Natural river sand and iron tailings sand samples

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... cement used was Ordinary Portland Cement (P·O 42.5), which complied with the requirement of Chinese standard GB175-2007. The iron tailings (FN, PS, CD, BD, and LY) were selected from different regions in Hebei Province of China, as shown in Fig. 1, and the natural river sand (TR) was used to make a comparison. Their chemical compositions and physical properties were listed in Tables 1 and 2, respectively, and their particle size distribution were presented in Fig. 2, which could meet the requirement of Chinese standard (GB/T 14684/2022) of "Sand for construction". The iron ...

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... of activated iron tailings after rinsing had a great decrease, and that of WHC5 was only comparable to WHB1. Moreover, the ion release concentration of iron tailings activated by 5% NaOH and after rinsing treatment (WNB5) was greatly reduced, indicating that the activity of the iron tailings powder activated by alkali was lower than that by acid. Fig. 10 shows the results of the ion release concentration of the samples in cement solution (S), which were a different form that in deionized water, and should be the sum of the ion concentrations of sample S and that in Fig. 9 if no reaction occurred. However, if the results were higher or lower than their sum, indicating that the cement ...

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... iron tailings powder and cement solution, and the generated products were filtered out. Furthermore, the reactivity of iron tailings powder after activation was higher than that of unactivated sample W0, especially for acid-activated samples, and that increased with the increase of acid concentration and decreased by the rinsing after activation. Fig. 11 shows the morphology of the tailings powder samples. The tailings power unactivated was designated as W0, and that activated by NaOH and HCl with a dosage of 5% (method B) were designated as WNB5 and WHB5, respectively. Obviously, the morphology of tailings powder had become rougher after 1-h immersion in an alkali/acid solution, the ...

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... unactivated was designated as W0, and that activated by NaOH and HCl with a dosage of 5% (method B) were designated as WNB5 and WHB5, respectively. Obviously, the morphology of tailings powder had become rougher after 1-h immersion in an alkali/acid solution, the particle was partially disintegrated and some micropores were formed on the surface. Fig. 12 presents the results of the FTIP spectra of the tailings powder samples. The bands at 3440 cm −1 and 1630 cm −1 are related to the Si-O-H and O-H stretching and bending vibrations of molecular water, respectively (Jiang, 2008). These absorption bands for the W0 sample were very weak, while that for the WHB5 sample was stronger. An ...

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... a sharp and very intense absorption band at 1010 cm −1 , which corresponds to the asymmetric stretching vibration of Si-O-Si(Al), and this band was weakened slightly after activation, especially for WHB5. Obviously, the integrity and symmetry of mineral crystals were affected, and the Si-O, and Al-O bonds were destroyed by chemical activation. Fig. 13 shows the XRD pattern of tailings power samples. Their main mineral compositions are albite, quartz, tremolite, and so on. However, the diffraction peaks of WHB5 and WNB5 were all weakened compared with control W0, especially that of albite, indicating that the crystal structure was destroyed and the degree of amorphous ...

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... mortar prepared with iron tailings powder by compound activation were higher than that by single activation. Among them, the activity index of HB5NA3 was the highest and could reach up to 92% at the age of 3 days, but little growth after that, indicating that compound activation can greatly improve the early activity of iron tailings powder. Fig. 15 represents the isothermal calorimetric curves for the control cement containing no mineral admixture and for cement containing different iron tailings powder. From Fig. 15a, it can be seen that the control sample J first reached the minimum heat flow peak at about 1.4 h and shifted into the acceleration period, whereas the addition of ...

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... 15 represents the isothermal calorimetric curves for the control cement containing no mineral admixture and for cement containing different iron tailings powder. From Fig. 15a, it can be seen that the control sample J first reached the minimum heat flow peak at about 1.4 h and shifted into the acceleration period, whereas the addition of iron tailings powder in samples extended this time. The heat flow of the W sample with unactivated iron tailings was the lowest whether in the induction period or acceleration period, whereas that of the NA3 sample with alkali-activated iron tailings powder was higher in the induction period and the first reached the maximum heat flow peak, indicating that the NaOH brought in by tailings powder promoted the cement hydration, but the heat flow in both acceleration and Kong et al. ...

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... the maximum heat flow peak of HB5 and HB5NA3 samples were even higher than the control J sample, and the time to reach the peak was also in some advance. Besides, the HB5NA3 showed an almost identical cumulative heat curve as HB5, and both of them had sustained growth in hydration heat, and even exceeded the J sample after about 48 h, as shown in Fig. 15b In general, the cumulative hydration heat of W and NA3 was lower than the other samples, and that of NA3 was the lowest after 20 h, indicating little effect of NaOH on the activity of iron tailings powder. In addition, the hardened cement paste with different iron tailings powder was tested by TGA at 28 days, and the results are shown ...

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... Fig. 15b In general, the cumulative hydration heat of W and NA3 was lower than the other samples, and that of NA3 was the lowest after 20 h, indicating little effect of NaOH on the activity of iron tailings powder. In addition, the hardened cement paste with different iron tailings powder was tested by TGA at 28 days, and the results are shown in Fig. 16a The weight loss of the samples between 50 and 400 ℃ (TG 1 ), is mainly due to the dehydration of hydrated calcium silicates (CSH) and ettringite, and that between 400 and 550 ℃ (TG 2 ) and 550-770 ℃ (TG 3 ), are caused by the dehydration of CH, CSH, and ettringite, and the decomposition of the carbonization product. Therefore, the CH ...

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... Fig. 16b, it can be seen that both the contents of CH and bound water of the control sample J were the (1 Kong et al. Int J Concr Struct Mater (2023) 17:24 highest, compared with the samples mixed with iron tailings powder. This is because the cement was partly replaced by iron tailings powder, resulting in less generation of CH, and the ...

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... 17 presents the morphology of the samples with different iron tailings powders. For the W sample with unactivated tailings, the boundary between iron tailings powder and cement paste was apparent, there was little trace of reaction, and many micropores could be observed in the hardened cement paste (Fig. 17a). For the NA3 sample with alkali-activated iron tailings, although the clear boundary could also be observed, the surface of iron tailings powder particles was rougher, and some hydrates attached to it, moreover, some CH crystals were formed around the tailings due to the reaction between dissolved Ca 2+ from iron tailings and OH − ...

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... sample with alkali-activated iron tailings, although the clear boundary could also be observed, the surface of iron tailings powder particles was rougher, and some hydrates attached to it, moreover, some CH crystals were formed around the tailings due to the reaction between dissolved Ca 2+ from iron tailings and OH − introduced by an activator (Fig. 17b). Furthermore, both the acid activation and acid-alkali combined activation could increase the activity of iron tailings significantly, few unreacted tailings powder particles were left in HB5 and HB5NA3, and it has been difficult to distinguish the boundary between iron tailings powder and dense cement paste ( Fig. 17c and d), ...

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... by an activator (Fig. 17b). Furthermore, both the acid activation and acid-alkali combined activation could increase the activity of iron tailings significantly, few unreacted tailings powder particles were left in HB5 and HB5NA3, and it has been difficult to distinguish the boundary between iron tailings powder and dense cement paste ( Fig. 17c and d), indicating that most of the iron tailings participated in the cement ...

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... addition, the microstructure of cement-based materials was characterized by EIS. Fig. 18 Page 14 of 16 Kong et al. Int J Concr Struct Mater (2023) 17:24 contrasting the 3 days and 28 days results, both the left coordinate values and high-frequency semicircle diameters had an evident increase with the increase of curing age, reflecting the gradually denser microstructure of materials (Song, 2000). Furthermore, it is obvious ...