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Oil-based drilling cutting pyrolysis residues(ODPR) and phosphogypsum(PG) are typical types of industrial solid waste in China, characterized by low utilization rate and high output. The large amount of untreated accumulation will release heavy metals(HMs) and other pollutants, posing risks to the environment. Therefore, there is an urgent need to develop a high value-added building material product that can reduce environmental hazards while improving utilization rate. Based on this background, this study uses ODPR and PG as raw materials to explore their potential applications in the field of foamed ceramics. Research has shown that different sintering processes have a significant impact on the appearance and performance of products. By adjusting the preparation process, foamed ceramic products with excellent performance can be prepared. When the sintering temperature is 925℃, the foaming agent dosage is 3 %, and the raw material ratio ODPR:PG:Borax=35:45:20, a foamed ceramic product with a porosity of 60.95 %, water absorption rate of 3.4 %, compressive strength of 4.8 MPa, thermal conductivity of 0.8016 W/(m·k), and acid and alkali resistance of 98.57 % and 99.44 % can be prepared. The product meets the relevant requirements of "Fired heat preservation brick and block (GB/T 26538)" and " General Specification for porous ceramic products (GB/T 16533)". The HMs content test showed that the Ni and Pb contents in the pre-sintered blanks were the highest, at 0.6308 mg/kg and 0.3182 mg/kg, respectively. However, after high-temperature calcination, the solidification rate of HMs could reach up to 98.93 %, and the leaching amount was significantly reduced. The three further evaluation methods indicate that HMs in the pre-sintered blanks and foamed ceramic products do not pose significant ecological risks. The research results provide a green inorganic insulation material in the field of solid waste control and building materials. • Basic properties of ODPR- PG foamed ceramics was carried out. • Microsintering mechanism of foamed ceramics was analyzed. • 3.Heavy metals leaching and solidification were presented. [ABSTRACT FROM AUTHOR]

Oil-based Drilling Cutting Pyrolysis Residue (ODPR) is a waste produced during oilfield drilling using oil-based mud. Recycled Fine Powder (RFP) consists of particles less than 0.16 mm, crushed and sieved from waste concrete. China's solid waste is characterized by high production, low utilization rates, and high pollution levels. This study explores the feasibility of preparing ceramsite from ODPR and RFP. By examining the effects of varying temperatures and proportions on the macroscopic and microscopic properties of ODPR-RFP ceramsite (ORC), the optimal process was determined: ODPR: RFP = 7:3, 2 % borax flux, 10 minutes ball milling, 1200℃ sintering temperature, and 30 minutes insulation. The resulting ORC, with a bulk density of 1120 kg/m³, cylinder compression strength of 10.50 MPa, and water absorption rate of 7.8 %, meets the "Lightweight aggregates and its test methods (GT/B17431.2)" standard. Batch production of ORC products of various sizes was conducted to evaluate their practical application in LC30 lightweight aggregate concrete. Replacing the aggregate in lightweight concrete with ORC yielded a concrete with excellent mixing performance, reaching a maximum strength of 31.2 MPa after 7d and 44.8 MPa after 28d. The damage pattern of ORC lightweight concrete is characterized by longitudinal splitting, with varied crack initiation and expansion paths. In the interfacial transition zone of ORC concrete, the ORC form a strong bond with the cement mortar, enhancing the strength of the lightweight concrete. Additionally, the leaching of heavy metals (HMs) from the ORC was examined to assess potential environmental pollution. The results indicated that preparing ORC from these two types of solid waste can effectively immobilize HMs, with a solidification rate of up to 92.10 %. Pb with high content is mainly solidified in the form of solid solution to form (Ba, Pb) SO 4. The ecological risk assessment method for HMs shows that using this solid waste and process to prepare ORC does not pose HMs risks and is an environmentally friendly building material. • Basic properties of ODPR-RFP ceramsite was carried out. • Microsintering mechanism of ODPR-RFP ceramsite was parsed. • Lightweight concrete application and heavy metals solidification were analyzed. [ABSTRACT FROM AUTHOR]

