reduced by replacing slag powder with fly ash. Content of fine sand less than 20% had little effect on the strength of alkali slag cement mortar; however, when the content of fine sand exceeded 30%, the strength decreased significantly. The hydration degree at 3 d was large, and the density of slurry increased with the extension of age. Increased fly ash or fine sand content decreased the density of the slurry, and increased fly ash resulted in a large number of unhydrated fly ash particles in the cementitious materials. Addition of fine sand resulted in a large number of microcracks in the slurry, which gradually decreased with the extension of hydration age.
... It is thought that on one hand, the active silicon and aluminum substances on the surface of iron tailings could participate into the pozzolanic reaction under a suitable alkali activation effect of red mud to form aluminous C-S-H gels. On the other hand, the iron tailings mainly acted as fine aggregates in RFT, and they were wrapped by the C-S-H gels, therefore a strong bonding effect occurred between the aggregates and cementitious matrix (Zhang et al. 2016c;Li et al. 2022). Virgate ettringite were dispersed in the cementitious matrix, and fly ash microspheres were coated by the C-S-H gels. ...
... However, microcracks would occur during this quick hydration, which inhibited the further strength development of K2 sample at 28 days. In RFT mortar materials, red mud, as an alkaline solid waste, could provide a suitable alkali activation effect along with OPC and BSC to activate the active silicon and aluminum substances on the surface of fly ash and iron tailings, forming aluminous C-S-H gels with a cross-linked structure which are helpful for strength development (Li et al. 2022;Zhang et al. 2011aZhang et al. , 2021b. Under a same proportion of iron tailings, higher proportion of fly ash could generate more C-S-H gels with a cross-linked structure, resulting in the compressive strength improvement at 28 days. ...
A specific mortar material (abbreviated as RFT) was designed from industrial solid wastes, such as red mud, fly ash, and iron tailings. It was mainly developed for 3D printing in this work. Mechanical properties, microstructure and heavy metal leaching properties were discussed. The RFT composed of 15% red mud, 45% iron tailings, 9% fly ash, 30% cement, and 1% FDN water reducing agent attained good mechanical properties. Hydration products including Ca(OH)2, ettringite and C-S-H gel were found in RFT through SEM observation. Iron tailings mainly acted as fine aggregates in RFT, and they were wrapped by the C-S-H gels, producing a strong bonding effect between aggregates and cementitious matrix. The leaching toxicity test results proved that the developed RFT mortar materials were environmentally acceptable. Finally, RFT was subjected to a 3D printing test to verify its feasibility as 3D printable construction material.
