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Sintering-free lightweight aggregates were prepared with high proportions of red mud and a binder material derived from whole solid wastes through rolling granulation at room temperature. The preparation process was optimized by changing the material matching and size parameters of the SFLAs. The physico-chemical performance, including the density, mechanical strength, water absorption, hydration products, heavy metal leaching, and microstructure were evaluated by jointly employing X-ray Fluorescence, X-ray Diffraction, and Inductively Coupled Plasma Optical Emission Spectrometry, Shadow Electron Microscope, etc. The results indicated that the red mud and waste-based binders were highly compatible in the granulation process, with up to 80% red mud being successfully added. The sintering-free lightweight aggregates products at the binder content of 30% and the size coverage of 10&ndash, 16 mm exhibited a bulk density of 900&ndash, 1000 kg&middot, m&minus, 3, a 28 d cylinder compressive strength of 9.2&ndash, 11.3 MPa, and water absorption of less than 10%. Owing to the formation of important hydration products, ettringite, the heavy metal leaching of the sintering-free lightweight aggregates was also proven to be environmentally acceptable. This work provides a promising pathway to prepare low-cost, high-strength, and green lightweight aggregates through the large-scale utilization of solid waste red mud.

Because the disposal of phosphogypsum (PG) can lead to serious contamination of the air, soil, and water, recycling of PG has attracted wide attention. This study investigated the effect and solidification of phosphorus in the production of calcium sulfoaluminate (CSA) cement using PG as the sole CaO source. The effects of three phosphorus impurities (Ca3(PO4)2, CaHPO4, Ca(H2PO4)2) on the decomposition of CaSO4, formation of minerals, microstructure of the clinker, and the hydration and mechanical properties of the cement were studied. Experimental results show that Ca3(PO4)2 and Ca(H2PO4)2 promoted the decomposition of CaSO4 and the formation of clinker minerals with the increase in P2O5 content, whereas CaHPO4 showed a promoting effect only when the P2O5 content was more than 1.5 wt%. The increase in phosphorus incorporation in Ca2SiO4 leads to the transformation of β-Ca2SiO4 to α′-Ca2SiO4 and then to Ca7Si2P2O16. The presence of three phosphates in the clinker enhanced the growth of crystal grains and the generation of a liquid phase. Compared with Ca4Al6SO16 without phosphorus, the hydration reaction of phosphorus-bearing Ca4Al6SO16 started later and ended earlier, and the reaction time was shorter. The presence of phosphorus impurities reduces the 1-day strength of CSA cement but does not affect the development of the 3-day and 28-day strengths. Considering environmental aspects, the solidification of phosphorus in the production of CSA clinker were quantified by measuring the distribution of elements. The results indicated that phosphorus is solidified by Ca4Al6SO16, Ca2SiO4, and Ca4Al2Fe2O10, and Ca2SiO4 has a stronger ability to solidify phosphorus than the other two minerals. Ca3(PO4)2 is more difficult to solidify than CaHPO4 and Ca(H2PO4)2. This study is of great significant to guide the large-scale clean utilization of PG in the production of CSA cement.

Although many types of simulated radionuclides have been widely used as a substitute for actual nuclear waste in the studies of nuclear waste solidification, the understanding of the applicability and validity of simulated radionuclides is still insufficient. In particular, the selection and use of simulated radionuclides, which can play a decisive role in the accuracy of the experimental results, still lack unified or integrated references. This paper provides a critical review on the selection, experimental methods, and applicability of the most commonly studied simulated radionuclides, followed by a careful discussion and recommendation of simulated radionuclides suitable for different solidified bodies. The main factors (e.g., temperature, pH, and atmosphere) affecting the choice of simulated radionuclides were analyzed in detail. This work helps to integrate the selection and use of simulated radionuclides, and it will be beneficial for improving the effectiveness of nuclide solidification research.

Although many types of simulated radionuclides have been widely used as a substitute for actual nuclear waste in the studies of nuclear waste solidification, the understanding of the applicability and validity of simulated radionuclides is still insufficient. In particular, the selection and use of simulated radionuclides, which can play a decisive role in the accuracy of the experimental results, still lack unified or integrated references. This paper provides a critical review on the selection, experimental methods, and applicability of the most commonly studied simulated radionuclides, followed by a careful discussion and recommendation of simulated radionuclides suitable for different solidified bodies. The main factors (e.g., temperature, pH, and atmosphere) affecting the choice of simulated radionuclides were analyzed in detail. This work helps to integrate the selection and use of simulated radionuclides, and it will be beneficial for improving the effectiveness of nuclide solidification research.

