Abstract:Environmentally-friendly calcium sulphoaluminate clinkers were obtained from a mixture of aluminium dross, fluorgypsum, fly ash and CaCO 3 at temperatures within the range of 1100 to 1400 °C. After the heat treatments Ca 4 Al 6 O 12 SO 4 was the main phase. Three different cements were prepared using the clinkers synthesized at 1250, 1350 and 1400 °C; the clinker powders were mixed with 20 wt% of hemihydrate. Cement pastes were prepared using a water/cement ratio (w/c), 0.4 followed by curing at 20 or 40 °C fo… Show more
“…5 and Table 2 ). It is worth mentioning that the listed values are close to those presented in the relevant literature 42 , 43 . Figure 5 Curves of the cumulative heat of eco-friendly cement samples.…”
Section: Resultssupporting
confidence: 86%
“…Two compositions of eco-friendly cement were prepared by mixing industrial wastes and natural raw materials. The targeted mineralogical composition of eco-friendly cement was selected according to the composition of such a kind of cements presented in the literature data 30 , 41 , 42 . The main difference between the compositions of S1 and S2 is that S2 sample was prepared by using natural raw materials and GCW, meanwhile, in S1 sample, a part of GCW was replaced with silica gel by maintaining the same targeted mineralogical composition (Table 1 ).…”
In this work, the optimal conditions of the synthesis of eco-friendly cement by using industrial wastes as well as the peculiarities of its early stage hydration were investigated. The eco-friendly cement was synthesized within the 1000–1250 °C temperature range when the targeted composition was 60% of belite, 20% of ye’elimite, and 20% of brownmillerite. It was determined that the optimal sintering temperature for eco-friendly cement is 1100 °C because the primary compounds were fully reacted, and hydraulic active compounds were dominant in the products. Microcalorimetry analysis was performed for the investigation of early stage hydration. The best results of hydration were obtained with the eco-friendly cement which was produced by using mixtures with silica gel waste: three exothermic reactions were observed in the heat evolution curve, while the cumulative heat was equal to 264 J/g after 72 h. Additionally, the sequence of compounds formation during the first day of hydration was analyzed. It was determined that the composition of the initial mixture impacts the hydration rate of synthetic eco-friendly cement; however, it did not affect the mineralogical composition of the hydration products. These results were confirmed by XRD, STA, and SEM analysis.
“…5 and Table 2 ). It is worth mentioning that the listed values are close to those presented in the relevant literature 42 , 43 . Figure 5 Curves of the cumulative heat of eco-friendly cement samples.…”
Section: Resultssupporting
confidence: 86%
“…Two compositions of eco-friendly cement were prepared by mixing industrial wastes and natural raw materials. The targeted mineralogical composition of eco-friendly cement was selected according to the composition of such a kind of cements presented in the literature data 30 , 41 , 42 . The main difference between the compositions of S1 and S2 is that S2 sample was prepared by using natural raw materials and GCW, meanwhile, in S1 sample, a part of GCW was replaced with silica gel by maintaining the same targeted mineralogical composition (Table 1 ).…”
In this work, the optimal conditions of the synthesis of eco-friendly cement by using industrial wastes as well as the peculiarities of its early stage hydration were investigated. The eco-friendly cement was synthesized within the 1000–1250 °C temperature range when the targeted composition was 60% of belite, 20% of ye’elimite, and 20% of brownmillerite. It was determined that the optimal sintering temperature for eco-friendly cement is 1100 °C because the primary compounds were fully reacted, and hydraulic active compounds were dominant in the products. Microcalorimetry analysis was performed for the investigation of early stage hydration. The best results of hydration were obtained with the eco-friendly cement which was produced by using mixtures with silica gel waste: three exothermic reactions were observed in the heat evolution curve, while the cumulative heat was equal to 264 J/g after 72 h. Additionally, the sequence of compounds formation during the first day of hydration was analyzed. It was determined that the composition of the initial mixture impacts the hydration rate of synthetic eco-friendly cement; however, it did not affect the mineralogical composition of the hydration products. These results were confirmed by XRD, STA, and SEM analysis.
“…Generally, the highest values of compressive strength were obtained for the three clinker mixtures subjected to the highest temperature, i.e. 1320°C, a result in agreement with similar studies reported in the literature (15). The lower compressive strength of the cement pastes composed of clinker mixtures heated at 1120 and 1220°C is the result of their phase composition, which did not contribute to cement mechanical properties during the selected curing period of 28 days.…”
Fly ash and phosphogypsum were used as Naturally Occurring Radioactive Materials (NORM) by-products for the synthesis of belite-sulfoaluminate clinkers. The influence of raw mixture composition and firing temperature was investigated. Clinkers and cements were examined by X-ray powder diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy. The compressive strength of the cements was determined after 28 days. Clinker phases identified included ye’elimite, ß-phase of belite, ternesite and gehlenite, while the main hydration product of the cement pastes was ettringite. The results showed that belite-sulfoaluminate cements can be fabricated with a compressive strength of 45.9 N/mm2 by firing the raw mixture (70 wt.% marl, 10 wt.% bauxite and 20 wt.% phosphogypsum) at a temperature of 1320°C/1h.
“…[6]. Gallardo et al [28] and Velazco et al [29] were shown in the previously published results that the ettringite as the main hydration product although traces of monosuphate phase were also found. The addition of citric acid increased the setting time, modified the morphology of the ettringite needles, changed the microstructural configuration and prevented the decreasing in compressive strength of the samples caused by delayed ettringite formation, also Bazaldúa et al [30] demonstrated that the main hydration products of supersulphated cements were C-S-H and Ettringite.…”
Abstract. This paper investigates the mineralogical evolution of sulfoaluminate clinker elaborated from moroccan prime materials limestone, shale and phosphogypsum as a byproduct from phosphoric acid factories. The advantage of the production of this type of clinker is related to the low clinkerisation temperature which is known around 1250°C, and to less consumption quantity of limestone thus enabling less CO 2 emissions during the decarbonation process compared to that of Portland cement. In this study we determine the stability conditions of belite sulfoaluminate clinker containing belite (C 2 S) ye'elimite (C 4 A 3 $) and ternesite (C 5 S 2 $). The hydration compounds of this clinker are also investigated. The monitoring of the synthesized and hydrated phases is performed by X-Ray Diffraction and Infrared spectroscopy. The results show the formation of ternesite at 800°C and the stabilization of clinker containing y'elminite, belite and ternesite at temperatures between 1100 and 1250°C.
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