In the production processes of phosphoric acid and alumina, chemical enterprises generate solid waste such as red mud (RM), phosphogypsum (PG), and fly ash (FA). The environmentally friendly utilization of these waste materials is of crucial significance. Therefore, this study focuses on investigating the impact of collaborative modification using diverse solid wastes on the macroscopic properties and internal microstructure of self-leveling mortar. Through a careful selection process, the optimal ratio for red mud and phosphogypsum self-leveling mortar(RPSM) has been identified during the research. This study not only provides substantial support for the effective utilization of solid waste but also contributes to the improvement of overall performance and structural characteristics of the mortar. Based on this, the hydration characteristics, leaching patterns, and spatial distribution characteristics of heavy metals in RPSM were evaluated. The research revealed that the optimal ratios of RM, PG, FA, PC, river sand, and heavy calcium carbonate powder in RPSM were 20.7%, 13.8%, 17.1%, 13.8%, 17.3%, and 17.3%, respectively. Under a water-binder ratio of 0.18, the flexural and compressive strength of the mortar specimens after 14 d of curing can reach 4.3 and 31.6 MPa. Through comprehensive analysis and discussion of the performance, microstructure, and dynamics of the hydration process of RPSM, the main processes of mortar hydration were elucidated. Environmental risk assessments indicated no environmental risks from heavy metals in RPSM. Human health risk assessment suggested carcinogenic risks from Cr and Cd in RPSM through oral exposure, leading to restrictions on the content of characteristic heavy metals in different application scenarios. Furthermore, fitting results of the release kinetics of heavy metals indicated that the leaching of heavy metals in RPSM can be well fitted with kinetic models, allowing the determination of the optimal safe age of RPSM containing harmful heavy metals. Finally, using interpolation and vertical distribution simulation by software such as ArcGIS, the spatial distribution characteristics of heavy metals in RPSM during use were analyzed. The research can supply fundamental academic support for the recycling of solid wastes like RM and the control of environmental risks associated with heavy metal leaching in building materials. ● A technology of red mud modified phosphogypsum composite cementitious material was developed. ● Heavy metals coupling mechanism and spatial distribution characteristics were systematic analyzed. ● Heavy metal migration and transformation model was constructed. [ABSTRACT FROM AUTHOR]

There is a huge stock of industrial solid waste piles such as phosphogypsum (PG), desulfurization ash (DA), and waste soil (WS) in China, and their utilization rate is insufficient. These have potential risk for environmental safety due to pollutants contained in them. In this study, after proportioning design, raw material pretreatment, bubble regulation and multi-temperature section maintenance process, successfully prepared a high blending solid waste based functional prefabricated autoclaved aerated concrete slabs (FPAS) with excellent functional performance, and the optimal ratio of each raw material is PG: WS: DA: cement: lime = 8:50:20:10:12, and the dry mass ratio is up to 75%, the compressive strength of the slabs is up to 5.2 MPa, the standard dry density is 606 kg/m3, the dry shrinkage value is 0.36 mm/m, and the post-freezing strength is 4.0 MPa, which is in line with the basic requirements in the standard "Autoclaved aerated concrete slabs" (GB/T15762) , and at the same time, its fire-resistant integrity is qualified for 240 min, and the coefficient of thermal conductivity is 0.15w(m.k), airborne sound-weighted sound insulation is 46 dB, also can show different functional characteristics. In order to investigate the environmental safety of heavy metals (HMs) in the slabs, the simulation experiment of HMs leaching from outdoor stacking of slabs was carried out. The results show that the HMs in the slabs do not pose obvious risks to the natural environment and human body, but three of the characteristic HMs, Cr, Cd and Hg, have significant leaching patterns, which can be expressed by a second-order kinetic model. Finally, the life cycle assessment and cost analysis of the high blending PG-DA-WS based FPAS and the conventional aerated slabs were carried out. The main environmental damage category of the high blending PG-DA-WS based FPAS is land ecological risk, and it has obvious environmental and economic benefits compared with the conventional aerated slabs. • High blending phosphogypsumbased aerated concrete slabs were developed. • A ternary solid waste synergistic enhancement mechanism was studied. • A systematic study of heavy metals and life cycle assessment of FPAS were analyzed. [ABSTRACT FROM AUTHOR]