Here, solid-waste-based cementitious material (SCM) and red mud (RM) were innovatively applied to produce cold bonded lightweight aggregate (CBLAs) via synchronous pelletizing and foaming process. To integrally demonstrate the feasibility of developing the acceptable CBLAs, the following were investigated: (1) the effects of the production parameters on the pelletizing efficiency of CBLAs was investigated, and the results showed that SCM and RM exhibited the best compatibilities for CBLAs with a pelletizing efficiency of 91.9 %; (2) the effects of SCM and the addition of a novel hydrogen peroxide (HP, a foaming agent) on the properties of CBLAs was investigated, and the results revealed that the coordination of SCM with HP promoted synchronous pelletizing and foaming, thereby generating unified hierarchical pores on CBLAs and significantly decreasing their density. Viable CBLAs with low loose bulk density of 680 kg/m3, crushing strength of 3.1 MPa and water absorption of 20.7 % were obtained; (3) two surface modification methods of organosilicon waterproofing agent (OWA) spraying and SCM coating were carried out to further reduce water absorption of the prepared CBLAs, and the results indicated that the spraying of an OWA can effectively reduce the water absorption to 8.7 %. Additionally, the durability and environmental impact of CBLAs were evaluated acceptable employing the frost resistance and leaching tests. This work offers a new method for producing CBLAs from 100 % solid wastes and is a promising approach for the large-scale recycling of RM.

Iron-rich calcium sulfoaluminate (IR-CSA) cement is a low-carbon cement that contains small amount of aluminum. In this study, IR-CSA cement preparation method using gypsum as the source of calcium oxide was developed. The effects of iron on the decomposition of gypsum, formation of phases, microstructure of the clinker, and hydration of cement paste were investigated. The results indicated that the decomposition of gypsum and the formation of the target phase were first slightly promoted and then hindered when the iron content in the raw material increased. The presence of iron enhanced the growth of crystal grains and densification of the microstructure in the clinker. The early hydration behavior of IR-CSA cement mainly depended on the hydration of the iron-bearing ye’elimite and ferrous phases. Furthermore, the incorporation of iron into mineral phases was studied. The maximum incorporation content of Fe2O3 in ye’elimite and belite phase reached 19.36 wt%, expressed as C4A2.61F0.39 S - , and 2.83 wt%, respectively. The chemical composition of the ferrous phase was similar to that of C4AF, and its mineral phases were C2F, C6AF2, C4AF, and C6A2F from the center to the edge. Finally, the feasibility of preparing IR-CSA cement using phosphogypsum as the sole calcium oxide source was evaluated for engineering applications. This unique preparation method reduces the use of aluminum in raw materials and thus promotes recycling of iron-containing or low-aluminum-containing industrial solid waste materials.

With the development of automated drilling technology, various automated pipe handling devices are constantly being introduced. It is an inevitable trend to apply these equipment on new drilling rigs, while it is also an important work to apply these new technologies and equipment to a large number of servicing rigs. At present, most of the existing drilling rigs in China do not have automatic pipe handling system. It is urgent to carry out automation retrofitting due to the poor field working environment, hard labor, poor safety and low efficiency. In the paper, the current status of the automated pipe handling system is firstly introduced, and the advantages and disadvantages of these automated pipe handling systems are expounded. Then the comparative analysis of applicability, complexity and the retrofitting cost of the automated pipe picked-up and laid-down drilling floor device, pipe handling device on racking board and the offline stand building device in both domestic and foreign are made. Finally, the suitable types of automated pipe handling system can be used to retrofit servicing rigs in China are pointed out. Cameron's automatic up-and-down rig device, Weatherford's racking board automatic pipe handling system and National Drilling Company's offline stand building system are most suitable for the automation retrofitting of servicing rigs. The results show that, these automated pipe handling systems can not only reduce the labor of field operators, improve pipe handling efficiency, reduce the retrofitting workload of servicing rig, but also save retrofitting costs. The retrofitted servicing drilling rigs will be with new vitality and play a greater role in the development of ultra-deep wells and unconventional oil and gas in China.

8000-meter drilling rig and quadruple joint 9000-meter drilling rig have been developed for ultra-deep and complex wells of the complicated geological structure area in Tarim Basin, China. The key components of the drilling rigs are redesigned and innovated, including optimization of the high bearing capacity derricks and substructures and a completely new design of integrated single shaft drawworks with the compacted strand wire rope. The rotary table and its driving device with larger torque and load capacity, the high-pressure drilling pump with a high power, intelligent top drive system, casing running device with good compatibility, and automated pipe handling system are equipped. Field application shows that 8000 meters drilling rig, compared with the conventional 9000-meter drilling rig, can save equipment procurement costs by about 20%, reduce drilling operational costs 37%. In addition, the quadruple joint 9000-meter drilling rig can reduce the tripping time by more than 20%, and that the pressure is difficult to control in the complicated formation by conventional drilling rigs can be avoided to a certain extent. At the end of this paper, the advantages and the problems to be solved urgently of the ultra-deep well drilling rigs are expounded.