The exploration and development of shale gas technology provide a way to utilize clean fuels with high efficiency and minimum environmental impact. However, the accumulation of water-based drilling cuttings (WDC) from oil and gas field development is causing serious waste of land resources and environmental safety problems. This work presents an experimental study on the feasibility of recycling original WDC as replacements for fine aggregates and as part of cementitious materials for the manufacture of non-fired bricks. Mechanical and physical properties, detailed environmental performance, and microstructure analysis were carried out. Meanwhile, the original hydrated products and hydration process of WDC brick were evaluated with, FT-IR (Fourier transform infrared), XRD (X-ray diffraction), SEM (scanning electron microscopy) and EDX (energy-dispersive X-ray spectroscopy). The outcomes indicated that WDC have certain pozzolanic characteristic and a significant impact on the durability and strength of non-fired bricks. The best properties achieved with the help of 50% WDC which meet grade M10 according to a Chinese standard (GB/T2542-2012). Environmental performance tests provides that the WDC used as the raw material for non-fired bricks, and from the technical point of view, does not have environmental pollution. [ABSTRACT FROM AUTHOR]

The overall objective of this research project is to investigate the feasibility of incorporating oil-based drilling cuttings pyrolysis residues (ODPR) and fly ash for the preparation of non-autoclaved aerated concrete. Within this thesis, mechanical and physical properties, detailed environmental performance, and microstructure analysis were carried out. Meanwhile, the early hydration process and hydrated products of ODPR non-autoclaved aerated concrete (ONAAC) were analyzed with X-ray diffraction analysis (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM). The results showed that the following optimal mix proportion is ideal for preparing ODPR non-autoclaved aerated concrete (about 600 kg/m 3 ), that is to say, is 25–30% for fly-ash, 15–20% for ODPR, 20–30% for cement, 15–20% for quicklime and 4% for gypsum, W/S is 0.61. Furthermore, the best curing steam temperature is 80 °C. The compressive strength, dry unit weight and thermal conductivity of products can basically meet the requirements of Chinese standard GB 11969-2008. The results also showed that ODPR had a certain pozzolanic activity which could play the role of active materials. Environmental performance tests came to the conclusion that when ODPR serves as recycled aggregates and admixture for preparation of non-autoclaved aerated concrete, from the technique’s perspective, it wouldn’t be the substance of environmental contamination. [ABSTRACT FROM AUTHOR]

• Physical performances of representative ordinary Portland cement were analyzed. • A systematic study of heavy metal risk assessment was carried out. • A heavy metal migration model was constructed. As an important basic material in the construction industry, the potential harm of heavy metal elements contained in Portland cement (PC) to the ecosystem and human health cannot be ignored. In this research, PC from five representative areas of China was chosen to systematically research its heavy metal risk assessment, leaching release kinetics and hydration coupling mechanism using the advanced scientific testing techniques and research methods, so as to provide reasonable suggestions for the efficient, safe and environmentally friendly utilization of PC. The research indicated that the chemical constituents of PC are CaO, SiO 2 , Al 2 O 3 , Fe 2 O 3 , etc. The primary mineral composition were calcite, quartz, magnesite and mullite. Through the detection and analysis of the contents of Cr, As, Cd and Pb in PC, in accordance with the analysis results of environmental evaluation model, there were no obvious environmental risks of the four heavy metals, but the contents of Cr and Cd in PC need to focus on. At the same time, Cr in PC needs to be key-point controlled as human health risk assessments indicated that they posed a carcinogenic risk to the human body through oral administration. However, as the cumulative effect of As and Pb, their toxicity cannot be ignored in human health evaluation. Therefore, As and Pb need to be re-incorporated into the category of characteristic noxious heavy metals. But the control level was marked as medium; Cr and Cd control level was high.The fitting results of release kinetics showed that most of the heavy metal leaching in PC can be well fitted by Elovich model and second-order kinetic model. This indicated that Elovich model, second-order kinetic model and parabolic model were more worthy of study in the leaching release kinetics of heavy metals. In the meantime, the study showed that the leaching of heavy metals in PC was controlled by a series of effects such as parabolic model. On the basis of the dynamic model of heavy metal content in five kinds of PC with curing duration, the optimum safe age of noxious heavy metals in PC after PC hydration was explored. Through XPS test results, it was discovered that the Cr, As, Cd and Pb in PC present in the formation of Cr3+, Cr6+, As3+, As5+, Cd2+ and Pb4+. These noxious heavy metal ions were harmful to the human body by means of the infiltration and migration of soil and groundwater. Lastly, the hydration coupling mechanism of heavy metals in PC were discussed, and the content of characteristic heavy metals in PC under various usage scenes were limited. [ABSTRACT FROM AUTHOR]

• An optimal composite cementitious materials systerm were analyzed. • A systematic study of hazardous risk assessment were carried out. • Evaluation system of safety and environmental protection utilization are proposed. Phosphogypsum (PG) and red mud (RM) are solid wastes produced by chemical enterprises when producing phosphoric acid and alumina. Therefore, the harmless utilization of them is of great significance to the environment. This study explored the effect of the synergistic activity enhancement effect of solid waste on the macroscopic properties and internal microstructure of RMPS, and explored the optimal ratio of composite cementitious materials and ceramic aggregate. Based on the synergistic enhanced activation effect of multiple solid wastes, it is necessary to evaluate the human health and ecological security risks of heavy metals in the prepared red mud modified phosphogypsum system (RMPS) to ensure the environmental safety of the product. The results showed that the optimum ratio of PG, RM, FA, quicklime and cement in the preparation of cementitious materials by RMPS were 46.9 %, 26.5 %, 4.1 %, 12.2 % and 10.2 %, respectively. Under the water-binder ratio of 0.33, the 14 days compressive strength of the mortar specimen could reach 19.0 MPa, the 14 days flexural strength could reach 4.3 MPa. The optimum ratios of PG, RM, FA, quicklime, cement and river sand in the prepared ceramic aggregate were 36.5 %, 20.6 %, 19.5 %, 3.2 %, 7.9 % and 22.2 %, respectively. The raw materials were mixed and prepared into ceramsite, which was placed in a drying oven and cured at 20 °C for 14 days. The 14 days cylinder compressive strength of ceramic aggregate could reach 2.4 MPa, which met the standard requirements of "Lightweight aggregates and its test method-Part 1: Lightweight aggregates" (GB/T 17431.1–2010). With 10 % cementitious materials content, the road water-stable layer materials was prepared by using ceramic aggregate to replace 4.75 mm crushed stone in equal volume. The 7 days unconfined compression strength of the cylinder specimen was 4.7 MPa, and the 7 days splitting tensile strength was 0.6 MPa, which met the strength requirements of the highway water-stable layer in the "Specification for design of highway asphalt pavement" (JTG D50-2017). The risk assessment of heavy metals in RMPS was carried out. The single factor index indicates that more attention should be paid to Hg and Cd. The geo-accumulation index showed that Hg in the system had a high environmental pollution risk. At the same time, in accordance with the result of human health risk assessment, Cr in RMPS can cause carcinogenic effects through oral intake and need to be controlled. Finally, based on the risk assessment model constructed in this study, the limit values of RMPS applied to three heavy metals in road water stability layer were given and the safety and environmental protection control model of heavy metals in RMPS was proposed. [ABSTRACT FROM AUTHOR]

• An environment-friendly disposal for the utilization of ODCSB. • The product quality of ODCSB cement was very well. • The particular pollutants of ODCSB were all meet Chinese standard. Large amounts of oil-based drilling cuttings (ODC) will be generated from shale gas exploitation, and the traditional way to deal with it is to solidify the drilling cuttings. There are potential environmental risks associated with this endeavor. So, the safe and environment-friendly disposal and utilization of oil-based drilling cuttings solidified body(ODCSB) were studied. The chemical composition, mineral composition, thermal analysis, radionuclide and other basic physical characteristics of the ODCSB were analyzed by modern test methods. Also, the kiln entry characteristics of the ODCSB were deeply studied, and the raw meal calcination formula of the ODCSB was reasonably designed. The chemical composition, mineral composition and microstructure of the cement clinker obtained are almost the same as those produced by a large cement plant, and the tail gas in the calcination process also meets the requirements of the Chinese standard(GB 30485). In addition, the clinker was used as a raw material to prepare ordinary Portland cement. The results show that the compressive strength, setting time, water requirement of standard consistency, mineral composition and microstructure of ODCSB cement are basically the same as those of cement produced in a large cement plant. It can be seen that the cement prepared by the right amount of ODCSB can meet the relevant requirements of Chinese standard(GB 175). At the same time, the leaching toxicity of heavy metals in the cement was also tested. Results show Cd was not detected, Cr was 50.3 mg/kg, Pb was 44.6 mg/kg, As was 12.8 mg/kg, Ni was 9.1 mg/kg, Hg was 0.11 mg/kg, are lower than the relevant limit requirements in the Chinese standard(GB 30760). In conclusion, the quality and heavy metal content of common Portland cement produced by ODCSB meet the requirements of corresponding standards, and the micro properties of ODCSB cement are also close to the commercially available cement. So, it is an effective way of safe and environment-friendly disposal and utilization of ODCSB. [ABSTRACT FROM AUTHOR]